bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction and Measurement of the Total Pressure Loss in an Engine Representative Diffuser System
Authors: Little A. R. , Denman P. A. , Manners A. P.
Published: February 2015

An experimental and computational investigation of the flow in an engine representative diffuser system has been performed. Many parametric changes to the system were considered including inlet conditions, pre-diffuser geometry, cowl geometry and pre-diffuser strut position. The focus of this paper is an overview of the results from the twelve configurations that were both predicted and experimentally tested.

It was shown that the CFD predictions contained a high degree of numerical error and that to reduce this to a low level would be currently impractical for a parametric study of this type. However, by carefully maintaining approximately the same degree of numerical error in the predictions, it was shown that a valid parametric study could be performed to the extent that the same conclusions about the parametric changes can be drawn equally from the predictions or measurements with one small exception. It was recognised that the level of agreement between the predicted and measured losses was to a degree fortuitous and that the k-ε turbulence model performs poorly for this type of flow.
Studies on Lean-Blowout Characteristics of a Premixed Jet Flame
Authors: Katta Viswanath R. , Roquemore W. M.
Published: February 2015

The stability characteristics of a fuel-lean premixed jet flame are investigated using a time-dependent, axisymmetric numerical model with a detailed-chemical-kinetics mechanism for H2-O2-N2 combustion. Temperature- and species-dependent transport properties are incorporated. The mathematical model is validated by computing the burning velocities for different equivalence ratios and comparing them with experimentally measured values. Premixed flames that are stably attached to the fuel tube are obtained over a wide range of equivalence ratios. The lower limit for equivalence ratio at which the flame lifts-off from the fuel tube is found to be 0.4. Calculations have also correctly predicted the following scenario: when a premixed flame lifts-off at the base, it becomes unstable and is eventually blown out of the computational domain. The blow-out process is studied by analyzing the stable flame at Φ = 0.4 and the unstable flame at Φ = 0.395. Entrainment of ambient air by the fuel jet upstream of the lifted-flame base reduces the local equivalence ratio which, in turn, is found to be responsible for the blow-out of the flame.
Flight Research Using F100 Engine P680063 in the NASA F-15 Airplane
Authors: Burcham Frank W. , Conners Timothy R. , Maxwell Michael D.
Published: February 2015

The value of flight research in developing and evaluating gas turbine engines is high. NASA Dryden Flight Research Center has been conducting flight research on propulsion systems for many years. The F100 engine has been tested in the NASA F-15 research airplane in the last three decades. One engine in particular, S/N P680063, has been used for the entire program and has been flown in many pioneering propulsion flight research activities. Included are detailed flight-to-ground facility tests; tests of the first production digital engine control system, the first active stall margin control system, the first performance-seeking control system; and the first use of computer-controlled engine thrust for emergency flight control. The flight research has been supplemented with altitude facility tests at key times. This paper presents a review of the tests of engine P680063, the F-15 airplanes in which it flew, and the role of the flight test in maturing propulsion technology.
Experimental Evaluation of Air Injection for Actuation of Rotating Stall in a Low Speed, Axial Fan
Authors: Khalak Asif , Murray Richard M.
Published: February 2015

This paper presents an experimental investigation of the effects of air injection on the rotating stall instability in a low speed axial compressor. Two experiments concerning air injection were tried. The first experiment used a continuous forcing perpendicular to the flow in the same or opposite direction of the tip velocity. The results show a dramatic difference between the two directions, with opposite direction forcing causing a significant increase in performance, and same direction forcing causing a significant decrease in performance. This result contradicts the Emmons stall propagation model. The second experiment investigated the differences with respect to different frequencies of air injection, with the injector pointed at the fan, parallel to the flow. We found that the change in the compressor characteristic in the unstalled region was highly dependent upon the forcing frequency with the maximum change occurring near the frequency of stall.
Probabilistic Assessment of Combustor Liner Design
Authors: Pai Shantaram S. , Chamis Christos C.
Published: February 2015

A typical hot structural component within an engine such as composite combustor liner is computationally simulated and probabilistically evaluated in view of the numerous uncertainties associated with the structural, material, and thermo-mechanical load variables (primitive variables) that describe the combustor. The combustor is evaluated for buckling (eigenvalue) loads, vibration frequencies, and local stresses. Results show that the scatter in the combined stress is not uniform along the length of the combustor. Furthermore, coefficient of thermal expansion, hoop modulus of the liner material, and the thermal load profile dominate stresses near the support and the intermediate location of the combustor liner. However, the liner thickness, the liner material hoop modulus, and pressure load profile have significant impact on stresses near the free end of combustor.
Experimental Investigation of Boundary Layer Transition and Turbulence Structures on a Highly Loaded Compressor Cascade
Authors: Wunderwald Dirk , Fottner Leonhard
Published: February 2015

Detailed measurements have been performed on a compressor cascade in order to obtain information about the overall performance, the state of the boundary layer, and the topology of turbulent boundary layers.

The analysis of profile pressure distributions and wake traverse measurements across the midspan section of the cascade blade provide information on the loss behaviour. Using surface-mounted hot-film gauges on the suction side of the measuring blade different transition phenomena have been investigated under the influence of various inlet flow conditions representative of engine operation. Extensive measurements with 3D-hot-sensor anemometry have been evaluated to show essential features of the turbulent boundary layer.

The results point out the dependence of turbulence characteristics, e.g. turbulent kinetic energy distribution and Reynolds stresses, on the inlet flow conditions and the upstream boundary layer development. The influence of free-stream turbulence intensity is discussed and the non-isotropy of the Reynolds normal stresses is presented.
Experiment-Aided Controller Design of Rotor Systems With a Magnetic Bearing
Authors: Sheu G. J. , Yang C. D. , Yang S. M.
Published: February 2015

A new design methodology for the vibration control of rotor systems with a magnetic bearing is developed in this paper. The methodology combines the experimental design method in quality control engineering and the conventional PD control technique such that their advantages in implementation feasibility and performance-robustness can be integrated together. A quality loss index defined by the summation of the infinity norm of unbalanced vibration is used to characterize the system dynamics. By using the location of the magnetic bearing and PD feedback gains as design parameters, the controller of experiment-aided design achieves the best system performance. In addition, it is robust to operating speed variations. A rotor system consisting of 4 rigid disks, 3 isotropic bearings, and 1 magnetic bearing is applied to illustrate the feasibility and effectiveness of the experiment-aided controller design.
Application of Aero-Engine Technology to Heavy Duty Gas Turbines
Authors: Janssen Manfred , Zimmermann Holger , Kopper Frederick , Richardson John
Published: February 2015

A description of an advanced version of a Siemens heavy duty gas turbine is presented which is based on a collaboration between Siemens Power Generation and United Technology Corporation. The main objective of this collaboration was to utilize the R&D capabilities of Siemens Power Generation and Pratt and Whitney to improve an existing heavy duty gas turbine (V84.3) by increasing compressor and turbine efficiency, refining the cycle and increasing turbine inlet temperature.

This paper presents a description of the redesigned components, focusing on the features derived from aero engine technology. The main features of the advanced compressor are custom tailored blading to account for end wall boundary layer flow at the hub and casing wall, as advanced controlled diffusion airfoil (CDA) and a revised flowpath. These features result in both improvements in efficiency and surge margin over a wide operating range. The design features of the advanced turbine blading are 3D aerodynamics to reduce profile and secondary losses, aero-engine derived cooling configurations and use of single crystal materials to increase turbine durability.

The performance improvement predicted for the redesign was demonstrated in a back-to-back test with the baseline engine, a 60 Hz Model V84.3. Testing was conducted at the Siemens Berlin facility which is capable of acquiring extensive performance and durability related data for full scale engines at design point and off-design conditions. Test results showed that over a 5 percent heat rate improvement was achieved by the application of aero-engine technology to the baseline machine.
Conversion of an Aerodynamic Wind Tunnel to a Gas Turbine Combustor Test Stand
Authors: Cresci Daniel
Published: February 2015

A Mach 12, blowdown-type, storage heated, aerodynamic test facility, previously adapted to provide Mach 3.5 ramjet engine propulsion testing, has been further modified to provide high pressure, gas turbine combustor emission testing capability. Pressure control and temperature control systems have been incorporated into the original facility to provide constant flow properties for run times up to 30 minutes. An on-line gas sample system has also been designed and integrated with the facility to provide continuous combustor emission information.

These features now combine with the existing pebble bed storage heater, blowdown air supply and heated fuel supply systems to provide very high Mach number aerodynamic simulation, intermediate Mach number aeropropulsion testing and low Mach number, full scale, gas turbine combustor emission testing capability. Pressures of 1500 psia can be achieved with temperatures up to 2000 degrees Fahrenheit and flow rates up to 50 lb/sec.

This unique facility is described, with emphasis on the facility modifications necessary to provide the gas turbine combustor emission testing capability. To appreciate the modifications made, some of the differences between Mach 12 aerodynamic and low Mach number, gas turbine combustor emission testing are discussed. Results from some recent gas turbine emissions tests are also provided.
Flow and Turbulence Survey for a Model of Gas Turbine Exhaust Diffuser
Authors: Desideri Umberto , Manfrida Giampaolo
Published: February 2015

This paper presents the results of an extensive set of measurements on a model of an exhaust diffuser for gas turbines. The diffuser is of the straight-wall annular-axial type, typically employed in small-to-medium size gas turbines. It features six high-solidity struts, which support, in the real machine, one of the shaft bearings and have piping for oil supply inside.

The 35%-scale model has been tested on a special test stand developed at the University of Perugia, using the suction side of a centrifugal-flow industrial fan of suitable capacity. Inlet speed is around 80 m/s, allowing satisfactory accuracy for flow measurements and the similarity in terms of Reynolds number.

The instrumentation, the movement of the measurement point and data acquisition system were designed for automatic running of the tests. Both pneumatic and hot-wire or hot-film probes can be used on the same facility. The same wind tunnel, previous a quick replacement of the model with a probe calibration test section, can be used for calibration of both pneumatic and hot-wire/hot-film probes. A three hole directional pneumatic probe was used for stationary flow measurements to determine the global performance parameters of the model and a split-film probe was used to determine the turbulence characteristics.

For four test sections, contour plots are produced of average velocity components, flow angle and turbulence quantities as three components of the Reynolds stress tensor.
Numerical Investigations of Flow Pattern and Heat Transfer in a Rotating Cavity Between Two Discs of the Compressor of a Siemens KWU V84.3 Gas Turbine
Authors: Bohn Dieter , Krüger Uwe , Nitsche Klaus
Published: February 2015

The rotor of modern gas turbines often consists of single discs forming air-filled rotating cavities. During stationary operation each disc in the compressor section is of nearly uniform temperature. This results from the radial heat conduction in the disc material and from the negligible axial temperature gradients between surface and air in the adjacent cavities. The situation changes rapidly during cold start-ups of the engine. The disc rims respond quickly to the temperature of the mainstream (500 to 600 K), whereas the average temperature of the massive hub section follows with some delay thus forming a radial thermal gradient. This induces a buoyancy-driven flow inside the cavity, which is superimposed by a controlled hot gas ingress. A defined amount of hot air flows radially inwards through the Hirth-type serration at the head of the discs, causes increased convection within the cavity and speeds up the thermal equilibration process in the discs.

Numerical investigations of the very complex flow situation have been carried out to get a better knowledge of both the flow-physics and the heat transfer from the hot fluid to the cold rotating wall.

A modern numerical Finite-Volume-Code with multiblock and body-fitted grid-options has been used to calculate three different cases: one cavity without hot gas ingress and two cases with two different mass flow parameters. The boundary conditions have been chosen in such a way that they cover real gas turbine conditions at the very beginning of the start-up. The most stringent case has been investigated, i. e. the head of the discs and the hot gas mass flow having the mainstream temperature while the discs in the hub region remain at ambient temperature.

It has been found that in the case without throughflow the core-region rotates approximately with the speed of a solid body. In the case of superimposed hot gas flow directed radially inwards, the flow has the character of a potential-vortex-flow, with exception of the regions near the wall. The hot gas is transported to the hub-region so that the heat transfer in this region is very large in the first period of the start-up-procedure.

Some aspects are presented which should be investigated in more detail in future work, especially the 3-D effects and the conjugate heat transfer. First results of a 3-D calculation are shown.
Application of Different Turbulence Models for Duct Flow Simulation With Reduced and Full Navier-Stokes Equations
Authors: Hirsch Charles , Khodak Andrei E.
Published: February 2015

An S-shaped diffusing duct flow is analysed with various turbulence models: standard high-Reynolds-number k-ε model with wall functions, a low-Reynolds-number k-ε model, and an explicit non-linear algebraic Reynolds stress closure model (ASM). In addition, computations were obtained with parabolic and partially-parabolic approximations along with solutions of the full Navier-Stokes equations. Results of the numerical simulation are compared with LDA measurements of the turbulent flow as reported by Whitelaw and Yu (1993). Detailed comparisons of mean velocity and Reynolds stress distributions are presented. It is shown that the partially-parabolic approach gives a significant improvement over parabolic approximation in predicting mean velocities and pressure distributions. However, the turbulence models used are still not able to reproduce all the observed flow features, although the ASM results appear to be slightly but consistently closer to the experimental data.
A Collaborative Venture: The Advanced Gas Turbine Systems Research Program
Authors: Fant Daniel B. , Golan Lawrence P.
Published: February 2015

The Advanced Gas Turbine Systems Research (AGTSR) program is a university-industry research consortium that was established in September 1992. The AGTSR program is sponsored by the Department of Energy–Morgantown Energy Technology Center. The South Carolina Energy Research and Development Center (SCERDC) heads the effort and is responsible for administering and managing the AGTSR program, which is expected to continue to the year 2000. At present, 67 American Universities are AGTSR Performing Members, representing 35 states. Two RFP’s have already been announced and the third RFP was released in December, 1994. There are presently 23 research subcontracts underway at Performing Member universities. Approximately seven new subcontracts are expected to be awarded in 1995. The research is focused on topics as defined by the AGTSR Industry Review Board composed of five major cost-sharing U.S. gas turbine manufacturers, including EPRI and GRI as advisors. All university projects must be relevant to advancing stationary gas turbines for the next generation of electrical power generation systems. Research areas being addressed include: turbine heat transfer, combustion modeling and instability, thermal barrier coatings, aerodynamic losses, and advanced cycle analyses. This paper will present the objectives and benefits of the AGTSR program, progress achieved to date, and future planned activity in fiscal year 1995.
Prediction of Film Cooling Effectiveness and Heat Transfer due to Streamwise and Compound Angle Injection on Flat Surfaces
Authors: Neelakantan S. , Crawford M. E.
Published: February 2015

The distributed Yavuzkurt injection model is extended to predict the effectiveness and heat transfer coefficients for film cooling injection from a single row of holes, aligned both along the direction of the freestream and at an angle with it. The injection angles were 24° and 35°. The compound angles considered were 50.5° and 60°. The Yavuzkurt film cooling model is used in conjunction with a one-equation model to yield the effectiveness and heat transfer predictions. The density ratios considered were 1.6 and 0.95 for the effectiveness predictions and 1.0 and 0.95 for the heat transfer predictions. For the effectiveness predictions, the blowing ratios range from 0.5 to 2.5, and the momentum flux ratios from 0.16 until 3.9. The hole spacings were 3, 6, and 7.8 hole diameters. The Yavuzkurt model constants are seen to be definitely correlated with the momentum flux ratio. Correlations for the model constants are obtained in terms of the momentum flux ratio. For the heat transfer predictions, the blowing ratios ranged from 0.4 to 2.0, and the momentum flux ratios from 0.16 to 3.9. The spacing between the holes was 3, 6, and 7.8 hole diameters. The matching between the effectiveness correlations and the heat transfer predictions is done on the basis of the momentum flux ratio. Results indicate that the Yavuzkurt model predictions are best for the in-line round holes. Heat transfer predictions are close to the experimental results for lower blowing ratios, until the ratio exceeds 1. For higher blowing ratios, the predictions, though less accurate, follow the experimental trends.
Turbulent Transport Measurements in a Heated Boundary Layer: Combined Effects of Free-Stream Turbulence and Removal of Concave Curvature
Authors: Kestoras Michael D. , Simon Terrence W.
Published: February 2015

Turbulence measurements for both momentum and heat transport are taken in a boundary layer over a flat, recovery wall downstream of a concave wall (R=0.97m). The boundary layer appears turbulent from the beginning of the concave wall and grows over the test wall with negligible streamwise acceleration. The strength of curvature at the bend exit, δ99.5/R, is 0.04. The free-stream turbulence intensity is ∼8% at the beginning of the curve and is nearly uniform at ∼4.5% throughout the recovery wall. Comparisons are made with data taken in an earlier study, in the same test facility, but with a low free-stream turbulence intensity (−0.6%). Results show that on the recovery wall, elevated free-stream turbulence intensity enhances turbulent transport quantities such as -uv¯ and vt¯ in most of the outer part of the boundary layer, but near-wall values of vt¯ remain unaffected. This is in contrast to near-wall vt¯ values within the curve which decrease when free-stream turbulence is increased. At the bend exit, decreases of -uv¯ and vt¯ due to removal of curvature become more profound when free-stream turbulence intensity is elevated, compared to low-TI behavior. Measurements in the core of the flow indicate that the high levels of cross transport of momentum over the upstream concave wall cease when curvature is removed. Other results show that turbulent Prandtl numbers over the recovery wall are reduced to −0.9 when free-stream turbulence intensity is elevated, consistent with the rise in Stanton numbers over the recovery wall.
Computing Engine Efficiencies by Neural Nets
Authors: Long T. W.
Published: February 2015

The Performance Seeking Control (PSC) system for the Pratt & Whitney 1128 Engine requires estimates of engine performance; however, the current estimation method of Kalman Filtering imposes a heavy computation overhead. Thus fast on-line applications may be limited. A neural network approach to estimating engine performance is investigated as an alternative method. This neuro-estimator emulates the Kalman Filter based on off-line training. Good agreement between Kalman Filter output and the neuro-estimator output was achieved for steady state conditions.
Designing and Simulating the Engine Speed Governor for Helicopter Applications
Authors: Wong T. H.
Published: February 2015

Designing a turboshaft engine speed governor of a typical helicopter application for digital electronic engine controls is presented. In the transition from hydromechanical to electronic control of the power turbine speed governing, the importance of using the notch filter compensation technique to accomplish a stable and wide bandwidth speed governor is discussed. Emphasis will be placed on designing the power turbine speed governor for steepest descent autorotation recovery maneuver which is considered especially challenging to the integration of engines in operational helicopters. Simulation of the integrated airframe/engine/control system is also presented.
Improved Silicon Nitride Materials and Component Fabrication Processes for Aerospace and Industrial Gas Turbine Applications
Authors: Pollinger John P.
Published: February 2015

New and improved silicon nitride structural ceramic materials and component fabrication processes are being developed and refined for implementation and insertion into aerospace, industrial, and automotive gas turbine applications. These improved materials and forming processes offer the potential of meeting turbomachinery manufacturers’ performance, quality, cost, and production volume goals. AlliedSignal has developed a new generation of silicon nitride materials with isotropic acicular microstructures that result in a number of property improvements compared to current HIP’ed fine-grained silicon nitride materials. Concurrently, new silicon nitride component forming processes such as gelcasting and refinements of current forming processes such as presintered component machining are being developed and refined to achieve production volume fabrication capability, yields, and short cycle times at low costs. As these materials and component fabrication processes are maturating, a number of applications are being investigated and demonstrated including hot section turbomachinery components for aircraft auxiliary power units (APU’s), industrial gas turbines, and automotive hybrid electric vehicle turboalternators.
Combustor Rebuild Effects on Gas Turbine Performance
Authors: MacLeod J. D. , Barry B.
Published: February 2015

The Institute for Aerospace Research of the National Research Council of Canada (NRCC), has established a program for the evaluation of component deterioration on gas turbine engine performance. The effort is aimed at investigating the effects of typical in-service faults on the performance characteristics of each individual engine component. As part of this project, a study of the effects of combustor rebuild tolerances on overall engine performance was undertaken. This study investigated the range of performance changes that might be expected for simply disassembling and reassembling the combustor module of a gas turbine engine, and how these changes would influence the results of any component modification testing.

To evaluate the effects of rebuilding the combustor on the performance of a single spool engine, such as an Allison T56 turboprop engine, a series of three rebuilds was carried out. This study was performed in a similar way to two previous NRCC studies on the effects of compressor and turbine rebuilding. While the compressor and turbine rebuild studies found performance changes in the order of I% on various engine parameters, the effects of rebuilding the combustor have proven to be of similar magnitude. Based on the results of the combustor rebuild study, new methods to improve the assurance of the best possible tolerances during the rebuild process are currently being addressed.

This paper describes the project objectives, the experimental installation, and the results of the performance evaluations. Discussed are performance variations due to combustor rebuilds on engine performance characteristics. As the performance changes were significant, a rigorous measurement uncertainty analysis is included.
Conversion of an Advanced Natural Gas-Fueled Combustion Turbine to Coal-Based Fuel Applications
Authors: Newby R. A. , Archer D. H. , Bannister R. L.
Published: February 2015

Westinghouse is developing an advanced, natural-gas-fired, combustion turbine system that will produce electricity at net efficiencies exceeding 60% (LHV). The 8-year development program, supported by the U.S. Department of Energy, Morgantown Energy Technology Center, incorporates innovations and advances in component design, materials, and cycle configurations. As part of the program, a conceptual evaluation of the adaptation of the system to the use of coal-based fuels has been conducted. Fluidized bed coal gasification with hot gas cleaning, and advanced pressurized fluidized bed combustion have both been assessed. These coal-based applications are described and their potential performance and development issues with respect to the required turbine modifications are reviewed.
A Theoretical and Numerical Development of the Concept of the Active Control Foil Bearing (ACFB)
Authors: Braun M. J. , Choy F. K. , Dzodzo M. , Hsu J. , Veillette R. , Deckler D.
Published: February 2015

The authors of the present paper envisage far reaching applications of the foil bearing technology when merged with the concept of active control. Thus, this paper proposes and presents a comprehensive procedure for feedback control design for an active foil bearing. Two types of controllers are introduced, and discussed: i) the active feedback control for online adjustment, and ii) the supervisory control for anticipatory event management. A numerical procedure to simulate the steady state and transient dynamics of a foil bearing was also presented.

Successful introduction of such a new type of bearing will allow: (a) tolerance and ‘on-line’ adaptation to large time-dependent distortions and misalignment, (b) continuous adjustment for enhanced stability and resilience to high speed rubs, (c) reduced wear and power loss, (d) relative immunity from foreign object damage (FOD), (e) high load capacity due to thicker film lubricant, (f) lighter weight and reduced spatial envelope over active magnetic bearings, and (g) inherent stability without feedback control as compared with the magnetic bearing which has no stable equilibrium without feedback.
Stall Inception Measurements in a High-Speed Multi-Stage Compressor
Authors: Escuret J. F. , Garnier V.
Published: February 2015

This paper presents unsteady measurements taken in a high-speed four-stage aero-engine compressor prior to the onset of aerodynamic flow instabilities. In this experiment, forty fast-response pressure transducers have been located at various axial and circumferential positions throughout the machine in order to give a very detailed picture of stall inception.

At all the compressor speeds investigated, the stall pattern observed is initiated by a very short length-scale finite-amplitude disturbance which propagates at a fast rate around the annulus. This initial stall cell leads to a large-amplitude system instability in less than five rotor revolutions. Varying the IGV setting angle is found to have a strong influence on the axial location of the first disturbance detected. In particular, transferring the aerodynamic loading from front to downstream stages moves the first disturbance detected from the first to the last stage of the compressor. Other repeatable features of the stall inception pattern in this compressor have been identified using a simple analysis technique particularly appropriate to the study of short length-scale disturbances. It is found that the origins of instabilities are tied to particular tangential positions in both the stationary and rotating frames of reference.

These measurements lead to the conclusion that the stall inception process in high-speed multi-stage compressors can be characterised by some very local and organised flow phenomena. Moreover, there is no evidence of pre-stall waves in this compressor.
Assessment of the Cold Wire Resistance Thermometer for High Speed Turbomachinery Applications
Authors: Dénos R. , Sieverding C. H.
Published: February 2015

The paper first describes the fundamentals of cold wire resistance thermometry. The transfer function with and without wire-prong heat conduction effects are discussed and a new method for the description of complicated transfer functions describing both the prongs and wire frequency response is proposed.

The experimental part of the paper starts with an investigation of the transfer function of various probes differing by the wire diameter, the l/d ratio and the wire-prong connection using two simple methods: (1) electrical heating of the wire by a sine current and (2) a temperature step test consisting in injecting the probe into a hot air stream. The first test provides information on the wire response whereas the second serves to study wire prong heat conduction effect.

The tests cover a wide range of velocities and densities. A frequency bandwidth of 2 kHz is obtained with a 2.5 µm wire probe at an air velocity of 200 m/s at atmospheric pressure. A numerical compensation system allows to extend the use of this probe to much higher frequencies. Finally, the probe is mounted onto a wheel in a high speed rotating test rig allowing probe traverses through a stationary hot air jet at rotational speeds up to 5000 RPM with the probe positioned at a radius of 0.380 m. The probe signal is transmitted via an opto electronic data transmission system. It is demonstrated that using the numerical compensation method, it is possible to reconstruct the hot jet temperature profile at frequencies up to 6 kHz.
Feedback Linearizing Control of Surge in an Axial Compression System: Theory and Experimental Validation
Authors: Badmus O. O. , Chowdhury S. , Nett C. N.
Published: February 2015

This paper presents experimental demonstration of surge stabilization in an axial compressor rig with a feedback linearizing controller. The controller design approach is model-based, and hence a nonlinear surge model for the facility is first validated. The surge model is a modification of the classic one-dimensional incompressible fluid surge model, with an effective length function incorporated, to account for the increased path-length of the fluid in the compressor due to the imparted tangential forces of the blade. This model, which adequately describes the observed surge dynamics both in terms of amplitude and frequency of oscillation, is then used to develop the feedback control law. The feedback linearizing control input implicitly linearizes the dynamics between the system input, throttle area parameter, and the system output, inlet dynamic pressure. A linear state feedback control input, implemented on the feedback linearized system thus ensures stabilization of the surge dynamics in the original nonlinear model. Finally, the nonlinear based observer is included in closed loop implementation to enhance the tracking of the system output, and also to minimize the adverse effect of measurement noise, thereby improving closed loop system performance.
Experimental Leakage and Rotordynamic Results for Helically Grooved Annular Gas Seals
Authors: Childs Dara W. , Gansle Anthony J.
Published: February 2015

Rotordynamic-coefficient and leakage test results are presented for three grooved seals with helix angles of 0°, 15°, and 30° against rotation. The seals are 50.8 mm long and 152.4 mm in diameter. Tests were done for two supply pressures (up to 17 bars), three speeds (5000, 12000, and 16000 rpm), four pressure ratios, and three inlet fluid prerotation conditions.

The results showed that increasing the helix angle yields a progressive reduction in the cross-coupled stiffness coefficient k and a progressive increase in leakage. The helically-grooved seals consistently yield negative cross-coupled stiffness coefficients for nonprerotated inlet flow; hence, k in these seals would oppose forward whirl of a rotor. Helically grooved seals become less effective at reducing k with increasing preswirl; hence, for optimum effectiveness they should be used with a swirl brake.

Comparison between helically-grooved and honeycomb-stator seals showed that helically-grooved stators had reduced (negative) whirl-frequency ratios for nonprerotated flows but were no better than honeycomb-stator seals for elevated fluid prerotation. The 15° and 30° helix grooves leaked about 1.6 and 2.2 times, respectively, as much as the honeycomb-stator seals.
Design and Analysis of a Sensorless Magnetic Damper
Authors: Chen H. Ming
Published: February 2015

An analytical method for designing magnetic bearing controllers with no displacement sensors has been developed and laboratory tested. The method was applied to the design of a sensorless magnetic damper for replacing a rolling element bearing of a vertical rotor with a large unbalance. The synchronous vibration force transmitted to ground was predicted to be reduced by a factor of ten.
A Navier Stokes Analysis of Airfoils in Oscillating Transonic Cascades for the Prediction of Aerodynamic Damping
Authors: Abharl Reza S. , Giles Michael
Published: February 2015

An unsteady, compressible, two dimensional, thin shear layer Navier Stokes solver is modified to predict the motion-dependent unsteady flow around oscillating airfoils in a cascade. A quasi 3-D formulation is used to account for the streamwise variation of streamtube height. The code uses Ni’s Lax-Wendroff algorithm in the outer region, an implicit ADI method in the inner region, conservative coupling at the interface, and the Baldwin-Lomax turbulence model. Computational mesh consists of an O-grid around each blade plus an unstructured outer grid of quadrilateral or triangular cells. The unstructured computational grid was adapted to the flow to better resolve shocks and wakes. Motion of each airfoil was simulated at each time step by stretching and compressing the mesh within the O-grid. This imposed motion consists of harmonic solid body translation in two directions and rotation, combined with the correct inter-blade phase angles.

Validity of the code is illustrated by comparing its predictions to a number of test cases, including an axially oscillating flat plate in laminar flow, the Aeroelasticity of Turbomachines Symposium Fourth Standard Configuration (a transonic turbine cascade), the Seventh Standard Configuration (a transonic compressor cascade). The overall comparison between the predictions and the test data is reasonably good. A numerical study on a generic transonic compressor rotor was performed in which the impact of varying the amplitude of the airfoil oscillation on the normalized predicted magnitude and phase of the unsteady pressure around the airfoil was studied. It was observed that for this transonic compressor, the non-dimensional aerodynamic damping was influenced by the amplitude of the oscillation.
A Semi-Empirical Theory for Surface Mounted Aerodynamic Wall Shear Stress Gauges
Authors: Davies Mark R. D. , Duffy James T.
Published: February 2015

A new semi-empirical theory relating aerodynamic wall shear stress to the mean voltage from a surface mounted constant temperature hot film gauge is presented. High spatial resolution thermal images of the sensor area are used to obtain values for the mean sensor temperature and the thermal dimensions of the sensor. These thermal dimensions are shown to be invariant with Reynolds number. This data is used in the derivation of a new theory that effectively decouples the convection and conduction and hence removes the need for a fully conjugate analysis. The correct form of the relationship between sensor voltage and wall shear stress is a necessary prerequisite for gauge calibration and hence the quantification of aerodynamic wall shear stress. A calibration methodology is presented in an accompanying paper.
A New Throughflow Approach for Transonic Axial Compressor Stage Analysis
Authors: Sayari N. , Bölcs A.
Published: February 2015

Throughflow theory is based on an axisymmetric treatment of the circumferentially averaged flow. The present study proposes a new averaging procedure working normal to the central streamline. Used in a throughflow calculation process, this technique offers a more accurate and realistic modeling inside the blading; in addition it is well suited for the nearly normal shock calculation as well as the choking prediction. Based on pressure equilibrium, a numerical integrating procedure was developed. It provides the physically correct solution stemming from calculation without driving the flow towards an imposed one. In order to evaluate the shock position and the associated losses, a rapid and exact method derived from the quasi-3D characteristics method is incorporated. The reliability of this approach is proven by comparison with measurements conducted on an axial transonic compressor stage, as well as to a 3D viscous numerical simulation of the rotor flow. The results show a good representation of the flow outside the casing boundary layer and reveals the sensitive behavior of the predicted performance to the quality of the quasi-3D shock modeling.
Nonlinear Analysis of a Rigid Rotor on Magnetic Bearings
Authors: Nataraj C.
Published: February 2015

A simple model of a rigid rotor supported on magnetic bearings is considered. A proportional control architecture is assumed, the nonlinear equations of motion are derived and some essential nondimensional parameters are identified. The free and forced response of the system is analyzed using techniques of nonlinear analysis. Both qualitative and quantitative results are obtained and stability criteria are derived for safe operation of the system.
Gas Turbine Model Scaling
Authors: Davies Mark R. D. , Wallace John D.
Published: February 2015

A dimensional analysis, of both the equations governing boundary-layer flow with heat transfer and of the steady and unsteady boundary conditions, demonstrates that twelve non-geometric, dimensionless parameters are required for the complete similarity of a three-dimensional, compressible, viscous flow with a freestream pressure gradient. The analysis shows that non-dimensional groups describing the machine can be reduced to a function of metal angles and twelve fundamentally derived, dimensionless scaling parameters. The equation describing the rate of local entropy generation caused by fluid friction and heat transfer is also non-dimensionalised. This leads to an estimate of the relative magnitude of entropy generation due to fluid friction and heat transfer. A comparison of the principle operating parameters for a number of existing gas turbine test facilities, designed to model the aerodynamic and heat transfer conditions in real engines, suggests that full modelling of engine boundary-layer phenomena has not been achieved. A semi-empirical, boundary-layer analysis suggests that measured velocity boundary-layer profiles from adiabatic test facilities differ significantly with those from a gas turbine operating at engine gas to wall temperature ratios. Similarly, the analysis established the shape of the velocity boundary-layer to be dependent upon the specific-heat ratio.
Development of Shell-and-Tube Type Ceramic Heat Exchanger for CGT301
Authors: Yoshimura Yukihiro , Itoh Katsunori , Ohhori Kunio , Hori Masayoshi , Hattori Mitsuru , Yoshida Toshihiro , Watanabe Keiichiro
Published: February 2015

The development of a 300kW-class recuperative ceramic gas turbine (CGT301) for continuous load has been conducted by the New Energy and Industrial Technology Development Organization (NEDO) as one of the programs in the Moonlight Project. In this program, the development of a ceramic heat exchanger has been carried out under the cooperation of Ishikawajima-Harima Heavy Industries, Ltd. (IHI) and NGK Insulators, Ltd. (NGK). since 1988.

In this paper, the process of the development of the ceramic heat exchanger is described. A three pass shell-and-tube type of heat exchanger is considered. As the heat exchanger is to be operated at gas temperature over 825°C, the reliability is expected to be improved by applying high-temperature resistant silicon-nitride ceramics to its hot tube-bundle. In consideration of the limitation in the size of the ceramic tube-bundle, the heat exchanger was designed as the assembly of six identical modules.

Tests of a single module with ceramic tube-bundle were conducted. It was confirmed that the ceramic tube-bundle had reasonable structural reliability, and that the module gave a sufficient performance i.e., temperature effectiveness and pressure drop characteristics.
New 200 MW Class 501G Combustion Turbine
Authors: Southall L. , McQuiggan G.
Published: February 2015

The 501G 60-Hz Combustion Turbine has been developed jointly by Westinghouse Electric Corporation, Mitsubishi Heavy Industries, Ltd., and FiatAvio. It continues a long line of large heavy-duty single-shaft combustion turbines by combining the proven efficient and reliable concepts of the 501F with the latest advances in aero technology via the Westinghouse Alliance with Rolls-Royce. The output of the 501G is over 230 MW with a combined cycle net efficiency of 58%. This makes the 501G the largest 60-Hz combustion turbine in the world and also the most efficient.
Optimization of Bearing Locations for Rotor Systems With Magnetic Bearings
Authors: Srinivasan Sriram , Maslen Eric H. , Barrett Lloyd E.
Published: February 2015

This paper presents a method for quickly evaluating the effect of changes in bearing location on bearing design for stability of rotating machinery. This method is intended for use by rotating machinery designers to select the “best” bearing locations prior to the bearing design process. The purpose of the method is to improve the design process by separating the problem of determining the “best” bearing locations from that of determining the actual bearing design. The method is independent of the type of bearing employed. For each candidate bearing configuration, the method provides a scalar measure of the relative ability of bearings to meet stability specifications. Within certain limits, the stability specifications are defined by the designer. The scalar measure is used to rank the candidate bearing locations and thereby select the best one. The scalar measure is compared to a practical measure of magnetic bearing design such as the infinity norm of the controller for an example design of a multi-stage centrifugal compressor.
Combustion Oscillation Control by Cyclic Fuel Injection
Authors: Richards G. A. , Yip M. J. , Robey E. , Cowell L. , Rawlins D.
Published: February 2015

A number of recent articles have demonstrated the use of active control to mitigate the effects of combustion instability in afterburner and dump combustor applications. In these applications, cyclic injection of small quantities of control fuel has been proposed to counteract the periodic heat release that contributes to undesired pressure oscillations. This same technique may also be useful to mitigate oscillations in gas turbine combustors, especially in test rig combustors characterized by acoustic modes that do not exist in the final engine configuration.

To address this issue, the present paper reports on active control of a subscale, atmospheric pressure nozzle/combustor arrangement. The fuel is natural gas. Cyclic injection of 14% control fuel in a premix fuel nozzle is shown to reduce oscillating pressure amplitude by a factor of 0.30 (i.e., −10 dB) at 300 Hz. Measurement of the oscillating heat release is also reported.
Hydrocarbon Fuel Cooling Technologies for Advanced Propulsion
Authors: Sobel David R. , Spadaccini Louis J.
Published: February 2015

Storable hydrocarbon fuels that undergo endothermic reaction provide an attractive heat sink for future high-speed aircraft. An investigation was conducted to explore the endothermic potential of practical fuels, with inexpensive and readily available catalysts, under operating conditions simulative of high-speed flight applications. High heat sink capacities and desirable reaction products have been demonstrated for n-heptane and Norpar 12 fuels using zeolite catalysts in coated-tube reactor configurations. The effects of fuel composition and operating condition on extent of fuel conversion, product composition and the corresponding endotherm have been examined. The results obtained in this study provide a basis for catalytic-reactor/heat-exchanger design and analysis.
The Design and Performance of a High Work Research Turbine
Authors: Vlasic E. P. , Girgis S. , Moustapha S. H.
Published: February 2015

This paper describes the design and performance of a high work single stage research turbine with a pressure ratio of 5.0, a stage loading of 2.2 and cooled stator and rotor. Tests were carried out in a cold flow rig and as part of a gas generator facility. The performance of the turbine was assessed, through measurements of reaction, rotor exit conditions and efficiency, with and without airfoil cooling. The measured cooled efficiency in the cold rig was 79.9%, which, after correcting for temperature and measuring plane location, matched reasonably well the efficiency of 81.5% in the gas generator test. The effect of cooling, as measured in the cold rig, was to reduce the turbine efficiency by 2.1%. A part load turbine map was obtained at 100, 110 and 118% design speed and at 3.9, 5.0 and 6.0 pressure ratio. The influence of speed and the limit load pattern for transonic turbines are discussed. The effect of the downstream measuring distance on the calculated efficiency was determined using three different locations. An efficiency drop of 3.2% was measured between the rotor trailing edge plane and a distance four chords downstream.