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Aircraft Engine

1986;():V002T02A001. doi:10.1115/86-GT-1.
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The small gas turbine jet fuel starter (JFS) and the expendable turbojet share common technology. Both designs are essentially constrained by high power density, low costs, and technology levels for small turbomachinery. Recognized early by the Air Force through the promotion of its expendable gasifier program, this common technology is now reaching fruition with initial development of the F-16 T-62 “Titan” JFS into a low cost turbojet. The relatively high production base for the T-62 Titan, which has more than 15,000 units of all models in service, plus a high degree of component commonality holds promising potential for realistic achievement of a low cost turbojet. Technical features of the Titan JFS and the turbojet are presented in this paper to demonstrate their common technology. Profitable technology avenues for improving power density and life cycle costs are discussed and recommendations made for development of higher performance levels.

Topics: Jet fuels , Turbojets
Commentary by Dr. Valentin Fuster
1986;():V002T02A002. doi:10.1115/86-GT-2.
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Today’s high technology gas turbine engines incorporate the world’s most exotic alloys and are built to some of the most precise dimensional tolerances encountered in any industry.

The constant drive for increased performance while substantially reducing fuel consumption and weight has pushed engine components and their designers to limits never before realized. To achieve these limits new methods and materials have evolved; not exclusively in the production of the engines but also in the repair and maintenance of them.

The typical problems encountered in repair and maintenance are numerous and varied as are their solutions. This paper, however, will concentrate on one in particular and that is the typical damage encountered on a first stage power turbine vane ring and the technology employed to repair such damage.

The vane ring was chosen because it is representative of a common problem encountered by all gas turbine engine manufacturers and simultaneously involves some of the most up to date repair techniques to restore it.

Commentary by Dr. Valentin Fuster
1986;():V002T02A003. doi:10.1115/86-GT-24.
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The increasing emphasis on engine durability requires that an analytical capability be acquired to assess engine component lives during the conceptual/preliminary design phases. A generalized methodology has been developed to provide a fundamental understanding of the impact of engine design decisions, material selections, and a detailed consideration of engine usage for critical gas turbine engine components.

Commentary by Dr. Valentin Fuster
1986;():V002T02A004. doi:10.1115/86-GT-28.
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In response to the need of the new generation of commuter airliners, General Electric has developed the CT7 Turboprop engine so that it may be used as an Auxiliary Power Unit (APU) in addition to its normal mission as a prime propulsion unit. The General Electric CT7 Turboprop is a 1700 shaft horsepower class engine (Figure 1) developed for the new generation of 30+ passenger commuter and executive aircraft(1). Beyond this, the CT7 engine now offers the airlines a self-contained APU system to provide bleed air for the Environmental Control System (ECS) and electrical power for the aircraft during ground operation. This negates the need for a separate on-board APU with its extra cost, weight and fuel consumption and also eliminates the requirements for ground power units at the airlines’ operational terminals. The development of the engine as an APU generated a new set of technical requirements for the design and development and necessitated the development of special certification requirements as this was a new and unique operating condition for an aircraft prime propulsion system. A propeller brake had to be developed to lock the propeller and power turbine system and the engine had to be designed to operate at or near idle while producing large amounts of bleed air and electrical power. This development program was successfully completed in mid-1985 with the certification of the aircraft to operate with the CT7 Turboprop engine running as an APU.

Topics: Engines
Commentary by Dr. Valentin Fuster
1986;():V002T02A005. doi:10.1115/86-GT-37.
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A major portion of the Life Cycle Cost (LCC) of a modern high technology weapon system is determined by design decisions made very early in the development process. Many of these decisions affect the design so fundamentally that later changes become impractical. Although a computerized weapon system LCC methodology has been developed at Pratt & Whitney to evaluate engine trades, its complexity limits its usefulness during preliminary design when the largest number of decisions must be made. This paper describes a technique used to provide a simplified version of this methodology to design engineers to conduct configuration/cost/performance trades. By supplying the designer with a simple, effective evaluation tool, LCC becomes an integral part of the design system from the beginning.

Commentary by Dr. Valentin Fuster
1986;():V002T02A006. doi:10.1115/86-GT-38.
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The critical nature of the TF34-100 engine to the Air Force’s A-10 Close Air Support weapon system made it important to obtain the best possible visibility of the engine’s future structural maintenance needs and component life limits. Accordingly, an in-depth structural durability and damage tolerance assessment was performed on this engine by a joint Air Force/General Electric team.

Results of the assessment team’s unprecedented analysis efforts culminated in a comprehensive Structural Maintenance Plan that identified both current and future maintenance actions necessary for insuring maximum flight safety. The plan entailed component inspection and replacement intervals, inspection systems, preferred modifications/reworks, and a life growth plan for extending the useful life of the TF34-100 upwards to 8000 A-10 mission hours.

This paper details the nature and extent of effort undertaken in conducting the 18 month structural assessment.

Topics: Engines , Durability , Damage
Commentary by Dr. Valentin Fuster
1986;():V002T02A008. doi:10.1115/86-GT-80.
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Since 1967 the Aviation Applied Technology Directorate (AATD) has sponsored four technology demonstrator engine programs. These programs have been established for purposes of verifying the engine technology level appropriate for the initiation of full scale engine development. While these were all highly successful, significant improvements have evolved in the approach to these programs. This paper discusses this evolution, lessons learned, and results.

Commentary by Dr. Valentin Fuster
1986;():V002T02A011. doi:10.1115/86-GT-172.
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NASA is sponsoring the Turbine Engine Hot Section Technology (HOST) Project to address the need for improved durability in advanced combustors and turbines. Analytical and experimental activities aimed at more accurate prediction of the aerothermal environment, the thermomechanical loads, the material behavior and structural responses to such loading, and life predictions for high temperature cyclic operation have been underway for several years and are showing promising results. Progress is reported in the development of advanced instrumentation and in the improvement of combustor aerothermal and turbine heat transfer models that will lead to more accurate prediction of thermomechanical loads.

Commentary by Dr. Valentin Fuster
1986;():V002T02A012. doi:10.1115/86-GT-181.
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Exciting developments have occurred over the past two years in the technological status and production aspects of Stratified Charge Rotary Engines. A program is currently underway for the development, certification and production of a 400 HP aircraft engine in early 1990. The joint program is being conducted by John Deere’s Rotary Engine Division and AVCO Lycoming Williamsport Division. The engine will offer to the General Aviation community Jet-A fuel capability at substantial cost savings, improved altitude capability and lower fuel consumption over turbine power plants. Application to fixed wing and rotary wing aircraft are planned.

Other stratified charge rotary engine development work in progress involves ground power units, airborne APU’s, shipboard gensets and vehicular engines, supported by Deere production capabilities and DOD interests. Technology enablement efforts by NASA, aimed at highly advanced output and efficiency are in progress leading toward revolutionary engine capability for aircraft and other applications.

Topics: Engines , Aviation
Commentary by Dr. Valentin Fuster
1986;():V002T02A013. doi:10.1115/86-GT-191.
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In the field of helicopter turboshaft engines, TURBOMECA is present in the range of 400 to 1 600 kW with four new engines, all under development. Naturally all these engines, born of a same general philosophy, have a pronounced ≪family likeness≫ from the general mechanical and aerodynamic point of view.

Topics: Engines
Commentary by Dr. Valentin Fuster
1986;():V002T02A014. doi:10.1115/86-GT-211.
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A new Interactive Cycle System has been developed by General Electric’s Aircraft Engine Business Group for the cycle analysis and performance optimization of conceptual and preliminary engine designs. This paper will explore some of the considerations in moving from a large, well-known, batch, detailed design, modeling system to a low-cost, flexible, responsive, user-friendly, interactive cycle analysis system. The resulting system utilizes menu screens for user input and data review, a modular program structure with stacking of modules to achieve the desired engine configuration, a library of component characteristics augmented by parametric component map generators, and an interpretive reader to permit real-time logic creation without the need for compiling.

Topics: Cycles
Commentary by Dr. Valentin Fuster
1986;():V002T02A015. doi:10.1115/86-GT-252.
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The NASA Ames-Dryden Flight Research Facility is sponsoring a flight research program designated Highly Integrated Digital Electronic Control (HIDEC), whose purpose is to develop integrated flight-propulsion control modes and evaluate their benefits in flight on the NASA F-15 test aircraft.

The Adaptive Engine Control System (ADECS I) is one phase of the HIDEC program. ADECS I involves uptrimming the P&W Engine Model Derivative (EMD) PW1128 engines to operate at higher engine pressure ratios (EPR) and produce more thrust. In a follow-on phase, called ADECS II, a constant thrust mode will be developed which will significantly reduce turbine operating temperatures and improve thrust specific fuel consumption.

A Performance Seeking Control mode is scheduled to be developed. This mode features an onboard model of the engine that will be updated to reflect actual engine performance, accounting for deterioration and manufacturing differences. The onboard engine model, together with inlet and nozzle models, are used to determine optimum control settings for the engine, inlet, and nozzle that will maximize thrust at power settings of intermediate and above and minimize fuel flow at cruise.

The HIDEC program phases are described in this paper with particular emphasis on the ADECS I system and its expected performance benefits. The ADECS II and Performance Seeking Control concepts and the plans for implementing these modes in a flight demonstration test aircraft are also described. The potential pay-offs for these HIDEC modes as well as other integrated control modes are also discussed.

Commentary by Dr. Valentin Fuster
1986;():V002T02A016. doi:10.1115/86-GT-266.
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This paper presents the results of a study using Pratt & Whitney’s probabilistic-based life analysis system to define the impact of damage tolerance requirements now being written into design specifications. An advanced turbine disk design was considered for several combinations of NDE starting with baseline values representative of actual material and NDE capabilities. Significant conclusions are:

(1) Conventional single-valued descriptions of NDE capability (e.g. 90/95, etc.) are incomplete for comparing competing NDE systems.

(2) The scatter about the mean NDE capability has little influence on system behavior.

These conclusions suggest that more complete descriptions of damage tolerance requirements should be considered. NDE requirements, for example, might be better stated in terms of system performance goals – acceptable failure and removal rates – rather than any specific POD/confidence limit requirement.

Topics: Damage
Commentary by Dr. Valentin Fuster
1986;():V002T02A017. doi:10.1115/86-GT-274.
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Incorporation of the Turbine Engine Structural Integrity Program (ENSIP) has provided a more organized and disciplined approach to the durability related aspects of the engine demonstrator program. As a result, engine capabilities are more easily related and the number of durability problems is reduced. This is accomplished by increased contractor/customer interface in the design analysis, material characterization and verification testing of the engine programs. The demonstrator program has been affected by the ENSIP requirements, particularly the Damage Tolerance aspects. The design analysis is more complex while the configurations tend to be simpler with fewer notched locations. Materials are developed for improved crack propagation life while component and engine testing is expanded to verify this capability. The ENSIP specification effects increases in analysis, materials development, verification testing and durability.

Topics: Engines
Commentary by Dr. Valentin Fuster
1986;():V002T02A018. doi:10.1115/86-GT-277.
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In the field of today’s military aircraft engines, the engine control system consists in most cases of hydromechanical controls, as such, with an electronic supervisory system. This type of control makes the integration of engine and aircraft systems rather difficult. Even with the Tornado engine which features a full authority electronic engine controller, only initial steps in systems integration are realized.

With the introduction of digital electronics into both the engine control and the aircraft systems, together with the availability of data highway systems, large scale systems integration can be envisaged on future fighter aircraft, with the resultant improvement in overall weapon system performance.

This paper puts forward a proposal for a control concept for a reheated fighter engine, and outlines possibilities for integration with aircraft systems.

Commentary by Dr. Valentin Fuster
1986;():V002T02A019. doi:10.1115/86-GT-280.
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I have developed and implemented a computer subroutine (UNCERT) that greatly simplifies the immense problems associated with most uncertainty analyses. This paper presents an overview of the most fundamental and important concepts in uncertainty analysis, a technique which can be used by a test engineer to estimate the accuracy of measured data and values calculated from measured data. Implementation of these uncertainty concepts in a computer code is also explained. Some of the results of an uncertainty analysis which was accomplished for a turbine engine compressor test are used to illustrate the analysis procedure and results. Finally, the benefits of doing an uncertainty analysis as part of a test are briefly discussed.

Commentary by Dr. Valentin Fuster
1986;():V002T02A020. doi:10.1115/86-GT-295.
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In this paper propulsion system integration is considered for an advanced twin engined, high performance agile air to air fighter aircraft in view of its requirements for extreme flight conditions and maneuvers.

The propulsion system mainly consists of air inlets, engines and nozzle/afterbody systems.

The air inlet, a propulsion subsystem within the aircraft manufacturers responsibility, is physically well integrated with the aircraft flight control system, processing hardware being part of it.

The engine itself, as the most complex propulsion subsystem and not within the aircraft manufacturers responsibility, is to have very simple and clearly defined interfaces with the aircraft. Its integration must therefore be on this basis i.e. functional.

A central utility data bus allows for easy communication between the engine control system and all relevant aircraft systems through a single point interface in normal operation.

This improved communication allows for better performance, operation and handling of the engine.

A special feature of the propulsion system is the vectoring nozzle system with thrust deflection for maneuvers at high angles of attack beyond maximum lift. This system is also integrated with the flight control system.

Commentary by Dr. Valentin Fuster
1986;():V002T02A021. doi:10.1115/86-GT-300.
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Engine Condition Monitoring (ECM) for an airline is a basic need to make its engine operation as economic as possible.

This paper describes the ECM development at KLM-Royal Dutch Airlines.

The objectives and philosophy of the systems are discussed, as well as the current and future functions and the use in the airline organisation.

Commentary by Dr. Valentin Fuster

Marine

1986;():V002T03A001. doi:10.1115/86-GT-142.
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This paper discusses the use of 570/571-KF engine in patrol boat propulsion applications. The text is composed of two basic sections — 1. The Engine, and 2. The Applications:

The engine section includes a brief review of the background and development of this free turbine engine, as well as a description of the main components and design features. The performance characteristics and fuel consumption rates are discussed relative to patrol missions.

In the applications section a comparison is made of the current 570 installations (both civil and military), along with a survey of the planned applications. Finally a review of proposed uses of these engines in other naval vessels is included to show the adaptability of this size engine in FPB and PB missions, and demonstrate the feasibility of retrofitting other turbine or diesel powered patrol boats with 570/571-KF engines.

The conclusion is drawn that for patrol boats with conventional or modified hull forms, the Allison 570/571 engines are well suited due to their excellent performance and power density ratios.

Commentary by Dr. Valentin Fuster
1986;():V002T03A002. doi:10.1115/86-GT-202.
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This paper discusses the prospects of using coal as the primary source of energy to power gas turbines for marine propulsion applications. The problems associated with burning coal for generating power are reviewed in terms of their inherent limitations, environmental effects, compatibility with turbomachinery combusters, and economic considerations. Various forms of coal-based heat sources and their applicable combuster system configurations are identified. Integration of these fuel/combustor combinations with different gas turbine cycles yields a number of possible coal-fired gas turbine systems. A comparison of these candidate systems with marine propulsion system requirements resulted in the selection of a COGAS system burning coal-oil slurry. Candidate COGAS system configurations are presented, and the overall propulsion engine performance is defined.

A baseline coal-oil fired marine COGAS propulsion system was selected, and its performance characteristics were estimated, taking into account the exhaust gas flow effect on the waste-heat steam generator. The payload capabilities and endurance limitations for a coal-fired COGAS ship are presented and compared with those of a conventional oil-fired ship to show the possible fuel cost savings.

Commentary by Dr. Valentin Fuster
1986;():V002T03A003. doi:10.1115/86-GT-203.
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Adverse consequences of losing electrical power to complex electronic and fire control equipment, or of the sudden variations of shore power, cause naval combatants to operate two generators most of the time, each at light load where specific fuel consumption of simple-cycle gas turbines is particularly high. The recuperated gas turbine with variable power-turbine nozzles has a much better specific fuel consumption, especially at part load. Herein described is a compact recuperated gas turbine with variable power-turbine nozzles designed for marine and industrial use, suitable with or without intercooling. These features yield a specific fuel consumption that is comparable to marine diesels used for generator drive, and essentially flat across the entire usable load range.

Topics: Engines , Generators
Commentary by Dr. Valentin Fuster
1986;():V002T03A004. doi:10.1115/86-GT-224.
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Modifying a simple-cycle gas turbine to include heat exchangers can improve its thermal efficiency significantly (as much as 20%). Advanced regenerative and intercooled regenerative gas turbines for marine application have recently been the subjects of numerous studies, most of which have shown that lower fuel comsumption can be achieved by adding heat exchangers to existing simple-cycle gas turbines. Additional improvements in thermal efficiency are available by increasing the efficiency of the turbomachinery itself, particularly that of the gas turbine’s air compressor. Studies by Caterpillar Tractor Company and Solar Turbines Incorporated on a recuperated, variable-geometry gas turbine indicate an additional 8 to 10% improvement in thermal efficiency is possible when an improved higher efficiency compressor is included in the gas turbine modification. During these studies a novel (Axi-Fuge) compressor was devised. This paper discusses the Axi-Fuge concept, its origin, design criteria and approach, and some test results.

Topics: Compressors
Commentary by Dr. Valentin Fuster
1986;():V002T03A005. doi:10.1115/86-GT-256.
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The paper gives a basic description of the stratified charge combustion process in the Stratified Charge Omnivorous Rotary Engine - SCORE. The inherent advantages of the Wankel geometry combined with spark ignition of a stratified mixture for a unique combustion cycle are explained with diagrams. The discussion points out why the engine is neither octane or cetane sensitive, making it a truly multifuel (omnivorous) intermittent combustion engine.

A brief description of the parts and their function help to explain the inherent compactness of the engine and confirm its simplicity and efficiency. The engine specific size, weight, air flow and fuel flow are compared to an equivalent output turbine engine to place the performance in a familiar context.

A most impressive feature of the engine, attractive cost of production, is demonstrated by the modular nature of its design. This feature is amplified by an in-depth description of the “Family of Engines” concept, highlighting the large number of common parts in a family of one to six rotor models. The ability to cover a complete market segment with one geometry is attractive for production costs, service, training and logistics.

Modular design also enhances application flexibility. Development programs are underway for a diversity of applications for families of SCORE engines. Each application utilizes the unique characteristics available with this engine and is further justified by the economies realized in volume production. Thus low volume, high power applications (1000kW and up) can realize savings by utilizing the same major parts tooled for higher volume use in smaller engines.

Some potential applications are discussed with particular emphasis on marine installations. Specific comparisons with other powerplants for shipboard electrical generation are presented.

Topics: Engines
Commentary by Dr. Valentin Fuster
1986;():V002T03A006. doi:10.1115/86-GT-269.
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The General Electric LM2500 Marine Gas Turbine, currently used by the United States Navy as main propulsion on various classes of ships, lends itself very easily to a procedure known as photoborescopy. Photoborescopy is that process where discrete, color photographs are taken of various internal parts of the engine. Borescoping in itself is not new, but maximizing the borescopes capabilities is a program that the U.S. Navy continuously is developing at the Naval Ship Systems Engineering Station (NAVSSES) in Philadelphia, Pennsylvania.

This paper will describe the photoborescopy technique used by NAVSSES and also give and show graphically the Fleet experience with two LM2500’s which had accumulated 10,000 hours of successful at-sea operation.

The opinions expressed herein are those of the author and not necessarily of the Department of Defense or the Navy Department.

Commentary by Dr. Valentin Fuster
1986;():V002T03A007. doi:10.1115/86-GT-270.
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Since the widespread adoption of gas turbines as the main power sources on offshore platforms throughout the world the special problems associated with the filtration of the air entering such engines have naturally received some attention.

Commentary by Dr. Valentin Fuster
1986;():V002T03A008. doi:10.1115/86-GT-284.
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The paper will describe the engine and its derivation from the AGT1500 automotive gas turbine. Changes and variations of the AGT-1500 control system to accommodate the requirements of marine propulsion will be described. Some of the proposed propulsion system schemes will also be discussed.

Commentary by Dr. Valentin Fuster

Microturbines and Small Turbomachinery

1986;():V002T04A003. doi:10.1115/86-GT-23.
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The design of a small inward flow turbine with a 3.6 expansion ratio has been undertaken by MICROTURBO, in cooperation with ONERA for calculations and test results analysis.

Initially, the purpose and constraints of this study are underlined. Preliminary calculations have led to the design of the blade shape of the Nozzle Guide Vane and of the rotor. Following this, the results of the quasi-3D-flow computations, performed for the stator and the rotor, are given. Both the cold bench tests on this turbine and the corresponding hot tests on the turboshaft engine enable performances to be checked. The value of the calculations is confirmed when we look at the high total and static adiabatic efficiencies obtained. These good results are encouraging for the future use of this kind of turbomachine.

Topics: Turbines
Commentary by Dr. Valentin Fuster
1986;():V002T04A004. doi:10.1115/86-GT-93.
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The AGT 100 is an advanced gas turbine designed for passenger car application. The most significant of its advanced features is the use of structural ceramic components for the hot section of the engine’s flow path. The engine was expressly designed for ceramic components; previously, ceramic materials were simply substituted for metal components. Early experimental builds of the AGT 100 contained many ceramic components and metal substitutes for the more complex ceramic components that were not yet fabricated.

Engine testing has continued to accumulate operating time on the ceramic components that have always been engine-worthy (combustor, regenerator, vanes, rings and spacers, piston ring). Recent engine tests have included both a ceramic turbine rotor and static structure (scroll, vanes, backplates, coupling). Each type and shape of ceramic component has now been engine tested. Development is continuing to improve them even further.

Commentary by Dr. Valentin Fuster
1986;():V002T04A005. doi:10.1115/86-GT-130.
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Centrifugal impeller with splitters is one of the design techniques used in small engines. Many such engines are operating in different environmental conditions. One of which is where the atmosphere is polluted by small solid particles. Engines operating in such particulate environment are exposed to erosion and performance deterioration.

In this paper the flow field through an impeller with two different size splitters is presented. The mean streamline pattern in the meridional plane was estimated by the computer code ‘MERDIL’, and an improved panel method was used to calculate the blade-to-blade flow solution. In addition, the particle trajectories were calculated by direct integration of the particle equations of motion. Particle collisions with the blade, hub and casing surfaces were determined. The data obtained from this analysis can be applied for calculating the erosion and performance deterioration in turbomachinery with such impellers.

Commentary by Dr. Valentin Fuster
1986;():V002T04A006. doi:10.1115/86-GT-168.
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A conventional diffusion-flame combustor and a two-stage combustor, both made of ceremics, were tested using various fuels.

In both combustors, CO, HC and smoke emission were extremely low even when using heavy-B fuel because of higher than normal inlet temperature of up to 1200 K; however, a great amount of NOx emission was observed in the conventional diffusion-flame combustor. When low-nitrogen fuels such as kerosene were used, a successful reduction of NOx was achieved by providing lean combustion in an improved diffusion-flame combustor. For high-nirogen fuels, the conversion fraction of fuel nitrogen to NOx could be minimized by keeping the equivalence ratio slightly rich in the first stage of the two-stage combustor.

Commentary by Dr. Valentin Fuster
1986;():V002T04A007. doi:10.1115/86-GT-198.
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In a rotary regenerator, the matrix- and fluid-temperature distribution in space and time on either side (hot and cold) of the matrix is governed by a coupled system of partial differential equations (PDEs). These are derived from a heat balance under the usual assumption that heat transfer between fluid and matrix is by convection only.

The system of PDEs for the temperature distribution has generally been believed to be not analytically solvable in the case of a regenerator with finite heat transfer coefficients.

In this paper, the analytical solution is given by means of a Laplace transform combined with linear operator theory.

Furthermore, an iterative numerical scheme for calculating the regenerator performance under steady state and transient conditions, based on the analytical representation, is given.

Topics: Temperature , Fluids
Commentary by Dr. Valentin Fuster
1986;():V002T04A008. doi:10.1115/86-GT-199.
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The paper considers the design and the application of ceramic components in a high temperature gas turbine, which is being developed as an alternative for passenger-car propulsion. Silicon nitride turbine wheels were analyzed using 3-dimensional finite element methods.

Calculations of temperatures and stresses were carried out for several steady-state and transient load conditions. Time dependent reliability was also computed using the theory of Weibull including subcritical crack growth.

The results of these calculations are presented and discussed. The basic theory for ceramic life prediction methodology is reviewed, including the relative importance of various parameters. From the results, conclusions are derived for ceramic design. Finally some operating-experiences of ceramic turbine wheels are reported.

Commentary by Dr. Valentin Fuster
1986;():V002T04A009. doi:10.1115/86-GT-272.
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Nondestructive evaluation of ceramic turbine components has to give special consideration to geometrical as well as to material requirements of these parts. Test procedures have to be able to detect all essential defects. As present X-ray penetration, especially the microfocus technique, is the most promising examination routine for special ceramics of complex shape.

Actual developments discussed, include the use of image intersifiers for real time monitoring and utilization of digital image processing to increase defect detectability, to decrease costs and to fabricate ceramic turbine parts of higher reliability.

Commentary by Dr. Valentin Fuster
1986;():V002T04A010. doi:10.1115/86-GT-282.
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Gas turbine driven Auxiliary Power Units (APU) have been used in both military and commercial aviation support systems for more than 30 years. APUs installed on-board aircraft provide electrical, hydraulic and pneumatic power to assist and support the vehicle and the main propulsion systems. Ground carts provide similiar functions for mission preparation and maintenance as well as mobile electric power. Other applications include tracked combat vehicles and ground shelter units.

The primary attributes of the gas turbine have given it a solid foothold in the aircraft APU market. Non-aviation applications, however, have been limited because of the turbine’s high acquisition cost and high fuel consumption relative to other available engines. Reducing specific fuel consumption is not as inherently valuable as reducing cost and increasing reliability since engine acquisition and maintenance costs of APUs dominate life cycle costs.

Commentary by Dr. Valentin Fuster
1986;():V002T04A011. doi:10.1115/86-GT-285.
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The Garrett GTCP36-300 Series Auxiliary Power Unit is being developed for use on advanced technology transport aircraft in the 150-passenger size class. The first application will be the Airbus Industries A320 Aircraft. The APU uses a 6:1 pressure ratio, single-stage compressor and turbine, driving a single-stage load compressor and accessory gearbox. The 480 horsepower APU delivers compressed air to the aircraft pneumatic system and drives a customer furnished 90 kva, 24,000 rpm electrical generator. State-of-the-art aerodynamics, materials, and digital electronics are used to give the user-airlines an APU delivering maximum performance with minimum envelope, weight, and cost of ownership.

Commentary by Dr. Valentin Fuster
1986;():V002T04A012. doi:10.1115/86-GT-301.
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Operating tests on a Lysholm helical expander have been done to develop a data base for comparing the performance of helical expanders with turbine expanders by using simple scaling arguments. The eventual goal of such work would be to develop a rugged and reliable ceramic helical expander for operating at temperatures up to 1300°C (2400°F). We used a 127.5 mm (5.020 in.) metal expander on which we measured seven performance variables against applied pressure ratio at six shaft speeds and an inlet gas temperature of 100°C (212°F).

Our data system included: a torque and angular-speed cell to measure power; flow, pressure, and temperature instrumentation; and a data reduction program. Test results are presented in seven data plots; equations for computing the performance variables are tabulated.

Adiabatic efficiency was found to be at least 85% in the pressure ratio range of 2.75 to 5.00. Performance is strongly influenced by gas leakage. Large machines with clearance ratios the same as smaller machines would benefit by size scaling effects. We expect that ceramic helical expanders for 1300°C service would be able to operate at adiabatic efficiencies higher than 85%.

Commentary by Dr. Valentin Fuster
1986;():V002T04A013. doi:10.1115/86-GT-305.
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The Garrett/Ford Advanced Gas Turbine Technology Development Program, designated AGT101, has made significant progress during 1985 encompassing ceramic engine and ceramic component testing. Engine testing has included full speed operation to 100,000 rpm and 1149C (2100F) turbine inlet temperature, initial baseline performance mapping and ceramic combustor start and steady state operation. Over 380 hours of test time have been accumulated on four development engines. High temperature foil bearing coatings have passed rig test and a thick precious metal foil coating selected for engine evaluation.

Ceramic structures have been successfully rig tested at 1371C (2500F) for over 27 hours. Interface compatibility testing conducted during these runs indicate RBSN-to-RBSN or SASC-to-SASC result in “sticking” — however, RBSN-to-SASC in either planar or line contact show no evidence of sticking. Ceramic combustor rig tests have demonstrated acceptable lightoffs using either a conventional ignitor or a commercially available glow plug. Operation to 1371C (2500F) combustor discharge temperatures have also been demonstrated. Ceramic turbine rotor fabrication efforts have continued at ACC and Ford. Kyocera and NGK-Locke also have been working on the rotor. Several rotors have been received and are currently undergoing final machining and qualification tests. Testing of the all-ceramic AGT101 engine is currently scheduled for late 1985.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster

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