bluuebunny/crossref_metadata_2025 huggingface dataset:
Combustion Gas Properties: Part III—Prediction of the Thermodynamic Properties of Combustion Gases of Aviation and Diesel Fuels
Authors: Gu¨lder O¨mer L.
Published: October 2009

Empirical formulae are presented by means of which the specific heat, mean molecular weight, density, and specific heat ratio of aviation fuel-air and diesel fuel-air systems can be calculated as functions of pressure, temperature, equivalence ratio, and hydrogen-to-carbon atomic ratio of the fuel. The formulae have been developed by fitting the data from a detailed chemical equilibrium code to a functional expression. Comparisons of the results from the proposed formulae with the results obtained from a chemical equilibrium code have shown that the mean absolute error in predicted specific heat is 0.8 percent, and that for molecular weight is 0.25 percent. These formulae provide a very fast and easy means of predicting the thermodynamic properties of combustion gases as compared to detailed equilibrium calculations, and they are also valid for a wide range of complex hydrocarbon mixtures and pure hydrocarbons as well as aviation and diesel fuels.
Wet Peat Power Processes: A Thermodynamic Study
Authors: Lyngfelt A. , Stenberg P.
Published: October 2009

The efficiencies of four power processes for wet peat have been studied. These include gas turbine cycles, steam power cycles, and combinations thereof. It is concluded that wet peat can be used in power processes with reasonable efficiency. The paper suggests that wet peat power processes could be cost competitive relative to conventional power production.
A Steady-State Thermal Performance Model of Fire-Tube Shell Boilers
Authors: Huang B. J. , Yen R. H. , Shyu W. S.
Published: October 2009

A nonlinear steady-state thermal performance model of a fire-tube shell boiler was developed in the present study. The model consists of two semi-empirical equations for the radiative heat flux from the combustion gas to the boiling water and the heat loss flux from the body surface to the ambient. Using this model, we can simulate the boiler performance under standard conditions and draw standard performance curves from which the thermal performance comparison between different boilers can be made on a common basis.
The Mechanism of Corrosion–Erosion in Steam Extraction Lines of Power Stations
Authors: Sanchez-Caldera L. E. , Griffith P. , Rabinowicz E.
Published: October 2009

Corrosion-erosion occurs in steam extraction piping made of low carbon steel that conveys wet steam. The rate of metal removal peaks at 150°C and is most severe on the inside and outside of bends and in the vicinity of fittings. A theory is presented by which three processes are shown to give rise to the observed peak in the metal removal rate: (1) the oxidation reaction, (2) the mass transfer process, which governs at 150°C, and (3) the diffusion resistance of the oxide layer, which governs at higher temperatures. The results of the derived model agree well with the available experimental data in predicting wear rates and in establishing the temperature and the location of maximum material removal.
Computer Simulation of Transport Phenomena in Evaporative Cooling Towers
Authors: Benton D. J. , Waldrop W. R.
Published: October 2009

A computer model of the simultaneous heat, mass, and momentum transfer processes occurring throughout an entire cooling tower is described in this paper. The model includes the flexibility to analyze the several configurations, fill arrangements, and flow distributions commonly used by the power industry. The fundamental governing equations are solved using a finite-integral technique to provide a quasi-two-dimensional description of the flow and cooling process within the tower. The model has been successfully compared with field data from cooling towers at three TVA power plants as well as data from other utilities. Each of these towers was significantly different in design, thereby demonstrating the versatility of the model for correctly predicting the cooling performance of mechanical and natural draft towers, as well as crossflow and counterflow orientations, for a range of meteorological and plant operating conditions.
Sensitivity of the Acoustical Resonance Measurement of Particle Loading in Gas-Solids Flow
Authors: Vetter A. A.
Published: October 2009

Measurement of the frequency of transverse acoustic resonances of a duct can determine the mass loading and size of particles fluidized by a gas phase. A first-order perturbation-iteration acoustic analysis is applied to determine the sensitivity of this two-phase flow measurement, termed the Acoustical Resonance Measurement, to variations in particle size, particle size dispersion, particle heat capacity, temperature, and pressure for the application of pulverized coal fluidized by air.
Performance of the Integrated Gas and Steam Cycle (IGSC) for Reheat Gas Turbines
Authors: Takeya K. , Yasui H.
Published: October 2009

In 1978, the Japanese government started a national project for energy conservation called the Moonlight Project. The Engineering Research Association for Advanced Gas Turbines was selected to research and develop an advanced gas turbine for this project. The development stages were planned as follows: first, the development of a reheat gas turbine for a pilot plant (AGTJ-100A), and second, a prototype plant (AGTJ-100B). The AGTJ-100A has been undergoing performance tests since 1984 at the Sodegaura Power Station of the Tokyo Electric Power Co., Inc. (TEPCO). The inlet gas temperature of the high-pressure turbine (HPT) of the AGTJ-100A is 1573 K, while that of the AGTJ-100B is 100 K higher. Therefore, various advanced technologies have to be applied to the AGTJ-100B HPT. Ceramic coating on the HPT blades is the most desirable of these technologies. In this paper, the present level of development, and future R & D plans for ceramic coating, are taken into consideration. Steam blade cooling is applied for the IGSC.
A Modified, High-Efficiency, Recuperated Gas Turbine Cycle
Authors: El-Masri M. A.
Published: October 2009

The thermal efficiency of an intercooled/recuperated cycle may be increased by: (a) evaporatively aftercooling the compressor discharge; and (b) injecting and evaporating an additional amount of water in the recuperator. Comparative computations of such a modified cycle and intercooled/recuperated cycles carried out over a wide range of pressure ratios and turbine inlet temperatures and at two different levels of component technologies show an advantage of over five percentage points in efficiency for the modified cycle. About 60 percent of this improvement results from modification (a) and 40 percent from modification (b). The modified intercooled/recuperated cycle is compared with nonintercooled steam-injected gas turbine systems at each component technology level. The present cycle is found to be superior by about 2.75 percentage points in efficiency and to require a substantially smaller water flow rate. To assist in interpreting those differences, the method of available-work analysis is introduced and applied. This is identical to exergy analysis for systems with a pure-substance working fluid, but differs from the latter for systems using a mixture of pure substances insofar as the thermodynamic dead state is defined for the chemical and phase composition realized at the exhaust conditions of practical engineering devices and systems. This analysis is applied to the heat-recovery processes in each of the three systems considered. It shows that the substantial, fundamental available-work loss incurred by mixing steam and gases in the steam-injected system is the main reason for the superior efficiency of the precent cycle.
The Design and Development of an Advanced Heavy-Duty Gas Turbine
Authors: Brandt D. E.
Published: October 2009

Significant advances in all elements of gas turbine design technologies have occurred during the past decade. These developments have created a technical climate conducive to the creation of a totally new heavy-duty gas turbine, as opposed to the uprating of an existing design. This paper discusses the features and characteristics of a new heavy-duty gas turbine that takes advantage of the latest technological advances. Discussed are the basis for design parameter selection, the operating characteristics, the materials of construction, and the component design features. Also presented are the features and performance of the unique combustion system and the results of and plans for component and prototype testing. This paper represents a comprehensive treatment of this advanced gas turbine, which is in the initial manufacturing stage in preparation for extensive factory testing followed by shipment to a customer by mid-1988.
Research and Development on the HPT of the AGTJ-100B
Authors: Arai M. , Imai T. , Teshima K. , Koga A.
Published: October 2009

The final target of development of the advanced gas turbine sponsored by MITI of Japan is a thermal efficiency of over 55 percent at an HPT inlet temperature of 1400°C as a combined plant. In order to attain this target, a feasibility study of the design and various R & D tasks have been conducted. This paper will first present the basic plan and then some important R & D items.
Economic Considerations for a New Gas Turbine System in the U.S. Navy
Authors: Ness J. C. , Franks C. B. , Sadala R. L.
Published: October 2009

During the phases of a U.S. Navy acquisition program for any new system, such as a gas turbine system, various analyses are conducted to evaluate the economic and technical benefits that can be gained by the new system. It is important that the economic analyses provide a good estimation of the nonrecurring and recurring costs. For the development of a new gas turbine system, a test program to prove the system’s technical and operational capability will have to be conducted and a support system will have to be developed to operate and maintain it during its life cycle. The costs of the engine development, the test program, and the support system development are considered nonrecurring or investment costs. The operation and maintenance costs over the life of the system are the recurring costs. This paper presents the life cycle cost scenario that should be used to evaluate the economics of a U.S. Navy marine gas turbine and the considerations that should be included in a Return on Investment analysis of the engine. The major cost categories discussed include engineering, logistics support, program management, and deployment support. Also, the unique considerations that would apply to marine gas turbines for Naval use are discussed along with how these considerations affect the economics of a gas turbine acquisition program. In addition, the paper identifies the funding responsibility of each cost item and provides discussion on ways to reduce the investment cost.
Explosive Decompression Resistance of Centrifugal Compressor O-Ring Seals: A Comparative Test Summary and Procedure
Authors: Shade W. N. , Legg D. W.
Published: October 2009

Explosive decompression is a phenomenon that can destroy O-ring sealing elements in high-pressure (>3.4 MPa) natural gas compressors during rapid venting to atmospheric pressure. A test rig and procedure have been developed to identify important parameters influencing O-ring seal explosive decompression failure, consistent with utilization of these seals in high-pressure centrifugal compressors. The test rig and procedure are described and comparative test results presented.
Advanced Composite Turboprops: Modeling, Structural, and Dynamic Analyses
Authors: Aiello R. A. , Chi S.
Published: October 2009

This paper presents a structural and dynamic analysis of a scaled-down wind tunnel model prop-fan blade made from fiber composites. This blade is one of a series of prop-fan blades that have been tested at the Lewis Research Center wind tunnel facilities. The blade is highly swept and twisted and of the spar/shell construction. Due to the complexity of the blade geometry and its high performance, it is subjected to much higher loads and tends to be much less stable than conventional blades. The structural and dynamic analyses of the blade were performed using the NASA-Lewis COBSTRAN computer code. COBSTRAN is designed to generate the mesh and calculate the anisotropic material properties for composite blade analysis. Comparison of analytical and experimental mode shapes and frequencies are shown, verifying the model development and analysis techniques used. The methodologies and programs developed for this analysis are directly applicable to other prop-fan blades.
Advanced Real-Time Powertrain Systems Analysis
Authors: Powell B. K. , Lawson G. P. , Hogh G.
Published: October 2009

This paper describes a combined analytical and experimental hardware-in-the-loop powertrain systems analysis methodology. Central to the implementation of this methodology is a real-time dynamic system simulation computer such as the high-speed Applied Dynamics Model AD10. For automotive engine control system studies, wide bandwidth in-cylinder combustion pressure sensor signals are input to the AD10 computer. Control commands are calculated and communicated at high data rates to throttle valve, spark ignition, and fuel injector actuators. Both simulation and experimental results are presented. Using this approach, the functional improvements associated with various control philosophies can be determined.
A Natural Gas Engine Combustion Rig With High-Speed Photography
Authors: Snyder W. E. , Wright M. R. , Dexter S. G.
Published: October 2009

Engines today must satisfy stringent emission requirements but must at the same time have low fuel consumption. One method of approaching both of these goals in spark-ignited natural gas engines is with lean combustion. The use of as much as 80 percent excess air significantly reduces the peak combustion temperature and, as compared to a stoichiometric engine, reduces the NOx emissions by up to 90 percent and the fuel consumption by up to 15 percent. One limitation on lean combustion, however, is the high energy needed for ignition. In larger engines, a small prechamber containing an easily ignitable near-stoichiometric mixture has proved to be both successful and popular as one method of producing the necessary high ignition energy. Although this form of stratified charge combustion has been known for many years, its development has largely been the result of “cut and try” procedures. Lack of access for suitable instrumentation, combined with the difficulty of isolating the individual variables which affect performance, has limited the fundamental understanding of the mechanism of prechamber combustion. This paper summarizes results from a research program where a constant-volume combustion rig is used to simulate engine operation. Emphasis is placed on high-speed photography of the prechamber combustion. A second program on a single-cylinder prechamber spark-ignited gas engine and a third on a multiple-cylinder engine will be reported in subsequent papers.
Pielstick Experience With Dual-Fuel Engines and Cogeneration
Authors: Grosshans G. , Litzler M.
Published: October 2009

SEMT PIELSTICK has developed since 1971 a range of medium-speed dual-fuel engines with relatively high air-fuel ratios, which enable ratings similar to diesel engines. The PC 2.3 DF.C of 1971 was developed up to 535 hp/cyl. and was followed by the PC 2.5 DF.C of 600 hp/cyl. This later engine was applied in the West German cogeneration plan of a textile factory, giving more than 82 percent use of primary energy. This engine may also be used as a pollution-abating machine, because it traps toxic solvent vapors, which are burned in the engine, reducing furthermore the apparent (paid) energy consumption. Thanks to the lean air-gas mixture, the very severe West German limits on pollution could be fulfilled without any extra depolluting device. The newest development is the PA 5 DF engine of the same philosophy, which will cover the 1000 to 3600 kW range.
Experimental Investigation of Electrostatic Dispersion and Combustion of Diesel Fuel Jets
Authors: Bankston C. P. , Back L. H. , Kwack E. Y. , Kelly A. J.
Published: October 2009

An experimental study of electrostatically atomized and dispersed diesel fuel jets has been conducted. A new electrostatic injection technique has been utilized to generate continuous, stable fuel sprays at charge densities of 1.5–2.0 C/m3 of fluid. Model calculations show that such charge densities may enhance spray dispersion under diesel engine conditions. Fuel jets were injected into room temperature air at one atmosphere at flow rates of 0.25–1.0 cm3/s and delivery pressures of 100–400 kPa. Measured mean drop diameters were near 150 μm with 30 percent of the droplets being less than 100 μm in diameter at typical operating conditions. The electrical power required to generate these sprays was less than 10−6 times the chemical energy available from the fuel. The spray characteristics of an actual diesel engine injector were also studied. The results show considerable differences in spray characteristics between the diesel injector and electrostatic injection. Finally, ignition and stable combustion of electrostatically dispersed diesel fuel jets was achieved. The results show that electrostatic fuel injection can be achieved at practical flow rates, and that the characteristics of the jet breakup and dispersion have potential application to combustion systems.
Simulation of the Gas Exchange Process of a Two-Stroke Cycle Gasoline Engine
Authors: Sato K. , Nakano M.
Published: October 2009

This report deals with a study concerning the scavenging performance of a two-stroke cycle gasoline engine under the following conditions: the throttle of the carburetor is set at variable levels, the delivery ratio is set at a predetermined level, the engine speed is varied, and the scavenging and exhaust ports are set at different heights. If the properly selected factors stipulated for a scavenging model are used, the calculated results can be made as consistent as the measured results of the carburetor set at full throttle, as discussed in the previous reports [1, 2]. The mass diffusion, mixing, and short-circuit factors make up the essential coefficients. The factors represent major characteristics: blow-back, return-blow, and the loss of fresh gases. These phenomena are more clearly illustrated by three-dimensional representations of the gas components in the scavenging passage and exhaust pipe. The analyses of these functions may provide an effective means of improving the scavenging performance, i.e., the delivery ratio, trapping efficiency, and charging efficiency.
Progress on the Investigation of Coal-Water Slurry Fuel Combustion in a Medium Speed Diesel Engine: Part 1—Ignition Studies
Authors: Hsu B. D.
Published: October 2009

A micronized de-ashed coal-water slurry (CWS) fuel of approximately 50 percent coal loading has been successfully ignited and burned in one GE 7FDL engine cylinder at 1050 rpm. For this study, only about 1/3 of the full load fuel engery was supplied due to limitations of the fuel injection equipment used. Three types of ignition methods have been investigated: compression ignition with no ignition aid; separate diesel pilot fuel injection to ignite the CWS fuel; combined CWS and pilot diesel fuel injection (stratified pilot ignition). Conditions of ignition and the burning characteristics that immediately followed using the above three ignition methods are described.
A Study of Cylinder-to-Cylinder Distribution of Charge in a Six Cylinder Spark Ignition Engine
Authors: Woods W. A. , Sag O. K.
Published: October 2009

An experimental and theoretical study of inlet flow was carried out on a Ford V6 Zephyr four-stroke cycle spark ignition engine. Details of measurements of individual cylinder flows were made on one bank of three cylinders (Nos. 4, 5, and 6) over a range of engine speeds from 1500 to 3500 rpm and throttle positions, full (WOT) down to 1/4 position. The object of the investigation was, first, to determine experimentally the extent of the variation of flow rate from cylinder to cylinder with changes in throttle position and engine speed and, secondly, to determine whether the computer simulation could confirm the trend. The main results of the tests showed that the outer two cylinders, No. 4 and No. 6, had the same flow rate within a variation of about 1/2 percent and that the middle cylinder, No. 5, had about 3 percent more flow at low speeds and 1 percent more at high speeds. In the main these were confirmed by the computer calculations. The volumetric efficiencies were also determined; these produced fairly smooth curves decreasing about 4 to 6 percentage points over the speed range and decreasing progressively as the throttle was reduced. There was evidence of recovery in the magnitude of volumetric efficiency at higher speeds and smaller throttle openings. The computer results also produced these trends.
Promises and Challenges of the Low-Heat-Rejection Diesel
Authors: Amann C. A.
Published: October 2009

The low-heat-rejection (LHR) diesel promises decreased engine fuel consumption by eliminating the traditional liquid cooling system and converting energy normally lost to the coolant into useful shaft work instead. However, most of the cooling energy thus conserved is transferred into the exhaust stream rather than augmenting crankshaft output directly, so exhaust-energy recovery is necessary to realize the full potential of the LHR engine. The higher combustion temperature of the LHR diesel favors increased emission of NOx, with published results on hydrocarbon and particulate emissions showing mixed results. The cylinder insulation used to effect low heat rejection influences convective heat loss only, and in a manner still somewhat controversial. The cyclic aspect of convective heat loss, and radiation from incandescent soot particles, also deserve attention. The temperatures resulting from insulating the cylinder of the LHR diesel require advancements in lubrication. The engine designer must learn to deal with the probabilistic nature of failure in brittle ceramics needed for engine construction. Whether ceramic monoliths or coatings are more appropriate for cylinder insulation remains unsettled. These challenges confronting the LHR diesel are reviewed.
A Steady-State Air Motion Study in a V-6 Uniflow Scavenged Two-Stroke Diesel Engine
Authors: Doan T. D. , Crawford E. F. , Hinkle S. J.
Published: October 2009

This paper presents new insight into the causes of cylinder-to-cylinder variation in swirl torque and airflow in uniflow scavenged, two-stroke diesel engines. A V-6 model of such an engine was investigated as a flow rig under steady-state conditions. These variations were found to be primarily caused by the effect of the airbox walls on the air motion. The maximum difference in the baseline cylinder-to-cylinder swirl torque and airflow rate was 11 and 3.5 percent, respectively. Two airbox design modifications, resulting from the study, in turn demonstrated increased cylinder airflow rate and reduced cylinder-to-cylinder swirl torque variation on the flow rig.
The Effect of Inlet Velocity Distribution and Magnitude on In-Cylinder Turbulence Intensity and Burn Rate—Model Versus Experiment
Authors: Davis G. C. , Tabaczynski R. J.
Published: October 2009

Steady flow measurements of velocity and mass flux distributions around the intake valve were used as input to a General Engine Simulation Model (GESIM) to assess the assumptions of uniform velocity and mass flux distributions and their effects on in-cylinder turbulence intensity and burn rate. In addition, an improved submodel for calculating the instantaneous velocity past the intake valve was developed and its effects on intake generated turbulence and burn rate assessed. Using the improved, inlet velocity submodel, a study was carried out for three different intake port configurations. Burn rate measurements were compared with model results for these configurations, which utilized the same engine head and block assembly. Model predictions, based on the standard port/valve discharge coefficient, indicated that velocity and mass distributions alone had a small effect on the in-cylinder turbulence intensity and burn rate. Significant differences in burn rate and turbulence intensity were predicted when the improved submodel for valve discharge coefficient was used. The new predictions agreed well with experimental measurements of burn rate. This implies that the increased mean velocities (which occur due to the restriction that creates the velocity and mass flow distributions) are the major cause for increased turbulence levels.
A Three-Zone Scavenging Model for Two-Stroke Uniflow Engines
Authors: Kyrtatos N. P. , Koumbarelis I.
Published: October 2009

A three-zone scavenging model for two-stroke uniflow engines was developed and used in conjunction with a control-volume-type engine simulation code for performance prediction of long stroke uniflow-type marine engines. In this model it is attempted to simulate the three different regions perceived to exist inside the cylinder during scavenging, namely the air, mixing, and combustion products regions, by modeling each region as a separate control volume. Two time-varying coefficients are used to specify the rates of entrainment of the air and the burned gases into the mixing region. Results of the use of the model for predicting the performance of a large marine two-stroke engine are presented.
A New Concept of High-Performance Marine Reversing Reduction Gears
Authors: Folenta D. J.
Published: October 2009

This paper presents a brief description and several illustrations of a new concept of marine reversing gears that utilize high-performance differentially driven epicyclic gear arrangements. This new marine power transmission has the potential to offer high reliability, simplicity, light weight, high mechanical efficiency, compactness, and technological compatibility with aircraft derivative marine gas turbine engines. Further, this new reversing gear minimizes the danger of driving the free turbine in reverse as might be the case with conventional parallel shaft reversing gear arrangements. To illustrate the weight reduction potential, a modern naval ship propulsion system utilizing an aircraft derivative gas turbine engine as the prime mover in conjunction with a conventional parallel shaft reversing gear can be compared to the subject reversing gear differential. A typical 18,642 kW (25,000 hp) marine gas turbine engine might weigh approximately 5000 kg (11,000 lb) and a conventional marine technology parallel shaft reversing gear might weigh on the order of 90,000 to 136,000 kg (200,000 to 300,000 lb). Using gear technology derived from the aircraft industry, a functionally similar differentially driven marine reversing gear might weigh approximately 13,600 kg (30,000 lb).
Application of an Advanced Hybrid Rotordynamics Model to the Complete Structure of a Marine Gas Turbine Engine
Authors: Thompson B. D. , Badgley R. H.
Published: October 2009

Extensive fleet experience with the LM2500 marine gas turbine engine has identified it as an engine that exhibits wear-accelerating vibration effects. The critical speeds and associated mode shapes were not well understood by U.S. Navy engineers. To help deal with vibration-related problems, an analytical model was developed to calculate engine rotordynamic and structural response. The procedure is a multilevel, multirotor hybrid extension of the classical Myklestad-Prohl method. Presented herein are some of the model’s predictions, and correlations with actual engine vibration measurements. The model predicted in excess of 20 different critical speeds in the engine’s operating range. Because of the engine’s structural flexibility, most of the critical speeds were engine casing and structural support resonances, driven by imbalance or misalignment in one or both of the engine rotors. Rotor-bending critical speeds were found to be strongly influenced by engine casing and support structure stiffness and mass. Using the model’s predicted mode shapes, new mounting locations for accelerometers could be selected to determine vibration severity at various frequencies better. This has given the U. S. Navy new insights into fleet vibration problems, and provides a useful tool for achieving reduced engine removals.
Current Status and Future Trends in Turbine Application of Thermal Barrier Coatings
Authors: Sheffler K. D. , Gupta D. K.
Published: October 2009

This paper provides an overview of the current status and future trends in application of thermal barrier coatings (TBC) to turbine components, and in particular to high turbine airfoils. Included are descriptions of the favorable results achieved to date with bill-of-material applications of plasma-deposited TBC, and recent experience with developmental coatings applied by electron beam-physical vapor deposition.
Processing Aspects of Plasma Sprayed Ceramic Coatings
Authors: Novak R. C.
Published: October 2009

Experimental studies are described that demonstrate that variation in plasma spray process parameters has a substantial effect on the fundamental mechanical, thermal, and physical properties of ceramic coatings. This property variation is shown to influence the behavior of the coatings under rig tests that simulate exposure in gas turbine engines. Illustrative examples are given to demonstrate the value of the designed experiment approach to understanding the coating process/coating behavior interaction. Finally, statistical process control methods are discussed and shown to be useful for identifying process control limits utilizing sophisticated in-process sensors.
Predicting the Behavior of Solar Dynamic Closed Brayton Cycle Power Conversion Systems
Authors: Bons R. , Hanlon J. , Spencer S.
Published: October 2009

Since space power conversion systems must operate both in the sun and in the earth’s shadow, they seldom encounter design operating conditions. As a consequence, consideration of off-design performance is essential in the preliminary design of these systems. To illustrate the necessity and utility of an off-design system model, this paper presents the results of a study of the solar dynamic closed Brayton cycle power conversion system for use on the NASA Space Station.
A Four-Year Investigation of Brayton Cycle Systems for Future French Space Power Applications
Authors: Tilliette Z. P. , Proust E. , Carre F.
Published: October 2009

Within the framework of a joint program initiated in 1983 by the two French Government Agencies C.N.E.S. (Centre National d’Etudes Spatiales) and C.E.A. (Commissariat a l’Energie Atomique), in order to study space nuclear power systems for future ARIANE 5 applications, extensive investigations have dealt with the Brayton cycle, which has been selected as the energy conversion system. Several aspects can be mentioned in this field: matching of the power system to the available radiator dimensions up to 200 kWe, direct or indirect waste heat transfer to the radiator, the use of a recuperator, recent work on moderate (25 kWe) power levels, simulation studies related to various operating conditions, and general system optimization. A limited experimental program is starting on some crucial technology areas including a first contract to the Industry concerning the turbogenerator. Particular attention is being paid to the significance of the adoption of a Brayton cycle for space applications involving a nuclear heat source, which can be either a liquid-metal-cooled or a gas-cooled reactor. For a gas-cooled reactor, direct-cycle system, the relevance to the reactor technology and the concept for moderator thermal conditioning is particularly addressed.
Correlations of Fuel Performance in a Full-Scale Commercial Combustor and Two Model Combustors
Authors: Bowden T. T. , Carrier D. M. , Courtenay L. W.
Published: October 2009

A statistically designed correlation exercise has shown excellent agreement between the performance of Shell and Phillips model combustors and a full-scale Rolls-Royce Tyne combustor. These results are a strong vindication of the model combustor approach to predicting the response and performance of full-scale systems.
Analytical and Numerical Treatment of the Transient Behavior of Rotating Counterflow Regenerators
Authors: Huettner W. , Niggemann M.
Published: October 2009

The transient heat transfer in a rotating counterflow regenerator is analyzed analytically and numerically with the assumption of constant mass flows on both sides of the regenerator. Moreover, first results for the case of temperature-dependent mass flows are presented.
Ceramic Bearings for Use in Gas Turbine Engines
Authors: Zaretsky E. V.
Published: October 2009

Three decades of research by U.S. industry and government laboratories have produced a vast array of data related to the use of ceramic rolling-element bearings and bearing components for aircraft gas turbine engines. Materials such as alumina, silicon carbide, titanium carbide, silicon nitride, and a crystallized glass ceramic have been investigated. Rolling-element endurance tests and analysis of full-complement bearings have been performed. Materials and bearing design methods have improved continuously over the years. This paper reviews a wide range of data and analyses with emphasis on how early NASA contributions as well as more recent data can enable the engineer or metallurgist to determine just where ceramic bearings are most applicable for gas turbines.
Fuel Spray Evolution: Comparison of Experiment and CFD Simulation of Nonevaporating Spray
Authors: Dodge L. G. , Schwalb J. A.
Published: October 2009

Detailed spray characteristics were obtained for a small-capacity, pressure-swirl atomizer using an Aerometrics phase-Doppler particle analyzer. Measurements included drop size and velocity distributions, liquid volume fluxes, and air velocities at four axial locations, 25, 50, 75, and 100 mm, with complete radial traverses at each location. Drop size results were compared with measurements from a Malvern laser-diffraction instrument, and integrated liquid volume fluxes were compared with measured flow rates to estimate measurement uncertainties. Drop sizes measured by the two independent techniques and area-weighted-averaged over the radial traverses at each of the four axial stations varied on average by less than 4 percent. Integrated volume flux measurements by the phase-Doppler instrument at four axial stations differed from the nozzle flow rate by at most 19 percent, with some of the difference due to evaporation. The phase-Doppler data were used to begin an evaluation of a commercial two-phase, three-dimensional, CFD code (FLUENT). Using a simplified representation of the spray based on velocity measurements 2 mm from the atomizer, it is shown that the model predicts drop trajectories, velocities, and volume fluxes reasonably well, and air entrainment velocities fairly accurately except on the spray centerline. Drop velocity profiles indicate dense spray effects very close to the atomizer that are not properly predicted by the dilute spray model.
Effects of Subcritical Crack Growth on Fracture Toughness of Ceramics Assessed in Chevron-Notched Three-Point Bend Tests
Authors: Chao L. Y. , Singh D. , Shetty D. K.
Published: October 2009

Chevron-notched bend specimens in three-point loading are increasingly used for evaluation of fracture toughness of structural ceramics. Its advantages include stable precracking of the specimen during loading, a simple specimen geometry, and a compressive mode of loading that is convenient for testing ceramics at elevated temperatures. Subcritical crack growth caused by environmental interactions or mass transport phenomena at elevated temperatures, however, can affect the apparent fracture toughness measured. A numerical computational study was carried out to assess the effects of subcritical crack growth on crack stability in the chevron-notched three-point bend specimens. A power-law relationship between the sub-critical crack velocity (v) and the applied stress intensity (KI) was used along with compliance and stress-intensity relationships for the chevron-notched bend specimen to calculate the load response under fixed deflection rate and a machine compliance. The results indicate that the maximum load during the test occurs at the same crack length for all the deflection rates; the maximum load, however, is dependent on the deflection rate for rates below a critical rate. The resulting dependence of the apparent fracture toughness on the deflection rate is compared to experimental results on soda-lime glass and polycrystalline alumina.
Calibration of CFD Methods for High Mach Number Aeroengine Flowfields
Authors: Chawner J. R. , Spragle G. S. , Matus R. J.
Published: October 2009

The design and analysis of scramjet engines relies heavily on the use of Computational Fluid Dynamics (CFD) methods due to the lack of experimental facilities and engineering analysis techniques for high Mach number, high-temperature flows. This emphasis on CFD requires that the methods be calibrated through comparison with existing experimental data to determine their level of capability and range of applicability. At General Dynamics’ Fort Worth Division a level of confidence has been established in the use of CFD methods for scramjet flowfields. These methods include a Beam-Warming-based Unsteady Navier-Stokes (UNS) solver, a Beam-Warming-based Parabolized Navier-Stokes (PNS) solver, and a MacCormack-based PNS solver. Specifically, comparisons between CFD flowfields and experimental data for a blunt cone at Mach 10.6, an inlet at Mach 7.4, a combustor at Mach 2.4, and an axisymmetric plug nozzle at Mach 3.2 have been made. These calibrations show good overall agreement for wall pressures, integrated forces, and pressure, Mach number, and chemical species profiles. Examination of the disparities between the CFD and experimental results focuses concern on the treatment of boundary layer turbulence and finite rate chemistry. As a result, further developmental tasks are suggested, which, when complete, will further enhance the applicability of the subject CFD methods.
A Detailed Characterization of the Velocity and Thermal Fields in a Model Can Combustor With Wall Jet Injection
Authors: Cameron C. D. , Brouwer J. , Wood C. P. , Samuelsen G. S.
Published: October 2009

This work represents a first step in the establishment of a data base to study the interaction and influence of liquid fuel injection, wall jet interaction, and dome geometry on the fuel air mixing process in a flowfield representative of a practical combustor. In particular, the aerodynamic and thermal fields of a model gas turbine combustor are characterized via detailed spatial maps of velocity and temperature. Measurements are performed at an overall equivalence ratio of 0.3 with a petroleum JP-4 fuel. The results reveal that the flowfield characteristics are significantly altered in the presence of reaction. Strong on-axis backmixing in the dome region, present in the isothermal flow, is dissipated in the case of reaction. The thermal field exhibits the primary, secondary, and dilution zone progression of temperatures characteristic of practical gas turbine combustors. A parametric variation on atomizing air reveals a substantial sensitivity of the mixing in this flow to nozzle performance and spray symmetry.
Application of Laser Velocimetry for Characterization of Confined Swirling Flow
Authors: Nejad A. S. , Vanka S. P. , Favaloro S. C. , Samimy M. , Langenfeld C.
Published: October 2009

A two-component LDV was used in a cold flow dump combustor model to obtain detailed mean and turbulence data for both swirling and nonswirling inlet flows. Large samples were collected to resolve the second and third-order products of turbulent fluctuations with good accuracy. Particle interarrival time weighting was used to remove velocity bias from the data. The swirling flows, with and without vortex breakdown, exhibited significantly different mean flow and turbulent field behavior. A numerical scheme with the k–ε closure model was used to predict the flow fields. Comparison of the numerical and experimental results showed that the k–ε turbulence model is inadequate in representing the complex turbulent structure of confined swirling flows.
Scalar Characteristics of Combusting Flow in a Model Annular Combustor
Authors: Bicen A. F. , Senda M. , Whitelaw J. H.
Published: October 2009

Temperature and species concentration measurements have been obtained in a model combustor operating at an inlet temperature of 515 K and atmospheric pressure and are reported and discussed. The model comprises two rectangular sectors representing the primary and upper dilution zones of an annular combustor used in small gas-turbine engines. Natural gas (94 percent CH4) was used as fuel and was delivered through a T-vaporizer at rates that led to air-fuel ratios of 29 and 50, similar to those of take-off and ground-idle conditions, respectively. Temperatures were obtained at the exit of the combustor using fine-wire thermocouples and mean concentrations of major species were obtained in the primary zone and at the exit on a dry basis by gas sampling and analysis. The results show that the 200 K increase in inlet air temperature reduces the pattern factor from 0.55 to 0.3 and increases the combustion efficiency from 69 to 94 percent with the air-fuel ratio of 29. The higher air-fuel ratio improves the combustion efficiency to 97.6 percent but results in a worse pattern factor of 0.48. The results confirm the need for consideration of the rate-controlled CO → CO2 reaction in the dilution zone if CO emission is to be calculated correctly and temperatures are to be within 150 K. Examination of temperatures obtained from a local enthalpy balance shows that they are higher than measurements obtained with preheat, in contrast to a similar comparison without preheat.
Fluid Dynamics of a Conical Flame Stabilizer
Authors: Ballal D. R. , Chen T. H. , Schmoll W. J.
Published: October 2009

Turbulence measurements were performed on a 45 deg conical flame stabilizer with a 31 percent blockage ratio, mounted coaxially at the mouth of a circular pipe and supplied with a turbulent premixed methane-air mixture at a Reynolds number of 2.85 × 104. A two-component LDA system was used in the measurement of mean velocities, turbulence intensities, Reynolds stresses, skewness, and kurtosis. It was found that combustion accelerates mean-flow velocities but damps turbulence intensity via the processes of turbulent dilatation and viscous dissipation due to heat release. Measurements in the axial direction showed that the length of the recirculation zone was nearly doubled as a result of combustion. Also, the region around the downstream stagnation point where streamlines meet and velocities change direction was found to be highly turbulent. Skewness and kurtosis data indicated that large-scale eddies carrying fresh combustible mixture are entrained into the high-shear region surrounding the recirculation zone. Finally, a discussion of turbulence-combustion interaction is presented to explain these experimental results.
F100-PW-229 Higher Thrust in Same Frame Size
Authors: Koff B. L.
Published: October 2009

The F100-PW-229 fighter aircraft engine is a higher thrust derivative of the F100-PW-220 and in the same frame size. The engine was developed from the F100 Engine Model Derivative (EMD) Program and parallel IR&D efforts. The increased thrust was achieved by increasing the flow and pressure ratio of the two-spool compression system accompanied by an increase in turbine temperature. The increased length compression system was offset by an innovative design intermediate case and a reduced length combustor to maintain overall engine axial length. The –229 engine has a thrust-to-weight ratio of 8.0 with a 20–30 percent performance increase over the –220 model across the flight map. Significant improvements in maintainability have been incorporated while retaining the proven durability and operability features of the –220 engine. The Government-industry partnership is working well, continually providing increased performance engines for our first-line fighters.
A New 150-MW High-Efficiency Heavy-Duty Combustion Turbine
Authors: Scalzo A. J. , McLaurin L. D. , Howard G. S. , Mori Y. , Hiura H. , Sato T.
Published: October 2009

The 501F 60-Hz Combustion Turbine has been developed jointly by Westinghouse Electric Corporation and Mitsubishi Heavy Industries, Ltd. It continues a long line of large heavy-duty single-shaft combustion turbines by combining the proven efficient and reliable concepts of the W501D5 with the low NOx technology of the MW701D, together with the experience of the advanced cooled MF111. The new engine is described along with the improved evolutionary changes made from previous engines. Planned design and performance verification programs including model, full-scale component testing, and full-load engine tests are described. Mature output and efficiency in simple cycle mode will be 145 MW and 34 percent, respectively, with expected combined cycle efficiencies in excess of 50 percent.
Life Modeling of Thermal Barrier Coatings for Aircraft Gas Turbine Engines
Authors: Miller R. A.
Published: October 2009

Thermal barrier coating life models developed under the NASA Lewis Research Center’s Hot Section Technology (HOST) program are summarized. An initial laboratory model and three design-capable models are discussed. Current understanding of coating failure mechanisms is also summarized.
Fiber Optics Based Jet Engine Augmenter Viewing System
Authors: Murphy P. J. , Jones D. W. , Lennert A. E. , Jones R. R.
Published: October 2009

An augmenter viewing system employing a coherent fiber-optic array was developed for use in jet engine testing applications at AEDC. Real-time viewing of the test article afterburner was obtained in a severe environment under high temperature and vibration levels. The optical system consisted of a conventional front-end lens assembly coupled with the fiber-optic array, and a solid-state color video camera mounted inside the test cell. The advantages and problems associated with a fiber-optics-based viewing system will be discussed in comparison with more conventional viewing techniques for this application.
Fluid-Induced Rotordynamic Instability in Rotary Atomizers
Authors: Colding-Jorgensen J.
Published: October 2009

A theory is presented for the calculation of rotordynamic coefficients for the fluid-rotor interaction in rotary atomizers, based on calculation of the fluid flow through a whirling atomizer wheel. The theory predicts potentially unstable rotor whirl in high-speed rotary atomizers. The whirl frequency can be that of the first critical forward or the first critical backward precession of the rotor, depending on atomizer wheel geometry, speed, fluid properties, and flow rate. The predicted whirl phenomena have been produced in an atomizer test stand. Both forward and backward precession have been observed to become unstable. The observed whirl directions and amplitudes are consistent with the calculated coefficients. Some design parameters are identified that can help control and suppress the whirl.