bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerodynamics and Heat Transfer Investigations on a High Reynolds Number Turbine Cascade
Authors: Schobeiri Taher , McFarland Eric , Yeh Frederick
Published: March 2015

In this report the results of aerodynamic and heat transfer experimental investigations performed in a high Reynolds number turbine cascade test facility are analyzed. The experimental facility simulates the high Reynolds number flow conditions similar to those encountered in the space shuttle main engine. In order to determine the influence of Reynolds number on aerodynamic and thermal behavior of the blades, heat transfer coefficients were measured at various Reynolds numbers using liquid crystal temperature measurement technique. Potential flow calculation methods were used to predict the cascade pressure distributions. Boundary layer and heat transfer calculation methods were used with these pressure distributions to verify the experimental results.
Integrated Weld Automation for Gas Turbine Blades
Authors: Lowden P. , Pilcher C. , Liburdi J.
Published: March 2015

The automation of turbine blade welding provides both metallurgical benefits and production advantages. Heat-affected zone cracking in sensitive superalloys, such as IN738 and IN100, can be eliminated or greatly reduced by optimizing process control, and higher production yields can be achieved when welding jet engine blades.

However, the successful implementation of automated processes requires careful consideration and engineering of the technology package. In particular, the equipment packager must be experienced in the technology associated with turbine blade welding and incorporate appropriate tooling, measurement system, power source and robotic controls. An example of a welding system for high pressure blade tips is presented which required the development and integration of a novel vision system to measure the thickness of the squealer wall, in order to select the appropriate welding parameters. Several practical applications of the technology are demonstrated on turbine blades exhibiting typical dimensional and metallurgical variations.
Gas Turbine Main Shaft Internal Flow and Heat Transfer
Authors: Roscoe David V. , Buggeln Richard C. , Munsell Peter M. , Hsing F. C.
Published: March 2015

A CFD analysis of the cooling flow through a gas turbine engine low pressure turbine shaft is presented. Three cases are considered in which throughflow and rotation rate are varied. The primary objective of the analysis was to derive improved heat transfer coefficient information, over those obtainable via semi-empirical means. The coefficients so obtained were then used in a one-dimensional, time-dependent analysis for use in predicting shaft wall temperature throughout a snap acceleration phase of the engine. A second objective was to obtain insight into the flow structure within the shaft with a view to possible design input in future engine programs. Results presented include detailed velocity vector plots at select locations, heat transfer coefficient distributions for each case and finally, for Case 2 predicted wall temperature vs. time is shown in conjunction with engine test data.
On-Line Distortion Analysis System for Inlet-Engine Testing
Authors: Morton Wayne K. , Lazalier Glen R. , Rose C. Dennis , Lauer R. F. (Pete)
Published: March 2015

A system for “near-real-time” distortion analysis support of aircraft turbine engine-inlet altitude testing is described. Target applications include both subscale and full-scale inlet-engine compatibility testing in wind tunnel, direct-connect, and free-jet configurations. The system digitizes analog-format, time-dependent data and combines it with digital-format, steady-state data. A high-speed data bus and multiple array processors provide for on-line execution of complex distortion analysis algorithms to compute and display distortion indices, histograms, isobar plots, and surge margin consumption. Analysis algorithms are programmed using a high-level language (FORTRAN 77).
Subsonic Propulsion System Installation Analysis and Optimization
Authors: Colehour J. L. , Farquhar B. W. , Gengler J. E. , Reyhner T. A.
Published: March 2015

Computational fluid dynamics (CFD) now allows analysis of propulsion system installations on subsonic transports to an extent that many configuration decisions can be made without testing. The methods discussed here utilize low-cost potential flow methods to predict inviscid flow characteristics and utility methods to model geometry, generate computational mesh, estimate wave drag, and perturb geometry in ways that promise improved performance. Jet plume effects are included in the potential flow analysis by means of a plume simulation method. Wave drag predictions yield levels of drag that are consistent with wind tunnel results, and, through contour optimization, wave drag for a trial propulsion installation geometry was reduced by about 50%. We conclude that through the use of methods such as these, many propulsion system installation design decisions can be made by analysis relatively quickly, which should lead to reduced design development time and cost.
A Calculation Procedure for Three-Dimensional Turbulent Flow in a Centrifugal Impeller With any Blade Geometry
Authors: Guang Xi , Shangjin Wang , Yongmiao Miao
Published: March 2015

A method for calculating 3–D turbulent flow in a centifugal impeller is developed by solving the incompressible, steady, time averaged N–S equation in general curvilinear coordinates. The K–ε two–equation turbulence model is utilized to describe Reynolds stresses. A calculation scheme is proposed which divides a centrifugal compressor impeller into three calculation zones, i.e. the inlet zone, the channel zone, and the exit–vaneless diffuser zone. A simple and time–saving method for generating 3–D body–fitted coordinate system of a centrifugal impeller is established by means of combining an algebraic transformation with the solution of 2–D elliptic partial differential equations. This method is applied to calculate the turbulent flow in an industrial centrifugal compressor impeller. The tendency of the “jet–wake” formation and growth in the impeller can be clearly seen, and the secondary flow pattern calculated is similar to Eckardt’s measurements. The calculation results at the impeller exit are also in good agreement with the experimental results performed by the authors.
Analysis and Prediction of Transonic Turbine Blade Losses
Authors: Farn C. L. S. , Whirlow D. K. , Chen S.
Published: March 2015

The use of simple computational means to determine the performance of cascades of turbine blades is attractive because it can quickly and economically yield results that can be used for optimization of classes of blades. Fully viscous flow computations are not at the point where they are economical for use in a routine way, and most computational methods lack the resolution to determine shock losses in the transonic flow regime. There is still a need for approaches that combine computation and empiricism. We describe approaches that combine quasi-three dimensional inviscid codes and boundary layer methods for blade passage flow with empirical approaches for shock losses and base pressure deficits to predict the losses in cascades of blades. Downstream mixing losses are handled by a distributed variable approach that uses the inviscid and boundary layer results to determine the distribution of variables at the trailing edge plane. The method gives accurate predictions for the set of distinctly different steam turbine blades for which it was run, and forms the basis for the development of rule-based turbine blade design.
Thermodynamic Study of the Overall Performance of an Air-Turbine Steam-Turbine Combined-Cycle Power Plant Based on First-Law as Well as Second-Law Analysis
Authors: Huang Francis F.
Published: March 2015

The overall performance of an air-turbine steam-turbine combined-cycle power plant that is similar to a recent invention has been studied based on first-law as well as second-law analysis. It has been shown that the prerequisite for such a power plant to achieve a high overall performance is an air-turbine air-heater system having a high second-law efficiency which is not sensitive to the compressor compression ratio of the air-turbine cycle. For optimum performance, a moderate cycle pressure ratio (say 8 to 14) may be used for TIT of 1700°F (926.7°C).
Time-Dependent Aerodynamic Analysis of Ducted and Unducted Propfans at Angle of Attack
Authors: Hall Edward J. , Delaney Robert A.
Published: March 2015

A three-dimensional unsteady aerodynamic analysis is described for predicting the time-dependent flow about ducted and unducted propfans operating at angle of attack. Although the freestream is assumed to be uniform, the flow relative to the rotating blades varies with circumferential position, resulting in an inherent unsteadiness due to the nonaxial inflow. The time-dependent Euler equations are solved utilizing a Runge-Kutta time-stepping scheme. The analysis is based on a finite-volume discretization employing a multiple-block grid network. To permit the use of large calculation time steps, an implicit residual smoothing scheme previously tested for unsteady flow calculations in two dimensions is extended to three spatial dimensions. For unducted propfans, a single H-type grid block is used for each blade passage to determine the time-periodic flowfield. For ducted propfans (ultra-high bypass fans) a body-centered C-type grid is wrapped about the cowl to improve the accuracy of the analysis in the high gradient flow region near the cowl leading edge. Numerical results are compared with available data for both ducted and unducted propfans operating at angle of attack.
Development and Characterization of High Strength SiC Rotors
Authors: Ohnsorg R. W. , Srinivasan G. V.
Published: March 2015

Sintered α-SiC (Hexoloy® SA*) turbine engine components have been fabricated by Carborundum for the Advanced Gas Turbine (AGT) Program and, more recently, for the Advanced Turbine Technology Applications Project (ATTAP) using three primary forming procedures — injection molding, cold isostatic pressing (CIP) followed by green machining, and slip casting. The near net-shape fabrication of injection molded AGT-100 radial rotors for the Allison Gas Turbine Division (AGTD) of General Motors Corporation and, more recently, AGT-5 axial rotors, has been demonstrated. The current emphasis at Carborundum is to refine the injection molding process, bringing it to a performance and reproducibility level sufficient for production needs. The process changes leading to increases in component strength from approximately 380 MPa (55 ksi) to 595 MPa (86 ksi) will be discussed, as well as investigation of the failure mechanism and proposed process modifications to enhance properties even further.
The Impulse Blower
Authors: Sheets Herman E.
Published: March 2015

The impulse blower provides essentially constant relative flow velocity through the impeller so that impeller blade entrance and exit velocity are equal. This results in a large guide vane entrance velocity and requires relatively large guide vane flow deflections. Special consideration must be given to assure that the flow through the blower is established in the desired direction. The impulse blower can operate with a large pressure coefficient which in turn permits using a small impeller diameter together with a small casing. Two blowers have been built and tested to evaluate performance and noise of impulse blowers. They confirm the expected reduction in size, weight and space under otherwise similar operating conditions.
Design of a Small Axial Compressor for High Efficiency Over a Wide Operating Range
Authors: Reynolds B. , Etter S. , Torony J. , O’Connor J.
Published: March 2015

Textron Lycoming’s advanced compressor design system has been used to design and develop a three-stage axial compressor in the small flow class (less than 10 pps). New and innovative aerodynamic and mechanical design features identified in recent technology programs were used to optimize efficiency and range in the present design. Specific areas of technology development in this research program are: customized rotor airfoil shapes for minimum shock loss, airfoil endwall loading selected to reduce losses, variable geometry design for large range and high efficiency compressor operating requirements, variable stator hub contours and attachment design for minimum clearance loss, flowpath sealing for low leakage flow, and reduced frictional pumping losses. Performance objectives were experimentally verified with extensive prototype rig testing where sufficient instrumentation was installed to identify overall and individual stage operating charactertistics.

A complete description of the axial compressor aerodynamic design is presented; executed using meanline, axisymmetric and three-dimensional flow analysis. Elements of the mechanical design that impact overall performance potential were controlled in the design and are described. Mechanical integrity for rig development and engine operation were verified for all components of the design and are reviewed.
3-D Axisymmetric Viscous Internal Flows on Rotating and Stationary Surfaces in Turbomachines
Authors: Ktenidis P. D. , Kaldellis J. K.
Published: March 2015

A fast calculation method, able to predict three, dimensional axisymmetric viscous internal flows on rotating and stationary surfaces in turbomachinery components has been developed. Modern high bypass turbine engines are characterized by axisymmetric parts such as inlets, nacelles, the prediffuser whose primary function is the efficient transfer of flow from one component to another. The flow field in such ducts are characterized by streamline curvature and divergence resulting from sharp contour and rapid area rotations, with the appearance of high peripheral velocity components.

The detailed calculation of the flow field through the axisymmetric parts requires a solution of the three-dimensional Navier-Stokes equations. However, conventional design systems simplify the flow pattern to a two dimensional one. The proposed method is based on the two-zone model and uses the notions of the integral formulation for the meridional direction. The meridional vorticity transport differential formulation, in a modified form is used for the peripheral direction to include the dynamics of passing from stationary to rotating parts and vice-versa. The resulting algorithms are sufficiently versatile and reliable to be used as a part of a design system for industrial applications.

A series of test cases demonstrate the applicability of the proposed method to practical problems having moderate skew, sudden application of a transverse motion and moderate cross-sectional area variations with stationary or rotating boundaries.
Advanced Hybrid Gas Turbine Plant Concept for Electrical Power Generation and Alternate Transportation Fuels Production
Authors: McDonald Colin F.
Published: March 2015

In long–term U.S. energy planning three major factors are paramount, (1) environmental considerations will play a major role in power plant design, (2) alternate (and cleaner burning) transportation fuels must be introduced to wean the country from dependence on imported oil, and (3) increasing reliance will be placed on indigenous resources, namely uranium and coal. It will likely take several decades for the above goals to be implemented on a large scale, and will surely necessitate the utilization of advanced technologies. A proposed advanced version of the modular helium reactor (MHR) has bi–modal operating capability in that it can be used for power generation, and the emission–free production of clean–burning fuels to meet transportation needs. The advanced hybrid MHR plant concept utilizes a direct cycle helium nuclear gas turbine for electrical power generation (with an efficiency potential of 50%), and in addition embodies an intermediate heat transport loop for high temperature process heat needed for the emission–free conversion of coal into future cleaner burning transportation fuels, namely methanol, synthetic natural gas, or hydrogen. The high grade sensible reject heat from both the prime–mover and process heat loop is ideally suited for desalination, and thus gives the plant capability for generating three revenue streams. This paper highlights an advanced very high temperature hybrid plant concept, and discusses the enabling technologies necessary to make such an energy complex a reality, perhaps in the first decade of the 21st century. Such a power generating and fuel production facility would be in concert with improved clean air goals, and the national security and economic advantages of making U.S. power and fuel supplies dependent only on indigenous resources.
Numerical Simulation of Unsteady Viscous Compressible Flows Applied to Blade Flutter Analysis
Authors: Sidén L. D. Gunnar
Published: March 2015

A numerical method for simulating quasi three-dimensional unsteady viscous compressible flow is developed and applied to blade flutter analysis. The Reynolds-averaged Navier-Stokes equations are solved in a time accurate manner on a continuously deforming computational mesh. Turbulence is accounted for by the inclusion of a two-layer algebraic turbulence model. This method is compared with measurements and a full velocity potential solver for two different subsonic compressor cascades and a range of flow conditions. Both methods are found to predict unsteady attached flows reasonably well. However, the Navier-Stokes solver picks up the pressure fluctuations associated with the unsteady leading edge separation bubble. These types of fluctuations have large amplitudes and tend to dominate the cascade’s aerodynamic damping behavior.
Blade Repair With Adaptive Vision Tracking
Authors: Anderson James R. , Skinner Michael J.
Published: March 2015

The paper discusses the repair welding of compressor and other blades contained in a gas turbine engines. The specific topics of discussion are the application requirements, the general metallurgical considerations, the synchronized pulsation arc welding process, the adaptive vision system employed and the computer controlled welding system. Reference to an actual installation of this technology will be included.
Mechanical Behavior of Fiber Reinforced SiC/RBSN Ceramic Matrix Composites: Theory and Experiment
Authors: Chulya Abhisak , Gyekenyesi John P. , Bhatt Ramakrishna T.
Published: March 2015

The mechanical behavior of continuous fiber reinforced SiC/RBSN composites with various fiber contents is evaluated. Both catastrophic and noncatastrophic failures are observed in tensile specimens. Damage and failure mechanisms are identified via in-situ monitoring using NDE techniques throughout the loading history. Effects of fiber/matrix interface debonding (splitting) parallel to the fibers are discussed. Statistical failure behavior of fibers is also observed, especially when the interface is weak. Micromechanical models incorporating residual stresses to calculate the critical matrix cracking strength, ultimate strength and work of pull-out are reviewed and used to predict composite response. For selected test problems, experimental measurements are compared to analytical predictions.
Structural Reliability Analysis of Laminated CMC Components
Authors: Duffy Stephen F. , Palko Joseph L. , Gyekenyesi John P.
Published: March 2015

For laminated ceramic matrix composite (CMC) materials to realize their full potential in aerospace applications design, methods and protocols are a necessity. This paper focuses on the time-independent failure response of these materials and presents a reliability analysis associated with the initiation of matrix cracking. It highlights a public domain computer algorithm that has been coupled with the laminate analysis of a finite element code and which serves as a design aid to analyze structural components made from laminated CMC materials. Issues relevant to the effect of the size of the component are discussed, and a parameter estimation procedure is presented. The estimation procedure allows three parameters to be calculated from a failure population that has an underlying Weibull distribution.
Real-Time Estimation of Gas Turbine Engine Damage Using a Control Based Kalman Filter Algorithm
Authors: Kerr L. J. , Nemec T. S. , Gallops G. W.
Published: March 2015

A second generation Kalman filter algorithm is described that has sufficient accuracy and response for real-time detection and estimation of gas turbine engine gas path damage caused by normal wear, mechanical failures and ingestion of foreign objects. The algorithm was developed for in-flight operation of aircraft engines but also has application for marine and industrial gas turbines. The control measurement and microcomputer requirements are described. The performance and sensitivity to engine transients and measurement errors is evaluated. The algorithm is demonstrated with actual engine data of ice and bird ingestion tests.
Numerical Prediction of Wakes in Cascades and Compressor Rotors Including the Effects of Mixing: Part II — Rotor Passage Flow and Wakes Including the Effects of Spanwise Mixing
Authors: Suryavamshi N. , Lakshminarayana B.
Published: March 2015

The results of a numerical investigation to predict the flow field including wakes and mixing in axial flow compressor rotors has been presented in this paper. The wake behaviour in a moderately loaded compressor rotor has been studied numerically using a three-dimensional incompressible Navier-Stokes solver with a high Reynolds number form of the k–ε turbulence model. The equations are solved using a time dependent implicit technique. The agreement between the measured data and the predictions are good; including the blade boundary layer profiles, wake mean velocity profiles and decay. The ability of the pseudo-compressibility scheme to predict the entire flow field including the near and far wake profiles and its decay characteristics, effect of loading and the viscous losses of a three-dimensional rotor flow field has been demonstrated. An analysis of the passage averaged velocities and the pressure coefficients shows that the mixing in the downstream regions away from the hub and annulus walls is dominated by wake diffusion. In regions away from the walls, the radial mixing is predominantly caused by the transport of mass, momentum and energy by the radial component of velocity in the wake.
Development Potential of Combined-Cycle (GUD) Power Plants With and Without Supplementary Firing
Authors: Finckh H. H. , Pfost H.
Published: March 2015

Unfired combined cycles achieve superior efficiencies at low emission levels. The potential and efficiency limits are investigated and the possibilities for enhancing efficiency are described. It is demonstrated that limited supplementary firing of the heat recovery steam generator can be an interesting alternative and that this allows efficiency and plant size to be increased. The effects of supplementary firing on NOx emissions are also shown.
Precision Drilling of Ceramic-Coated Components With Abrasive-Waterjets
Authors: Hashish M. , Whalen J.
Published: March 2015

This paper addresses an experimental investigation on the feasibility of using abrasive-waterjets (AWJs) for the precision drilling of small-diameter holes in advanced aircraft engine components. These components are sprayed with ceramic thermal barrier coating (TBC), and the required holes are typically 0.025 inch in diameter with a drilling angle of 25°. The parameters of the AWJ were varied to study their effects on both quantitative and qualitative hole drilling parameters. The unique techniques of assisting the abrasive feed process, ramping the waterjet pressure during drilling, and varying the jet dwell time after piercing were effectively implemented to control hole quality and size. The results of the experiments indicate the accuracy and repeatability of the AWJ technique in meeting the air flow and hole size requirements. Production parts were drilled for prototype engine testing.
Optimization of LM2500 Gas Generator and Power Turbine Trim Balance Techniques
Authors: Thompson Bruce D.
Published: March 2015

A procedure has been developed by the U.S. Navy to trim balance, in-place, the gas generator and power turbine rotor of the LM2500 Marine Gas Turbine Engine. This paper presents the theoretical background and the techniques necessary to optimize the procedure to balance the gas generator rotor. Additionally, a method was developed to trim balance LM2500 power turbines. To expand the implementation of both gas generator and power turbine trim balancing, a capability had to be developed to minimize the effort required (trial weight runs etc.). The objective was to able to perform consistently what are called “First Shot” trim balances. “First Shot” trim balances require only one weight placement to bring the engine vibration levels to within the specified goals (less than .002 of an inch maximum amplitude) and that being the final trim weight. It was realized that the Least Squares Influence Coefficient method, even with a good set of averaged influence coefficients, can lead to a number of trial weight experiments before the final trim weights can be placed. The method used to maximize the possibility of obtaining a “First Shot” trim balance was to use modal information to tailor the influence coefficient sets to correct the most predominant and correctable imbalance problem. Since the influence coefficients were tailored, it became necessary to be able to identify, in the initial vibration survey, the type of response a particular LM2500 has. Using modal information obtained from a LM2500 rotor dynamics model and from the early trim balance efforts it was possible to identify the modal response of a given LM2500 and optimize the trim balance of that engine. With these improved techniques a 70% success rate for “First Shot” trim balance has been achieved and the success rate of the trim balance procedure, as a whole, has been near 100%.
Interference Effects of Very High Bypass Ratio Nacelle Installations on a Low-Wing Transport
Authors: Ingraldi Anthony M. , Kariya Timmy T. , Re Richard J. , Pendergraft Odis C.
Published: March 2015

A twin-engine, low-wing transport model, with a supercritical wing designed for a cruise Mach number of 0.77 and a lift coefficient of 0.55 was tested in the 16-Foot Transonic Tunnel at NASA Langley Research Center. The purpose of this test was to compare the wing/nacelle interference effects of superfans (very high bypass ratio turbofans, BPR = 18) with the interference effects of advanced turbofans (BPR = 6). Flow-through nacelles were used in this study. Forces and moments on the complete model were measured using a strain gage balance and extensive surface static pressure measurements (383 orifice locations) were made on the model’s wing, nacelles, and pylons. Data were taken at Mach numbers from 0.50 to 0.80 and model angle-of-attack was varied from −4° to +8°. Results of the investigation indicate that superfan nacelles can be installed with approximately the same drag penalty as conventional turbofan nacelles.
The Basics of Powder Lubrication in High-Temperature Powder-Lubricated Dampers
Authors: Heshmat Hooshang , Walton James F.
Published: March 2015

The objective of this investigation is to develop a novel powder-lubricated rotor bearing system damper concept for use in high-temperature, high-speed rotating machinery such as advanced aircraft gas turbine engines. The approach discussed herein consists of replacing a conventional oil lubrication or frictional damper system with a powder lubrication system that uses the process particulates or externally-fed powder lubricant. Unlike previous work in this field, this approach is based on the postulate of the quasi-hydrodynamic nature of powder lubrication. This postulate is deduced from past observation and present verification that there are a number of basic features of powder flow in narrow interfaces that have the characteristic behavior of fluid film lubrication. In addition to corroborating the basic mechanism of powder lubrication, the conceptual and experimental work performed in this program provides guidelines for selection of the proper geometries, materials and powders suitable for this tribological process. The present investigation describes the fundamentals of quasi-hydrodynamic powder lubrication and defines the rationale underlying the design of the test facility. The performance and the results of the experimental program present conclusions reached regarding design requirements as well as the formulation of a proper model of quasi-hydrodynamic powder lubrication.
Film Cooling Research on the Endwall of a Turbine Nozzle Guide Vane in a Short Duration Annular Cascade: Part 2 — Analysis and Correlation of Results
Authors: Harasgama S. P. , Burton C. D.
Published: March 2015

Results have been presented on the heat transfer characteristics of the film cooled endwall (platform) of a turbine nozzle guide vane in an annular cascade at engine representative conditions in a companion paper by Harasgama and Burton (1991). The present paper reports on the analysis of these measurements.

The experimental results are well represented by the superposition theory of film cooling. It is shown that high cooling effectiveness can be achieved when the data are corrected for axial pressure gradients. The data are correlated against both the slot-wall jet parameter and the discrete hole injection function for flat-plate, zero pressure gradient cases. The pressure gradient correction brings the present data to within ± 11% of the discrete hole correlation. Preliminary predictions of heat transfer reduction have been carried out using the STANCOOL program. These indicate that the code can predict the magnitude of heat transfer reduction correctly, although the absolute values are not in good agreement. This is attributed to the three-dimensional nature of the flow at the endwall.
Influence of Mainstream Turbulence on Leading Edge Film Cooling Heat Transfer Through Two Rows of Inclined Film Slots
Authors: Ou S. , Han J. C.
Published: March 2015

The effect of film slot injection on leading edge heat transfer coefficient and film cooling effectiveness under high mainstream turbulence conditions was experimentally studied for flow across a blunt body with a semi-cylinder leading edge and a flat afterbody. High mainstream turbulence levels were generated by a bar grid (Tu = 5.07%) and a passive grid (Tu = 9.67%). The incident mainstream Reynolds number based on the cylinder diameter was about 100,000. The spanwise and streamwise distributions of the heat transfer coefficient and film effectiveness in the leading edge and on the flat sidewall were obtained for three blowing ratios (B = 0.4, 0.8 and 1.2) with two rows of film slots located at ±15° and ±40° from stagnation line. The cross-sectional slot length-to-width ratio was two. The slots in each row were spaced three cross-sectional slot lengths apart and were angled 30° and 90° to the surface in the spanwise and streamwise direction, respectively. The results show that the heat transfer coefficient increases with increasing blowing ratio, but the film effectiveness reaches the maximum at an intermediate blowing ratio of B = 0.8 for both low (Tu = 0.75%) and high (Tu = 9.67%) mainstream turbulence conditions. The leading edge heat transfer coefficient increases and the film effectiveness decreases with mainstream turbulence level for the low blowing ratio; however, the mainstream turbulence effect reduces for the high blowing ratio. The leading edge heat load is significantly reduced with two rows of film slot injection. The blowing ratio of B = 0.4 provides the lowest heat load in the leading edge region for the low mainstream turbulence but B = 0.8 gives the lowest heat load for the high mainstream turbulence conditions.
The Influence of Density Difference Between Hot and Coolant Gas on Film Cooling by a Row of Holes: Predictions and Experiments
Authors: Haas W. , Rodi W. , Schönung B.
Published: March 2015

The two-dimensional boundary-layer procedure of Schönung and Rodi [1] for calculating film cooling by a row of holes was extended to account for density differences between hot gas and injected coolant gas. The extensions concern the injection model for leaping over the immediate blowing region in the boundary-layer calculation and also the dispersion model for taking into account three-dimensional effects. The extended model is tested for a density ratio of ρj/ρe ≈ 2 both for flat-plate situations and film cooling on a model turbine blade. The predicted laterally averaged film cooling effectiveness is compared with measurements for these cases. Results for the flat-plate experiments were taken from the literature, while experiments for a model turbine blade are also described in this paper. For a fixed injection angle of 32°, the film cooling effectiveness was measured for various spacings and velocity ratios Uj/Ue. The density ratio ρj/ρe ≈ 2 was achieved by adding Freon to the injection gas. The results are compared with those reported in [2] for negligible density difference. At the same blowing rate M = Uj/Ue, the film cooling effectiveness was found to increase with the density ratio ρj/ρe. In general, the influence of the density difference is well predicted by the model.
Gas Turbines Above 150 MW for Integrated Coal Gasification Combined Cycles (IGCC)
Authors: Becker B. , Schetter B.
Published: March 2015

Commercial IGCC power plants need gas turbines with high efficiency and high power output in order to reduce specific installation costs and fuel consumption. Therefore the well proven 154 MW V94.2 and the new 211 MW V94.3 high temperature gas turbine are well suited for this kind of application. A high degree of integration of gas turbine, steam turbine, oxygen production, gasifier and raw gas heat recovery improves the cycle efficiency. The air used for oxygen production is taken from the gas turbine compressor. The N2-fraction is recompressed and mixed with the cleaned gas prior to combustion. Both features require modifications of the gas turbine casing and the burners. Newly designed burners using the coal gas with its very low heating value and a mixture of natural gas and steam as a second fuel are developed for low NOx and CO emissions. These special design features are described and burner test results presented.
Validation of a Numerical Method for Unsteady Flow Calculations
Authors: Giles Michael , Haimes Robert
Published: March 2015

This paper describes and validates a numerical method for the calculation of unsteady inviscid and viscous flows. A companion paper compares experimental measurements of unsteady heat transfer on a transonic rotor with the corresponding computational results. The mathematical model is the Reynolds-averaged unsteady Navier-Stokes equations for a compressible ideal gas. Quasi-three-dimensionality is included through the use of a variable streamtube thickness. The numerical algorithm is unusual in two respects: a) for reasons of efficiency and flexibility it uses a hybrid Navier-Stokes/Euler method, and b) to allow for the computation of stator/rotor combinations with arbitrary pitch ratio a novel space-time coordinate transformation is used.

Several test cases are presented to validate the performance of the computer program, UNSFLO. These include: a) unsteady, inviscid flat plate cascade flows, b) steady and unsteady, viscous flat plate cascade flows, c) steady turbine heat transfer and loss prediction. In the first two sets of cases comparisons are made with theory, and in the third the comparison is with experimental data.
The Numerical Simulation of a High-Speed Axial Flow Compressor
Authors: Mulac Richard A. , Adamczyk John J.
Published: March 2015

The advancement of high-speed axial flow multistage compressors is impeded by a lack of detailed flow field information. Recent developments in compressor flow modeling and numerical simulation have the potential to provide needed information in a timely manner. This paper, which consists of two parts, will explore this topic. The first part will address the development of a computer program to solve the viscous form of the average-passage equation system for multistage turbomachinery. Programming issues such as in-core versus out-of-core data storage and CPU utilization (parallelization, vectorization, and chaining) will be addressed. Code performance will be evaluated through the simulation of the first four stages of a five stage, high-speed, axial flow compressor on a CRAY Y-MP8/8128 computer. The second part will address the flow physics which can be obtained from the numerical simulation. In particular, an examination of the endwall flow structure will be made, and its impact on blockage distribution assessed.
Inlet Flow Angle Determination of Transonic Compressor Cascades
Authors: Steinert W. , Fuchs R. , Starken H.
Published: March 2015

Tests of transonic compressor cascades require special measuring techniques to determine the inlet flow angle around sonic inlet flow conditions. One of the main requirements for these methods is the ability to adjust the inlet flow angle during the test to a prescribed value. A method has been successfully applied which relies on theoretically determined suction surface velocities. The described method was applied in testing cascades at inlet Mach numbers between M1=0.75–1.18. The test results confirmed the practicability of this method.
Control Systems for the Next Century’s Fighter Engines
Authors: Skira Charles A. , Agnello Mark
Published: March 2015

The paper describes a conceptual control system design based on advanced technologies currently in the exploratory development phase, and, in some cases, emerging into the advanced development phase. It explores future propulsion control systems that focus on improvements in three (3) areas: 1) significantly reducing control system weight; 2) enhancing engine performance (thrust, sfc, etc.); and 3) improving control system reliability and tolerance to high threat environments (temperature, vibration, EMI, EMP, etc.). The factors that will influence the design and hardware configuration of future propulsion control systems are described. Design goals for future systems, based on the DOD/NASA IHPTET Initiative, and projections of emerging technology capability (and availability) form the basis for future propulsion control system design requirements and for estimating future hardware configurations.
Performance Characteristics of Brush Seals for Limited-Life Engines
Authors: Chupp Raymond E. , Dowler Constance A.
Published: March 2015

Brush seals are potential replacements for air-to-air labyrinth seals in gas turbine engines. An investigation has been conducted to determine the performance characteristics of brush seals for application in limited-life gas turbine engines. An elevated temperature, rotating test rig was designed and built to test labyrinth and brush seals in simulated subsonic and supersonic engine conditions. Results from initial tests for subsonic applications demonstrated that brush seals exhibit appreciably lower leakage compared to labyrinth seals, and thus offer significant engine performance improvements. Performance results have been obtained showing the effect of various brush seal parameters including: initial interference, backplate gap and multiple brush seals in series.
Dynamic Simulation of the Gravel Bed Combustor-Gas Turbine System
Authors: Palmer Carl A. , Ragland Kenneth W.
Published: March 2015

A novel gravel bed, downdraft, woodchip combustor that directly-fires a gas turbine for use in a cogeneration system has been developed. In this combustor, the fuel burning rate is determined by pressure, temperature, air flow rate, and fuel moisture content, and not by the fuel feed rate. When the gravel bed combustor is connected to a gas turbine system, the operator loses the freedom to directly set the fuel flow rate, which is the primary control variable for conventional gas turbine systems. Other control problems introduced by the gravel bed include a large thermal lag and a sizable pressure drop. This paper presents a computer model that integrates the dynamic characteristics of an actual gas turbine with the characteristics of the gravel bed combustor. The program determines system behavior and helps evaluate possible control strategies. The system is controlled using the CO2 level leaving the gravel bed. The bypass valve setting determines the load level. Both the slow temperature dynamics and quick turbomachinery dynamics must be considered when operating the system.
NDE of Advanced Turbine Engine Components and Materials by Computed Tomography
Authors: Yancey R. N. , Baaklini George Y. , Klima Stanley J.
Published: March 2015

Computed tomography (CT) is an X-ray technique that provides quantitative 3-D density information of materials and components and can accurately detail spatial distributions of cracks, voids, and density variations. CT scans of ceramic materials, composites, and engine components were taken and the resulting images will be discussed. Scans were taken with two CT systems with different spatial resolution capabilities. The scans showed internal damage, density variations, and geometrical arrangement of various features in the materials and components. It was concluded that CT can play an important role in the characterization of advanced turbine engine materials and components. Future applications of this technology will be outlined.
The Use of NDE as a Process Development Tool for Ceramic Engine Components
Authors: Pollinger J. P.
Published: March 2015

The evaluation of various NDE techniques as in-process characterization tools during the fabrication development of structural ceramic components for advanced gas turbine applications is presented. Specific techniques and applications that will be discussed are X-ray microfocus real-time fluoroscopy of slip/cast solid interfaces in parts during slipcasting, NMR imaging of organic binder and moisture concentrations in injection molded and slipcast ceramic parts, and ultrasonic transmission and attenuation techniques used to examine parts during slipcasting and subsequent drying.
NDE Development for Ceramics for Advanced Heat Engines
Authors: McClung R. W. , Johnson D. R.
Published: March 2015

Following an assessment of needs for NDT and characterization of ceramics for the DOE program, Ceramic Technology for Advanced Heat Engines (CTAHE), many NDT projects have been implemented under the sponsorship of CTAHE to address the needs. Tasks at Argonne National Laboratory have involved X-ray computed tomography and nuclear magnetic resonance imaging. The Oak Ridge National Laboratory has emphasized high-frequency ultrasonics, low-voltage radiography, and an advanced system for X-ray computed tomography. A brief investigation was made by Radiation Sciences, Inc., into the feasibility of synchrotron-computed tomography for ceramics. New programs recently initiated at Allison and Garrett integrate ultrasonics, radiography, and other methods into a major effort on life prediction. New programs at Norton and GTE on advanced processing of ceramics also place heavy emphasis on several methods of NDT for process development and control. Initial work on NDT standards has begun in ASTM Committees E-7 and C-28.
Development of a Natural Gas-Fired, Ultra-Low NOx Can Combustor for an 800 KW Gas Turbine
Authors: Smith K. O. , Holsapple A. C. , Mak H. K. , Watkins L.
Published: March 2015

The experimental results from the rig testing of an ultra-low NOx, natural gas-fired combustor for an 800 to 1000 kw gas turbine are presented. The combustor employed lean-premixed combustion to reduce NOx emissions and variable geometry to extend the range over which low emissions were obtained.

Testing was conducted using natural gas and methanol. Testing at combustor pressures up to 6 atmospheres showed that ultra-low NOx emissions could be achieved from full load down to approximately 70% load through the combination of lean-premixed combustion and variable primary zone airflow.
Calculation Approach Validation for Airblast Atomizers
Authors: Rizk N. K. , Mongia H. C.
Published: March 2015

In order to formulate a common approach that could provide the spray parameters of airblast atomizers, various processes of liquid preparation, breakup and secondary atomization have been included in a semi-analytical calculation procedure. The air velocity components in the atomizer flow field are provided by mathematical expressions, and the spray droplets are considered to form at ligament breakup through a disturbance wave growth concept. The validation of the developed approach included the application to six atomizers that significantly varied in concept, design, and size. They represented both prefilming and plain-jet types, and their data utilized in the present effort were obtained with six different liquids. Satisfactory agreement between the measurements and the predictions has been achieved under wide ranges of air/fuel ratio and air pressure drop for various test liquids. The results of this investigation indicate the potential of using such an approach in the early phases of airblast atomizer design, and may be followed by more detailed calculations using analytical tools.
LDV Measurements of a Mixed-Flow Impeller at Design and Near Stall
Authors: Fagan John Robert , Fleeter Sanford
Published: March 2015

A series of experiments are performed to investigate and quantify the design and off-design three-dimensional mean flow in a centrifugal compressor impeller. The experiments entail the acquisition and analysis of LDV data in the impeller passages of a low speed research mixed-flow compressor operating at its design point and at a point near the inception of rotating stall. The LDV data at both operating points show regions near the impeller exit with a significant velocity deficit on the shroud surface characteristic of the traditional jet-wake structure observed in many centrifugal compressors. At design, the maximum velocity deficit occurs at a location 70% of the passage width from the pressure to the suction surface. At the incipient stall point, the maximum velocity deficit occurs in the shroud suction surface corner, with the data indicating reverse flow.
Transonic and Supersonic Inviscid Computations in Cascades Using Adaptive Unstructured Meshes
Authors: Bassi F. , Rebay S. , Savini M.
Published: March 2015

The paper describes a solution procedure for two dimensional compressible inviscid flows. The solution algorithm uses a finite volume spatial discretization on unstructured grids of triangles and an explicit Runge-Kutta time marching scheme; for steady problems efficiency is enhanced by using local time stepping and enthalpy damping. The use of unstructured meshes automatically adapted to the solution allows arbitrary geometries and complicated flow features to be treated easily and with high degree of accuracy, even if more work is needed to reach a computational efficiency comparable to those of existing structured codes. Adaptation criteria based on error estimates of significant flow variables have been implemented and tested. The method has been applied to the computation of transonic and supersonic flows in gas turbine nozzles and in impulse rotor cascades for spatial applications and the results have been compared with the experimental data.
Transonic Cascade Flow Prediction Using the Navier-Stokes Equations
Authors: Arnone A. , Stecco S. S.
Published: March 2015

This paper presents results which summarize the work carried out during the last three years to improve the efficiency and accuracy of numerical predictions in turbomachinery flow calculations.

A new kind of non-periodic C-type grid is presented and a Runge-Kutta scheme with accelerating strategies is used as a flow solver.

The code capability is presented by testing four different blades at different exit Mach numbers in transonic regimes. Comparison with experiments shows the very good reliability of the numerical prediction. In particular the loss coefficient seems to be correctly predicted by using the well-known Baldwin-Lomax turbulence model.