bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Excited Oscillation of Transonic Flow Around an Airfoil in Two-Dimensional Channel
Authors: Yamamoto Kazuomi , Tanida Yoshimichi
Published: March 2015

A self-excited oscillation of transonic flow in a simplified cascade model was investigated experimentally, theoretically and numerically. The measurements of the shock wave and wake motions, and unsteady static pressure field predict a closed loop mechanism, in which the pressure disturbance, that is generated by the oscillation of boundary layer separation, propagates upstream in the main flow and forces the shock wave to oscillate, and then the shock oscillation disturbs the boundary layer separation again. A one-dimensional analysis confirms that the self-excited oscillation occurs in the proposed mechanism. Finally, a numerical simulation of the Navier-Stokes equations reveals the unsteady flow structure of the reversed flow region around the trailing edge, which induces the large flow separation to bring about the anti-phase oscillation.
Automotive Research Compressor Experience
Authors: Pampreen R. C.
Published: March 2015

The design features and development experience of an advanced automotive gas turbine centrifugal compressor are presented. The compressor was designed with moderately low specific speed, high blade aerodynamic loading and design point on the choke characteristic. A cascade diffuser was used; a new design approach brought about an unusual performance characteristic. The influence of impeller blade loading on performance is presented. Lessons learned are summarized.
Experimental Investigation of Rotor-Stator Interaction in a Centrifugal Pump With Several Vaned Diffusers
Authors: Arndt N. , Acosta A. J. , Brennen C. E. , Caughey T. K.
Published: March 2015

This paper describes an experimental investigation of rotor–stator interaction in a centrifugal pump with several vaned diffusers. Steady and unsteady diffuser vane pressure measurements were made for a two–dimensional test impeller. Unsteady impeller blade pressure measurements were made for a second two–dimensional impeller with blade number and blade geometry identical to the two–dimensional impeller used for the diffuser vane pressure measurements. The experiments were conducted for different flow coefficients and different radial gaps between the impeller blade trailing edge and the diffuser vane leading edge (5% and 8% of the impeller discharge radius). The largest pressure fluctuations on the diffuser vanes and the impeller blades were found to be of the same order of magnitude as the total pressure rise across the pump. The largest pressure fluctuations on the diffuser vanes were observed to occur on the suction side of the vane near the vane leading edge, whereas on the impeller blades the largest fluctuations were observed to occur at the blade trailing edge. However, the dependence of the fluctuations on the flow coefficient was found to be different for the diffuser vanes and the impeller blades; on the vane suction side, the fluctuations were largest for the maximum flow coefficient and decreased with decreasing flow coefficient, whereas at the blade trailing edge, the fluctuations were smallest for the maximum flow coefficient and increased with decreasing flow coefficient. Increasing the number of the diffuser vanes resulted in a significant decrease of the impeller blade pressure fluctuations. The resulting lift on the diffuser vanes was computed from the vane pressure measurements; the magnitude of the fluctuating lift was found to be larger than the steady lift.
Mach Number Effects on Secondary Flow Development Downstream of a Turbine Cascade
Authors: Perdichizzi Antonio
Published: March 2015

The results of an investigation of the three-dimensional flow downstream of a transonic turbine cascade are presented. The investigation was carried out for a wide range of Mach numbers, extending from M2is = 0.2 up to 1.55. Measurements were made in five planes at different axial locations downstream of the trailing edge (covering more than one chord length), by using a miniaturized five hole probe especially designed for transonic flows. The results are presented in terms of local loss coefficient, vorticity and secondary velocity plots; these plots give a detailed picture of the secondary flow development downstream of the cascade and show how flow compressibility influences the vortex configuration. As Mach number increases, the passage vortex is found to migrate towards the endwall and secondary flow effects are more confined in the endwall region. The pitchwise mass averaged loss and flow angle distributions along the blade height appear to be affected by the expansion ratio; at high Mach number both underturning and overturning angles are found to be smaller than in low velocity flows. Overall losses, vorticity and secondary kinetic energy versus Mach number are also presented and discussed.
An Experimental Study of Turbine Vane Heat Transfer With Leading Edge and Downstream Film Cooling
Authors: Nirmalan V. , Hylton L. D.
Published: March 2015

This paper presents the effects of downstream film cooling, with and without leading edge showerhead film cooling, on turbine vane external heat transfer. Steady state experimental measurements were made in a three-vane, linear, two-dimensional cascade. The principal independent parameters — Mach number, Reynolds number, turbulence, wall-to-gas temperature ratio, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio — were maintained over ranges consistent with actual engine conditions. The test matrix was structured to provide an assessment of the independent influence of parameters of interest, namely, exit Mach number, exit Reynolds number, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio.

The vane external heat transfer data obtained in this program indicate that considerable cooling benefits can be achieved by utilizing downstream film cooling. The downstream film cooling process was shown to be a complex interaction of two competing mechanisms. The thermal dilution effect, associated with the injection of relatively cold fluid, results in a decrease in the heat transfer to the airfoil. Conversely, the turbulence augmentation, produced by the injection process, results in increased heat transfer to the airfoil. The data presented in this paper illustrate the interaction of these variables and should provide the airfoil designer and computational analyst the information required to improve heat transfer design capabilities for film cooled turbine airfoils.
Effective Tools for Diagnosing Elusive Turbomachinery Dynamics Problems in the Field
Authors: Simmons Harold R. , Smalley Anthony J.
Published: March 2015

This paper describes and discusses techniques which can effectively diagnose dynamics problems in turbomachinery. A variety of elusive dynamics problems are identified which require definition, quantification, diagnosis, and monitoring. The state of the art in measurement and signal processing techniques is discussed with reference to such factors as the directness of the measurement, the degree of intrusion required, the difficulty of installation, and the reliability or durability of the sensor. Several examples of techniques are provided which have proved to be effective in diagnosing elusive dynamics problems; some examples allow comparison of alternative techniques with different degrees of effectiveness. Problems addressed include rotating stall in the compressor section of a gas turbine, coupled lateral/torsional vibration in a gas turbine driven pipeline compressor, forced vibration of combustor parts, strain gage telemetry of blade vibrations, and nonintrusive measurement of blade vibrations using bearing mounted accelerometers.
The Measurement of Boundary Layers on a Compressor Blade in Cascade: Part 4 — Flow Fields for Incidence Angles of −1.5 and −8.5 Degrees
Authors: Zierke W. C. , Deutsch S.
Published: March 2015

Measurements, made with laser Doppler velocimetry, about a double-circular-arc compressor blade in cascade are presented for −1.5 and −8.5 degree incidence angles and a chord Reynolds number near 500,000. Comparisons between the results of the current study and those of our earlier work at a 5.0 degree incidence are made. It is found that in spite of the relative sophistication of the measurement techniques, transition on the pressure surface at the −1.5 degree incidence is dominated by a separation “bubble” too small to be detected by the laser Doppler velocimeter. The development of the boundary layers at −1.5 and 5.0 degrees are found to be similar. In contrast to the flow at these two incidence angles, the leading edge separation “bubble” is on the pressure surface for the −8.5 degree incidence. Here, all of the measured boundary layers on the pressure surface are turbulent — but extremely thin — while on the suction surface, a laminar separation/turbulent reattachment “bubble” lies between roughly 35% and 60% chord. This “bubble” is quite thin, and some problems in interpreting backflow data.
Casing Vibration and Gas Turbine Operating Conditions
Authors: Mathioudakis K. , Loukis E. , Papailiou K. D.
Published: March 2015

The results from an experimental investigation of the compressor casing vibration of an industrial Gas Turbine are presented. It is demonstrated that statistical properties of acceleration signals can be linked with engine operating conditions. The power content of such signals is dominated by contributions originating from the stages of the compressor, while the contribution of the shaft excitation is secondary. Using non-parametric identification methods, accelerometer outputs are correlated to unsteady pressure measurements taken by fast response transducers at the inner surface of the compressor casing. The transfer functions allow reconstruction of unsteady pressure signal features from the accelerometer readings. A possibility is thus provided, for “seeing” the unsteady pressure field of the rotor blades without actually penetrating through the casing, but by simply observing its external surface vibrations.
Effect of Blade Tip Configuration on Tip Clearance Loss of a Centrifugal Impeller
Authors: Ishida Masahiro , Ueki Hironobu , Senoo Yasutoshi
Published: March 2015

According to the theory presented by the authors, the tip clearance loss of an unshrouded centrifugal impeller mainly consists of two kinds of loss; one is the drag due to the leakage flow through the blade tip clearance and the other is the pressure loss to support the fluid in the thin annular clearance space between the shroud and the blade tip against the pressure gradient in the meridional plane without blades. The former is proportional to the leakage flow or the contraction coefficient of leakage flow. The authors have conducted performance tests using an impeller with sixteen backward-leaning blades in three configurations of the blade tip: round edge, sharp square edge and edge with an end-plate. The experimental tip clearance effects can be predicted by the theory assuming reasonable contraction coefficients. They are 0.91, 0.73 and 0.53 for the respective tip configurations. The impeller efficiency is improved by about 1.5 point by reducing the contraction coefficient from 0.91 to 0.53 providing that the tip clearance ratio at the exit of impeller is 0.1. More improvement is expected for an impeller with highly loaded blades where the leakage loss shares the major part of the tip clearance loss.
A Parametric Study of Radial Turbomachinery Blade Design in Three-Dimensional Subsonic Flow
Authors: Ghaly W. S. , Tan C. S.
Published: March 2015

An aerodynamic design method is described and used to implement a parametric study of radial turbomachinery blade design in three-dimensional subsonic flow. Given the impeller hub and shroud, the number of blades and their stacking position, the design method gives the detailed blade shape, flow and pressure fields that would produce a prescribed tangential averaged swirl schedule. The results from that study show that decreasing the number of blades increases the blade wrap, and that the blade loading is strongly affected by the rate of change of mean swirl along the mean streamlines. The results also show that the blade shape and the pressure field are rather sensitive to the prescribed mean swirl schedule which suggests that, by carefuly tailoring the swirl schedule, one might be able to control the blade shape and the pressure field and hence secondary flow.
Characteristics of Partial Length Circular Pin Fins as Heat Transfer Augmentors for Airfoil Internal Cooling Passages
Authors: Arora S. C. , Abdel-Messeh W.
Published: March 2015

Pin fins are commonly used as heat transfer augmentors for internal cooling of turbine airfoils. These pins may extend from one wall to the other or may be segmented to meet specific requirements of removing the airfoil’s varying heat load. Three configurations of the partial pins were tested in a 25:1 aspect ratio channel and the results are compared with those for the full pins. The array average heat transfer rate decreases linearly with increasing gap and is bounded by the value for full pins at one end and that for the smooth channel at the other. However, the local distribution of the Nusselt number and the average for each of the two walls depends on the configuration of the partial pins. The friction factor was lower for partial pins than for the full pins and also decreased with increasing gap. For the configuration with all partial pins on one wall, the friction factor was found to be the lowest with no change in the corresponding heat transfer rate from a wall with pins.
Prediction of the Aerodynamic Environment and Heat Transfer for Rotor-Stator Configurations
Authors: Griffin L. W. , McConnaughey H. V.
Published: March 2015

A numerical study of the aerodynamic and thermal environment associated with axial turbine stages is presented. Computations were performed using a modification of the unsteady viscous code, ROTOR1, and an improved version of the steady inviscid cascade system, MERIDL-TSONIC, coupled with boundary layer codes, BLAYER and STAN5. Two different turbine stages were analyzed: the first stage of the United Technologies Research Center Large Scale Rotating Rig (LSRR) and the first stage of the Space Shuttle Main Engine (SSME) high pressure fuel turbopump turbine. The time-averaged airfoil midspan pressure and heat transfer profiles were predicted for numerous thermal boundary conditions including adiabatic wall, prescribed surface temperature, and prescribed heat flux. Computed solutions are compared with each other and with experimental data in the case of the LSRR calculations. Modified ROTOR1 predictions of unsteady pressure envelopes and instantaneous contour plots are also presented. Relative merits of the two computational approaches are discussed.
Effects of Free Damping Layers on Harmonic Response of Rotating Blades
Authors: Young T. H. , Shiau T. N. , Chiu S. H.
Published: March 2015

This paper studies the forced vibration of a rotating blade with free damping layers to harmonic excitation by means of the finite element method. The damping layers are made of viscoelastic material with complex elastic modulus, and the excitation may be either distributed or concentrated. Triangular elements with totally 15 d.o.f. are used to allow for a great variety of shapes and boundary conditions. The effects of various parameters, such as loss factor, storage modulus and thickness of damping layers, are investigated. The results show that the vibration amplitudes near resonances can be significantly reduced by the free damping layers.
Surge Model: Predicting Damping and Excitation Frequencies of Complex Pumping Systems
Authors: Lifson Alexander , Sparks Cecil R.
Published: March 2015

Frequency domain analysis is presented to define susceptibility of complex pumping systems to surge oscillations. In the analysis, piping spans are considered as distributed elements, compressors or pumps, orifices, valves, and junctions as lumped acoustic four pole elements. The piping elements are connected into one network through the use of appropriate matching boundary conditions. The analysis is most readily applicable to single stage units, typical of gas transmission stations. The surge model is based on predicting damping (logarithmic decrement values) and mode shapes for pressure and flow pulsations of the interactive dynamic system at its various natural acoustic frequencies. The system design is optimized by assuring that all operating points are sufficiently removed from surge, i.e., logarithmic decrements are above certain specified value. The effects of mean flow on acoustic wave propagation, pipe friction, viscothermal dissipation, and pressure losses at various piping locations (junctions, valves, orifices) are accounted for in the model. Results of the computational modeling of a complex centrifugal compressor system is presented. The analytical model is also verified by comparing the analytical results with experimental data.
Experimental Examination of the Aerothermal Performance of a Gas Turbine Engine Test Facility
Authors: Cooper E. E. , Kodres C. A.
Published: March 2015

The U.S. Navy standard jet engine test cell was experimentally examined to determine aerodynamic and thermodynamic characteristics. Pressures and temperatures were measured throughout the facility while testing different engines at different power settings from idle through afterburning. The data include gas prescures and temperatures measured at both the test cell intakes and exhaust from which velocities were calculated and, subsequently, mass flow rates calculated and compared.

The highest test cell wall temperature recorded was about 300 degrees Centigrade reached during A/B testing of the TF30 engine. The vacuum drawn within the facility was within structural limits, reaching a minimum of only 2.5 cm of water. Airflow approaching the engine inlet was always steady and free of eddies or recirculation.

Although the facility performed well, some intuitively puzzling flow characteristics were observed. For example, the total test cell airflow increases with engine power setting from idle up to military power (100% rpm) but remains constant as afterburning is initiated. Another characteristic to be pondered is the skewing of the jet as it mixes with the entrained ambient air.
Experimental Study of the Effect of Dense Spray on Drop Size Measurement by Light Scattering Technology
Authors: Chin Ju Shan , Li Wei Ming , Zhang Yan
Published: March 2015

The effect of dense spray on drop size measurement by light scattering technology was studied by using Malvern instrument with five duplicated internal mixing airblast atomizers aligned in line with laser beam. The correction factor data for multiple scattering were obtained. By regression analysis, an empirical equation was obtained which correlated the correction factor as a function of obscuration (OBS), Sauter mean diameter under dilute spray condition SMD0. and drop size distribution parameter for Rosin–Rammler distribution under dilute spray conditions N0. The experimental data showed definitely that the correction factor is not only a function of OBS, SMD0, as proposed by Dodge, but also is a function of N0. The correlation fits the experimental data very well, and can be used for practical purposes to correct the data from Malvern drop sizer at high obscuration conditions.
Three-Dimensional Wake Decay Inside of a Compressor Cascade and its Influence on the Downstream Unsteady Flow Field: Part II — Unsteady Flow Field Downstream of the Stator
Authors: Poensgen C. , Gallus H. E.
Published: March 2015

A measuring technique based on multi-sensor hot-wire anemometry has been developed to determine the unsteady three-dimensional velocity vector and the structure of turbulent flows. It then has been applied to the passage and the exit flow of an annular compressor cascade, which is periodically disturbed by the wakes of a cylinder rotor, located about 50 percent of blade chord upstream. In Part I of this paper the decay of the rotor wakes will be described first without stator and secondly through a stator passage. The time-dependent turbulent flow field downstream of this stator is discussed in Part II of this paper.

The rotor wakes have a major influence on the development of three-dimensional separated regions inside the compressor cascade, and this interaction will be addressed in both parts of this paper.
Experimental Measurement of the Vortex Development Downstream of a Lobed Forced Mixer
Authors: Eckerle Wayne A. , Sheibani Hamdi , Awad Jean
Published: March 2015

An experimental study was conducted to investigate the mixing processes downstream of a forced mixer. A forced mixer generates large scale, axial (stirring) vorticity which causes the primary and secondary flow to mix rapidly with low loss. These devices have been successfully used in the past where enhanced mixing of two streams was a requirement. Unfortunately, details of the mixing process associated with these lobed forced mixers are not well understood. Performance sensitivity to design variables has not been documented. An experiment was set up to investigate the mixing processes downstream of a mixer. Air flow was independently supplied to each side of the forced mixer by separate centrifugal blowers. Pressures were measured at the entrance to the lobes with a pitot-static probe to document the characteristics of the approaching boundary layer. Interior mean and fluctuating velocities were nonintrusively measured using a two-component Laser Doppler Velocimetry (LDV) system for velocity ratios of 1:1 and 2:1. The wake structure is shown to display a three step process where initially secondary flow was generated by the mixer lobes, the secondary flow created counter-rotating vortices with a diameter on the order of the convolute width, and then the vortices broke down resulting in a significant increase in turbulent mixing. The results show that the mean secondary motion induced by the lobes effectively circulated the flow passing through the lobes. This motion, however, did not homogeneously mix the two streams. Turbulent mixing in the third step of the mixing process appears to be an important element in the enhanced mixing that has been observed with forced mixers. The length required for the flow to reach this third step is a function of the velocity ratio across the mixer. The results of this investigation indicate that both the mean secondary motion and the turbulent mixing occurring after vortex breakdown need to be considered for prediction of forced mixer performance.
Mixing of an Acoustically Excited Air Jet With a Confined Hot Crossflow
Authors: Vermeulen P. J. , Grabinski P. , Ramesh V.
Published: March 2015

The mixing of an acoustically pulsed air jet with a confined hot crossflow has been assessed by temperature profile measurements. These novel experiments were designed to examine the affects of acoustic driver power and Strouhal number on jet structure, penetration and mixing. The results showed that excitation produced strong changes in the measured temperature profiles. This resulted in significant increases in mixing zone size, penetration (at least 100% increase), mixing, and the length to achieve a given mixed state was shortened by at least 70%. There was strong modification to the jet-wake region. The increase in jet penetration and mixing was saturating near 90 W the largest driving power tested. The jet response as determined by penetration and mixing was optimum at a Strouhal number of 0.27. Overall, pulsating the jet flow significantly improved the jet mixing processes in a controllable manner.
The Effect of Swirl on the Velocity and Turbulence Fields of a Liquid Spray
Authors: de la Rosa A. Breña , Wang G. , Bachalo W. D.
Published: March 2015

This work reports an experimental study of the effect of swirl on the structure of a liquid spray, i.e., on the behaviour of drops and their interaction with the gaseous phase, and on the velocity and turbulence fields of the spray in the swirling flow. Three vane type swirlers having low, medium, and high swirl numbers were used in the tests. The swirlers were placed on the liquid supply tube of a pressure atomizer and tested in the wind tunnel under specified conditions. Properties of the dispersed phase such as velocity and size distributions, particle number density, and volume flux were measured at several locations within the swirling flow field. In addition, mean velocity and turbulence properties were obtained for the gas phase. The results show that flow reversal of the drops is present at the high swirl number within the recirculation region. The spatial distribution of drops reveals a widening of the spray with increasing swirl strength while the concentration of large drops is shown to increase near the core of the swirling field with increasing swirl number. Plots of the turbulence kinetic energy, normal Reynolds stresses, and Reynolds shear stresses show double-peak radial distributions which indicate regions in the flow where high energy content, mean velocity gradients, and large shear forces are present. The decay of turbulence velocities in the axial direction was observed to be very fast, an indication of high diffusion and dissipation rates of the kinetic energy of turbulence. The significance of the turbulence measurements is that these double peak profiles indicate a deviation of the swirling spray from isotropy. This information should be relevant to researchers modelling these complex flows.
Study of Internal Flows in a Mixed-Flow Pump Impeller at Various Tip Clearances Using 3D Viscous Flow Computations
Authors: Goto Akira
Published: March 2015

The complex three-dimensional flow fields in a mixed-flow pump impeller are investigated by applying the incompressible version of the Dawes’ 3D Navier-Stokes code. The applicability of the code is confirmed by comparison of computations with a variety of experimentally measured jet-wake flow patterns and overall performances at four different tip clearances including the shrouded case. Based on the computations, the interaction mechanism of secondary flows and the formation of jet-wake flow are discussed. In the case of large tip clearances, the reverse flow caused by tip leakage flow is considered to be the reason for the thickening of the casing boundary layer followed by the deterioration of the whole flow field.
Heat Transfer and Aerodynamics of a High Rim Speed Turbine Nozzle Guide Vane Tested in the RAE Isentropic Light Piston Cascade (ILPC)
Authors: Harasgama S. P. , Wedlake E. T.
Published: March 2015

Detailed heat transfer and aerodynamic measurements have been made on an annular cascade of highly loaded nozzle guide vanes. The tests were carried out in an Isentropic Light Piston test facility at engine representative Reynolds number, Mach number and gas-to-wall temperature ratio.

The aerodynamics indicate that the vane has a weak shock at 65–70% axial chord (mid span) with a peak Mach number of 1.14. The influence of Reynolds number and Mach number on the Nusselt number distributions on the vane and endwall surfaces are shown to be significant. Computational techniques are used for the interpretation of test data.
Gas Turbine Film Cooling: Flowfield due to a Second Row of Holes
Authors: Sinha A. K. , Bogard D. G. , Crawford M. E.
Published: March 2015

Flowfield measurements with relevance to gas turbine film cooling were carried out behind a second row of holes located 40 hole diameters downstream of a first row and staggered with respect to it. The effects of the thicker boundary layer and that of injection from the first row were examined. Experiments were carried out for jet-to-mainstream density ratios of 1 and 2 and results compared to those obtained by Pietrzyk et al. (1989a,b) behind the first row. Results show that the dominant structures identified in the flowfield downstream of the first row were also present behind the second row. Due to the thicker boundary layer, though, the mean flowfield and the turbulence and shear stress fields were altered. One of the significant results was that the thicker boundary layer enables the jets to penetrate deeper into the mainstream.
Two Dimensional Flow Analysis of a Laboratory Centrifugal Pump
Authors: Miner S. M. , Flack R. D. , Allaire P. E.
Published: March 2015

Two dimensional potential flow was used to determine the velocity field within a laboratory centrifugal pump. In particular, the finite element technique was used to model the impeller and volute simultaneously. The rotation of the impeller within the volute was simulated by using steady state solutions with the impeller in 10 different angular orientations. This allowed the interaction between the impeller and the volute to develop naturally as a result of the solution. The results for the complete pump model showed that there are circumferential asymmetries in the velocity field, even at the design flow rate. Differences in the relative velocity components were as large as 0.12 m/sec for the radial component and 0.38 m/sec for the tangential component, at the impeller exit. The magnitude of these variations was roughly 25% of the magnitude of the average radial and tangential velocities at the impeller exit. These asymmetries were even more pronounced at off design flow rates. The velocity field was also used to determine the location of the tongue stagnation point and to calculate the slip within the impeller. The stagnation point moved from the discharge side of the tongue to the impeller side of the tongue, as the flow rate increased from below design flow to above design flow. At design flow, values of slip ranged from 0.96 to 0.71, from impeller inlet to impeller exit. For all three types of data (velocity profiles, stagnation point location, and slip factor) comparison was made to laser velocimeter data, taken for the same pump. At the design flow, the computational and experimental results agreed to within 17% for the velocity magnitude, and 2° for the flow angle. The stagnation point locations coincided for the computational and experimental results, and the values for slip agreed to within 10%.
A Method for the Design of Optimum Annular Diffusers of Canted Configuration
Authors: Adkins R. C. , Wardle M. H.
Published: March 2015

A simple method is presented for the design of annular diffusers which can take into account the effects of compressibility and of canted configurations by use of the area bisector line. No complex boundary layer calculations are required.
Full Coverage Discrete Hole Film Cooling: The Influence of the Number of Holes and Pressure Loss
Authors: Andrews G. E. , Asere A. A. , Gupta M. L. , Mkpadi M. C. , Tirmahi A.
Published: March 2015

Experimental measurements of the overall cooling effectiveness for full coverage discrete hole effusion cooling are presented for a wide range of practical geometries and for a density ratio between the coolant and combustion gases of 2.5. The influence of the number of holes per unit surface area was investigated at two fixed total hole areas or design pressure losses of 3% and 0.1%, at a relatively low coolant flow rate per unit surface area. Hole configurations suitable for both combustor and turbine blade cooling were investigated with hole sizes from 1.4 to 0.6mm at 3% design pressure loss and 1.3 to 3.3mm at 0.1% design pressure loss. The diameter change at a fixed pressure loss was for a constant total hole area with more holes as the size was reduced. This was shown to increase the cooling effectiveness through improved film cooling. Enlarging the hole size for a fixed number of holes and hence reducing the pressure loss for a fixed coolant mass flow was also shown to improve the cooling effectiveness through better film cooling. Major reductions in current combustor wall cooling flows were demonstrated for some full coverage effusion geometries.
Solar Dynamic CBC Power for Space Station Freedom
Authors: Harper William B. , Boyle Robert V. , Kudija Charles T.
Published: March 2015

The National Aeronautics and Space Administration (NASA) has selected a closed Brayton cycle (CBC) solar dynamic (SD) power conversion system to provide electric power for the growth phase of Space Station Freedom. This selection was based in part on the comparitive reduction in solar radiation collection made possible by the high efficiency, closed Brayton cycle system when compared to the efficiency of static conversion systems. The smaller required collector area results in a significant reduction in drag in the low earth orbit which is planned for the Space Station.

Under contract to the Rocketdyne Division of Rockwell International, the Allied-Signal Aerospace Company, Garrett Fluid Systems Division is developing the Solar Dynamic Power Generating Subsystem (PGS). This subsystem consists of a solar receiver, which accepts sunlight from the multifaceted collector mirror (the concentrator), and a CBC heat engine that converts the solar heat into electricity. This paper will review the design requirements for the Space Station Solar Dynamic Power Module and present results of the PGS cycle analysis and preliminary design.
Aerodynamic Analysis of a Two Stage Transonic Compressor With Variable Stator Vanes
Authors: Broichhausen K.-D. , Harster P.
Published: March 2015

Within the scope of a compressor research program a highly loaded two stage transonic compressor was investigated.

The submitted paper presents global information on the performance characteristics of the compressor as a whole and of the two stages as a function of the variable Stator and inlet guide vane settings. For the investigated two stage compressor a variable stator 1 is able to improve the performance to the same extent as a variable inlet guide vane.

Subsequently on the basis of L2F velocimetry, hotfilm gauges and probe traverses a more detailed view of the flow inside of the compressor is given. The main results can be summarized as follows:

In spite of high supersonic relative Mach numbers in front of rotor 1 the incidence angles change evenly from hub to tip depending on the back pressure. This is in contrast to plane cascade experience and is attributed to the bow shocks.

In the downstream rotor the shock pattern is strongly influenced by the relative position between rotor 1 and rotor 2 blades. As the glue on hotfilms on the stator 2 suction side show, the influence of the rotor 1 wakes can still be recognized in the laminar separation bubble and the turbulent boundary layer. Downstream of the compressor the mixing of the rotor wakes causes strong pitchwise gradients of total temperature.
Viscous Flow Computations in Turbomachine Cascades
Authors: Chevrin P.-A. , Vuillez C.
Published: March 2015

Accurate prediction of the flow in turbomachinery requires numerical solution of the Navier-Stokes equations. A two-dimensional Navier-Stokes solver developed at ONERA for the calculation of the flow in turbine and compressor cascades was adapted at SNECMA to run on different types of grid.

The solver uses an explicit, time-marching, finite-volume technique, with a multigrid acceleration scheme. A multi-domain approach is used to handle difficulties due to the geometry of the flow. An H-C grid was used in the calculations. Two turbulence models, based on the mixing length approach, were used.

The flow in a transonic compressor cascade, a subsonic and a transonic turbine cascade were computed. Comparison with experiments is presented.
Development of Materials and Coating Processes for High Temperature Heavy Duty Gas Turbines
Authors: Nakamura S. , Fukui Y. , Kojima Y. , Siga M. , Yamaguchi S.
Published: March 2015

This paper describes materials developed for the first stage nozzle and all stages turbine disc, and the new coating processes of the first stage bucket for high temperature, heavy duty gas turbines.

A cobalt base casting superalloy (30Cr-10Ni-7W-0.2Nb-0.15Zr-0.2Ti-bal.Co), having high creep rupture strength and ductility, was used for the first stage nozzle and 12Cr forging material, having high creep rupture strength, was used for all stages turbine disc of the high temperature, heavy duty gas turbine, the H25. To increase hot corrosion properties of the first stage bucket, MCrAlY was applied on the bucket external surfaces by a low-pressure plasma-spray coating technique. A procedure of chemical vapor deposition for Al coating on the bucket internal cooling paths was also established for future high temperature gas turbines.
Experimental Evaluation of a Low Emissions, Variable Geometry, Small Gas Turbine Combustor
Authors: Smith K. O. , Samii M. H. , Mak H. K.
Published: March 2015

The results of an on-engine evaluation of an ultra-low NOx, natural gas-fired combustor for a 200 kW gas turbine are presented. The combustor evaluated used lean-premixed combustion to reduce NOx emissions and variable geometry to extend the range over which low emissions were obtained.

Test results showed that ultra-low NOx emissions could be achieved from full load down to approximately 50% load through the combination of lean-premixed combustion and variable primary zone airflow.
Measuring Rotor and Blade Dynamics Using an Optical Blade Tip Sensor
Authors: Simmons Harold R. , Michalsky Douglas L. , Brewer Kenneth E. , Smalley Anthony J.
Published: March 2015

This paper describes an optical measurement system for monitoring combustion turbine blade tips. The sensor measures distance to a blade tip using triangulation of reflected laser light. The system accomplishes triangulation using an optical position sensing device and high speed data acquisition. In this way, it is able to monitor not only average and minimum blade tip clearances, but to monitor the variations of individual blade tip clearances. By appropriate signal processing, it is possible to determine rotor vibration at the probe axial location, variations in shaft DC position, transient losses in blade tip clearance, the potential for tip and seal rubs, vibrations of individual blades in the tangential direction, and rotor torsional vibration at the probe location. Some aspects of blade and torsional vibrations would require more than one probe. The paper presents static calibration data for the measurement system, showing its degree of linearity and range. The paper also presents data obtained on a dynamic blade test rig with tip passing speeds and blade widths comparable to those encountered in high performance industrial combustion turbines. Data from this rig have been processed to show rotor vibration, shift in shaft average position, blade-to-blade tip clearance variation, and variation with speed of minimum blade tip clearance. The measurement system is designed to produce data suitable for use in the monitoring of advanced combustion turbine durability and the diagnosis of turbine functional problems, static and dynamic.
Low-Toxic Method of Fuel Firing in Gas Turbine Micro-Flame Combustors
Authors: Sudarev A. V.
Published: March 2015

The results of development and study of the microflame diffusive firing of fuels outside the flameholder system with alternating whirl swirlers, located between them, are shown. The principles of a rational organization of the nearby trace structure outside the bluff-bodies within a limited turbulent flow are stated. The dome geometric parameters effect on the firing stability, heat emission completeness, temperature and concentration patterns of the flame, complex heat exchange process, toxic component emission and other characteristics of combustion chamber are discussed.
Radial Swirlers With Peripheral Fuel Injection for Ultra-Low NOx Emissions
Authors: Al Kabie H. S. , Andrews G. E.
Published: March 2015

A 76mm outlet diameter radial swirler with a dump expansion into a 140mm diameter combustor was investigated with a simulated 43% primary zone air flow at a 600K inlet temperature and one bar pressure. Two modes of peripheral fuel injection were investigated: at the 76mm swirler outlet and at the 140mm combustor wall just downstream of the swirler. This 140mm wall injector resulted in fuel injection into the swirler expansion outer recirculation zone. It was shown that the 140mm wall injection gave much higher NOx emissions than for the 76mm swirler outlet injector. These results were compared with other methods of fuel injection and the 76mm peripheral injection was shown to have superior NOx emissions than vane passage injection for all fuels except gas oil. Ultra low NOx emissions of 1ppm with 20 ppm CO, both at 15% oxygen, were demonstrated for propane and natural gas.
The Mechanism of Fouling and the Cleaning Technique in Application to Flow Parts of the Power Generation Plant Compressors
Authors: Mezheritsky A. D. , Sudarev A. V.
Published: March 2015

The baseline principles and deposit formation mechanism in the axial and centrifugal compressors of the power plants of various applications are discussed in the paper. The results of experimental investigation of fouling effect on the compressor and plant performances as well as the dismantling technique of deposit cleaning are shown.
Calculating NH3 Slip for SCR Equipped Cogeneration Units
Authors: Anderson C. M. , Billings J. A.
Published: March 2015

The NH3 slip pollutant generated by a recently completed cogeneration plant equipped with an SCR system was accurately monitored by a calculation method without the expense of an NH3 analyzer. The method of calculating the NH3 slip developed by the authors is based on measured variables and material balances. Discussed in further detail is the cogeneration plant, SCR characteristics, source of NH3 slip, variable measurements required for the NH3 slip calculation, equation development, accuracy of results, and NH3 analysis methods.
Basic Analysis of Counter-Rotating Turbines
Authors: Cai R. , Wu W. , Fang G.
Published: March 2015

A comprehensive basic analysis for various counter–rotating turbines is given with the blade element stage assumption. Similar to the classical analysis of common turbine stages, the appropriate independent variables and evaluation criteria of the counter–rotating turbine stages are first presented and then three typical kinds of rotating blade rows are defined and all possible typical schemes of counter–rotating turbine stages are enumerated. Their performances of specific work, load factor distribution between two counter–rotating shafts and efficiency are analysed and discussed for different shaft rotating speed ratios. This information is useful for the selection and preliminary design of a counter–rotating turbine. From the analysis results, it is concluded that the load capacity per unit engine length of counter–rotating turbines can be much higher than that of common turbines (approximately twice) without efficiency penalty or even with higher efficiency. Some triple counter–rotating turbines suitable for three shaft gas turbine power plants are proposed and analysed briefly too.
Assessment of Hot Gas Cleanup Technologies in Coal-Fired Gas Turbines
Authors: Parsons Edward L. , Webb Holmes A. , Zeh Charles M.
Published: March 2015

This paper reviews the status of in situ gas stream cleanup technologies which are an integral part of the direct coal-fired gas turbine systems being developed through the U.S. Department of Energy (DOE), Morgantown Energy Technology Center (METC). The technical discussion focuses on the proof-of-concept systems under development in the DOE/METC Advanced Coal-Fueled Gas Turbine Systems (ACFGTS) program initiated in 1986. In this program, Solar Turbines Inc., the Allison Gas Turbine Division of General Motors Corporation, and Westinghouse Electric Corporation have completed bench-scale tests of integrated combustion and hot gas cleanup systems in preparation for full-size subsystem tests. All these projects include the development of cleanup systems for contaminants resulting from the combustion of coal. These systems will both control emissions of pollutants and protect the turbine gas path from fouling, erosion, and corrosion. The bench-scale tests have demonstrated efficient combustion of coal-water slurries (CWS) and dry coal in high-pressure, short residence-time combustors. The tests have also yielded promising results in the abatement of nitrogen oxides (NOx) and volatile alkali and in the removal of ash and sulfur species from the hot gas streams.
Combined Cycle Enhancement
Authors: Jericha H. , Hoeller F.
Published: March 2015

The Combined Cycle Plant (CCP) offers the best solutions to curb air pollution and the greenhouse effect, and it represents today the most effective heat engine ever created. At Graz University of Technology work is conducted in close cooperation with industry to further enhancement of CC systems with regard to raising output and efficiency. Feasibility studies for intake air climatization, overload and partload control, introduction of aeroderivate gas turbines in conjunction with high temperature steam cycles, proposals for cooling and the use of hydrogen as fuel are presented.
Design of Robust Controllers for Gas Turbine Engines
Authors: Moellenhoff David E. , Rao S. Vittal , Skarvan Charles A.
Published: March 2015

This paper describes robust controller design methodologies for gas turbine engines. A linear state variable model for the engine is derived using partial derivatives. The Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) and the Parameter Robust Linear Quadratic Gaussian (PRLQG) robust controller design methodologies have been used to design a controller for gas turbine engines. A new method is proposed by combining the features of LQG/LTR and PRLQG methods and yields good robustness properties with respect to both unstructured uncertainties in the frequency domain and structured parameter variations in the time domain. The new procedure is illustrated with the help of an aircraft gas turbine engine model.
Determination of Cycle Configuration of Gas Turbines and Aircraft Engines by Optimization Procedure
Authors: Tsujikawa Yoshiharu , Nagaoka Makoto
Published: March 2015

This paper is devoted to the analyses and optimization of simple and sophisticated cycles, particularly for various gas turbine engines and aero-engines (including scramjet engine) to achive the maximum performance. The optimization of such criteria as thermal efficiency, specific output and total performance for gas turbine engines, and overall efficiency, non-dimensional thrust and specific impulse for aero-engines have been performed by the optimization procedure with multiplier method. The comparisons of results with analytical solutions establishes the validity of the optimization procedure.
SNECMA M88 Engine Development Status
Authors: Corde Jean Christophe
Published: March 2015

After describing the historical origins of the SNECMA M88 engine development program, the paper presents the general development planning until the production engine flight qualification at the end of 1995.

Then the technical aspects of the program are emphasized: the main new technologies involved in the engine, the general arrangement and the performance are described, and the engine development status is fully presented (development philosophy, main component tests, and complete engine tests).
Laminar Boundary Layer Interaction With an Unsteady Passing Wake
Authors: Paxson D. E. , Mayle R. E.
Published: March 2015

An investigation was conducted to study the unsteady effects of a moving wake as it passes over a laminar boundary layer in a stagnation region. Arguments are presented which show that in this region, the wake-induced unsteadiness may be treated, for the most part, as an inviscid, unsteady freestream which impresses itself on the boundary layer flow. As a result, the boundary layer equations remain valid and, for relatively small oscillations, a solution to the equations may be obtained using standard perturbation techniques. A related experiment is then described and the results are examined in light of this analytical approach.