0

Aircraft Engine

1985;():V001T01A002. doi:10.1115/85-GT-175.
FREE TO VIEW

During the last twenty-eight years the capabilities of the Harrier have improved markedly, due in large measure to advances in the Pegasus propulsion system. New engine models and component improvements with their increased performance and/or weight reductions have produced increased range and payload capability for the aircraft. Because the Harrier is likely to continue in use well into the next century, an engine-aircraft-mission study has been conducted to identify the potential benefits arising from replacing the existing Pegasus engine with an advanced technology engine. These studies have shown that thrust increases associated with increased technology can improve mission capability substantially; radius can be increased by as much as 50% on a mission with a vertical takeoff requirement. However, as takeoff constraints are relaxed, aircraft restraints limit the benefits of the advanced technology engines.

Commentary by Dr. Valentin Fuster
1985;():V001T01A003. doi:10.1115/85-GT-176.
FREE TO VIEW

Airborne Early Warning for the Navy fleets has been provided for the past 20 years by the Grumman/Allison E-2 Airframe/T56 engine combination. Although avionic capability has been continually updated to meet the increased threat, the airframe and powerplant have seen only minor changes. Projected mission requirements and future avionic system enhancements require payload increases being limited by the power capability of the present T56 powerplant. Of paramount importance in the E-2 carrier deck operation is the single engine rate of climb capability of the aircraft. This paper discusses the logical evolution of a replacement engine for the E-2C — a derivative T56 engine contracted and designated by the Navy as the T56-A-427 — to meet the projected single engine takeoff and other mission requirements. The T56-A-427 provides 24% power and 13% fuel consumption improvements with identical installation interfaces, and substantially improves E-2C performance characteristics across the flight envelope. Furthermore, the paper shows that meeting these stringent performance requirements with a derivative engine results in a low risk development program and an engine with improved maintainability and reliability, which can capitalize on the in-place logistics support base of the T56 — the world’s longest production run gas turbine engine.

Topics: Engines
Commentary by Dr. Valentin Fuster
1985;():V001T01A004. doi:10.1115/85-GT-184.
FREE TO VIEW

The advantages of re-engining the F-14 aircraft with the F110 engine is presented. The areas of improvement and the engine development philosophy are explained. A summary description of the pertinent engine design features of the F110 are presented. The flight test results on inlet/engine compatability, afterburner operation, airplane performance, and maintainability/reliability/durability are interpreted. Finally, a description of the proposed version of the F110 engine for the F-14 is presented.

Topics: Engines
Commentary by Dr. Valentin Fuster
1985;():V001T01A006. doi:10.1115/85-GT-211.
FREE TO VIEW

This paper reviews the preliminary studies that led to the KC-135/CFM56 Re-Engine Program and discusses the motivation for re-engining an aircraft, designed in the mid 1950s, with a modern high bypass turbofan. The selected engine, the CFM56-2B-1, and other major aircraft modifications are described. The KC-135R test program methods and results are addressed with particular attention given to engine and aircraft performance. The overall benefits of the program relating to mission capability, environmental impact, and cost are also presented.

Topics: Engines
Commentary by Dr. Valentin Fuster
1985;():V001T01A007. doi:10.1115/85-GT-231.
FREE TO VIEW

In 1979 the United States Air Force elected under the Engine Model Derivative Program (EMDP) to explore derivative engine concepts by the General Electric Company and the Pratt and Whitney Aircraft Division of United Technology Corporation with the objective of improving engine durability and reducing engine ownership cost for future procurements of their first line fighter engines. Concurrently, General Dynamics was invited to develop the necessary airframe/engine interface definition to assure engine compatibility with the airplane requirements. This EMDP development culminated in 1981 with the Alternate Fighter Engine (AFE) competition with General Electric proposing the F110-GE-100 engine and Pratt and Whitney Aircraft proposing the F100-PW-220. Both engines were placed in Full Scale Development and both met the USAF objectives of 4000 TAC cycle life and improved engine cost and warranty for application to the F-15 and F-16 fighters. General Dynamics evolved the concept of the Common Engine Bay which has all aircraft interfaces compatible with either AFE engine and the current Pratt and Whitney Aircraft F100-PW-200 engine. The original F-16 nacelle design, with minor modification of the interfaces and engine mount structure, was adapted to permit full interchangeability for the F100-PW-200, F100-PW-220, or the F110-GE-100 engines. Design requirements were set to permit a common airplane with no break in the production line or aircraft model change and with appropriate simple kits to permit interchangeability of any of the three engines in the field at the organizational level. This manufacturing capability allows the USAF the flexibility to conduct subsequent competitive procurement of the engine.

Topics: Engines
Commentary by Dr. Valentin Fuster

Marine

1985;():V001T02A001. doi:10.1115/85-GT-75.
FREE TO VIEW

Major design changes to the Propulsion Gas Turbine Air Inlet on the US Navy’s CG47 Class Guided Missile Cruisers have resulted in significant superstructure weight savings. The majority of weight reduction resulted from use of finite element analysis (FEA) computer modeling techniques applied to structural optimization. FEA models of the forward and aft deckhouses provided the necessary capability to analyze each structure’s response to loads simulating a nuclear air blast, shock, and vibration. Integration of the moisture separator housings into each deckhouse structure allowed improved structural stability and additional weight reductions. FEA modeling and a redesign of the major inlet system 32% lighter than inlets installed onearly ships of this class. The first of the lightweight deckhouses has been installed on the CG52 Cruiser.

Commentary by Dr. Valentin Fuster
1985;():V001T02A002. doi:10.1115/85-GT-99.
FREE TO VIEW

In common with all responsible equipment operators the Royal Navy continues to seek ways to reduce ownership costs. In the particular case of gas turbines, over the last few years, this has taken the form of investment to achieve improvements in fuel efficiency. This route now ceases to offer large scope for improvement. The Royal Navy has therefore carried out an Investment Appraisal into the likely cost benefits which would result from improved life and reliability. The result of this study was to demonstrate a net present value cost advantage from entering into a joint venture development programme with Rolls-Royce to uprate and improve the Marine Spey SMIA.

Commentary by Dr. Valentin Fuster
1985;():V001T02A003. doi:10.1115/85-GT-127.
FREE TO VIEW

During the winter of 1983–84, the JEFF (A), a self-propelled air cushion vehicle owned by the U.S. Navy and leased to RMI, operated under a time charter to Sohio Alaska Petroleum Company in the arctic region contiguous to the Beaufort Sea. The purpose of the JEFF (A) operation was to gather engineering data to expand the data base for arctic-use air cushion vehicle design and to provide additional insight into the relationship between air cushion vehicles and the indigenous logistic network. In the process of the data gathering, the JEFF (A) operated for more than three hundred hours from two distinct operational sites, hauled in excess of 1.8 million pounds of oil field support cargo, and participated in the conduct of three discrete engineering test programs. This paper will cover the operational experience of the JEFF (A) during the period, the modification made to the craft to perform in the arctic environment and the lessons learned from the experience.

Topics: Arctic region
Commentary by Dr. Valentin Fuster
1985;():V001T02A004. doi:10.1115/85-GT-162.
FREE TO VIEW

This paper aims to discuss the factors which led to the selection of the Spey as a marine gas turbine, and the market forces which have made an uprating of the simple cycle unit necessary, and which are now leading to the conception of an advanced cycle version of the gas turbine at even higher power and efficiency. The operational characteristics of warships using these Spey units are compared with those of ships using other propulsion systems. While this paper stands on its own, it can also be regarded as the first part of a series of two; the second part, to be published in Beijing during the September 1985 ASME Gas Turbine Exposition, will deal with that further possible uprating of the Spey to about 22 MW using intercooling and heat exchange to improve its thermal efficiency to about 43%.

Commentary by Dr. Valentin Fuster
1985;():V001T02A005. doi:10.1115/85-GT-169.
FREE TO VIEW

Some helicopter and other engines have been shown in studies to be amenable to conversion to a low-pressure-ratio highly regenerated cycle. Typically the high-pressure compressor and high-pressure turbine would be removed, and shaft and ducting modifications would be made to introduce high-effectiveness rotary ceramic-honeycomb regenerators. In one case examined the low-pressure turbine could be used with slight modification; in others there would have to be reblading of the turbine stages and the manufacture of new shrouds. In another case the existing combustor could be used with little modification; in others new combustors would be required. Despite the extent of the modifications, the resulting high-efficiency performance over a large part of the power range and presumably relatively low capital and development costs could make this an attractive concept.

Commentary by Dr. Valentin Fuster

Turbomachinery

1985;():V001T03A003. doi:10.1115/85-GT-4.
FREE TO VIEW

A method for solving the Navier-Stokes equations of the rotating blade cascade flow on S1 stream surface of revolution is developed in the present paper.

In this paper a complete set of full and simplified Navier-Stokes equations is given which includes stream-function equation, energy equation and entropy equation, equation of state for a perfect gas, formula for estimating density and formulas for calculating viscous forces, work done by viscous force, dissipation function and heat-transfer term.

A comparison between the full and the simplified Navier-Stokes equations is made. The viscous terms of both full and simplified Navier-Stokes equation solutions are also compared in the present paper. The comparison shows that the simplified Navier-Stokes equations are applicable.

Commentary by Dr. Valentin Fuster
1985;():V001T03A004. doi:10.1115/85-GT-5.
FREE TO VIEW

All methods of solving the Euler equations face the problem of errors in entropy. These errors are especially important at the leading edge of blade rows where any numerical errors will cause entropy to be produced and to convect downstream to influence the downstream flow, especially that on the blade surfaces.

A new numerical method is described which overcomes this problem by solving a conservation equation for entropy. This equation effectively replaces the usual momentum equation along streamlines. Sources of entropy are introduced to allow for shock loss with the magnitude of the source being determined from the Rankine-Hugoniot relations. A semi-implicit scheme is used to solve the continuity equation whilst the entropy and flow direction are updated by conventional explicit methods.

The flow through a selection of test cascades has been calculated with this new method and its predictions compared with exact solutions as well as with experimental data and with a conventional Euler solver. The results show that the new method is more accurate than the conventional one, it converges in fewer iterations but requires slightly longer computer times.

Commentary by Dr. Valentin Fuster
1985;():V001T03A005. doi:10.1115/85-GT-6.
FREE TO VIEW

The computation methods of the inverse problem and several mixed aerodynamic problems for transonic cascades are presented. The calculations are completed directly on the physical plane by the stream function equation. The corresponding boundary conditions of these problems are transfered into the boundary conditions expressed by stream function with the help of the relations of the basic equations. The methods presented have a clear physical concept and use similar manners of iteration for different problems. The calculations of some examples for the transonic inverse problem indicate this method is very effective. An example is given of a shockless supercritical cascade designed successfuly by the transonic inverse code.

Commentary by Dr. Valentin Fuster
1985;():V001T03A006. doi:10.1115/85-GT-7.
FREE TO VIEW

A method is presented in this paper for determining the shape of the detached shock and flow field quantities in the supersonic entrance region on an arbitrary stream surface of revolution. The equation of characteristics and the corresponding equation of compatibility are derived. The shape of the detached shock obtained is taken as the initial-value curve to calculate the supersonic entrance region by means of the method of characteristics. Consequently, the unique inlet flow angle is also calculated. Typical computations show that this method is both effective and rapid.

Commentary by Dr. Valentin Fuster
1985;():V001T03A010. doi:10.1115/85-GT-20.
FREE TO VIEW

In order to obtain a better understanding of secondary flow in a turbine cascade, spatial development of a leading-edge horseshoe vortex has been investigated experimentally in a large-scale, low-speed, high-accelerated, plane turbine inlet guide vane cascade. Flow has been visualized by issuing kerosene vapor into the inlet boundary layer and the vane suction surface boundary layer, respectively.

Based on many cross-sectional photographs normal to the flow and supplemental measurements of the wall static pressure on the vane and the endwall, the evolution of a leading-edge horseshoe vortex into streamwise vortices and the generation of a new type streamwise vortex pair on the suction surface near the endwall are discussed.

Commentary by Dr. Valentin Fuster
1985;():V001T03A011. doi:10.1115/85-GT-21.
FREE TO VIEW

The prediction of losses in transonic flow in turbines is an important step in the design of turbine stages, but at the same time requirements of simplicity and speed are needed to allow the work of designers. The paper presents a procedure developed to match this goal. It uses classical codes, experimental correlations and simple geometrical models of the shock system. The result of a time marching method with standard mesh is used to run an Integral Boundary layer calculation in which shock wave interaction effects have been included. The shock system is made up of this information plus empirical correlation and a suitable procedure. A mixing calculation is then performed to get the downstream total pressure. The method has been tested with various kinds of turbine blades of which losses and data for calculations have been published. The results are quite good and the procedure appears simple and fast.

Topics: Turbines
Commentary by Dr. Valentin Fuster
1985;():V001T03A012. doi:10.1115/85-GT-22.
FREE TO VIEW

A calculation system has been set up to predict both the internal flow field and the overall performance of a transonic compressor blade row. The system iterates between an inviscid-viscous time-marching blade-to-blade (S1) treatment and a streamline curvature throughflow calculation for the pitchwise-averaged flow in the meridional plane (S2). A blade geometry package and a data transfer/display program are used to link the S1 and S2 methods to give a semi-automatic convergence procedure. The only empirically-based correlation or correction required is an extra loss imposed near the blade hub and tip to allow for end effects. The system has been applied to a high bypass ratio transonic fan rotor near design point. The converged solution was in good agreement with the measured performance.

Commentary by Dr. Valentin Fuster
1985;():V001T03A013. doi:10.1115/85-GT-46.
FREE TO VIEW

To investigate the influence of the vaneless space between impeller exit and the diffuser vanes, datailed flow measurements in two diffusers with the same vane geometry but different passage width are compared.

The three-dimensional character of the flow changes between impeller exit and the entry to the two dimensional vanes depending on the shape of the shroud. After initial measurements with a constant area vaneless space, the width of the vaned diffuser was later on reduced by 10%. The compressor maps show an increase in overall pressure rise and efficiency with the width reduction.

To get further details of the flow field, measurements of the static pressure distribution at hub and shroud have been performed at several operation points for both diffusers. At the same points the flow angle and total pressure distribution between hub and shroud upstream and downstream of the vanes have been measured with probes. The maximum efficiency of the narrow diffuser is nearly 2% higher than for the wide diffuser. The measurements give further details to explain this improvements.

Commentary by Dr. Valentin Fuster
1985;():V001T03A023. doi:10.1115/85-GT-73.
FREE TO VIEW

Single- and two-zone modeling, as used to describe the performance of centrifugal compressors, is evaluated against basic laboratory data. The historical industrial usage of single-zone modeling is reviewed and documented while indicating inherent errors as well as areas of applicability. Enhanced accuracy of two-zone modeling (also called jet-wake modeling in limited instances) is demonstrated and advantages for advanced design optimization studies are documented. An original and rigorous derivation of the two-zone (jet-wake) modeling equations is given which resolves discrepancies in earlier derivations. This paper is part of a seven-paper series presenting the foundation, history and application of two-zone modeling.

Topics: Compressors , Modeling
Commentary by Dr. Valentin Fuster
1985;():V001T03A024. doi:10.1115/85-GT-76.
FREE TO VIEW

A finite difference computer program has been developed to predict the subsonic compressible flow within a single cavity of a concentric-rotor labyrinth seal. The recent QUICK convective differencing scheme is employed to eliminate false diffusion. Previously unavailable distributions of important flow variables throughout a generic seal cavity are presented. Specifically, the dimensionless results of four seal leakage mass flow rates at given cavity inlet pressure and temperature have been compared and important variations are examined. Also, realistic approximations of flow variable distributions within a labyrinth seal cavity are made from the included figures.

Commentary by Dr. Valentin Fuster
1985;():V001T03A025. doi:10.1115/85-GT-77.
FREE TO VIEW

The use of a miniature pressure transducer to measure the flow field at the discharge of an industrial centrifugal pump impeller is described. Periodic signals were elucidated using a phase lock averaging program. A new technique was used in which, with one easily calibrated transducer, total and static pressures and flow angle were measured. Axial traversing enabled the discharge flow to be surveyed and the slip factor to be deduced directly. The measured slip factor was in good agreement with design correlations.

Commentary by Dr. Valentin Fuster
1985;():V001T03A026. doi:10.1115/85-GT-80.
FREE TO VIEW

Experimental investigations were conducted on a radial and a tangential inlet duct to an industrial centrifugal compressor. The tangential nozzle will replace the conventional radial nozzle if a block foundation is used with no pipes allowed on the upper casing half. Models were air tested with and without suction elbows. The tangential duct was tested with various positions of the shaped flow splitter and with variable intake rib angles with the objective to minimize distortions of axial and circumferential velocity profiles and the moment of momentum in the annular eye opening of the impeller. An optimum configuration for the tangential duct was found with smooth profiles and eliminated global vortex at the exit annulus.

Commentary by Dr. Valentin Fuster
1985;():V001T03A027. doi:10.1115/85-GT-85.
FREE TO VIEW

The influence of the impeller blade geometry on the calculated relative flow field has been studied by means of an impeller design program available at DFVLR [9]. Several geometrical parameters were varied, however, the meridional channel geometry was always kept constant. By this approach the blade wrap angle has been found to react significantly on the relative flow which is illustrated by comparing two designs with different wrap angles. Primarily in the hub/leading edge area a better boundary layer flow connected with a reduction of blade loading was obtained by increasing the wrap angle. But also in the shroud/pressure side area the increased blade looping attributed to an additional flow stabilization.

Commentary by Dr. Valentin Fuster
1985;():V001T03A028. doi:10.1115/85-GT-86.
FREE TO VIEW

A general computer code for pseudo-unsteady Euler equations integration in turbomachinery cascades has been developed. A quasi-three-dimensional flow hypothesis is assumed and only blade to blade calculation is considered here.

Cascades may be axial, radial or mixed flow type. First the computerized quasi-orthogonal network is shown. This network takes into account splitters and is designed to reduce the computation time.

Then, the numerical method is described and the major difficulties of this problem, which are boundary conditions, leading edge and trailing edge treatments, are presented. Finally, examples of calculations on turbines and compressors are given with emphasis on graphic representation.

Commentary by Dr. Valentin Fuster
1985;():V001T03A029. doi:10.1115/85-GT-87.
FREE TO VIEW

This paper consists of two parts. (1) General curved surface fitting and grid refining. A method of fitting a set of given discrete points on several stream lines to give a smooth and arbitraily twisted stream surface was developed. Based upon the small deformation theory for thin plate, the Kirchhoff’s Equation was solved and twofold transformations were incorporated. The first step is the transformation from physical surface into computational surface and the second is affine transformation. The accuracy of the result is about 0.004% and the CPU time needed is reasonable for engineering application. Then the refined computational grid and the calculation for the geometrical quantities of the grid are carried out on the fitted surface. (2) Calculation of the flow along the fitted stream surface. Employing non-orthogonal curvilinear coordinate system, the fitted stream surface is selected as a coordinate surface, so that there are only two velocity components even when the stream surface is arbitrarily twisted, and it is very convenient to define the stream function. The general equation for the quasi-linear stream function governing the flow along the fitted stream surface was employed. This was solved with the method of direct decomposition of matrix. The numerical examples are also included in this paper. The present method can be used for S1 and S2 stream surfaces and other engineering calculations.

Commentary by Dr. Valentin Fuster
1985;():V001T03A030. doi:10.1115/85-GT-97.
FREE TO VIEW

A method for estimations of performance characteristics of centrifugal compressors was examined by comparing the estimated results with those by experiments. Lots of empirical and semi-empirical factors which were introduced to the losses within compressor channels in the estimations, and the experimental results for the compressors with a wide variety of configurations, operating conditions and design techniques were investigated. After the extensive comparisons, the most appropriate combinations of the factors for the present method were given.

By employing this method, the major factors which are directly related to the performance characteristics were computed and the relationships among them were discussed. Thus, the ratio of the relative velocity at the impeller exit to that at the inlet, the non-dimensional relative velocity at the impeller inlet and that at the exit were obtained as the parameters of the slip factor, the flow coefficient and the specific speed.

Commentary by Dr. Valentin Fuster
1985;():V001T03A031. doi:10.1115/85-GT-108.
FREE TO VIEW

This paper describes the numerical investigation of the three dimensional flow through a low speed, low aspect ratio, high turning annular turbine nozzle guide vane with meridional tip endwall contouring. This rotational flow field has been simulated using a finite volume discretization and a time marching technique to solve the three dimensional, time dependent Euler equations expressed in a cylindrical coordinates system. The results are presented under the form of contour plots, spanwise pitch-averaged distributions and blade static pressure distributions. Detailed comparisons with the measurements described in part I of the paper are also provided.

Commentary by Dr. Valentin Fuster
1985;():V001T03A033. doi:10.1115/85-GT-126.
FREE TO VIEW

In ASME paper 83-GT-42, a simple method for designing optimum annular diffusers was proposed and good results were obtained. But it is essentially a 1-D approximate method adapted for axial annular diffusers only. Actually, within the same assumption and limitation, it can be modified and improved effectively by the Mean-Stream-Line Method developed by the Chinese scientists led by Prof. C.H. Wu. The calculation can be done rapidly for axial, radial and mixed type diffusers, and the 2-D flow field in the diffusers can also be determined easily. A set of simple BASIC codes has been programed on the pocket computer Sharp PC-1500 and some calculation examples are given.

Topics: Diffusers , Design
Commentary by Dr. Valentin Fuster
1985;():V001T03A037. doi:10.1115/85-GT-139.
FREE TO VIEW

A numerical method has been developed for predicting the aerodynamic damping of the last L.P. stages in a 900 MW steam turbine on a blade to blade surface using a boundary element method. The results obtained on the first flexural mode of the blades for several displacements and for several interblade phase angles show no unstability of the rotor except perhaps for low phase angles. They also prove that quasisteady calculations are relevant for all the cases tested.

Commentary by Dr. Valentin Fuster
1985;():V001T03A038. doi:10.1115/85-GT-163.
FREE TO VIEW

A two-dimensional Euler solver allowing the calculation of transonic flow conditions and weak shocks for turbomachinery blade rows is presented. The algorithm is based on a second-order-accurate finite-difference version of the implicit lambda scheme applied to the Euler equations assuming isentropic flow conditions. Using a fairly simple grid point network with equal spacing in meridional and tangential directions, this algorithm has been used successfully to calculate stationary and rotating stages of axial, radial and mixed flow turbomachinery cascades. Predictions are shown for a Laval nozzle and a high-turning turbine nozzle and compared against theoretically and experimentally available data.

Commentary by Dr. Valentin Fuster
1985;():V001T03A039. doi:10.1115/85-GT-164.
FREE TO VIEW

On the basis of Prof. Wu’s 3-D flow theory (ref.1, 2, 3, 4, 5), a general streamfunction equation in non-orthogonal curvilinear coordinates is developed. The equation can be used to calculate subsonic or transonic flows on S1 or S2 stream surfaces of turbomachinery. In this paper streamlines coordinates and a mixed difference scheme are adopted in solving the stream function equation. A procedure for pre-determination of the density is developed and used to determine the unique-value of density from the known value of the stream function. Numerical examples are given.

Commentary by Dr. Valentin Fuster
1985;():V001T03A040. doi:10.1115/85-GT-165.
FREE TO VIEW

This paper describes a new non-reflective inflow treatment for viscous and inviscid internal flow calculations. The method approximates the multi-dimensional governing equations at the inflow boundary in a series of one-dimensional split equations. This treatment allows the artificial inflow boundary to be brought in just in front of the leading edge, while allowing upstream running waves to penetrate without significant reflection. Calculation examples of two dimensional inviscid internal flows are presented. Extension of the method to three-dimensional problems is also discussed.

Topics: Inflow
Commentary by Dr. Valentin Fuster
1985;():V001T03A045. doi:10.1115/85-GT-188.
FREE TO VIEW

With modern turbines operating at a high level of efficiency, sophisticated design techniques are needed for further improvements. With the aid of computers 3-D aspect like end wall contouring and airfoil stacking can be integrated into the design process. The possibilities presented by the latter to control reaction, loading and secondary flow effects are analyzed and compared with experimental results. The implications for the resulting airfoil geometry are shown and limitations are discussed.

Topics: Design , Turbines , Airfoils
Commentary by Dr. Valentin Fuster
1985;():V001T03A051. doi:10.1115/85-GT-200.
FREE TO VIEW

Industrial pumps are generally used in a wide range of operating conditions from almost zero mass flow to mass flows larger than the design value.

It has been often noted that the head-mass flow characteristic, at constant speed, presents a negative bump as the mass flow is somewhat smaller than the design mass flows.

Flow and mechanical instabilities appear, which are unsafe for the facility.

An experimental study has been undertaken in order to analyze and if possible to palliate these difficulties. A detailed flow analyzis has shown strong three dimensional effects and flow separations.

From this better knowledge of the flow field, a particular device was designed and a strong attenuation of the negative bump was obtained.

Topics: Design , Pumps
Commentary by Dr. Valentin Fuster
1985;():V001T03A052. doi:10.1115/85-GT-208.
FREE TO VIEW

This paper describes how allowance for the thermal effects of non-adiabatic flow, altered boundary layer development, changes in tip clearances and changes in seal clearances have been incorporated into a general gas turbine transient program. This program has been applied to a two-spool bypass engine. Revised predictions of surge margins in three common transients have been obtained. When the engine undergoes a “cold” acceleration, the thermal effects on the trajectory and on the surge line give a much increased proportion of unused surge margin in the H.P. Compressor, as compared to adiabatic predictions. In a “hot” acceleration this improvement is considerably reduced.

Commentary by Dr. Valentin Fuster
1985;():V001T03A053. doi:10.1115/85-GT-209.
FREE TO VIEW

The paper describes a general program which has been developed for the prediction of the transient performance of gas turbines. The program is based on the method of continuity of mass flow. It has been applied successfully to a wide range of aero gas turbines, ranging from single to three-spool and from simple jet to bypass types with or without mixed exhausts. The results for three of these engine types are illustrated. Computing times are reasonable, increasing with the complexity of the engine.

A parallel paper describes the inclusion of thermal effects in the prediction program.

Commentary by Dr. Valentin Fuster
1985;():V001T03A055. doi:10.1115/85-GT-216.
FREE TO VIEW

Different types of fan blade flutter occur at the various compressor flow regimes. Sub/transonic stall flutter and two forms of supersonic started flow flutter have been studied in a straight cascade wind tunnel. Results show clearly that these three common forms of flutter can exist as single-degree-of-freedom (single-blade instabilities). Cascade effects, though at times important, are never the only flutter mechanism: flutter limits are essentially controlled by single-blade aeroelastic coefficients, though blade-to-blade coupling arising from cascade effects can modify these limits according to the mode order.

Thus, contrary to widespread practice, the fundamental approach to flutter problems should lie at least as much in the study of single blade flutter as in that of unsteady cascade effects. The two should anyhow best be considered separately when searching for a better physical insight.

Commentary by Dr. Valentin Fuster
1985;():V001T03A056. doi:10.1115/85-GT-217.
FREE TO VIEW

Using five-hole pitot tubes, detailed flow measurements were made before, within and after a low-speed three-dimensional turbine stator blade row to obtain quantitative information on the aerodynamic loss mechanism. Qualitative flow visualization tests and endwall static pressure measurements were also made.

An analysis of the tests revealed that many vortical flows promote loss generation. Within a large part of the cascade, a major loss process could be explained simply as the migration of boundary layer low energy fluids from surrounding walls (endwalls and blade surfaces) to the blade suction surface near the trailing edge. On the other hand, complexity exists after the cascade and in the vortical flows near the trailing edge. The strong trailing shedding vortices affect upstream flow fields within the cascade. Detailed flow surveys within the cascade under the effects of blade tip leakage flows are also included.

Commentary by Dr. Valentin Fuster
1985;():V001T03A057. doi:10.1115/85-GT-218.
FREE TO VIEW

Two types of contra-rotating stages are considered; the first uses guide vanes and the second is vaneless. The wheels of the first type use bladings which are mirror images of each other and they operate with inlet and outlet swirl. The second type uses dissimilar bladings in each of the two wheels with axial inlet velocity to the first wheel and axial outlet velocity for the second wheel. An analysis of their performance indicates that both types can reach stage loading coefficients comparable or larger than conventional turbines with the same number of wheels. A comparison of the contra-rotating stages with conventional ones indicate a significant stage efficiency advantage of the contra-rotating over the conventional single rotation stages due mainly to the elimination of stationary vanes. The off-design performance indicates that relative wheel speed must be controlled. The attributes of contra-rotating turbines suggest their potential use in high performance aircraft engines, in dynamic space power systems and in low speed industrial gas turbines.

Topics: Turbines , Axial flow
Commentary by Dr. Valentin Fuster
1985;():V001T03A058. doi:10.1115/85-GT-219.
FREE TO VIEW

The mathematical derivation, and FORTRAN code, of a comprehensive but easy to use geometry model for axial flow turbine nozzles and rotors is presented. To uniquely define an airfoil on a cylinder the aerodynamicist need only specify the number of blades, and at each radius of interest: the axial and tangential chord, throat, uncovered turning, leading and trailing edge radii, inlet and exit blade angles, and inlet wedge angle. Default values exist for six of these geometric variables, which proves useful when starting a design. Both the suction and the pressure surfaces are described entirely by analytical functions. Sample airfoils are included that demonstrate the effect of each parameter upon blade shape.

Topics: Turbines , Geometry , Airfoils
Commentary by Dr. Valentin Fuster
1985;():V001T03A059. doi:10.1115/85-GT-220.
FREE TO VIEW

Several methods are available for the optimization of basic design parameters and the preliminary efficiency prediction of axial flow turbine stages. However, their application is often questionable for stages having low specific speed and/or small volume flow rates. In particular, the question may arise whether a better performance is achieved by a partial admission, impulse stage or by a full admission reaction stage having lower blade height.

The paper firstly reviews the available loss correlation methods applicable to partial admission turbines, then a comparison is performed between the efficiency achievable by partial and full admission stages designed for the same operating conditions. The turbine design procedure for both options is fully automatized by an efficiency optimization method similar to the one described in previous authors’ papers.

The results of calculations are presented in the paper as a function of similarity parameters (specific speed, size parameter, expansion ratio). It is found that the results obtained with different correlations are relatively similar for “conventional” turbine stages (low expansion ratio, moderate size parameters), while important differences take place for very small sizes and/or in presence of important compressibility effects.

The presented results can be useful: 1) to decide whether selecting full or partial admission solutions; 2) to optimize the degree of admission and the other basic design parameters, and 3) to predict with reasonable accuracy the stage efficiency.

Topics: Turbines
Commentary by Dr. Valentin Fuster
1985;():V001T03A061. doi:10.1115/85-GT-223.
FREE TO VIEW

The response of temperature measuring devices to pulsating flow fields has been a source of concern to compressor designers. A conventional temperature sensing device is known to respond to the highly energetic wake flow leaving a rotor and due to the long thermal time constant of the probe a temperature lying between the hot wake temperature and the relatively cooler main stream temperature tends to be indicated. This indicated temperature can be in serious error if included in a calculation to define the energy flux.

This work is concerned with a theoretical and experimental examination of temperature sensor response to an unsteady pulsating flow typical of that occuring in a compressor.

Commentary by Dr. Valentin Fuster
1985;():V001T03A062. doi:10.1115/85-GT-224.
FREE TO VIEW

A theoretical study of the development of rotating stall in axial compressors is presented. A small perturbation analysis is used for this purpose. The compressor is considered as a series of vaneless spaces and blade rows. The axisymmetric mean flow is of the free vortex type and blade rows are represented as actuator discs. The perturbations are three dimensional and steady with respect to a rotating reference frame. For high hub-tip ratio annuli the transfer relations for the perturbations are expressed in a matrix form. This formulation allows the prediction of the occurrence and development of rotating stall in single or multiple blade row configurations. The results of the prediction compare favourably with experimental data.

Commentary by Dr. Valentin Fuster
1985;():V001T03A064. doi:10.1115/85-GT-227.
FREE TO VIEW

In this paper we present the results of a detailed experimental study of the development of small rotating stall, as it appears in a one stage axial compressor. Stationary hot-wire probes are used to measure the variation of amplitude and propagation speed of the disturbances caused by small stall. Measurements near the rotor blade surface with rotating probes provide additional information on the nature of the phenomenon. The development of the cell pattern for different operating conditions is studied. The different character from what is known as “big stall” is demonstrated.

Topics: Compressors
Commentary by Dr. Valentin Fuster

Microturbines and Small Turbomachinery

1985;():V001T04A001. doi:10.1115/85-GT-123.
FREE TO VIEW

Turbocharger “lag” or poor response to engine load changes can be improved by reducing the rotating inertia of the turbocharger turbine, compressor and shaft system. Recently designed, second generation turbochargers all have small diameter, light weight rotating assemblies in an effort to minimize inertia and improve response. An automotive turbocharger with an axial flow turbine rather than a conventional radial inflow turbine is presented here as an alternative method of reducing inertia. The rotating inertia of the axial flow turbine and a centrifugal compressor is about one half that of the same compressor combined with a radial inflow turbine. In steady-state engine dynamometer tests, the same wide-open throttle performance was obtained with both turbochargers. Engine dynamometer transient tests showed that the turbocharger with the axial flow turbine attained full boost 25–40% faster than did the turbocharger with the radial inflow turbine.

Commentary by Dr. Valentin Fuster
1985;():V001T04A002. doi:10.1115/85-GT-124.
FREE TO VIEW

Future high performance aircraft will require more compact, lighter weight, and self-sufficient secondary power equipment capable of faster starting and delivering high specific powers over wider operating envelopes of inlet temperatures and altitudes.

Meeting these requirements may not be entirely compatible with improving thermal efficiency, particularly for the small air-breathing gas turbine since optimum cycle conditions differ for maximum specific power and specific fuel consumption. Further conflict lies in the necessity to provide faster start times with a limited capacity of stored on-board start energy, because compressor and turbine inertias must be minimized although compressor and turbine airflow-swallowing capacity must be maximized.

This paper discusses the numerous design disciplines which constrain power density for small gas turbine auxiliary power units. Several potentially profitable development avenues are suggested for continuing the improvement of aircraft system performance.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster
1985;():V001T04A003. doi:10.1115/85-GT-125.
FREE TO VIEW

The Patriot Air Defense Missile System (formerly SAM-D) is being deployed in Europe. The powerplant supplying electricity to the radar set and to the engagement control station is DOD Model D-424A, powered by the Allison Model GT-404 industrial gas turbine (IGT) engine. Designed as a vehicular engine, the application in a generator set is an interesting one, utilizing many of the following features originally intended to enhance the performance of trucks and buses:

• Dual, rotating disk regenerators dramatically improve fuel consumption by transferring heat energy from the exhaust gas stream to compressor discharge.

• Power transfer, intended to provide part load fuel economy in vehicles, is modified to furnish free-shaft start-fixed shaft run in generator sets.

• Free-shaft starts allow successful operation down to −50°F without auxiliary heaters.

The resultant gas turbine engine driven generator set — 150 kW, transportable, skid mounted, alternating current 400 Hz, tactical — has met the military requirements for performance and reliability.

Commentary by Dr. Valentin Fuster
1985;():V001T04A005. doi:10.1115/85-GT-177.
FREE TO VIEW

The Garrett/Ford AGT101 program has made significant progress during 1984 in ceramic component and engine test bed development, including initial ceramic engine testing. All ceramic components for the AGT101 [1644K (2500F)] engine are now undergoing development. Ceramic structures have been undergoing extensive analysis, design modification, and rig testing. AGT101 [1644K (2500F)] start capability has been demonstrated in rig tests. Also, 1644K (2500F) steady-state testing has been initiated in the test rigs to obtain a better understanding of ceramics in that environment.

The ceramic turbine rotor has progressed through cold spin test 12,040 rad/sec (115,000 rpm) and hot turbine rig test, and is currently in initial phases of engine test. Over 400 hours of engine testing is expected by March, 1985, including approximately 150 hours of operation and 50 starts on the 1422K (2100F) engine. All activities are progressing toward 1644K (2500F) engine testing in mid 1985.

Commentary by Dr. Valentin Fuster
1985;():V001T04A006. doi:10.1115/85-GT-182.
FREE TO VIEW

The precision generator set is a device required to be capable of step changes in electrical output from no-load to full-load almost instantaneously with essentially no change in frequency. As a result of the time required for a conventional turbocharger to respond to a load change, the precision generator set application has been the exclusive realm of relatively large naturally-aspirated engines, despite the potential weight and fuel consumption advantages of smaller, turbocharged units. The advent of variable turbine geometry for small, inexpensive turbochargers may provide the means by which turbocharged engines may enter into this specialized service. This paper describes the application of variable geometry turbocharging to the precision generator set from the feasibility study to the proof-of-concept as verified in the standard test series for such a generator set.

Commentary by Dr. Valentin Fuster
1985;():V001T04A007. doi:10.1115/85-GT-203.
FREE TO VIEW

A gas turbine/battery hybrid system adopted as the power plant to propell a passenger car has been in development to seek a better fuel economy to drive. The gas turbine engine is a single-shaft type having 86000 rpm which is coupled directly with a generator to yield electricity. The power is used either to propell wheels and/or to charge battery depending upon the operating conditions of the system. The aim of this study is to attain a better fuel economy by operating the engine only around its rating point regardless to the driving conditions of the vehicle. The experimental vehicle has been studied to evaluate the potential of this unique system. Based on the detailed study of the components of the system and the road-load testings of the vehicle, the potential is seen for the system to be superior than a conventional vehicle. This paper will descrive the experimental results of the vehicle performances by this stage suggesting a good potential of the system when developed fully.

Commentary by Dr. Valentin Fuster
1985;():V001T04A008. doi:10.1115/85-GT-204.
FREE TO VIEW

The KTT system is a gas turbine propulsion system designed especially for the automotive application. It’s main features are the three turbines on three different shafts and the close integration of the turbine and transmission into one unit.

The first experimental engine, the MkI, based on this system is being developed by United Turbine, a subsidiary to AB Volvo, in Sweden. This paper describes some results of the development of the main components for this engine; the compressor, the turbines and the heat exchanger system. Details on test equipment are given.

The results presented are not final and development continues. These results also provide a base for future engine designs.

Commentary by Dr. Valentin Fuster
1985;():V001T04A009. doi:10.1115/85-GT-205.
FREE TO VIEW

Recent activities on the AGT 100 Advanced Gas Turbine Program have included engine testing, aerodynamic component development, and ceramic material and component development. Engine testing has progressed in total hours and hours per build, without a major failure. A special mechanical loss test was conducted. Aerodynamic component activity has included the compressor, combustor and regenerator. Ceramic development was continued in areas of basic materials, processing, component fabrication and evaluation, and engine testing.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In