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Aircraft Engine

1997;():V001T01A001. doi:10.1115/97-AA-112.
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The vortical structure of the turbulent, confined, coaxial geometry with a central lobe forced mixer have been determined by measurements using a two-component fibre-optic laser-Doppler anemometer at a Reynolds number of 5.1 × 104 (based on the baseline circular nozzle diameter, Di = 30 mm, and bulk mean velocity, Ur, of the two streams at 1.7 m/s). Ratios of the annular mean to the core mean velocity (λ) were kept at 0.4, 1.1 and 2.0 respectively. Results showed that the mixing processes were greatly enhanced by the formation and interactions of the normal and streamwise vorticity. In particular, the deformation and the subsequent stretching of the normal vortices shed at the nozzle walls by the streamwise vortices played a crucial role in the mixing processes. The higher speed stream appeared to determine the form of mixing downstream. For all the cases considered, strength of the streamwise vorticity were dissipated within 6Di from the nozzle exit plane.

Topics: Nozzles , Geometry
Commentary by Dr. Valentin Fuster
1997;():V001T01A002. doi:10.1115/97-AA-113.
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The windmilling characteristics of twin-spool, high bypass ratio turbofan engine have been analyzed. This analysis is an extension of the previously reported analysis for a single-spool turbojet engine. As before, the aerodynamic performances of engine components are determined by incorporating the available cascade loss correlations. For a given flight condition, the steady-state windmilling conditions are determined by iteratively balancing the mass flow rate and angular momentum through the two spools. Compared to the turbojet analysis, the new analysis requires determination of bypass ratio and work split between the two spools. Some of the calculation results have been compared against the limited data available for a CF-6 engine, and the two show good agreement. The present method is thus shown to be capable in predicting turbofan engine’s windmilling characteristics during its design stage.

Topics: Engines , Turbofans
Commentary by Dr. Valentin Fuster
1997;():V001T01A003. doi:10.1115/97-AA-114.
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The performance of the aero gas turbine engine requires optimization because it is directly related to overall aircraft performance.

In this study, a modified DYNGEN, a dynamic simulation program with component maps of the small aircraft turbojet engine, was used. Nonlinear dynamic simulation was performed to predict overall engine performance.

Each response characteristic of various cases, such as the 6% rpm step model, the 5% rpm step model, the 3% rpm step model, and the real-time linear model of the interpolation scheme within the operating range were compared. Among them, the real time linear model was selected for the turbojet engine with nonlinear characteristics.

Finally control schemes such as the PI (Proportional-Integral Controller) and the LQR (Linear Quadratic Regulator) were applied to optimize engine performance.

As a result of comparison of the PI and the LQR controller, the overshoot of the turbine inlet temperature was effectively eliminated by the LQR controller with the proper control gain K.

Commentary by Dr. Valentin Fuster

Marine

1997;():V001T02A001. doi:10.1115/97-AA-023.
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In December 1991, the United States Navy awarded a contract to Northrop Grumman Marine Systems (then Westinghouse Electric Corporation) for the design and development of an intercooled, recuperated gas turbine engine system (ICR). The system is known by the designation WR-21. The development team includes Northrop Grumman as the prime contractor and system integrator, Rolls-Royce (RR) as the gas turbine developer, Allied Signal as developer of the recuperator cores, recuperator housing, and intercooler cores, and CAE Electronics Ltd. as the digital controller developer.

After the development program began, the Royal Navy and the French Navy became interested in the ICR technology and have since become active program participants. The Navy team’s joint goal is to design, develop, and qualify a fuel efficient engine for future surface combatants. This paper provides an overview and update of the WR-21 requirements, principles of operation, system description/performance, and the development program.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster
1997;():V001T02A002. doi:10.1115/97-AA-108.
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The paper describes the modifications required to make the GT35 industrial gas turbine suitable for use in fast ferries as propulsion machinery. The modifications made to get the unit to meet pitch and roll requirements are dealt with, as well as the engine support system modifications.

The GT35’s capability to burn low quality, liquid fuels is discussed, and a close look is taken at the effect such fuel has on the life of the unit and the time between service.

In order to facilitate power production on the ship, the GT35 has been equipped with a starting motor which during operation is used as a shaft driven generator. The generator is driven by the low pressure rotor. Each generator can produce 500 kW, which means 1000 kW for the ferry. The effect of the arrangement on the rotor system behavior is described.

At the time of writing this paper ABB has sold 6 GT35 units for operation in 3 fast ferries. The speed of the ferries varies between 40 knots and 60 knots. At the time of writing this paper, the first of the two HSS 900 ferries for Stena Line, Sweden, has just completed its first set of sea trials.

Commentary by Dr. Valentin Fuster
1997;():V001T02A003. doi:10.1115/97-AA-116.
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Det Norske Veritas (DNV), has been in the process of updating its Rules for Marine use for some time now. Regulatory bodies such as the International Maritime Organisation (IMO), Norwegian Petroleum Directorate (NPD), and many others, change their requirements from time to time. IMO has introduced a revised code a few years ago. The requirements of these codes/standards and the implications are often very difficult to understand and implement both for the manufacturers and the class societies such as ours. Further, DNV’s Rule requirements need to be understood and acceptable world-wide, if the gas turbine industry, and the maritime industry as a whole is to function in a rational, safe, and profitable manner. This paper is mainly based on DNV Rules of January 1996, Part 4. Chapter 2. Section 4. - Gas Turbines, and is intended to at least open the dialogue between the gas turbine industry and DNV.

Commentary by Dr. Valentin Fuster
1997;():V001T02A004. doi:10.1115/97-AA-117.
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The Redundant Independent Mechanical Start System (RIMSS) is a gas turbine powered, mechanically coupled start system for the Allison AG9140 Ship Service Gas Turbine Generator Sets (SSGTGs) of the U.S. Navy’s DDG-51 Class ships. The system will be original equipment on DDG-86 and follow. It will also be a candidate for backfit onto earlier DDG-51 Class ships.

This paper describes RIMSS and details a very successful phase of the RIMSS program. All U.S. Navy testing was conducted on an Allison AG9140 located at the Carderock Division, Naval Surface Warfare Center-Ship Systems Engineering Station, DDG-51 Gas Turbine Ship Land Based Engineering Site (NSWCCD-SSES LBES), Figure 1. The test agenda included 516 SSGTG starts and 75 SSGTG motoring cycles. The primary goal was to validate engine life predictions for the Allison 250-C20B gas turbine engine in the RIMSS application. A secondary goal was to evaluate the overall RIMSS system during an extended period of operation.

Commentary by Dr. Valentin Fuster

Turbomachinery

1997;():V001T03A001. doi:10.1115/97-AA-002.
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The centrifugal compressor for a marine use turbocharger with its design pressure ratio of 3.2 was tested with a vaneless diffuser and various vaned diffusers. Vaned diffusers were chosen to cover impeller operating range as broad as possible. The analysis of the static pressure ratio in the impeller and the diffusing system — consists of the diffuser and scroll — showed that there were four possible combinations of characteristics of impeller pressure ratio and that of diffusing system pressure ratio.

The flow rate, QP, where the impeller achieved maximum static pressure ratio was the critical flow rate determined surge flow rate of the centrifugal compressor. In order to operate the compressor less than QP, the diffusing system whose pressure recovery factor was steep negative slope near QP was needed. Using the diffuser throat area less than a certain value, the compressor efficiency deteriorated, however the compressor stage pressure ratio was almost constant. In this study, the compressor by reducing the diffuser throat area could be operated at the flow rate less than 40% of its design flow rate. Analysis of the pressure ratio in the impeller and diffusing systems at design and off design speeds showed that the irregularities in surge line occurred when the component which controlled the negative slope on the compressor stage pressure ratio changed.

Commentary by Dr. Valentin Fuster
1997;():V001T03A002. doi:10.1115/97-AA-007.
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Unsteady load predictions on steam turbine blades are needed for a better understanding of high cycle fatigue blade failures. The forced response due to rotor-stator interaction and the unsteady loads due to blade oscillatory motion are major factors for the cause of stresses. In addition, turbulence, which is generated through the stator nozzle passages of a turbine, significantly affects the flow characteristics and heat transfer of the rotor blades.

This paper presents a numerical modeling of turbulence effects of a flow around a rotor blade which was extended to demonstrate unsteady calculations due to blade oscillations. The grids were generated by employing the boundary-fitted algebraic grid generation technique. In the computations, the unsteady compressible Navier-Stokes equations were solved for the simulation of the flows in the above mentioned regions to determine mean velocity components, the turbulence energy levels, pressures, and thermodynamic properties such as temperatures and densities. The computed pressure distributions along a blade were compared with the published experimental data and the code was validated by showing reasonable agreement with the results. Some numerical examples are presented by using different turbulence models to investigate the nature of the turbulence occurring in the flow around a blade. Furthermore, the computational model was tested for its applicability to blade flutter in three vibrational modes — tangential, axial, and twist modes.

Commentary by Dr. Valentin Fuster
1997;():V001T03A003. doi:10.1115/97-AA-009.
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Good aerodynamic design of the compressor intake contributes to a gas turbine’s performance and compressor surge margin. The combination of empirical design correlations, optimization with CFD and experiments leads to a successful design. The GT24 compressor intake was tested in a rig test. Both tests from the rig and measurements from the first GT24 at the Gilbert power station confirm a low level of losses and flow distortion.

Topics: Design , Gas turbines
Commentary by Dr. Valentin Fuster
1997;():V001T03A004. doi:10.1115/97-AA-010.
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During the commissioning of the prototype of the sequential combustion turbine GT24 extensive measurements of the compressor performance at design- and off-design-operation were accomplished besides the investigation of the other components of the GT. While the compressor performance at design operating conditions was as expected the data obtained showed some unexpected deviations from previously performed measurements of a 1/3-scale test rig of the low pressure compressor. This paper summarizes the results of the measurements and presents a detailed comparison between the measured performance of the GT compressor, the design data and the test rig. The discussion is focused on the influence of scaling effects on the aerodynamic performance and stage matching with particular emphasis on the Reynolds Number influence at different aerodynamic speeds. Furthermore some aspects of the starting behavior of the compressor are presented.

Topics: Compressors
Commentary by Dr. Valentin Fuster
1997;():V001T03A005. doi:10.1115/97-AA-011.
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A solver for compressible turbulent flow has been developed for a single stage environment. The current work presents the results of numerical simulations of ‘proposed high pressure compressor’ (HPC) using an exact geometry dimensions with full flow conditions. The flow solver is based on the Reynolds averaged Navier-Stokes (RNS) equations in which the algebraic Baldwin-Lomax model is adopted. This numerical scheme simulates the steady flow phenomena of stator-rotor interaction in single stage environment. The numerical method used in the solver serves as a basis for many CFD works in the group. The accurate numerical analysis of complex flows associated with stator/rotor configurations in turbomachinery can be very helpful for understanding the flow phenomena. A comprehensive and satisfactory theoretical prediction of the whole process of blade row interaction will only be available when viscous and mixing effects can be taken into account numerically. The current analysis is used to predict the convective heat transfer on the suction and pressure surfaces of the ‘proposed HPC’.

Commentary by Dr. Valentin Fuster
1997;():V001T03A006. doi:10.1115/97-AA-018.
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Many liquid rocket engines for space launch vehicles use high performance turbopumps to deliver fuel and oxidizer to the thrust chamber. Such turbopumps have been plagued by rotordynamic instability caused by non-axisymmetric turbine tip clearance. Yet, there is dearth of experimental data on this phenomenon, and reliable damping data are non–existent. This paper describes a new experimental facility designed and built to obtain aerodynamic stiffness and damping forces in an unshrouded turbine with a whirling rotor.

The experimental facility consists of an air supply system, single turbine stage test section, instrumentation, and auxiliary systems. The test turbine is a 1: 1 replica of an unshrouded turbine stage used in an actual turbopump. This impulse turbine has a design flow coefficient of 0.76 and work coefficient of 5.9. To measure aerodynamic stiffness forces, the turbine casing is mounted so that it is eccentric relative to the turbine rotor which is concentric with the turbine shaft. Thus, static turbine tip clearance asymmetry is obtained. To obtain aerodynamic damping forces, the turbine casing is mounted concentric relative to the turbine shaft, and the turbine rotor is mounted eccentric relative to the shaft. Thus, synchronous forward whirling condition, or dynamic turbine lip clearance asymmetry, is simulated. Currently, the mean tip clearance is 2% of the rotor blade span, and the specified eccentricity is 1% of the rotor blade span. This test rig facilitates acquisition of both stiffness and damping rotordynamic forces due to turbine aerodynamics. In contrast, past experiment designs required two separate drives — one for rotation and second for whirling motion — to simulate whirling turbine. Therefore, the new facility offers a comparably inexpensive and reliable alternative testing method.

Instrumentation consists of pilot static probes, thermocouples, and optical encoder (tachometer) to monitor turbine operating conditions. Proximity probes are used to measure tip clearance. Steady pressure data are obtained through a set of static pressure taps on the casing. Dynamic pressure data are obtained through flush-mounted, Kulita unsteady pressure transducers. Finally, steady and dynamic velocity data are acquired via 2–D hot wire probes. Thus, steady and unsteady flow fields in turbines with statically offset rotor and whirling rotor, respectively, can be measured.

Commentary by Dr. Valentin Fuster
1997;():V001T03A007. doi:10.1115/97-AA-021.
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This paper described a 3-D, finite-volume procedure for simulating the entire viscous flow field within the impellers of a high subsonic radial compressor with uniform tip-clearance. The aim of the calculation is to verify the compressible Navier-Stokes solvers by comparing the computation against the experimental data of Krain backswept compressor at choke condition. The time-marching implicit technique used is a modified form of the basic Beam-Warming algorithm with a mixing length turbulence model in the blade-relative frame using rotating cylindrical coordinate system and appropriate source terms. An outline of the scheme is addressed and the present capabilities of the solver are assessed. The numerical calculations of the well-known jet/wake-type flow patterns agree well with measurement for the compressor rotor, and detailed comparisons indicate that the tip-clearance effect must be accurately modeled to compute the impeller flow patterns properly. In the case of larger separation region near suction surface of Krain compressor, it is due to the larger tip gap used in the model which causes the thickening of the casing boundary layer followed by the deterioration of the entire flow field.

Commentary by Dr. Valentin Fuster
1997;():V001T03A008. doi:10.1115/97-AA-022.
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This paper describes an extension of 3D time-marching compressible Navier-Stokes solver (Part 1) for an incompressible application through the pseudo-compressibility technique suggested by Chorin. Effect of tip clearances on the mixed-flow pump is investigated. Static pressure distribution and intricate internal flow pattern is reasonably well predicted. Fine-tuning of the pseudo-compressibility parameter and grid size is required for improve convergence and stability.

Commentary by Dr. Valentin Fuster
1997;():V001T03A009. doi:10.1115/97-AA-109.
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A calculational model for predicting the surge line of a turbocompressor system has been established which is composed of a centrifugal compressor, duct, coolers and condensers (gas-liquid separator). The influences of various parts of the system on the surge point have been studied in detail, and some discussion has been focused on the coolers and condensers. The influences of cooler, condenser and thermodynamic parameters of working medium on stability of the system is calculated and explained. This analysis is useful for predicting system character during the of design compressors and systems, as well as safety for operation of practical industry process.

Commentary by Dr. Valentin Fuster
1997;():V001T03A010. doi:10.1115/97-AA-118.
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A modified geometry for the internal cooling passages of a gas turbine rotor blade is suggested here. In this modified geometry, the Coriolis force induced enhanced heat transfer coefficients are experienced by both the coolant channel walls adjacent to the blade pressure and blade suction surfaces. This is made possible by permitting the flow to have a radially outward and a radially inward direction at different locations along the blade thickness at a given chordwise location. However, the flow geometry is complex and the corresponding pressure losses are also likely to be larger. The present investigation is a preliminary study of the pressure drop characteristics for the modified channel suggested above and the simplest case of a straight channel with ribs on only one surface is reported here. The pressure drop in a rectangular cross-sectioned duct with an aspect ratio of 2.0 rotating about an axis normal to the free-stream direction in the presence of rib turbulators glued on one of the surfaces of the test section with ribs normal to the flow direction is measured. The study has been conducted for Reynolds number varying from 10000–17000 and the rotation number varying from 0–0.21. Experiments were carried out for various pitch-to-rib height ratios (P/e) of 3, 5, 7.5 & 10 with a constant rib height-to-hydraulic diameter ratio (e/D) of 0.15. A significant increase of the friction factor is observed when the ribbed surface is the coolant channel trailing (pressure) surface in the presence of rotation. The highest friction factor is observed in a channel with a P/e ratio of 5 which would imply that there could be a significant increase in the heat transfer coefficient for this configuration. A pitch-to-height ratio of about 10, which is the most preferred choice for a stationary configuration, no longer appears to be the optimum in the presence of rotation.

Topics: Pressure drop
Commentary by Dr. Valentin Fuster
1997;():V001T03A011. doi:10.1115/97-AA-128.
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Rotor torsional (angular, steady and dynamic) motion, in response to the interaction of torque and torsional/lateral cross coupled forces with torsional dynamic stiffness, exist in rotating and reciprocating machinery for many reasons. The dynamic torsional response however, is commonly not measured on a continual basis. In the torsional dynamic stiffness, damping parameters are generally several magnitudes weaker than their lateral counterpart. This yields the opportunity for torsional responses, especially when exciting a resonance, to produce relatively large deflections and corresponding stresses, sometimes large enough to cause machine failure.

Due to their rigid coupling, long shaft system lengths (a series of shafts coupled together), and large polar moments of inertia, the turbomachinery used in the power generation industry are particularly sensitive to forced torsional excitation. The forcing can come from many sources, including lateral forces which cross couple into torsional forces. Recent research introduces new sources of cross coupled excitation and a method to indirectly measure their and other effects on the mechanical integrity of the mechanical system.

A modified and a prototype technique for continuously measuring directly and indirectly the rotor torsional response, and using it to evaluate rotor torsional dynamic stiffness as a machinery management tool is discussed in this paper.

Topics: Machinery , Rotors
Commentary by Dr. Valentin Fuster

Coal, Biomass and Alternative Fuels

1997;():V001T04A001. doi:10.1115/97-AA-017.
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Air-blown coal gasification for combined-cycle power generation is a technology soon to be demonstrated. A process evaluation of air-blown IGCC performed to estimate the plant heat rate, electrical output and potential emissions are described in this paper. A process model of an air-blown IGCC power system based on the Westinghouse 501F combustion turbine was developed to conduct the performance evaluation. Parametric studies were performed to develop an understanding of the power plant sensitivity to the major operating parameters and process options. Advanced hot fuel gas cleaning and conventional cold fuel gas cleaning options were both considered.

Commentary by Dr. Valentin Fuster
1997;():V001T04A002. doi:10.1115/97-AA-024.
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In the partial oxidation concept, a high pressure, low-heating-value fuel gas is generated by partially combusting fuel with air. This fuel gas is expanded in a high-pressure turbine prior to being burned in a second-stage, conventional combustion turbine. This process reduces the specific air requirements of the power system and increases the power output. The performance, practicality, and cost of a heavy duty combustion turbine power system incorporating partial oxidation (PO) of natural gas has been estimated to assess the potential merits of this technology. Compared to conventional combustion turbine power cycles, the PO power cycle shows the potential for significant plant heat rate and cost-of-electricity improvements. However, significant development remains to verify and commercialize PO for combustion turbine power systems.

Commentary by Dr. Valentin Fuster
1997;():V001T04A003. doi:10.1115/97-AA-111.
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The design, construction and operation of an IGCC cogeneration plant requires commercial planning, regulatory processing and financial coordination as well as technical engineering. This paper is an overview of the ISAB Energy Project a heavy oil fueled IGCC cogeneration plant that produces electric power and process steam. Crucial activities before and after design include formation of the equity partnership, early feasibilities studies, basic design and permitting, structuring of cogeneration contracts, and financing the project. Particular attention is given to the parties involved in project financing and how they manage the various aspects of financial risk that characterize this type of plant.

Commentary by Dr. Valentin Fuster

Combustion and Fuels

1997;():V001T05A001. doi:10.1115/97-AA-001.
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Planar laser scattering (PLS) and planar laser-induced fluorescence (PLIF) techniques are currently being used for rapid characterization of fuel sprays associated with gas turbine atomizers, Diesel injectors, and automotive fuel injectors. These techniques can be use used for qualitative, quantitative, and rapid measurement of fuel mass, spray geometry, and Sauter mean diameters in various sprays. The spatial distribution of the fuel mass can be inferred directly from the PLIF image, and the Sauter mean diameter can be measured by simultaneously recording the PLIF and PLS images, and then ratioing the two. A spray characterization system incorporating the PLS and/or PLIF techniques has been loosely termed an Optical Patternator, and in this study, it has been used to characterize both steady and pulsed sprays. The results obtained with the Optical Patternator have been directly validated using a Phase Doppler Particle Analyzer (PDPA).

Topics: Fuels
Commentary by Dr. Valentin Fuster
1997;():V001T05A002. doi:10.1115/97-AA-012.
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Simultaneous two-component laser Doppler velocimeter measurements were made in an axisymmetric sudden expansion to measure the flow properties of a confined, isothermal flowfield of a research dump combustor. Measurements of mean velocities, Reynolds stresses, and triple products were carried out at axial distances ranging from 0.38H (H = step height) to 18H downstream of the dump plane. Detailed experimental data are provided to help in the understanding of the behavior of turbulent transport characteristics of a confined shear layer. In addition, the data from this study will be available for upgrading / or evaluating advanced numerical codes used to predict complex turbulent flows. The turbulent kinetic energy terms: convection, diffusion, and production terms were computed directly from the experimental data using central difference, while the viscous dissipation term was obtained from balance of energy equation. The results indicate that the shear layer flow created by the sudden expansion enhances the combustor performance by serving as a turbulence generator mechanism.

Topics: Turbulence
Commentary by Dr. Valentin Fuster
1997;():V001T05A003. doi:10.1115/97-AA-013.
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Allison Engine Company has introduced a dry low emissions lean premixed combustion system, designated LE4, for the 501-K series industrial gas turbine engines. The design goals were 1) to develop a retrofittable combustion system which limits exhaust gas emission levels to less than 25 ppm NOx, 50 ppm CO and 20 ppm UHC while operating on natural gas fuel at full load conditions, and 2) to maintain system cost to less than that for alternate control methods.

Extensive in-house engine tests were completed to ensure successful combustion system operation including acceptable engine transient operation during load dumps, and also to optimize the window of operation for emissions performance. These tests have demonstrated engine emissions levels which are below the goals, with NOx less than 15 ppm, CO less than 20 ppm, and UHC less than 10 ppm, all corrected to 15% O2. These emissions can be maintained at the target levels for engine operation from 85 to 100% power. For applications requiring wider power operation, a diffuser bleed system has been engine demonstrated which maintains less than 25 ppm NOx, 50 ppm CO and 25 ppm UHC from 50 to 100% power. The combustion system employs a dual mode combustion approach to meet engine operability requirements and emissions targets. The control algorithm developed for the LE4 combustion system allows easy tailoring of the pilot-to-main fuel ratio schedule setting to meet the customer needs on a site by site basis to account for different ranges of ambient conditions. Use of Streamwise Oriented Effusion Cooling (SOEC) design in the liner wall met the maximum wall temperature goals of less than 1650°F.

The LE4 combustion system is operating currently in two applications: 501-KC5 ANR Pipeline application in Woodstock, IL, and 501-KB7 Cogeneration application in Scandiano, Italy. Measured emissions over time and a range of ambients in these engines show NOx, CO and UHC results which are better than the goals. The 501-KC5 engine has accumulated more than 3500 hours, and the 501-KB7 engine has accumulated more than 5500 hours. Both sites have been running with problem free operation, and borescope inspections have indicated excellent condition of the combustion systems.

Commentary by Dr. Valentin Fuster
1997;():V001T05A004. doi:10.1115/97-AA-014.
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Most failures of fuel system components, such as flow dividers and fuel pumps, are caused by the effects of corrosion. Rusting of iron and steel can jam rotating components, while surface pitting of many materials from traces of acids in the fuel can weaken parts. It can be shown that preventing fuel system corrosion can substantially increase the reliability and availability of the gas turbine.

Part of the reason that corrosion is such a problem in gas turbine liquid fuel systems is that most land based turbines operate most of the time on natural gas. This means that the liquid fuel system sits idle for most of the time. The liquid fuel almost always contains some water from sources such as condensation in the tank. Water also enters the fuel system from moisture rich combustion gases that can leak past check valves while the turbine is operating on natural gas. When the liquid fuel system is idle, this water separates from the fuel, collecting into a layer inside components. This forms an area of rust in the bottom of any unprotected component. This rust can prevent components from operating or can plug orifices and fuel nozzles downstream when the liquid fuel system is operated.

Corrosion in the fuel system can also come from traces of acid in the fuel. This usually comes about when operating on crude or residual oils with a high sulfur content. Water washing and heating of the fuel as part of the fuel treatment process may cause a chemical reaction that produces small amounts of sulfuric acid in the fuel. Over time, this acid may cause surface pitting in fuel system components. These pits can encourage and speed the formation of fatigue cracks in highly stressed parts such as shafts or bearings. These fatigue cracks will eventually cause the failure of these parts.

Two methods have been used to protect fuel system components against these corrosion problems. The first is to substitute inherently corrosion resistant materials, such as stainless steels, in place of existing materials. This is effective, but it is relatively expensive and creates lubrication and wear problems. These problems come from the poor wear characteristics of stainless steels and many other corrosion resistant materials when rubbing against other metals. Cathodic protection is the other method of protecting components against corrosion. This consists of introducing sacrificial anodes of a material, such as magnesium or zinc, that is more electrochemically active than frequently used materials such as cast iron or steel. The presence of these anodes reverses the corrosion process and makes the iron and steel parts the cathodic or protected end of the corrosion reaction. These anodes must be changed periodically since they are gradually consumed during use.

Commentary by Dr. Valentin Fuster
1997;():V001T05A005. doi:10.1115/97-AA-015.
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A combustor and a fuel nozzle for a small aircraft gas turbine were designed and appropriateness for design requirements were evaluated and confirmed through the cold and hot test. For the purpose of studying the flame stability of a pilot atomizer under ignition, firing tests were carried out at the various fuel supply pressures. As the results of the experiment and design revision, the optimal combination of the fuel nozzle which is suitable to the design requirement was obtained without the fuel splash phenomena and unstable flame. The combustor was designed and evaluated with detailed investigations and experiments for design requirements. As the results of the hot test, it was confirmed that the combustor in this study had proper profile and pattern factors, flammability limit, total pressure loss and combustor efficiency within design requirements.

Commentary by Dr. Valentin Fuster
1997;():V001T05A006. doi:10.1115/97-AA-016.
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The aromatic hydrocarbon content in a gas turbine fuel has a great influence during combustion. The aromatic hydrocarbon content governs the hydrogen content and has an indirect effect on fuel burning characteristics like the luminometer No and the smoke point.

ABB Stal got an oportunity to sell a standard GT35 gasturbine set for electrical generation to a refinery in Thailand, provided the customers prefered fuel, a naphtha containing up to 75 vol% aromatics, could be used.

A theoretical “state of the art” study indicated that 75 vol% aromatics certainly was in the unexperienced area.

Most gas turbine fuel specifications set an upper limit for the aromatic content at 30–35% for industrial GT and at 20–25% for aero engines. Higher values could result in smoke formation during combustion.

This paper describes a full scale test with the ABB GT35 standard industrial gas generator operating on a liquid fuel containing up to 75% aromatic hydrocarbon content. The measurements of CO, UHC, NOx and the smoke number, in Bacharach, taken from the exhaust during the test, will be presented as well as the influence of the combustion on the combustor wall temperature. The effect of the unique standard design on the GT35 air and fuel mixing of the primary combustor section (patented 1965) will be discussed to show how a very complete combustion was obtained also with a 75% aromatic content in the fuel.

After the test that showed that GT35 was able to burn 75% aromatics whitout smoke formation - the set was sold and delivered.

Commentary by Dr. Valentin Fuster
1997;():V001T05A007. doi:10.1115/97-AA-119.
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During the prototype shop tests, the Model V84.3A ring combustor gas turbine unexpectedly exhibited a noticeable “humming” caused by self-excited flame vibrations in the combustion chamber for certain operating conditions. The amplitudes of the pressure fluctuations in the combustor were unusually high when compared to the previous experience with silo combustor machines. As part of the optimization program, the humming was investigated and analyzed.

To date, combustion instabilities in real, complex combustors cannot be predicted analytically during the design phase. Therefore, and as a preventive measure against future surprises by “humming”, a feedback system was developed which counteracts combustion instabilities by modulation of the fuel flow rate with rapid valves (Active Instability Control, AIC). The AIC achieved a reduction of combustion-induced pressure amplitudes by 86%.

The combustion instability in the Model V84.3A gas turbine was eliminated by changes of the combustor design. Therefore, the AIC is not required for the operation of customer gas-turbines.

Commentary by Dr. Valentin Fuster
1997;():V001T05A008. doi:10.1115/97-AA-138.
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The results of research into development of engineering approaches to environmental update of the GTN-16 16 MW gas-pumping unit combustor are presented. The built-in “disc” combustor of the GTN-16 is noted for having a small length and very low hydraulic resistances. The multi-burner low-NOx combustor design was developed in a test rig. The “lean” fuel/air premix combustion was adopted as the basis for the design.

The proposed environmental update of the GTN-16 combustor does not bring about any changes in the most costly material-intensive and labour-consuming components of the combustor, viz. casing, frame, liners. No changes were also made in the automatic control system. It is noteworthy that a similar approach is appropriate for the “Turbomotorny Zavod” (Ekaterinburg, Russia) GTN-25 type 25 MW unit.

Commentary by Dr. Valentin Fuster
1997;():V001T05A009. doi:10.1115/97-AA-139.
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Besides coping with decreasing emissions limits set by international standards, it is necessary in today’s competitive gas turbine industry to design combustion systems, that do not only meet the emission requirements, but also provide an efficient and reliable burner operation performance. Since 1984, when the first Dry-Low-NOx combustor of ABB was put in service, the combustor development program at ABB continued to serve these needs. An important step in that development was the introduction of the EV-burner /1/ which is now available for the entire ABB gas turbine family.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster
1997;():V001T05A010. doi:10.1115/97-AA-141.
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Heavy fuel oil is of interest for firing in utility gas turbine and combined cycle plant, particularly in the developing economies of Asia and Latin America. There are few detailed studies published, which justify in commercial terms the use of heavy fuels in utility gas turbine plant or indicate the scenarios when this should be considered. Whilst this technology/fuel combination is mature and can be considered proven, awareness of the option and the technical and commercial implications is not widespread.

This paper outlines the technical and commercial implications of firing heavy fuels in open cycle peaking and base load combined cycle plant. An economic comparison is made with the alternative fuel and technology options. It is demonstrated that firing heavy fuels in base load combined cycle plant can yield significant cost savings compared to using alternative technologies and liquid fuels, provided the emissions limits are not restrictive.

Commentary by Dr. Valentin Fuster

Cycle Innovations

1997;():V001T06A001. doi:10.1115/97-AA-134.
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In this paper a new kind of steam cycle provided with internal combustion is proposed. The internal combustion of natural gas and compressed air inside the steam flow has been conceived to carry out a steam heating (SH a/o RH) until TIT (Turbine Inlet Temperature) much higher than those of the conventional steam power plants. By this internal combustion it seems possible to overcome the present limits to TIT in steam plants which are, as known, especially related to the technological problems of the superheater tube materials in the conventional external combustion steam boilers.

The proposed cycle has been named with the acronym GIST (Gas Injection STeam) since the hot gases resulting from a combustion close to stechiometric conditions are injected inside the steam flow.

This paper provides a first critical approach to these new kinds of thermodynamical cycles. At the first the thermodynamical and technological problems related to the combustion inside steam are explained and discussed. Then, different plant lay-out solutions are proposed with a critical discussion on their overall performance. At the last two GIST solution have been defined that seem very interesting: the first is an hybrid plant scheme (i.e. provided with multi-fuel supply) which involves performances higher than conventional steam power plants (net electric efficiency of about 47%); the second is a plant scheme with full natural gas supply (i.e. without multi-fuel steam boiler) wich involves very relevant performances (net electric efficiency of about 57%).

Topics: Combustion , Cycles , Steam
Commentary by Dr. Valentin Fuster
1997;():V001T06A002. doi:10.1115/97-AA-142.
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A Moisture Air Turbine (MAT) cycle is proposed for improving the characteristics of land based gas turbine by injecting atomized water at inlet to compressor.

The power boosting mechanism of MAT is understood as composits of those of following existing systems: inlet air cooling system, inter-cooling and steam injection. Experiments using a 15MW class axial flow load compressor have been carried out to reveal that water evaporation in compressor could reduce compressor work in an efficient manner. Moreover, this technology has been demonstrated by means of 130MW class simple cycle gas turbine power plant to show that a small amount of water consumption is sufficient to increase power output. Very efficient evaporation could be achieved provided the size of water droplet is controlled properly. The amount of water consumption is much less than that of conventional inlet air cooling system with cooling tower for heat rejection.

Incorporating water droplet evaporation profile into consideration, realistic cycle calculation model has been developed to predict power output with water injection.

It has been shown that this technology is economically achievable. It should be stressed that contrary to well known evaporative cooler, MAT cycle could provide power output at a desired value within its capability regardless of ambient humidity condition.

Topics: Gas turbines , Cycles
Commentary by Dr. Valentin Fuster

Heat Transfer

1997;():V001T07A001. doi:10.1115/97-AA-003.
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Numerical study on a three-dimensional turbulent flow in a turbine-rotor passage is presented in this paper. The standard k-ε model was used for the first phase of the turbulence computations. The computations were further extended by employing the full Reynolds-stress closure model (RSM). The computational results obtained using these models were compared in order to investigate the turbulence effect in the near-wall region. The governing equations in a generalized curvilinear coordinate system are discretized by using the SIMPLEC method with non-staggered grids. The oscillations in pressure and velocity due to non-staggered grids are eliminated by using a special interpolation method. The predicted midspan pressure coefficients using the k-ε model and the RSM are compared with the experimental data. It was shown that the present results obtained by using either model are fairly reasonable. Computations were then extended to cover the entire blade-to-blade flow passage, and the three-dimensional effects on pressure and turbulence kinetic energy were evaluated. It was observed that the two turbulence models predict different results for the turbulence kinetic energy. This variation was identified as being related to some non-isotropic turbulence occurring near the blade surface due to the severe acceleration of the flow. It was thus proven that the models based on the RSM give more realistic predictions for highly turbulent cascade flow computations than a Boussinesq viscosity model.

Commentary by Dr. Valentin Fuster
1997;():V001T07A002. doi:10.1115/97-AA-004.
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The scope of the present work is to characterize the heat transfer between a ribbed surface and an air flow. The convective heat transfer coefficients, the Stanton number and the Nusselt number were calculated in the Reynolds number range, 5.13 × 105 to 1.02 × 106.

The tests were performed inside a turbulent wind tunnel with one roughness height (e/Dh = 0.07). The ribs had triangular section with an attack angle of 60°.

The surface temperatures were measured using an infrared (IR) thermographic equipment, which allows the measurement of the temperature with a good spatial definition (10.24 × 10−6 m2) and a resolution of 0.1°C.

The experimental measures allowed the calculation of the convective heat transfer coefficient, the Stanton number and the Nusselt number. The results obtained suggested a flow pattern that includes both reattachment and recirculation. Low values of the dimensionless Stanton number, i.e. Stx*, are obtained at the recirculation zones and very high values of Stx* at the zones of reattachment. The reattachment is located at a dimensionless distance of 0.38 from the top of the rib. That distance seems to be independent of the Reynolds number. The local dimensionless Stanton number remains constant as the Reynolds number varies.

The convective heat transfer coefficient presents an uncertainty in the range of 3 to 6%.

Commentary by Dr. Valentin Fuster
1997;():V001T07A003. doi:10.1115/97-AA-005.
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Film-cooling has become a widely used cooling method in present day gas turbines. Cooling gas ejection at the leading edge serves to protect the entire vane surface from contact with the hot gas. With doing this, material temperatures are reduced in order to guarantee an economically acceptable life span of the vane.

This paper describes the application of a numerical method for the conjugate calculation of internal and external fluid flows and the heat transfer in and through the blade walls of a film-cooled turbine guide vane. The advantage of this approach is that it is possible to predict fluid flow properties and wall temperatures without the need for additional heat transfer conditions or temperature conditions at the external surfaces of the vane. This is a great advantage because the desired data are either unknown or not available for the calculation in the design process of new cooled blades or vanes. In a complete calculation of external and internal flows, no additional boundary conditions at the internal surfaces of the cooling geometry are needed either. Another advantage is the interaction of fluid flow and heat transfer which is taken into account by the conjugate calculation.

In the 3-D numerical experiment to be presented, the influence of leading edge cooling fluid ejection on the temperature distribution in the vane material is investigated. The cooling fluid is ejected through two slots at the leading edge. The calculations are performed for three blowing ratios in order to investigate the efficiency of the cooling method. Realistic temperature ratios of cooling-fluid flow and main flow are considered. Such information is very useful in the aero thermal design process of new cooling configurations, since the amount of experimental work can be minimized. The results show the influence of complex 3-D flow phenomena (e.g. passage vortex) on the cooling fluid distribution on the vane surface as a function of the chosen blowing factor. Due to the influence of the passage vortex, the cooling fluid is displaced and leaves the vane surface near the side-wall uncovered against the hot gas. Furthermore, cooling fluid displacement on the pressure side according to the ejection slot geometry leads to another unprotected region on the vane surface. These effects have severe consequences on the thermal load of the vane and can reduce its life span.

Commentary by Dr. Valentin Fuster
1997;():V001T07A004. doi:10.1115/97-AA-006.
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High cycle efficiencies and high power-weight ratios are two major requirements for the economic operation of present day gas turbines. These requirements lead to extremely high turbine inlet temperatures and adjusted pressure ratios. The permissible hot gas temperature is limited by the material temperature of the vane. Intensive cooling is required to guarantee an economically acceptable life span of the components which are in contact with the hot gas.

Convection cooling in blades and vanes has been a common cooling technique for decades. However, the optimization of the cooling configuration is still a great challenge in the thermal design process. One objective in the thermal design process is a general reduction of the temperatures in the vane material, especially in regions with high thermal loads, e.g. the leading edge. Another goal is to create a more equal temperature distribution in the vane walls. This will lead to a reduction in the thermal stress and strain. The aim of research is to minimize the supply of cooling fluid taking the physical restrictions mentioned above into consideration. Therefore, a new numerical procedure for CFD in combination with an FEM stress analysis represents a valuable tool for the thermal design of turbine vanes, minimizing the experimental effort.

This paper demonstrates the application of a new numerical method for the conjugate calculation of internal and external fluid flows and the heat transfer in and through the vane walls in a thermal design process of a convection cooled turbine guide vane. The advantage of this approach is the prediction of fluid flow properties and wall temperatures without requiring information on additional heat transfer conditions or temperature distributions at the external surfaces of the vane. This is a great advantage because the data desired are unknown or not available in the design process of new cooled blades or vanes. Another advantage is the fact that the interactions of fluid flow and heat transfer are taken into account by the conjugate calculation.

After a short description of the conjugate fluid flow and heat transfer method, results for the two-dimensional aerodynamic and thermal investigation of a convection cooled, high-pressure turbine nozzle guide vane are presented. The highly accurate determination of the temperature distribution is essential for the correct calculation of thermal stress and strain. The comparison of numerical and experimental results demonstrates the performance of the code since the differences in the surface temperature distributions are less than 2%. On basis of the numerical results for the original cooling configuration, two more configurations were designed and investigated using the conjugate method. It can be shown that surface temperature peaks can be reduced and a more equal temperature distribution in the vane material can be reached. This also has consequences for the thermal stress and strain in the vane walls as shown by an FEM stress and strain analysis.

Commentary by Dr. Valentin Fuster
1997;():V001T07A005. doi:10.1115/97-AA-008.
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An experimental study was performed in a confined circular single jet impingement. The effect of jet Reynolds number, nozzle-to-plate spacing and heat flux levels on heat transfer characteristics of the heated target surface was examined and presented. Flow visualization was made to broaden our fundamental understanding of the physical process of the type of flow. Transition and turbulent regimes are identified. The local heat transfer coefficient along the surface is measured and correlation of the stagnation point Nusselt number are presented and discussed.

Commentary by Dr. Valentin Fuster
1997;():V001T07A006. doi:10.1115/97-AA-110.
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Computations and measurements of time mean velocities, total fluctuation intensities, and Reynolds stresses are presented for spatially periodic flows past an array of bluff bodies aligned along the channel axis. The Reynolds number based on the channel hydraulic diameter and cross-sectional bulk mean velocity, the pitch to rib-height ratio, and the rib-height to channel-height ratio were 2 × 104, 10, and 0.133, respectively. The unsteady phase-averaged Navier-Stokes equations were solved using a Reynolds stress model with wall function and wall-related pressure strain treatment to reveal the feature of examined unsteady vortex shedding flow. Laser Doppler velocimetry measurements were performed to measure the velocity filed. Code verifications were performed through comparisons with others’ measured developing single-rib flow and our measured fully developed rib-array flow. The computed results and measured data are found in reasonable agreement, which justifies the turbulence model adopted. The calculated phase-averaged flow field clearly displays the vortex shedding behind the rib and is characterized in terms of shedding Strouhal number, vortex trajectory, vortex celerity, and vortex travelling distance in a phase cycle. Furthermore, the difference between the computed developing single-rib flow and fully developed rib-array flow is addressed.

Topics: Turbulence
Commentary by Dr. Valentin Fuster
1997;():V001T07A007. doi:10.1115/97-AA-115.
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Numerical 3-D investigations have been carried out in order to analyze the cooling gas flow pattern inside a turbine blade configuration. The blade is not an actual industrial configuration but is representative for contemporary configurations. The cooling gas enters the serpentine cooling channels through the blade foot. The cooling gas mass flow is divided into two serpentine flows. One covers the front part of the blade and is ejected at the tip, the other serves the rear region and is ejected through a slot in the trailing edge. Internal turbulence promoters are neglected. Boundary conditions typical for front stage blade cooling gas states were chosen.

The computations have been performed with the modern CHTFlow computer code, which solves the fully compressible 3-dimensional Navier-Stokes equations. First the influence of the diffusive transport mechanisms is investigated and shown to be quite important. Through comparison of computation in a fixed and rotating frame of reference, the significant influence of rotation is demonstrated.

Commentary by Dr. Valentin Fuster
1997;():V001T07A008. doi:10.1115/97-AA-126.
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Experiments have been conducted to study the effect of rib size on the local heat (mass) transfer distribution for radial outward flow in a rotating channel with transverse ribs on the leading and trailing walls. The test channel modeled internal turbine blade cooling passages. Results were obtained for Reynolds numbers of 5,500 and 10,000, rotation numbers of 0.09 and 0.24, and for a fixed rib pitch that was equal to the channel hydraulic diameter. For a fixed rib configuration on the leading wall, increasing the size of the ribs on the trailing wall increased the heat (mass) transfer on the leading wall. Ribs with D/e = p/e = 16 on the trailing wall performed better than ribs with D/e = p/e = 10. When the rotation number was large, the heat (mass) transfer on the leading wall was quite low, regardless of the sizes of the ribs on the leading and trailing walls. There was very little spanwise variation of the local heat (mass) transfer between the transverse ribs on the trailing wall. When the rotation number was large, however, there was a significant spanwise variation of the local heat (mass) transfer between ribs on the leading wall.

Topics: Rotation , Heat
Commentary by Dr. Valentin Fuster
1997;():V001T07A009. doi:10.1115/97-AA-137.
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Heat transfer and fluid flow processes in enclosed spaces have been extensively studied due to their importance in energy conversion, storage and transmission systems. Concentric and eccentric annular geometries are most commonly encountered in solar collector-receiver system, cooling system in nuclear reactors etc. For mixed flow in the annulus between concentric or eccentric cylinders in a rotating system, most work were performed for the cases of vertical cylindrical annulus. More recently, the effects of recirculation on the natural convection between the annular region in horizontal rotating cylinders have become a topic of interest to researchers. The applications of these studies include food processing and the interest in seeking improved methods for crystallographic perfection in industrial processes, above studies are for air with Pr≅1.0. However, other effects of rotation on heat transfer characteristics for low Prandtl number fluids are encountered in high power electric machines with heated shafts, such as a mercury slip ring assembly. For the present study, natural convection is driven by vertical temperature gradient and vertical gravity force. The interaction with the effect of rotation of the inner cylinder is expected to lead to complicated flows. Studies show that the mean Nusselt number increases with Rayleigh number. At a Prandtl number of order 1.0 with a fixed Rayleigh number, when the inner cylinder is made to rotate, the mean Nusselt number decreases through out the flow. At lower Prandtl number of the order 0.1 to 0.01, the mean Nusselt number remained fairly constant with respect to the rotational Reynolds number.

Commentary by Dr. Valentin Fuster

Electric Power

1997;():V001T08A001. doi:10.1115/97-AA-120.
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The Royal Commission power, desalination and seawater cooling (PD&SC) plant located in Madinat Yanbu Al-Sinaiyah, Saudi Arabia, includes eight MS-7001 E frame 7 gas turbine generators (GTGs). The GTGs are used in cogenerating electricity and process steam primarily required for desalinating seawater by a multi-stage flash (MSF) evaporation process. This paper describes the operating experience of the GTGs in a simple cycle and a cogeneration mode coupled to heat recovery steam generation. The significant problems, countermeasures and the GTG and heat recovery steam generator (HRSG) reliability, availability and performance are also discussed in the paper.

Commentary by Dr. Valentin Fuster
1997;():V001T08A002. doi:10.1115/97-AA-121.
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At the beginning of the Sixties the concept of Combined Cycle Power Plants (CCPP) was introduced to the market in parallel to the Standard Steam Power Plants.

Based on the experience of Waste Heat Boilers, built behind the blast oxygen furnaces of steel mills, Heat Recovery Steam Generators (HRSG) with forced or assisted circulation as well as of the natural circulation type were developed.

The latest version of HRSG’s, the vertical type with heating surfaces horizontally arranged and natural circulation only, was put into succesfull operation in 1995.

Development and experiences shall be presented.

Commentary by Dr. Valentin Fuster
1997;():V001T08A003. doi:10.1115/97-AA-122.
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As more new power plants based on gas turbines enter service, the need for these plants to participate in grid frequency regulation, as opposed to providing blocks of base load power on a dispatchable basis, increases dramatically, exposing this equipment to the potential for accelerated thermal fatigue duty. This paper proposes a methodology for quantifying and limiting the maintenance impact of rapid load changes imposed on gas turbines when required to provide frequency regulation service to the connected utility.

The paper includes a discussion of the need for prime movers to participate in system frequency regulation and the impact of this type of service on gas turbine operation. The physics of thermally induced low cycle fatigue is then discussed, and the relationships are quantified using a multiple time constant approach that provides guidance for estimating the transient thermal characteristics of the turbine airfoils that are susceptible to thermally induced low cycle fatigue. This is used to develop the thermo-mechanical relationships that are pertinent to gas turbines in generator drive service. Finally, this material is related back to operational considerations in utilizing gas turbines for system frequency regulation duty.

Commentary by Dr. Valentin Fuster
1997;():V001T08A004. doi:10.1115/97-AA-123.
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New high temperature materials and improved blade cooling techniques have led 10 design of advanced models of industrial gas turbines with inlet or “firing” temperatures of 2350 degrees F. and higher. All major vendors now offer large new commercial gas turbine-generators, with outputs of 150 megawatts and higher, based on these new designs. These new turbine units offer higher overall performance and fuel efficiencies, with promise of better reliability and availability, as well as lower operating and maintenance costs.

EPRI began to assess the durability of early models of these advanced gas turbines (AGT) in 1991, by closely monitoring their performance during electric utility operation. The durability surveillance program, involving several AGT installations outlined below, will be described. However, only the first two sites involving GE units have produced a substantial operating history for discussion. The latter two sites have only recently had new AGT units installed by ABB and Siemens respectively. At the time of this writing, those new units are still being readied for utility operation. Their operating history under the durability surveillance program will be monitored, and discussed in a future paper.

• General Electric Gas Turbine Model MS7001F in peaking service at Potomac Electric Power Co. Station H at Dickerson, Maryland.

• General Electric Gas Turbine Model MS7001FA in baseload service at Florida Power & Light Co. Martin Plant at Indiantown, Florida.

• ASEA Brown Bovert Gas Turbine Model GT 24 initially in peaking service at Jersey Central Power & Light Co.(now GPU GenCo) Gilbert Station at Milford, New Jersey.

• Siemens Gas Turbine Model V84.3A in peaking service at Kansas City Power & Light Co. Hawthorn Station at Kansas City, Missouri.

The purpose is to determine the prospects for improved unit life cycle costs as a result of higher levels of performance, availability, reliability, and mantainability achieved by adding these engines to the industry fleet. This paper will describe the initial results from the Durability Surveillance studies, including observations from unit maintenance inspections as well as the output of advanced diagnostics and monitoring systems.

Commentary by Dr. Valentin Fuster
1997;():V001T08A005. doi:10.1115/97-AA-124.
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This paper reviews the development of the Electricity Corporation of New Zealand’s first gas turbine based cogeneration project, discusses the design work performed, the project implementation and provides lessons learnt for future projects.

The Project employs a TP&M FT4 TwinPac Gas Turbine Generator Set which has been relocated to Anchor Product’s dairy factory at Te Awamutu where it provides hot exhaust gas for a Heat Recovery Boiler which generates steam for use in the dairy factory processes and a steam turbine.

The gas generators were converted from liquid fuel to natural gas and the free turbines were overhauled. All auxiliaries were relocated and upgraded as required by the new operating regime or changes in legislation, and a new microprocessor based Control and Instrumentation system purchased. Plant design is such that the Heat Recovery Boiler can accept hot gas from only one gas turbine at a time while the second is available for peaking duty as required.

Commentary by Dr. Valentin Fuster
1997;():V001T08A006. doi:10.1115/97-AA-130.
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The growing desire for sponsors of power generation projects to share risk with the lenders has promoted the use of computational tools, simulating and evaluating from a techno-economic viewpoint long-term, high-risk projects. Such models need to include reliable engine diagnostics, life-cycle costing and risk analysis technique.

This paper presents a Decision Support System (DSS) for the assessment of power generation projects using industrial gas turbines. The software, programmed in Visual Basic in Excel, runs the object-oriented software Pythia which has been developed by the Department of Propulsion, Power and Automotive Engineering at Cranfield University and which can perform gas turbine performance calculations, including off-design conditions, with or without degradation effects providing thus very reliable engine diagnostics. Moreover, a life cycle cost, assessed using manufacturer methodology for instance, can be integrated into the economic model. The degree of uncertainty relating to technical and economic factors is assessed using a normal distribution and the level of risk can then be evaluated using a risk analysis technique based upon the Monte Carlo Method. The DSS therefore provides charts and result tables to support the decision making, allowing the user to achieve a good level of confidence using new techniques of risk management.

Commentary by Dr. Valentin Fuster
1997;():V001T08A007. doi:10.1115/97-AA-140.
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The electric power generation world is currently confronted with new challenges: deregulation, open competition, new players entering the business, new regulations governing the return on investment, increased complexity and risk.

In order to maintain or enhance their competitive position the electricity generators have as main objectives to lower generating costs, increase operating and dispatching flexibility and manage fuel related risks: availability, supply diversification, prices and price escalation and finally to capture value added profits.

In order to meet new requirements of electricity generators, ABB has developed a hybrid power plant concept integrating the sequential combustion gas turbines GT24/GT26 with existing or new conventional steam power plants: the High Efficiency Coal and Gas (HE-C&G).

The HE-C&G, with its unique design, operating and dispatching flexibility, provides our customers with the benefits of competitive power generation: the owner/operator can optimise — on line — the plant fuel and O&M costs, increase the availability, extend economic life and lower the environmental impact of the power plant. And even more, the HE-C&G creates the ability to benefit of the market opportunities: buy cheaper fuels and sell the electricity when profitable.

This paper evaluates the feasibility of combining conventional steam power plants with sequential combustion gas turbines GT24/GT26 and recommends the HE-C&G as one of the most competitive alternatives for power generation, especially for re-evaluation of existing assets and positioning in the competitive environment.

Commentary by Dr. Valentin Fuster

Industrial and Cogeneration

1997;():V001T09A001. doi:10.1115/97-AA-127.
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This paper presents an analysis of the influence of control logic on gas turbine operation, when machine load adjustments are carried out.

An examination is made of the control logics that are possible for a two-shaft gas turbine with variable power turbine nozzle in order to reach the following objectives:

- operation in maximum efficiency conditions;

- operation in the conditions of maximum thermal power of exhaust gases at the turbine outlet;

- operation at constant turbine outlet temperature;

- operation with the maximum Surge Margin.

The control logics necessary for reaching the predetermined objectives in the part-load operation are provided by the map of gas turbine’s main performance, thermodynamic and control parameters.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster
1997;():V001T09A002. doi:10.1115/97-AA-133.
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Stricter environmental regulations and the need for high-efficiency energy generation have led an increasing number of industrial users to investigate alternatives to burning waste gases from the industrial plants in conventional thermal power plants. Combined cycle power plants using gas turbines capable of burning low-caloric fuels such as blast furnace gas can meet these requirements with thermal efficiencies of more than 45%.

Commentary by Dr. Valentin Fuster
1997;():V001T09A003. doi:10.1115/97-AA-135.
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The influence of gas turbine degradation on operating costs is high. Gas turbine cleaning is one of many actions taken for power recovery and is considered preventive maintenance. It is generally performed within the industrial and occasionally within the aero sector. Following a survey about potential for cost reduction in gas turbine operation the cleaning issue appears to be overlooked from an engineering point of view and there is a large potential for efficiency improvements. Engine development with corresponding high blade loads and ever-increasing temperatures require more efficient and careful cleaning methods. Together with emission taxes and environmental regulations, optimized cleaning methods will play an ever-growing role in future gas turbine operation. In order to achieve cost effectiveness regarding hardware, man-hour and consumables a new cleaning method has been evaluated for a standard process. The economic evaluations show that a standardisation of cleaning with the new method would enable the aviation sector to perform engine cleaning on a routine basis as well as the stationary sector to make significant cost savings in equipment purchase and operation.

Commentary by Dr. Valentin Fuster

Manufacturing Materials and Metallurgy

1997;():V001T10A001. doi:10.1115/97-AA-131.
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Many modern industrial processes require high-temperature alloys with superior environmental resistance and high-temperature mechanical properties. This paper describes a recently developed Fe-Ni-Cr-Nb-N alloy (HAYNES® HR-120® alloy) which is being used in several modern high-temperature industries. This alloy utilizes niobium (columbium) nitride and carbide strengthening mechanisms for its excellent tensile and creep-rupture strength characteristics. These properties are significantly higher than those of regular Fe-Ni-Cr alloys and some Ni-base alloys. The alloy also exhibits excellent resistance to oxidation and sulfidation needed for applications in many of these industrial processes. This alloy is increasingly being used in the petroleum refinery, waste incineration, oil and gas recovery, heat treating and land base gas turbine industries. Major properties, alloy characterization and industrial applications for this alloy are reviewed in this paper.

Topics: Alloys
Commentary by Dr. Valentin Fuster
1997;():V001T10A002. doi:10.1115/97-AA-132.
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Reverse engineering proceeds in the reverse of conventional manufacturing order, based on the pull system instead of the traditional push system. This paper is concerned with applying the reverse engineering concept to the development of parts. With this procedure the development of parts involves an iterative reverse process from the scanning of a developmental prototype towards the design model.

The focus is on the use of two set-ups of network in providing computerized data of the prototype that are exchangeable among Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) systems. The first set-up applies a direct approach to manipulate the scanned data in the CAM environment for generating Numerical Control (NC) programs used for machining the workpiece. The second set-up applies an indirect approach to manipulate the scanned data in a CAD environment prior to generating the NC programs. The major benefits gained from the reverse engineering application in the development of parts are also described.

Commentary by Dr. Valentin Fuster
1997;():V001T10A003. doi:10.1115/97-AA-136.
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The proposed algorithm permits one to determine the sensitivity coefficients of natural frequencies and dynamic displacements and stresses in the free- and forced vibration analysis. This algorithm is presented in a computer program with the help of finite element method (FEM). The design variables is the thickness of the blades. Usually a maximum resonance accounts more than half the damage and deterioration of machine components. The analysis of dynamic stress sensitivity distribution for this resonance permits us to control for both the endurance of machines and their components based on the thickness. In this study the sensitivity coefficients for both free vibration, dynamic resonances are investigated by acceleration and braking the regimes.

Commentary by Dr. Valentin Fuster

Structures and Dynamics

1997;():V001T11A001. doi:10.1115/97-AA-019.
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Blades with damper structures have been widely used in gas and steam turbines. Operation experience indicate that damper structures can reduce the dynamic stress of the blade effectively, so it is essential to predict the oscillating characteristics of damped blade accurately. In this paper, a modified Oden friction model, which can consider the difference between static friction and dynamic friction, for analyzing nonlinear friction damping, is presented and the dynamic equations of motion of blade system is given also. The response of blade group with 5 blades is analyzed using the model presented in this paper. Factors such as the placement of connectors, external exciting force frequency, and normal pressure that influence the blade vibration characteristic are studied. Some results available for reference have been obtained.

Topics: Friction , Damping , Blades
Commentary by Dr. Valentin Fuster
1997;():V001T11A002. doi:10.1115/97-AA-025.
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Identification of crack location and magnitude through measurement in changes in system characteristics, such as modal measurements has been studied by various researchers. In the present work based on the new method proposed by Gounaris et al (1996) for crack detection through coupled response measurements, experiments were carried out on a cracked cantilever beam for eigenfrequencies, bending and axial response measurements. It has been observed that the rate of change of direct response (bending) is much less at small cracks while that of the coupled response (axial) changes, substantially allowing diagnoses of smaller cracks.

Commentary by Dr. Valentin Fuster

Controls, Diagnostics and Instrumentation

1997;():V001T12A001. doi:10.1115/97-AA-125.
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In any rotating machinery, unbalance and misalignment of the rotor are the two major malfunctions. Perfect alignment of shafts never exists. Improper aligning of shafts through couplings often leads to severe vibration problems in many rotating machines. In the present work effect of flexible coupling misalignment on lateral vibrational characteristics of a rotor-bearing system has been studied in an Object Oriented Programming framework using finite element method. An off-line rule based expert system has been developed for condition monitoring of a gas turbine, which predicts the machine condition severity and the cause of the problem. The system is implemented in C++.

Commentary by Dr. Valentin Fuster
1997;():V001T12A002. doi:10.1115/97-AA-129.
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The design of a modern Linear Quadratic Regulator (LQR) is described for a test steam injected gas turbine (STIG) unit. The LQR controller is obtained by using the fuel flow rate and the injected steam flow rate as the output parameters. To meet the goal of the shaft speed control, a classical Proportional Differential (PD) controller is compared to the LQR controller design. The control performance of the dynamic response of the STIG plant in the case of rejection of load is evaluated. The results of the computer simulation show a remarkable improvement on the dynamic performance of the STIG unit.

Commentary by Dr. Valentin Fuster

General

1997;():V001T13A001. doi:10.1115/97-AA-020.
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Vibrations are the great hazard for state-of-the-art gas and steam turbomachine blading. To improve the vibration behavior of the turbomachine blading, the blades are connected into packets. The influence of such connection on blading dynamics is complex, and additional investigations are required for every single structure.

In this paper, numerical vibration analyses of the blade packets are carried out using detailed three-dimensional finite element models. As such problems are complex and expensive to solve, a method, considerably reducing the cost of eigenproblem solution, is proposed. The efficiency of the technique described is achieved due to the assumption that the packeted blades are identical.

The results of the vibration analyses of the single blade and the blade packets using the technique discussed are presented. The complexity of the vibration mode shapes is shown. The numerical efficiency of the approach is analyzed.

Topics: Vibration , Blades
Commentary by Dr. Valentin Fuster
1997;():V001T13A002. doi:10.1115/97-AA-026.
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A compact and fast temperature-response heat pump water heater was designed using multiple tanks and a sequential control device. The supply tank was heated as a priority by a freon-line switching device to increase the temperature recovery speed. A dual-tank prototype with 100-liter capacity was built and tested. The experimental results show that the time for temperature recovery of the supply tank from 42°C to 54°C reaches 10–20 minutes and COP reaches 2.0–3.0 during various seasons. The prototype tests show that an energy saving around 50%–70% as compared to the electrical water heater can be obtained. The hot water discharge efficiency of the heat pump is 0.912.

Commentary by Dr. Valentin Fuster
1997;():V001T13A003. doi:10.1115/97-AA-027.
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The effect of heat resistance and heat leak on the performance of irreversible heat pumps using a generalized heat transfer law is analyzed in this paper. The relationship between the optimal cooling load and the cop (coefficient of performance) for a steady-state irreversible heat pump is derived.

Topics: Heat pumps
Commentary by Dr. Valentin Fuster
1997;():V001T13A004. doi:10.1115/97-AA-028.
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A high temperature electrically-operated heat pump water heater is evaluated in terms of the viability of employing capacity control using non-azeotropic refrigerant mixtures (NARMs). The system coefficient of performance (COP) is improved by introducing capacity control, which offers continuous modulation by varying heat pump capacity to match the load. This is accomplished by using a non-azeotropic refrigerant mixture (NARM) and changing the composition (x) of the circulating mixture. The NARM R-22/ R-142b is selected due to the requirement for a high condensing temperature and a wide capacity range. The life-cycle cost effectiveness of this heat pump is compared with that of a conventional heat pump (operating a pure fluid). Computer simulations show that the capacity-controlled heat pump, operating between compositions of 100% R-22 and 70% R-22, shows a 29.6% improvement in energy conversion when compared with a conventional R-22 heat pump water heater. The payback periods of the capacity-controlled systems, are strongly dependent on electricity tariff, additional system cost, and period and duration of heat pump operation.

Commentary by Dr. Valentin Fuster
1997;():V001T13A005. doi:10.1115/97-AA-029.
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In the present study, a heat pump dryer was designed and constructed. The performance of a heat pump assisted dryer was studied. The system was operated by using R22. The experimental data of the drying rates of shiitake mushroom was used to predict the specific moisture extraction rates (SMER). The maximum coefficient of performance (COP) of heat pump was also specified. The optimum operating condition was determined by the percentage of air recirculation from the total air mass flow rate. Finally, the key parameter that influence on the performance of the system and drying rate were specified.

Commentary by Dr. Valentin Fuster
1997;():V001T13A006. doi:10.1115/97-AA-030.
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Air Source heat pump/chiller is used to provide chilled water for cooling and hot water for heating purposes. This is one investment for both applications with no requirement for boiler and fuel with the advantage of heat pump efficiency.

In this paper we are going to analyse both air side and water side heat exchangers used in air source heat pump/chiller with special attention and emphasis on brazed plate heat exchanger which is used in refrigerant to water side of this unit in order to achieve optimum performance in both the heat pump and chiller operations. Due to compactness of brazed plate heat exchangers it is very important to balance system volume in both operating conditions which will also be examined in this paper.

Commentary by Dr. Valentin Fuster
1997;():V001T13A007. doi:10.1115/97-AA-031.
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Finned tube evaporators are commonly used as cross flow heat exchangers in air conditioning and refrigeration systems for cooling and dehumidification. A simulation model for the steady-state performance of evaporator coils is developed in this paper. The coils are simulated as equivalent, parallel refrigerant circuits. The governing equations for heat and mass balance across the tube are presented. Local heat and mass balances are applied to a control volume of infinitesimal tube length along the surface of each row for different heat transfer zones, and the uneven distribution of air temperature inside the coils and the local flow characteristics of the refrigerant are simulated. The effects of evaporating temperature, coil face velocity, inlet air temperature and relative humidity on the evaporator performance are presented. The simulation results related to the humid environment with a fixed coil geometry are discussed.

Commentary by Dr. Valentin Fuster
1997;():V001T13A008. doi:10.1115/97-AA-032.
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This study experimentally investigates the film condensation of R-22 and R-410A on two horizontal enhanced tubes. The test tubes include a GEWA-C and a GEWA-TWX. Data was measured at three different saturation temperatures (35°C, 40°C and 45°C) in accordance with the range of practical condensation conditions in the air-conditioning and refrigeration applications. Average heat transfer coefficients were determined by overall heat transfer coefficients based on energy balance. The comparisons of heat transfer coefficients between R-22 and R-410A for both test tubes were presented.

Commentary by Dr. Valentin Fuster
1997;():V001T13A009. doi:10.1115/97-AA-033.
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The heat and mass transfer on adsorption beds is decisive for the operational characteristics of adsorption refrigerators. To overcome its heat and mass transfer limitations a consolidated silica gel adsorption heat exchanger has been designed and successfully developed. It was made of composite as 4.3 wt% graphite, 86.4 wt% silica gel and binders, which was pressed into a heat exchanger module and then dried under a temperature of 90°C for 24 hours. With use of this adsorption heat exchanger, we measured an overall heat transfer coefficient of 62.2 W/m2K at the beginning of desorption cycle and 61.5 W/m2K during desorption, respectively. Whereas corresponding values of a granular silica gel bed were 44.8 W/m2K and 25.9 W/m2K, respectively.

This paper presents the operational characteristics of consolidated silica gel adsorption heat exchanger in refrigeration cycles, in addition to its isoster measurements for silica gel-water pair compared to that of the granular heat exchanger.

Commentary by Dr. Valentin Fuster
1997;():V001T13A010. doi:10.1115/97-AA-034.
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Variable Air Volume (VAV) air-conditioning system presents great energy savings potential especially in hot and humid climate and has been recommended in the Building Energy Code of Taiwan since 1996. Simulation results indicated that the annual energy savings of VAV system in typical commercial buildings in Taiwan could be up to 70% of total fan power.

A full-scale experiment has been performed which validated this result successfully, and would be adapted with the PACS index in the second phase of national Building Energy Code in Taiwan.

Commentary by Dr. Valentin Fuster
1997;():V001T13A011. doi:10.1115/97-AA-035.
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In this paper the irreversibilities and second law efficiency of an automobile air-conditioner with R22/R124/R152a refrigerant blend have been carried out. The engine is 1,300 c.c. capacity and operated at different compressor speeds between 13–55 rps. The irreversibility at each component of the air-conditioner increases with higher compressor speed. Significant irreversibilities have been found at the condenser and the compressor. In the case of the cycle second law efficiency, the unit with 30% mass fraction of R22 shows better performance than those with 20 and 40% mass fraction.

Commentary by Dr. Valentin Fuster
1997;():V001T13A012. doi:10.1115/97-AA-036.
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The purpose of this study is to develop an infant incubator that is efficient, simple to implement, and can be utilized especially in the rural area of Thailand. Instead of the current one which employed electrical heater, an electrical operated heat pump infant incubator is designed. The requirement of the air conditioning system to provided the room temperature lower than the desired temperature in the incubator (30–38 °C) in no longer needed. An electrical operated heat pump infant incubator using a simple four ways control valve will switch the incubator side to become evaporator when the ambient temperature is higher than the desired temperature and, in contrary, condenser in the when the ambient temperature is lower. A large mass heat exchanger attached to the indoor coils is desired to store energy sufficient that air temperature in the incubator would not drop lower than 0.5 °C from the set point between the compressor cut-out and cut-in. This application of heat pump could provided the opportunity for over six thousand small hospitals in the rural area of Thailand to employ the infant incubator.

Topics: Heat pumps
Commentary by Dr. Valentin Fuster
1997;():V001T13A013. doi:10.1115/97-AA-037.
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Theoretical analysis indicated that, a typical centrifugal chiller could lose over 8% to 10% of its cooling capacity after converting from R-11 into using R-123 refrigerant. In this study, an attempt to recover some of this capacity loss by slightly decreasing its operating speed was analyzed.

A full-scale experiment was performed to change the gear train of a 300 RT centrifugal chillier, which validated that 3%∼6% capacity recovery could be expected. This is a break-through to promote the chiller conversion for wide engineering applications and is discussed in detail in this paper.

Topics: Refrigerants
Commentary by Dr. Valentin Fuster
1997;():V001T13A014. doi:10.1115/97-AA-038.
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A municipality water reticulation R22 ground-coupled reversible heat pump, was investigated as an alternative to conventional air source systems. The study covers the testing of a heating and cooling system that utilises the ground as its source. The ground source comprises of a municipality water supply line that is modified to allow water to flow through the outdoor coil thus delivering or extracting heat from the system. The investigation was conducted by developing analytical models that were used for the design of a ground-coupled reversible heat pump and a conventional, also reversible air-to-air system. The models were verified with a commercially available computer program as well as with measurements on the two systems. The results show an overall increase in performance with the use of a ground source system over the conventional air source systems. Thus the ground-coupled reversible heat pump system can provide a cost effective alternative to the more conventional air-to-air systems.

Topics: Heat pumps , Water
Commentary by Dr. Valentin Fuster
1997;():V001T13A015. doi:10.1115/97-AA-039.
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A revolutionary hydrothermal steam generator is being developed by a federal, state university and industry partnership in the US to enhance economic growth and trade. The new generator is designed to accept solutions and slurries without corrosion and deposition on heat transfer surfaces up to the supercritical conditions of water, above 221 bar (3205 psia) and 374 C (705 F). The generator will produce steam from low quality water, such as from geothermal sources, for increased electric power generation. Water treatment costs and effluents will be eliminated for “zero discharge.” To improve efficiency and limit carbon dioxide and other emissions, the new steam generator will be tested for converting wastewater slurries of low-cost fuels and “negative value” wastes such as hazardous wastes, composted municipal wastes and sludges, to clean gas turbine fuel, hydrocarbon liquids, and activated carbon. Bench-scale results at sub- and supercritical conditions for lignite, refuse derived fuel, tire rubber and activated carbon are presented. An advanced continuous-flow pilot plant is being designed to test the generator over a wide range of operating conditions, including slurry feed up to 30 percent solids. Demonstration of the hydrothermal steam generator will be followed by design and construction of combined-cycle energy systems.

Commentary by Dr. Valentin Fuster
1997;():V001T13A016. doi:10.1115/97-AA-040.
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Systems analysis is performed for a diesel engine of the 10,000 kW class with CO2 recovery equipment using aqueous monoethanolamine solution on the basis of a CO2 mass transfer calculation model for a packed column.

The calculation model is based on the film theory, and gives calculation results in good accuracy, being compared with the experiments on CO2 absorption and on CO2 stripping.

The net output power of the engine reduces in order to recover the CO2 in the exhaust gas of the engine, and reduction of the output power depends on the ratio of the gas-to-liquid feed rate ratio of the stripper to that of the absorber. The operating parameters such as the stripping temperature, the highest loading factor, and the MEA concentration of the solution have an influence on the maximum attainable CO2 recovery ratio. The maximum attainable CO2 recovery ratio depends on the allowable level of the output power reduction, and with reduction of 10% of the engine output power, 70% of CO2 in the exhaust gas is recovered.

Commentary by Dr. Valentin Fuster
1997;():V001T13A017. doi:10.1115/97-AA-041.
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For small developing countries such as Fiji being devoid of conventional energy resources such as petroleum products, coal or natural gas, there is always heavy, and in many cases total, reliance on conventional energy sources for transportation, industries and for electricity generation. Fiji, like most of its South Pacific island neighbours, has relied very heavily on petroleum products for all of these, except for electricity generation since 1983, when hydro-electricity became the major source of electricity for the country.

Commentary by Dr. Valentin Fuster
1997;():V001T13A018. doi:10.1115/97-AA-042.
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The applications of hot water in the industrial, domestic and mining applications are numerous, and these are only a few of the core areas of use. In these applications fossil fuels and electrical resistance systems are usually used to heat water to temperatures near boiling point. The refrigerant R22, that is currently being used in hot water heat pumps, delivers hot water temperatures from 60 °C to 65 °C. This limits the applications of hot water heat pumps.

This analytical study uses three comparison methods to investigate and compare the potential of a non-azeotropic refrigerant mixture consisting of R22 and R142b. From the results different advantages of non-azeotropic refrigerant mixtures are evident. Depending on the application, if the results of a non-azeotropic refrigerant mixture are compared with a pure R22 heat pump, an increase in hot water temperatures to above boiling point, an increase in coefficient of performance, an increase in capacity and a decrease in compressor pressure ratio are possible. Unfortunately, not all these advantages are valid for each application. For instance, extremely high hot water temperatures are obtained, whilst the heating capacity is excessively low.

Commentary by Dr. Valentin Fuster
1997;():V001T13A019. doi:10.1115/97-AA-043.
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World is now endangered by the threat of fuel source scarcity and environmental degradation. Researchers all over the world are searching for the alternative energy resources to supplement the present energy needs and to conserve the conventional resources from depletion which are less costly and environmentally friendly. Harnessing the wind power and its utilization is one of the best possible answers. Investigations for recent years have revealed that wind energy has been the great deals to the rural farmers for their water pumping. Wind power can be used effectively in maintaining livestock, water supply, fish & ice farming, water desalination, sawing wood, irrigation, electrification, agricultural operations etc. If all possible considerations are given in exploiting wind energy, in the coming 4 to 5 decades it can meet 30% to 45% of the world’s total energy demand contributing no unwanted emissions into the atmosphere. It can adjust more jobs and occupies fewer lands. It is cheaper than any other sources.

Bangladesh possesses flat terrain, hilly & mountainous regions, open river banks & harbors, and a vast lengthy coastal belt by the sea “the Bay of Bengal” where reasonable wind flow round the year available. For most of the said areas, electricity supply from the mother grid is almost inaccessible due to various difficulties and limitations. Moreover, a total of 2105 MW national generation capability absolutely unable to meet the present suppressed peak demand of 2114 MW for the consumers already in the grid. This continuously causing a severe regular load shedding up to 30% of the peak demand. The large sized population of the above areas is being maintained over decades mostly from fuel wood, charcoal plant & agricultural residues, dung and very few from imported petroleum and derivatives as the only energy sources. The energy scarcity let the locality remained economically backward and noncontributing to the GDP. In some of the areas namely Chittagong Harbor, Coastal belts & City periphery, from recent observations the monthly mean wind speeds (m/s) ranging between 4.5 and 8.5 are recorded which show the genius prospect of reaping wind power in Bangladesh. Despite a promising future of this free fuel, benefits for utilizing this energy in Bangladesh are being missed because too little is known about either the resource or the technology. Wind energy can successfully be utilized in utility for supplementing our generation and to meet decentralized needs or wind-solar hybrids for Bangladeshi modern multistory buildings which are now meeting their energy deficit by individual diesel generators at higher money and environmental costs. In the context of Bangladesh, wind power to come to use, this paper is an attempt to describe the methodologies for site selection; wind data collection & regime modeling; power availability, conversion & storage; turbine performance monitoring & augmenting wind speed using cloth scoops including costs and environmental impact Assessment. This paper also discusses Bangladesh energy scenario and strategies for meeting deficit demand and summarizes global wind development and proposes that Bangladesh government and other agencies must take immediate initiatives towards implementing wind projects.

Commentary by Dr. Valentin Fuster
1997;():V001T13A020. doi:10.1115/97-AA-044.
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Reconstruction of surface models is a vital part in reverse engineering. Because of the huge amount of data from Coordinate Measuring Machine (CMM), processes for division of data into groups, surface patch reconstruction, and patch joining are inevitable in the CAD systems tailored for reverse engineering applications. Existing techniques of surface patch joining have the disadvantages, such as computational complication or lack of desired geometric continuity. A GC2 joining technique for B-spline surface patches by utilising a Bezier patch joining technique was proposed in this paper. This method possesses the merits in which only the control vertices near the joining boundaries of patches are modified and no additional blending surfaces at the joints of patches are created.

Commentary by Dr. Valentin Fuster
1997;():V001T13A021. doi:10.1115/97-AA-045.
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The purpose of this work is to develop a virtual simulation system for crane-operating training. It includes an operating chamber to simulate the driving chamber of a truck crane and a motion chair to offer additional vibrating effect. The virtual scenes, generated by a VR software, is displayed on a screen in front of the operating chamber through a 3D projector. A data communication structure is proposed to deliver the information among three personal computers. The hardware configuration of the simulator is discussed and the VR techniques used to generate the virtual scenes are addressed. A performance evaluation in terms of the frame rate is provided also.

Topics: Cranes , Simulation
Commentary by Dr. Valentin Fuster
1997;():V001T13A022. doi:10.1115/97-AA-046.
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In this paper, a non-contact 3D profile measurement technique was presented which is based on the projection of parallel beams. An arc light which was assumed to be point light source was positioned in the focal point of an parabolic mirror. After it was reflected by the parabolic mirror, uniform parallel beams were projected. These parallel beams, passing through LCD, produce 27 coded patterns. The purpose of these coded patterns is to ensure their relative positions. CCD images where then taken on these coded patterns in order to perform space coding on each of the measurement points. It was followed by the calibration process with special designed model to obtain the internal and external parameters of the CCD such as focal length and ratio of pixel size. Using the triangulation theory, coordinate transformation between the measured object and the CCD will transform the 2D image plan into 3D coordinate profile. The parallelism of these projection beams eliminates the disadvantages of diffused projection light patterns, simplifies the mathematical algorithms, and reduces image processing error of the projected patterns. This can be more efficient and accurate technique for 3D profile measurement as compared with other non-contact structured light techniques.

Commentary by Dr. Valentin Fuster
1997;():V001T13A023. doi:10.1115/97-AA-047.
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In recent years, vectorial tolerancing has emerged as a new alternative of representing workpiece tolerances. In contrast with conventional geometric tolerances that originated from hard gauging practice, vectorial tolerancing follows the working principle of coordinate measuring machines and CAD/CAM systems. Moreover it provides feedback from measurement directly to manufacturing process control. Many believe it is a better tolerancing method to tie design, manufacturing, and measurement together. However, current proposal of vectorial tolerancing has several limitations. First, the current orientation vector is inadequate for representing true 3D orientation. As a result, the orientation of a free form surface can not be properly established. Second, there has not been much discussion on the subject of vectorial tolerance evaluation. This paper proposes a new orientation vector which provides a more general mathematical basis for representing vectorial tolerances. It enables true 3D orientation representation and relates tolerances to functional requirement. With the mathematical definition, a systematic evaluation approach becomes possible for both analytical geometric elements and free form surfaces. Computer simulation and real-world application were studied to validate this new approach.

Commentary by Dr. Valentin Fuster
1997;():V001T13A024. doi:10.1115/97-AA-048.
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The characteristics of evaporation heat transfer and pressure drop for refrigerant R134a flowing in a plate heat exchanger were investigated experimentally in this study. Two vertical counter flow channels were formed in the exchanger by three plates of commercialized geometry with a corrugated sine shape of a chevron angle of 60°. Upflow boiling of refrigerant R134a in one channel receives heat from the hot downflow of water in the other channel. The effects of the heat flux, mass flux, quality and pressure of R134a on the evaporation heat transfer and pressure drop were explored. The preliminary measured data for the water to water single phase convection showed that the heat transfer coefficient in the plate heat exchanger is about 9 times of that in a circular pipe at the same Reynolds number. Even at a very low Reynolds number, the present flow visualization in a plate heat exchanger with the transparent outer plate showed that the flow in the plate heat exchanger remains turbulent. Data for the pressure drop were also examined in detail. It is found that the evaporation heat transfer coefficient of R134a in the plates is quite different from that in circular pipe, particularly in the convective evaporation dominated regime at high vapor quality. Relatively intense boiling on the corrugated surface was seen from the flow visualization.

More specifically, the present data showed that both the evaporation heat transfer coefficient and pressure drop increase with the vapor quality. At a higher mass flux the pressure drop is higher for the entire range of the vapor quality but the heat transfer is only better at high quality. Raising the imposed wall heat flux was found to slightly improve the heat transfer. While at a higher system pressure the heat transfer and pressure drop are both slightly lower.

Commentary by Dr. Valentin Fuster
1997;():V001T13A025. doi:10.1115/97-AA-049.
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This paper describes a predictor-corrector theory based on a general higher-order layerwise model for the accurate prediction of the linear static and dynamic response of thick laminated composite plates and shells. The general polynomials introduced in the model account for the arbitrary variation of the transverse shear stresses across the thickness of each layer. The main purpose of the approach is to reduce the differences between the assumed variation of the transverse shear stresses provided by the constitutive equations and the computed variation of the same stresses from the equilibrium equations of elasticity. The present predictor-corrector layerwise model satisfies the continuity of the in-plane displacements and the transverse shear stresses at the interfaces. The numerical results for the bending and vibration of thick laminated composite plates and shells show that a high level of accuracy can be achieved with the same number of variables as that in Mindlin’s theory.

Commentary by Dr. Valentin Fuster
1997;():V001T13A026. doi:10.1115/97-AA-050.
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A Rayleigh-Ritz analysis is presented for the free vibration of skew sandwich plates composed of an orthotropic core and laminated facings. By proposing a set of Ritz functions consisting of the product of mathematically complete polynomial functions and the the boundary equations raised to appropriate powers, the Rayleigh-Ritz method can be automated to handle such composite plates with any combination of edge conditions. For convenience and better accurarcy, the Ritz formulation was derived in the skew coordinate system. Vibration frequencies of rectangular plates (a special case of skew plates) obtained via this method have been found to be in good agreement with previous researchers results. Owing to length limitation, only sample vibration frequencies for skew sandwich plates are presented.

Commentary by Dr. Valentin Fuster
1997;():V001T13A028. doi:10.1115/97-AA-052.
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An approach to model slug flow in horizontal pipeline is presented which is based on a transient Lagrangian formulation. The effect of slug growth is modelled by considering the gas expansion, picking up of liquid film ahead of the slug and shading of liquid from the slug tail. This method is particular useful for slug flows approaching the end of a pipeline. The validation of the theoretical prediction is confirmed by comparing with the experimental measurement. The proposed model is further used to analyse shock phenomenon caused by a rapid valve closure in a gas-liquid slug flows system. The results show that the pressure surge is highly dependent on the local void fraction at the valve during closure. Good agreement has been obtained between prediction and experimental data by Akagawa et al (1982).

Commentary by Dr. Valentin Fuster
1997;():V001T13A029. doi:10.1115/97-AA-053.
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Three estimates of the 10-yr significant wave height (Hs) are developed for 16 tow scenarios from Perth, Singapore, and Korea to the northwest shelf of Australia. One of the estimates is based on Global Wave Statistics (Hogben, et al., 1986), a database of visual ship observations that has been used extensively by the oil industry. These results are compared to estimates derived from two recently released commercial satellite altimeter databases, SOS and CLIOSat. The mean of the 10-yr Hs for the 16 scenarios calculated from the ship data is 40% (2.6 m) larger then the satellite databases while the variance is 40% less. Evidence suggests the ship-based values are unrealistically high for a number of the scenarios. Results SOS are internally consistent and generally compare favorably with high-quality model hindcast studies in the region. The first-order statistics from CLIOSat compare well to SOS but there are substantial differences for some of the scenarios. Several of the CLIOSat-derived extremes are internally inconsistent and don’t compare well to hindcast results However, firm conclusions must await further work.

Topics: Ships , Satellites
Commentary by Dr. Valentin Fuster
1997;():V001T13A030. doi:10.1115/97-AA-054.
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Immediately after the Exxon Valdez incident, the United States Oil Pollution Act of 1990 was passed. This Act clarified the lines of responsibility associated with future oil spills. In addition to this Federal legislation, Louisiana lawmakers in 1991 enacted the Oil Spill Prevention and Response Act. Financial awards associated with this Act support a wide-range of research activities. Since 1993, 24 projects have been funded. The scope and nature of this research includes:

• Oil Spill Awareness through Geoscience Education (OSAGE);

• Used Oil Recycling in Louisiana’s Coastal Communities;

• Evaluation and Characterization of Sorbents;

• Landsat TM and Synthetic Aperture Radar to Facilitate Coastline Delineation;

• Environmental Effects and Effectiveness of In-Situ Burning in Wetlands;

• Bioremediation Protocol for Small-Scale Oil Spills;

• Oil Spill Risk on Louisiana’s Largest Waterway;

• River Time-of-Travel Modeling;

• Composting Technology for Practical and Safe Remediation of Oil-Spill Residuals;

• Predictability of Oceanic and Atmospheric Conditions off the Mississippi Delta; and

• Phytoremediation for Oil Spill Cleanup and Habitat Restoration in Louisiana’s Marshes.

Each of these projects, and others, are the result of the marriage of industry and university researchers in the identification and solution of applied oil-spill-related problems. The alliance is a good one. Important environmental issues are addressed because the selection process ensures each research initiative has the potential of being implemented by the response community. The work and knowledge gained from these projects is a clear indication of how industry and the university community can function in a collaborative manner to solve important issues — a significant partnership that clearly shows how both can benefit and a model for others to follow.

Commentary by Dr. Valentin Fuster
1997;():V001T13A031. doi:10.1115/97-AA-055.
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A new process for converting natural gas into liquid fuels and other petroleum products is described, as is the increased market opportunity this technology portends for gas turbine manufacturers. The GTL technology, developed by Syntroleum Corporation, utilizes Autothermal Reforming with air to produce a nitrogen-diluted synthesis gas having a near ideal ratio for converting into synthetic hydrocarbons via Fischer-Tropsch synthesis. A proprietary catalyst system achieves conversion rates comparable to conventional F-T processes without the need for recycling. This results in plant capital costs low enough to make conversion of remote and/or sub-quality gas into synthetic fuels economical at current oil prices. The process is energy self-sufficient and compact enough to be constructed in small sizes for plants in remote areas, including floating or platform facilities to utilize offshore gas reserves. It can also be scaled up for 50,000 BPD or larger applications.

Topics: Natural gas
Commentary by Dr. Valentin Fuster
1997;():V001T13A032. doi:10.1115/97-AA-056.
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This paper derives a set of parametric equations for finding the maximum stresses developed in the cylindrical vessel which is supported by two saddles firmly secured to the foundation and subjected to thermal expansion loading. Three types of stresses are considered: maximum stress intensity, maximum circumferential stress and maximum axial stress. The maximum stresses in the vessel are found to be governed by the height and width of the saddle, the spacing between the two supports and the relative structural rigidity between the support and the vessel. This paper is an extension of the work reported by Tooth, et.al (1996).

Using a least square curve fitting procedure, parametric equations for the maximum stresses developed in the vessel have been established. Raw data used for the curve fitting were obtained from a carefully-planned finite element study which covers a wide range of key dimensions. A total of 900 finite element runs have been performed.

The derived parametric equations are subsequently validated against the raw data and their error bounds are established. In all cases the maximum errors are found to be within 20%. The established parametric equations can be used directly in design calculations. The curve fitting procedure outlined in this paper has wide application for any set of generated or measured data.

Commentary by Dr. Valentin Fuster
1997;():V001T13A033. doi:10.1115/97-AA-057.
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When storing liquids at high temperature, in horizontal vessels, the current design methods aim to minimise the thermal stresses by introducing a sliding surface at the base of one of the twin saddle supports. However, regular site maintenance is required to ensure that adequate sliding is achieved This may be difficult and costly to carry out.

The aim of the present work, therefore, is to dispense with the sliding support and to provide saddle designs which although fixed to the platform, or foundation, do not result in the storage/pressure vessel being over-stressed when thermal loading occurs. The paper provides general recommendations for the most appropriate saddle geometries, and details the way in which ‘Design by Analysis’ and ‘Fatigue Life Assessments’ may be carried out using the stresses which arise from these designs.

Commentary by Dr. Valentin Fuster
1997;():V001T13A034. doi:10.1115/97-AA-058.
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Numerically calculated stress in the region of two normally intersecting pipes due to in-plane bending moments using finite element program MECHANICA are presented in this paper. The computer results were processed and then presented in stress versus location (along several lines) diagrams. Other investigators’ results for similar problem are not easy to obtain due to differences in the problem, in modelling, in finite element program used and in methods of data presentation. Lock et al (1985) and Moffat et al (1984) works were the closest for comparison purposes.

Commentary by Dr. Valentin Fuster
1997;():V001T13A035. doi:10.1115/97-AA-059.
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A common flow system arrangement in piping system consists of a lower reservoir, a group of pumps with a check valve in each branch, and a pipeline discharging into a upper reservoir. In earlier studies of check valves performances in transient flow, none considered the effects of air entrainment into a pipeline system and the subsequent effects on the check valve performances in transient flow. Studies on pressure surges during pump tripped in pumping systems showed that by including an air entrainment variable wave speed model, reasonable predictions of fluid transient responses with proper phasing and attenuation of pressure peaks can be obtained. The most severe case where all the pumps in the station fail simultaneously due to power failure was analysed for their maximum and minimum pressure variation along the pipeline. A numerical model is now set up in the present work to investigate the check valve performances in transient flow for a pumping system with air entrainment. The analyses examine a fluid system with a variable air entrainment content (ε) and studied numerically it effects on the flow reversal time and hence determine the appropriate valve selection for a given fluid system to minimize problems of check valve slamming. Present numerical computations show that the air content in a fluid system can adversely affect the check valve transient responses. With the fluid system operating within a critical range of air entrainment values, analysis showed that there is a possibility of “check valve slamming” when the check valves were selected based on the analysis of an air free system. The above phenomena is confirmed through physical field measurements.

Commentary by Dr. Valentin Fuster
1997;():V001T13A036. doi:10.1115/97-AA-060.
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High vibration problems resulting in damage to supports, instrument stubs etc. have been experienced in many compressor piping systems installed at different fertilizer plants. Investigations aimed at a solution to the problem included vibration measurements on the suction and discharge piping, and mathematical modeling of the piping. The measurements indicated presence of an excitation frequency in the range of 30–35% of the compressor running speed. Dynamic analysis of the piping system showed the presence of natural frequencies coinciding with or very near to the excitation frequencies. This has been further confirmed by impact tests. Analytical mode shapes clearly show that the antinodes match with high vibration zones observed at the site. The mathematical models were used to determine optimum configurations which would separate mechanical responses from excitation frequencies. These modifications have been implemented at site and the piping vibrations are within normal limits.

Commentary by Dr. Valentin Fuster
1997;():V001T13A037. doi:10.1115/97-AA-061.
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This paper investigates leak effect on the outlet pressure at pipeline exit. A modified Weymouth equation (includes inclination effect) was used as a governing equation for this study. First, a brief summary of the modified Weymouth equation was reviewed. Next, predicted results by the equation were compared to those by field data for checking discrepancy. Then, to investigate leak effect, outlet pressure and ratio of outlet to inlet pressure were compared between no leak and leak conditions for horizontal, upward, and downward flows, respectively. Finally, effects of leak location as well as leak rate on the outlet pressure were also investigated for all pipeline inclinations.

Topics: Pressure , Pipelines , Leakage
Commentary by Dr. Valentin Fuster
1997;():V001T13A038. doi:10.1115/97-AA-062.
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High frequency (50–120) MHz, ultrasonic, AIN-sensors have been successfully applied to the study of wear, chipping/breakage and temperature of triangular ceramic and carbide inserts. These sensors readily differentiate between signals from wear and chipping/breakage and, in flight-identify the damage location with simultaneous measurement of signal amplitude and transit time. The signals are unaffected by the machining process. The temperature of the chip/tool interface can be readily obtained during the cutting process by monitoring the transit time. Preliminary studies suggest these sensors also monitor the hardness of the workpiece and the chatter during the cutting. A specially-designed ultrasonic process-control system with 100 ps time resolution with data collection speed 1–10 kHz was necessary to observe the on-line data. The same system integrated with a focused transducer can be used to follow the workpiece dimension and surface finish, on-line. The ultrasonic, process control system that has been developed is robust and can be used for other NDE applications with a resolution of sub-micron thickness. It can also monitor residual stresses.

Commentary by Dr. Valentin Fuster
1997;():V001T13A039. doi:10.1115/97-AA-063.
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Shearography is a laser interferometric method developed originally for full field observation of surface strains of components. Since flaws usually induce strain concentrations around them, shearography can be employed to detect the flaws. Conventional shearography involves exposing high resolution films before and after the components are loaded. The exposed films are developed and then viewed via a high-pass filtering optical setup. Though the images obtained are good, this method is time-consuming. With the advent of high-speed computers, associated sophisticated imaging hardware and software, the Digital Speckle Shearing Interferometry (DSSI) method which employs a CCD (charged-coupled device) camera and computer image processing to produce the interferometric fringe patterns has been developed. In contrast with the conventional shearography, the electronic version does not require any film and is faster. The techniques are used to detect and characterise (a) flaws simulating delaminations in composites and (b) thinning in pipes.

Commentary by Dr. Valentin Fuster
1997;():V001T13A040. doi:10.1115/97-AA-064.
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Failure analysis of integrated circuit (IC) packages is a critical element for in house quality control and for problems encountered in service. Plastic IC packages are routinely inspected for delaminations, voids, cracks, and corrosion using the C-mode acoustic microscopy (C-AM). Plastic IC packages are hygroscopic and can absorb moisture subjected to environmental cycling depending on the quality of the plastic chemical compound used to encapsulate the IC chip. The new advanced ultrasonic interference spectroscopy (UIS) technique used by the author elsewhere to detect presence of moisture in adhesively bonded joints is applied to the problems of the plastic IC packages in this research work. The new UIS technique was used on manually fabricated simulated plastic packages with thin water film trapped between two layers of plastic material (Lexan) and the silicon wafer. The technique successfully detected the presence of an extra water layer in the assembly inspected and estimated its thickness accurately to be 110 μm. At present the technique is under development for detection of water films thinner than 110 μm in actual plastic IC packages.

Topics: Spectroscopy
Commentary by Dr. Valentin Fuster
1997;():V001T13A041. doi:10.1115/97-AA-065.
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Papua New Guinea lies just north of Australia (Fig. 1). It is a developing island nation, with 462,839 km of land area, a population of 3.9 million people, and vast natural resources (Compton’s Interactive Encyclopedia, 1996). It is the largest island in the Oceania region of the world, which also includes Fiji, the Solomon Islands and Vanuatu. Most of these islands share similar resources, and prudent development of the resources requires utilization of nondestructive evaluation (NDE). NDE provides the means for flaw detection and size assessment, as well as evaluation of material degradation such as corrosion and hydrogen attack. These are factors which affect the service life of components and systems. Being aware of the state of degradation of these components and systems will enable cost effective maintenance, and reduce costly and dangerous failures. Recognizing the need for NDE expertise, the Papua New Guinea University of Technology at Lae has initiated a Center for Nondestructive Evaluation. Once operational, the center should serve the entire Oceania region, and provide resources, trained students and expertise that will enable the growth of the NDE industry within that area. It is widely accepted that NDE adds value to a product or process, not just cost. The amount of value is directly related to the engineering education of the personnel making NDE decisions. The growth of the NDE industry in these South Pacific Islands will add to the economy, as well as aid in the further creation of a population of engineers who are well educated in NDE.

Commentary by Dr. Valentin Fuster
1997;():V001T13A042. doi:10.1115/97-AA-066.
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During nondestructive evaluation (NDE), an instrument is used to receive inspection signals and display them for visual interpretation. Southwest Research Institute (SwRI) has developed technology that allows NDE signals generated from conventional ultrasonic instrumentation to be completely converted into audible (aural) signals to enhance reliability of evaluation through the use of two senses (ears and eyes) to improve inspection reliability.

For example, detection of hidden corrosion on aircraft structures using conventional ultrasonic testing (UT) techniques is difficult because of thin walls and corrosion topography. These characteristics require use of high-frequency, high-spatial-resolution transducers to attempt to detect backwall signal amplitude. It is difficult to visually discriminate backwall signals of thin wing structure from the normal ringdown of the transducer.

Using aural UT, a trained inspector can listen to sounds generated by aural UT equipment and detect the presence of hidden corrosion with higher reliability than using conventional UT.

Commentary by Dr. Valentin Fuster
1997;():V001T13A043. doi:10.1115/97-AA-067.
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An absence of proper design rules has limited the application of composite materials to specific areas. However, within these application areas there is still a need to regular monitor the component resulting in significant downtime and loss of revenue. To overcome this it is proposed to have an on-line monitoring system capable of global checking of the component. Fiber optic polarimetric sensors are chosen in this study to globally characterize the health of a component. Polarimetric sensors have better sensitivity than intensity sensors and at the same time are more rugged than interferometric sensors. In this study, the effect of debonds and fiber breakages are investigated in composite bend specimens.

Commentary by Dr. Valentin Fuster
1997;():V001T13A045. doi:10.1115/97-AA-069.
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This paper describes an evaluation of the capability of a mechanical impedance instrument, for detecting delamination defects in aluminium honeycomb structures. The resonant frequency was found to decrease as the centre of a defect was approached. The defects have been found to be accurately represented by a model for a vibrating plate, which is rigidly clamped at its edges. It was also possible to use resonant frequency to determine the size of the defects in the specimens used in this paper. An irregularly shaped defect showed that the rate of drop in resonant frequency across an extremity of the defect was affected by the radius at the extremity and the proximity to the main central area of the defect. An important result was that an ellipsoidal shaped defect would be sized as a circular defect of diameter equal to the minor diameter of the ellipse. Also a boron skinned honeycomb was found to behave similarly to a glass fibre skinned honeycomb.

Commentary by Dr. Valentin Fuster
1997;():V001T13A046. doi:10.1115/97-AA-070.
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One of the most important tasks through the 21st century is to ensure a stable supply of energy and maintain a balanced clean global environment. The principal advantage of fuel cell power plants lies in their favorable environmental impact. Fuel cell development is of utmost important in the light of the recent worldwide clean air movement.

Topics: Fuel cells
Commentary by Dr. Valentin Fuster
1997;():V001T13A047. doi:10.1115/97-AA-071.
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Recent theoretical developments in droplet and spray combustion have been reviewed with due emphasis placed upon the modern interpretation of phenomena and the elucidation of unified theoretical approaches and the foundation of concepts in the area of selected outstanding problems previously identified. Universal laws of a droplet for a dilute and a non-dilute spray, developed recently by the techniques of canonical integration and renormalizaton, offer remarkably broad based knowledge and quantitative prediction of droplet exchange rates in a general hydrodynamic environment. The phenomena and criteria of state transition and the principles of partition of gasification among all the major subprocesses at the transition state are presented. Also reviewed is the multi-state behavior of an isolated converting droplet in the critical ranges of Reynolds number and Damkohler number. Recent experimental validations of group combustion phenomena in laminar sprays and turbulent premixed sprays are presented and the concept of hierarchical group combustion in practical liquid sprays are discussed. Emerging interest in the large scale structures, featured by inhomogeneous local clustering and declustering of droplets in liquid sprays are presented. Various mechanisms of the formation of complex configurations of structures are identified and theoretical categorization based on hierarchical distribution functions are proposed. Kinetic theoretic approach of many-droplet system based on Born, Bogoliuvob, Green Kirkwood, and Yvon’s hierarchy is extended for the classification of structural configuration and the predictions of the dynamic evolution as well as the exchange of scalar and vectorial properties are discussed.

Topics: Combustion , Drops , Sprays
Commentary by Dr. Valentin Fuster
1997;():V001T13A048. doi:10.1115/97-AA-072.
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The flammability limits of hydrogen and methane in air were determined experimentally at elevated initial mixture temperatures up to 350°C at atmospheric pressure for upward flame propagation in a conventional steel test tube apparatus. Additionally the extent to which a prolonged exposure (i.e., residence time) of the mixture to elevated temperatures before spark ignition and, consequently, the existence of pre-ignition reactions that may influence the value of the lean and rich flammability limits was also investigated. It was shown that the flammability limits for methane widened approximately linearly with an increase in the initial mixture temperature over the whole range of temperatures tested. These limits were not affected by the length of the residence time before spark ignition. Different behaviour was observed for flammability limits of hydrogen. They were also widened with an increase in the initial temperature but only up to 200°C. In this initial temperature range the limits were not affected by the length of the residence time. However, at initial temperature exceeding 200°C the flammability limits, especially, the rich limits narrowed with an increase in the temperature and were significantly affected by the residence time before spark ignition. The results of detailed chemical kinetic simulation showed that the gas phase reactions of hydrogen oxidation could not be responsible for the substantial drop in the value of the rich limit. It was therefore, suggested that this drop in the value of the rich limit with the increase in the residence time was caused by the relatively low temperature catalytic reactions on the stainless steel surface of the flame tube. Simple method for calculating the hydrogen conversion to water was proposed. The results of calculations are in fair agreement with the experimental evidence.

Commentary by Dr. Valentin Fuster
1997;():V001T13A049. doi:10.1115/97-AA-073.
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A two dimensional axisymmetric computational model based on a finite difference scheme has been developed to model the transient formation of flammable atmospheres upon the diffusion of fuel vapour following the exposure of liquid fuel surfaces to air within cylindrical vessels at constant pressure and initial temperature. The Transient equations of Momentum, Energy, Species Continuity and Transport properties are solved.

Two typical common fuels, n-pentane and methanol where modeled. The effects of convection and temperature gradients produced by the extraction of the latent heat of vaporization from the liquid fuel surface were taken into account and the thermodynamic and transport properties were taken to be variable. The results of the 3-D axisymmetric model were compared with the corresponding values obtained using a 1-D model and checked favorably with some experimental results obtained with n-pentane and air.

Commentary by Dr. Valentin Fuster
1997;():V001T13A050. doi:10.1115/97-AA-074.
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The flow structure of cold and ignited jets issuing into a co-flowing air stream was experimentally studied using a laser Doppler velocimeter. Methane was employed as the jet fluid discharging from circular and elliptic nozzles with aspect ratios varying from 1.29 to 1.60. The diameter of the circular nozzle was 4.6 mm and the elliptic nozzles had approximately the same exit area as that of the circular nozzle. These non-circular nozzles were employed in order to increase the stability of attached jet diffusion flames.

The time-averaged velocity and r.m.s. value of the velocity fluctuation in the streamwise and transverse directions were measured over the range of co-flowing stream velocities corresponding to different modes of flame blowout that are identified as either lifted or attached flames. On the basis of these measurements, attempts were made to explain the existence of an apparent optimum aspect ratio for the blowout of attached flames observed at higher values of co-flowing stream velocities. The insensitivity of the blowout limits of lifted flames to nozzle geometry observed in our previous work at low co-flowing stream velocities was also explained.

Commentary by Dr. Valentin Fuster
1997;():V001T13A051. doi:10.1115/97-AA-075.
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The composition and performance optimisation of cathode catalyst platinum and catalyst layer structure in a proton exchange membrane fuel cell has been investigated by including both electrochemical reaction and mass transport process. It is found that electrochemical reactions occur in a thin layer within a few micrometers thick, indicating ineffective catalyst utilization for the present catalyst layer design. The effective use of platinum catalyst decreases with increasing current density, hence lower loadings of platinum are feasible for higher current densities of practical interest without adverse effect on cell performance. The optimal void fraction for the catalyst layer is about 60% and fairly independent of current density, and a 40% supported platinum catalyst yields the best performance amongst various supported catalysts investigated. An optimal amount of membrane content in the void region of the catalyst layer exists for minimum cathode voltage losses due to competition between proton migration through the membrane and oxygen transfer in the void region. The present results will be useful for practical fuel cell designs.

Commentary by Dr. Valentin Fuster
1997;():V001T13A052. doi:10.1115/97-AA-076.
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In this system, an MHD generator is used instead of a gas turbine. The cycle efficiency is reaching 50%. The system is based on a cycle using CO2 as the working fluid and oxygen as oxidant. The fuel is pulverized coal. All the pollutants, including the CO2 produced in the combustion process, are fully removed and diposed of. This highly pressurized excess CO2 is easily separated from the working fluid without any costly and energy consuming device and, being in liquid state, is ready for transportation and disposal or possibly reuse in other applications.

The most important parameter determining the cycle efficiency is shown to be the isentropic effectiveness of the MHD expander. This latter is depending, on the one hand, on the design of the channel and on the other hand, on the conductivity of the gases which can be optimized with respect to the cycle parameters.

In conclusion, the assets of the proposed system are high performance and no pollutant releases. As a consequence, MHD generators may be considered as viable options for coal-firing and possible competitors of advanced coal-based plants. One of the spin-off of this study is the possible revival of existing MHD facilities.

Commentary by Dr. Valentin Fuster
1997;():V001T13A053. doi:10.1115/97-AA-077.
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Three catalysts based on X-zeolite have been developed by exchanging its Na+ ion with Copper, Iron and Nickel metal ions and tested in a SI engine exhaust for a wide range of exhaust and operating conditions. Of the three catalysts, the Cu-X catalyst exhibits the best NOx and CO conversion performance while Ni-X shows slightly better performance compared to the Fe-X catalyst at any catalyst temperature. Unlike noble metals, the doped X-zeolite catalysts, studied here, exhibit significant NOx reduction for a wide λ range and exhibit a slow rate of decrease with increase in λ ratio. Back pressure developed across the catalyst bed is found to be well-afford able and power loss due to back pressure is only 0.216% at space velocity of 52500 /h. During 30 hours of testing of each catalyst, no significant deactivation of any catalyst is observed.

Commentary by Dr. Valentin Fuster
1997;():V001T13A054. doi:10.1115/97-AA-078.
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The effect of soot formation on a flamelet structure and radiation in a laminar methane flamelet is presented in this paper. A new kinetics mechanism, GRI-Mech2.1, for methane combustion is used. TDMA computer code is used to solve the coupled mass conservation, momentum, energy, species, and soot transport equations to determine the properties of the flamelet. The flamelet structure and soot concentration profiles are presented over the entire range of mixture fraction. The soot enhancement by preheating is examined. Effects of soot formation and gaseous species on flame radiation are also investigated.

The calculations show that the methane/air flamelet is a light sooting flame, and that the soot formation does not have a profound effect on flame radiation and flamelet structure. It is shown that preheating the combustion air can lead to a great enhancement in soot formation but not in flame radiation. While the soot formation contributes to larger Planck mean absorption coefficient for emission, the emission lowers the flame temperature. These opposing effects dampen the effectiveness of soot formation on flame radiation enhancement in methane/air flames.

Commentary by Dr. Valentin Fuster
1997;():V001T13A055. doi:10.1115/97-AA-079.
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A digital image processing technique is used to investigate the ignition and combustion characteristics of an isolated coal water slurry droplet in low Re flow. Coal water slurry droplet study is useful for dilute coal suspensions based on the premise that ignitability of a spray of coal water slurry must depend on the ignition characteristic of an isolated coal water slurry droplet. A flat flame burner is used for optical accessibility and also for simulating vitiated gases as existing in boiler burners. A quartz wire of 0.175 mm dia is chosen for low thermal conductivity to hold the droplet above the flat flame burner. The following sequence of events are observed: (i) Ignition occurs at the leading edge of the droplet, (ii) For coal water slurry droplet of the order less than 1 mm ejection of volatiles as jets in the direction of convective flow followed by coalescence, (iii) For a droplet with diameter of the order greater than 1 mm it was observed that the volatile combustion occurs away from the droplet in the wake of the combustible gases made upstream, (iv) Combustion of coal water slurry droplet is intermittent. Ignition time and volatile combustion times were obtained for a typical coal water slurry droplet. Calculations were carried out to determine the number of particles, interparticle spacing and density of coal water slurry droplet.

Commentary by Dr. Valentin Fuster
1997;():V001T13A056. doi:10.1115/97-AA-080.
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This paper discusses how equipment failure history stored in a computerised maintenance management system has been effectively used through the application of Weibull analysis to give an indication of the component failure mechanism (e.g., infant mortality, random failure, premature wear-out). Weibull analysis was also used to predict plant and equipment reliability by calculating the number of failures expected to occur in the future using Mean Time Between Failures (MTBF). Examples are given for component, equipment, and system failure studies for crude oil pump stations shipper pumps, steam turbines, and natural gas liquidation compression trains.

Topics: Maintenance , Failure
Commentary by Dr. Valentin Fuster
1997;():V001T13A057. doi:10.1115/97-AA-081.
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Computational Fluid Dynamics (CFD) is a valuable tool for the process and petroleum industries. CFD reduces development timescales and costs by replacing expensive and lengthy laboratory investigation with numerical predictions of processes.

However, there are several reasons why some companies are unwilling to use CFD. These include the cost of the software and hardware, the need for in-house CFD expertise and the time required to solve complex simulations.

CHAM has developed a solution to these problems, in the form of a Virtual Reality Interface linked via the Internet to powerful parallel-processor computers. Virtual reality makes CFD accessible to non-CFD experts and allows the engineer to concentrate on the solution of his problem. Remote computing makes it possible to access from a PC the necessary computing power to solve the problem.

Several examples will be shown, demonstrating the application and benefits of the PHOENICS-VR interface and the advantages of remote computing to the process and petroleum industries.

Commentary by Dr. Valentin Fuster
1997;():V001T13A058. doi:10.1115/97-AA-082.
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Foil journal bearings come under the category of air lubricated journal bearings where the lubricant is atmospheric air. In this type of bearings the pressure developed is due to the aerodynamic wedge developed between the rotating shaft and the foil bearing surface. This paper is concerned with the analysis of the bending dominated type foil bearing, in which the compliance is effected mainly through the bending of foils. The nonlinear Reynolds equation has been used for the aerodynamic pressure solution. Effect of elastohydrodynamics on foil journal bearing has been studied. The problem has been formulated using incremental finite element method. Two types of bending dominated foil bearings have been considered for analysis, namely straight foil type and curved foil type bearings. The equations for the dynamic coefficients were obtained by a perturbation technique and the results were computed using the finite element method. The effect of bearing compliance and the bearing number on performance parameters has been studied, the results were compared with the available literature.

Commentary by Dr. Valentin Fuster
1997;():V001T13A059. doi:10.1115/97-AA-083.
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The impact of Polynuclear Aromatic Hydrocarbons (PAHs) on sediments, together with the ultimate transport and migration of constituent chemicals in their dissolved or sorbed states, has led to environmentalists to develop several techniques for cleaning contaminated sediments. Dredging operations for opening new channels or just for maintenance of the existing channels will resuspend the sediments increasing the release of PAHs into the aquatic environment.

The impact of Polynuclear Aromatic Hydrocarbons (PAHs) on sediments, together with the ultimate transport and migration of constituent chemicals in their dissolved or sorbed states, has led to environmentalists to develop several techniques for cleaning contaminated sediments.

Cleanup of petroleum contaminated sediments using reactors is presented in this paper. Applicability of biological treatment alone or in combination with other technologies is discussed in detail.

Topics: Sediments
Commentary by Dr. Valentin Fuster
1997;():V001T13A060. doi:10.1115/97-AA-084.
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This paper reports the results of a series of compound wear experiments conducted using heat treated 1042 steel sliding against A2 tool steel under normal atmospheric environmental conditions for severe wear. Compound wear takes place where there is sliding and impact motion occurring simultaneously. The influential variables that are considered in the statistically designed experiment are: normal impact load, frequency, and the rotational sliding speed with lubrication as an extra class variable. Experiments were conducted using a multi-purpose wear testing facility. The frictional force was determined from strain gauges. LabView™ software was used to monitor and store the continuous load and strain signals for further analysis. Using these data an empirical relationship modeling wear has been determined.

Commentary by Dr. Valentin Fuster
1997;():V001T13A061. doi:10.1115/97-AA-085.
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Particles collected during in situ gasification of Texas lignite experiments were analyzed for chemical elements. Results obtained by energy dispersive x-ray analysis revealed that the dominating elements in both particles and lignite are Si, S, Al, Fe, and Ca. The concentration of these elements depends on the selected region and varies within the particle size range. Semi-quantitative analysis revealed the same results. This paper presents the scanning electron microscopy (SEM) micrograph and energy dispersive x-ray analysis (EDXA) for particles and Rockdale lignite.

Commentary by Dr. Valentin Fuster
1997;():V001T13A062. doi:10.1115/97-AA-086.
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The paper presents a numerical procedure for the simulation of a marine propulsion plant in transient conditions: the model describes in detail the various elements of the propulsion system and the interactions existing between each of them.

The thermodynamic behaviour of the main engine as well as of the turbocharger group is modelled, in order to predict not only the mechanical stress of the plant due to the transient conditions, but also the thermal stresses and working point of the compressor and of the turbine (pressure and temperature at inlet/outlet).

As a first application of the model, the case is considered of a twin screw vessel powered by two four stroke medium speed diesel engines with controllable pitch propellers. The simulations presented in the paper regard two transient manoeuvres of the ship: slam-start (from zero speed to full ahead) and crash stop (from full ahead to zero speed with a “full astern” command).

The results of the simulations are compared with the available experimental data, regarding the time histories of the vessel speed, space run before a complete stop, propeller r.p.m. and shaft power, showing a good accordance.

The procedure can be utilised to check the behaviour of the turbocharger group during a transient manoeuvre and to identity possible improvements in the ship control system or in the pitch-r.p.m. combination law to optimise the performances, in term of e.g. stopping space of the vessel or thermal and mechanical stresses of the plant.

Commentary by Dr. Valentin Fuster
1997;():V001T13A063. doi:10.1115/97-AA-087.
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The Brayton Cycle is the ideal cycle for simple gas turbine applications. The heat transfer process in such a cycle is of practical importance as far as power output is considered. The present work focusses on the power output from an ideally reversible Brayton cycle and criteria for optimum power based on its operating parameters like the specific heat of hot and cold fluids, working fluid and heater inlet temperature is discussed here.

Commentary by Dr. Valentin Fuster
1997;():V001T13A064. doi:10.1115/97-AA-088.
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Maximizing heat recovery in the heat exchanger network has to be considered as one of basic steps in a process design. Heating and cooling duties not serviced by heat recovery must be provided by external utilities. Simple thermodynamic models of various types of utilities (furnaces, steam boilers, steam turbines, gas turbines) are described in this paper. These models provide us with a tool for the analysis of utilities selection (provided the process heat and power demand are given), enable us to evaluate fuel burnt, power generated, costs for fuel and for exported/imported power and emissions (CO2, SO2) flowrates on a “local” or a “global” basis. This approach is convenient at the targeting stage of a design and can contribute to a substantial energy saving and flue gas emissions reduction.

Commentary by Dr. Valentin Fuster
1997;():V001T13A065. doi:10.1115/97-AA-089.
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The eigenvalue problem plays a central role in the dynamic and buckling analyses of engineering structures. In practice, one is interested in only a few dozens of the eigenmodes of a system of thousands of degrees of freedom within a particular eigenvalue range. For linear symmetric eigenproblems, [K]{x} = λ[M]{x}, the eigensolutions are well behaved. The recommendations are subspace iteration or the Lanczos method working with [A] = [K-λ0 M]−1 where λ0 is the middle of the eigenvalue range of interest. Subspace iteration gets both eigenvalues and eigenvectors. Lanczos gives the approximate eigenvalues which can easily be improved by inverse iteration to obtain the eigenvectors as by-products. For real nonsymmetric or complex symmetric linear eigenprohlems and polynomial eigenproblems, the eigensolutions may be defective. All classical methods, including subspace iteration fail. We recommend to use the Lanczos method to obtain the approximate eigenvalues of interest and to improve them by a new variance of inverse iteration, one vector at a time, and to get the independent generalised vectors as hy-products. We develop solution method for the special case that the approximate eigenvalue is indeed exact rendering a set of singular linear equations which can not be solved by existing algorithms.

Commentary by Dr. Valentin Fuster
1997;():V001T13A066. doi:10.1115/97-AA-090.
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A new active controller for vibration reduction of secondary structures is studied. The secondary structure is exemplified by a steel Euler beam. The output electromagnetic force from an electric current whirling machine is used as controller force. The excitation is given by a shake table to represent earthquake ground motion. The effectiveness of the controller is examined by varying the phase angle and electromagnetic force amplitude of the electric current whirling machine. We quantify the effectiveness as equivalent added modal damping of the Euler beam.

Commentary by Dr. Valentin Fuster
1997;():V001T13A067. doi:10.1115/97-AA-091.
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The paper presents the Euler Newton formulation of oscillatory behaviour of a multi-body system interconnected by discrete stiffness elements. The dynamical system is treated as geometrically and materially linear, where assembly of the global stiffness matrix may be achieved. The formulation is extended to incorporate flexible shafting systems. It is assumed that flexible shafts are connected to rigid bodies of finite size and the connection is assumed to be built-in or pin jointed. Flexible shafting system is formulated using beam finite element formulation.

Commentary by Dr. Valentin Fuster
1997;():V001T13A068. doi:10.1115/97-AA-092.
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The eigenvalues in the modal co-ordinate frame are varied and the corresponding changes in the stiffness matrix is investigated. To represent the modified eigenvalues as a function of the stiffness matrix is the main focus of this paper. It is shown that the change in eigenvalue is proportional to the change in the stiffness matrix. This approach may be applied to shift certain natural frequencies of a structure away from the critical operating frequency by structural modification.

Commentary by Dr. Valentin Fuster
1997;():V001T13A069. doi:10.1115/97-AA-093.
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This paper presents a brief review of the signal processing techniques being used in industrial condition monitoring and diagnostics. Four main types of monitoring methods are discussed; Neural Networks, Wavelets, Time-Frequency methods, and Non-linear series. References to existing applications are also included throughout the paper. This aims to introduce the most common techniques which are being used today, namely the multilayer perceptron network, orthogonal and non-orthogonal wavelets, spectrogram, Wigner and Choi-Williams distributions, and Volterra series.

Commentary by Dr. Valentin Fuster
1997;():V001T13A070. doi:10.1115/97-AA-094.
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The finite element method is used to determine the response of a new lightweight rail track system (LR55) to various loading environments.

To calculate the vertical displacement of the rail track system and the vertical pressure in the sub-base and sub-grade layers due to wheel loads and loads exerted by transversely passing vehicles across the track, the global stiffness matrix of the structure is determined. This is done by using one and two dimensional finite element programs. In the two dimensional finite element analysis, linear isoparametric elements with 4-node quadrilateral and 3-node triangular shapes in the discretised mesh of the whole structure are used, also non-homogeneous materials with isotropic of linear elastic behaviour are assumed for all the components forming the track system and surrounding media.

The results of the one dimensional finite element program are compared with those predicted from analytical approach in order to validate the finite element program developed. From the various examples presented the LR55 proves to withstand the main-line railway loading and the vertical pressure distribution in the sub-base and sub-grade of the pavement are within the allowable limit.

Topics: Rails
Commentary by Dr. Valentin Fuster
1997;():V001T13A071. doi:10.1115/97-AA-095.
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The stiffness relationship and the distributed mass matrix for a geometrically nonlinear three dimensional straight axial element is derived for use in prestressed cablenet structures. The justification for the use of a linearised stiffness relationship is provided through a theoretical derivation. Results using this simple element have shown a high degree of correlation with results to those available in the literature obtained with more complex curved finite elements, analogous membrane models and other techniques.

Commentary by Dr. Valentin Fuster
1997;():V001T13A072. doi:10.1115/97-AA-096.
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The finite element method is used to determine the natural frequencies of flat square plates containing centrally located circular or square holes. The plates are subjected to either inplane uniaxial, biaxial or uniformly distributed shear along the four outer edges. These edges are either simply supported or clamped.

To determine the stiffness and mass matrices, non conforming rectangular and triangular displacement elements are used to model the out of plane behaviour of the plate. The inplane stress distribution within the plates, which are required in the analysis are determined by using inplane finite elements having displacement fields based on assumed strains. These satisfy the exact requirements of strain free rigid body modes of displacements.

The natural frequencies of simply supported and clamped plates are initially determined when no inplane loads are applied. This showed the influence of the size of the hole on the natural circular frequency. These plates were then subjected to inplane loads and the effect of these forces on the natural frequencies are given. The results show the natural frequencies of square plates with central circular holes decrease with increasing compressive forces, and that the frequencies become zero when the compressive forces are equal to the elastic buckling loads of the plates.

By repeating this process for all boundary conditions and applied loads a comprehensive set of results is obtained for the buckling and vibrational properties of square plates containing centrally located holes.

Commentary by Dr. Valentin Fuster
1997;():V001T13A073. doi:10.1115/97-AA-097.
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The natural frequencies of square plates containing circular holes is investigated using the finite element method. The holes are eccentrically located, and the effect of this eccentricity on the natural frequency is examined when the plates are subjected to a variety of inplane loads.

The natural frequencies are calculated by using the 12 degree of freedom non conforming rectangular and the 9 degree of freedom non conforming triangular bending elements. To determine the inplane stress distribution, strain based inplane elements are used. The displacement fields for these elements are based on assumed strain functions which satisfy the exact requirement of rigid body motion.

In the present paper, the lowest natural frequencies and the corresponding modes of vibration are determined for simply supported or clamped plates containing circular holes. Initially the plate is unloaded at the middle surface, and the effect of the degree of eccentricity on the natural frequency is examined. Result are also given for plates subjected to uniform uniaxial and biaxial compression.

For plates loaded by inplane uniformly distributed shear, tension and compression regions are produced. Hence for these plates, the natural frequencies are determined when the circular holes are located either in the tension or compression zones.

Commentary by Dr. Valentin Fuster
1997;():V001T13A074. doi:10.1115/97-AA-098.
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In order to analyze the stresses and deformations of a crankshaft of a truck-mounted compressor by means of finite element method, the most important and difficult thing is how to determine the external force model on a crankshaft. The objective of this paper is to present a new load model of 3-D finite element analysis for a crankshaft of a truck-mounted compressor used in an oil field, i.e., the contacting-distribution forces are transferred into equivalent nodal forces. Firstly, the contacting-distribution forces between the crankshaft and the links are analyzed; secondly, formulations of equivalent node forces for the working conditions of 0° and 75° are deduced; finally, the crankshaft of a gas-engine driven truck-mounted compressor is taken as an illustration.

Commentary by Dr. Valentin Fuster
1997;():V001T13A075. doi:10.1115/97-AA-099.
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Large scale floating structures, such as floating airport and amusement park having two dimensional expanse in horizontal direction, which structural concept can be considered as plate-type structural system. This structural system has a great deal of potential to be applied to oceanic structures like a artificial ground. This practical fabrication will be done by a combination of units. The hydroelastic interaction problem and structural design have attracted the attention of researchers and structural engineers.

This paper presents consideration and conclusion through the numerical calculation results of the natural frequency studied under the various supporting conditions by developed computer program. The theoretical development is obtained by a way of combination of finite element method (FEM) and boundary integral equation method (BIEM). As to natural frequency analysis of oceanic structures based on the fluid-structure interaction, in general, there is an assumption to make it possible by estimating properly the added mass of the structure surrounding by water. The added mass of floating plate obtained by BIEM is modified and transformed into mass matrix of plate in FEM analysis. Herein, FEM analysis is based on the bending vibration assumption.

Commentary by Dr. Valentin Fuster
1997;():V001T13A076. doi:10.1115/97-AA-100.
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Cyclones are the most common dust-removal systems used in combined cycle fluidized bed combustion boilers. Analysis of a cyclone separator combining flow and structural aspects is carried out using detailed three dimensional finite element modeling including stiffeners and supporting arrangement. The fluid flow study involves the solution of continuity, energy and Navier-Stokes equations. The fluid analysis gives the variation of pressure on cyclone shell, which in turn is imparted on the structural model using fluid structure interface routine. The pressure distribution obtained from the fluid-flow analysis is mapped on to the structure. Then a linear static analysis is performed considering thermal, wind and seismic loads besides the pressure loads. The results for various loads include the reaction forces at the supports and stress levels in the cyclone. The stresses are checked against the allowable values as per Indian Standard Structural Codes. A separate computer code is developed and is interfaced with the FEM program. Results indicate higher stresses in some of the beam stiffeners and at support locations. These are suitably modified and a reanalysis confirmed the stresses to be within limits. The analysis methodology combining the fluid, structure and code requirement developed shall be very useful for the design improvement and safe operation of a cyclone separator.

Topics: Boilers , Design
Commentary by Dr. Valentin Fuster
1997;():V001T13A077. doi:10.1115/97-AA-101.
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This paper presents effective extensional stiffness of plain-weft knitted fabric reinforced composites obtained from finite element analysis and analytical calculations. For micro-mechanical analyses, a unit cell, enclosing the characteristic periodic repeat pattern in the knitted fabric, is isolated and modeled. Psuedo three-dimensional finite element model is constructed using laminated shell elements. Composite extensional stiffness is estimated for plane-stress and plane-strain conditions. Further, stiffness and compliance averaging methods have been used to determine the upper and lower limits of composite stiffness. The models are explicitly based on the properties of fiber and matrix materials and orientation of yarns. Results obtained from the models are compared with experimental values.

Commentary by Dr. Valentin Fuster
1997;():V001T13A078. doi:10.1115/97-AA-102.
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This paper provides an analysis of the transient behaviour of a right-angled bent cantilever beam subjected to a suddenly applied force at its tip perpendicular to its plane. A double-hinge mechanism is required to complete the possible deformation under a rectangular force pulse (constant force applied for a finite duration) with a four-phase response mode. The kinematics of the various response phases are described and the partitioning of the input energy at the plastic hinges during the motion is evaluated.

Commentary by Dr. Valentin Fuster
1997;():V001T13A079. doi:10.1115/97-AA-103.
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In this paper, a unified formulation is given for the bending, buckling and vibration problems of uniform Timoshenko and Euler-Bernoulli beams resting on various models of elastic foundation. Canonical Green’s functions have been derived for these beams which can be readily used to furnish exact solutions. In addition to elucidating the behaviour of the beams, the exact solutions serve as important benchmark results for checking the convergence and accuracy of various solutions obtained from numerical methods.

Commentary by Dr. Valentin Fuster
1997;():V001T13A080. doi:10.1115/97-AA-104.
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Treated herein is the elastic buckling of circular plates based on the Reddy plate theory. This plate theroy extends the Kirchhoff (or the classical thin) plate theory to allow for the effect of transverse shear deformation. Unlike the Mindlin’s shear deformation plate theory, there is no need for a shear correction factor in the Reddy plate theory. In this paper, exact buckling solutions are derived for circular plates whose edges are simply supported and elastically restrained against rotation as well. This general edge condition includes the classical simply supported and clamped edges at the limiting, values of the elastic rotational restraint constant. The buckling solutions are expressed in terms of the well-known Kichhoff buckling solutions. A comparison of buckling loads between the Mindlin, Reddy and three-dimensional elasticity plates is also given.

Commentary by Dr. Valentin Fuster
1997;():V001T13A081. doi:10.1115/97-AA-105.
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Taking a multibody system of the oil field pumping unit into a multibody elastic system, this paper analyzes its kinematics and dynamics by means of finite element method, deduces the kinematics and dynamics function after doing the element’s and global analysis, and puts forward the procedures of this method, i.e., (1) dividing the system into elements; (2) calculating for the elements; (3) calculating the matrix of external force; (4) piling the element stiffness and mass matrixes up; and (5) solving the function. As an example, this paper illustrates the process of analyzing the multibody system of a PUMPING UNIT used in an oil field.

Commentary by Dr. Valentin Fuster
1997;():V001T13A082. doi:10.1115/97-AA-106.
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This paper reports on the numerical and experimental research on saddle mounted horizontal pressure vessels subjected to heating by its hot liquid contents. The overall purpose of the research is to obtain design formulae relating design variables of horizontal pressure vessels mounted on fixed non-sliding saddle supports. Two experimental techniques were utilised to obtain stresses and strains for the situation of the saddle supports being rigidly fixed to ground. The first technique involves room temperature testing whereby one saddle base is displaced by the expected thermal expansion displacement (i.e. isothermal push-pull). The other technique utilised direct thermal heating by introducing hot liquid into the vessel, a more complicated yet more realistic test. These two techniques are not equivalent because in the hot test, the vessel will expand both axially and radially, whereas the radial expansion will be absent in the isothermal push-pull test. Experimental tests were conducted for the above two loadings techniques on two model vessels with different saddle designs. The resulting strains measured at the maximum stress locations showed that they can be reliably predicted when push-pull tests are carried out. Additionally, FE analyses were conducted for the two techniques for comparison. The experimental results are discussed with the FE predicted values, with particular reference to their agreement with push-pull tests and the hot liquid tests.

Commentary by Dr. Valentin Fuster
1997;():V001T13A083. doi:10.1115/97-AA-107.
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Based upon research experience on fuel cell technology at the Fukui University of Technology, an effort has been made to develop a hydrogen powered electric vehicle as a means of applying fuel cells, A polymer electrolyte fuel cell stack was chosen as the device of energy conversion from hydrogen to electricity. First, a detailed study on the performance of the fuel cell stack was carried out to assure compatibility with the vehicle energizing system. It was found that it should function well as the prime power source for electric vehicles. Selection of the traction motor was one of the optimization studies. As a result of tests with various motors, two brushless d-c motors were adopted. A small electric vehicle, weighing 300kg and loaded with a H2-tank of 10 litres (15MPa), achieved 20 km/h and the duration was 2 hours.

Commentary by Dr. Valentin Fuster
1997;():V001T13A084. doi:10.1115/97-AA-143.
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Spray combustion in an axisymmetric combustor is analyzed numerically with three droplet models; (1) Ranz and Marshall droplet law (2) droplet laws by canonical droplet theory, accounting for the droplet blowing effect and flow convecting effect, and (3) renormalized canonical droplet theory, which accounts for the drop-drop short range interaction as well as convection and blowing. Results are compared to assess the effects of the droplet models on the combustion and aerodynamic characteristics of a spray. The concept of droplet state spectra are proposed to aid in understanding the state of droplet and its evolution at different locations. Spray combustion is classified into “core combustion”, “transition combustion”, and “wall-bound combustion” patterns, with “transition combustion” spray generally giving the highest combustion efficiency for a given mass flow rate and mixture ratio.

Topics: Combustion , Sprays
Commentary by Dr. Valentin Fuster
1997;():V001T13A085. doi:10.1115/97-AA-144.
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Combustion of a droplet, either in stationary or convective motion under the effect of radiative heat transfer is studied. The closed form expression of gasification laws and the radiative flux distribution surrounding a stationary droplet are calculated using Potential Theory of Radiation in conjunction with the canonical theory of droplet recently developed. Various mechanisms contributing to gasification rate of a combusting droplet under radiative condition are determined by the Canonical Integral Method to assess their importance. It is found that radiation effect plays an important role when the droplet considered is of large size and under high environmental temperature. It is seen from the present study that for a typical application in turbine combustor, the enhancement of droplet combustion rate due to radiation ranges from 5 percents to 15 percents depending on the droplet size and the environmental conditions.

Commentary by Dr. Valentin Fuster

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