bluuebunny/crossref_metadata_2025 huggingface dataset:
Multistage Simulations of the GE90 Turbine
Authors: Turner Mark G. , Vitt Paul H. , Topp David A. , Saeidi Sohrab , Hunter Scott D. , Dailey Lyle D. , Beach Timothy A.
Published: December 2014

The average passage approach has been used to analyze three multistage configurations of the GE90 turbine. These are a high pressure turbine rig, a low pressure turbine rig and a full turbine configuration comprising 18 blade rows of the GE90 engine at takeoff conditions. Cooling flows in the high pressure turbine have been simulated using source terms. This is the first time a dual-spool cooled turbine has been analyzed in 3D using a multistage approach. There is good agreement between the simulations and experimental results. Multistage and component interaction effects are also presented. The parallel efficiency of the code is excellent at 87.3% using 121 processors on an SGI Origin for the 18 blade row configuration. The accuracy and efficiency of the calculation now allow it to be effectively used in a design environment so that multistage effects can be accounted for in turbine design.
Numerical Investigations on the Optimum Design of Return Channels of Multi-Stage Centrifugal Compressors
Authors: Lenke L. J. , Simon H.
Published: December 2014

Numerical simulations of the flow within return channels for the aerodynamic design are presented. The investigated return channels are typical to join the exit from one stage of a centrifugal machine to the inlet of the next stage and cover the range of high flow coefficients.

Due to the strongly three-dimensional flow structure with high streamline curvature and secondary flows on hub and shroud of the return channel vanes, a modified explicit algebraic Reynolds stress model will be used. Starting with a comparison between measurements and numerical results to demonstrate the performance of the turbulence model in the prediction of losses, exit flow angle and separation behavior, further numerical investigations with different variations of the geometry of the channel will be considered. 3-D turbulent calculations at the design point and part load range show the influence of the design especially of the crossover bend onto the flow structure.
Development Summary of the 300 kW Ceramic Gas Turbine CGT302
Authors: Tatsumi Tetsuo , Takehara Isashi , Ichikawa Yoshihiro
Published: December 2014

Japanese Ministry of International Trade and Industry has been promoting a 300 kW Ceramic Gas Turbine (CGT) research and development program for 10 years. It was begun in 1988 as a part of the “New Sunshine Project”. The development target is to achieve thermal efficiency of over 42% at a turbine inlet temperature (TIT) of 1350°C. We have been taking a part in this project and developing a regenerative two-shaft CGT302.

This project will be finished at the end of FY1998. In 1998, we confirmed 31.7 ppm NOx emission at 1350°C by engine test. This result cleared the target emission level of 70 ppm. We also achieved 40.5% of thermal efficiency at 1412°C TIT and we are working to achieve the final target and cumulating operating hours to confirm reliability of ceramic components at 1200°C TIT which is considered to be reasonable temperature for commercial use.

This paper describes about ten years development summary of the CGT302.
Detailed Analysis of the Acoustic Mode Shapes of an Annular Combustion Chamber
Authors: Walz Günther , Krebs Werner , Hoffmann Stefan , Judith Hans
Published: December 2014

To get a better understanding of the formation of thermoacoustic oscillations in an annular gasturbine combustor, an analysis of the acoustic eigenmodes has been conducted using the Finite Element (FE) method. The influence of different boundary conditions and a space dependent velocity of sound has been investigated. The boundary conditions actually define the eigenfrequency spectrum. Hence, it is crucial to know e.g. the burner impedance. In case of the combustion system without significant mixing air addition considered in this paper, the space dependence of the velocity of sound is of minor importance for the eigenfrequency spectrum leading to a maximum deviation of only 5% in the eigenvalues.

It is demonstrated that the efficiency of the numerical eigenvalue analysis can be improved by making use of symmetry, by splitting the problem into several steps with alternate boundaries conditions, and by choosing the shift frequency ωs in the range of frequencies one is interested in.
PLIF and Temperature Measurements in an Actively Forced Swirl-Stabilized Spray Combustor
Authors: Santhanam V. , Knopf F. C. , Acharya S. , Gutmark E.
Published: December 2014

The effect of synchronized liquid fuel injection into combustion zones within excited air vortices was studied using Planar Laser Induced Fluorescence (PLIF) imaging of OH. A small-scale model of a swirl-stabilized combustor was investigated. Both the liquid fuel and air streams were forced at a normalized frequency (St) of approximately 6. Air vortices were produced by acoustically forcing the air stream. The liquid fuel was modulated at the same frequency and injected at different phase angles relative to the air vortex formation. Air was forced at two levels, and both non-swirling and swirling flow situations (Swirl number of 0.3) were considered. Instantaneous, and phase-averaged PLIF images of OH, and time-averaged temperature measurements were obtained for different phase differences between the two forcing signals.

The PLIF images indicated that with forcing there was an increase in the radial distribution of the reaction zones and a decrease in the height of the flame above the nozzle exit for both non-swirling and swirling conditions. Swirl also produced better mixing along the radial direction for low forcing amplitudes. The phase difference between the two forcing signals produced a significant change in the reaction zones particularly at a low forcing level and with swirl. The PLIF images indicated that the inner region of the flame was the primary reaction zone. When intense combustion occurred at the flame center, high vaporization rate prevented fuel droplets from reaching the external shear layer. The effect of the outer shear layer on combustion was enhanced by swirl, as the swirl increased the droplet dispersion away from the axis.
Control of Combustion Driven Oscillations by Equivalence Ratio Modulations
Authors: Paschereit Christian Oliver , Gutmark Ephraim , Weisenstein Wolfgang
Published: December 2014

Unstable thermoacoustic modes were investigated and controlled in an experimental low-emission swirl stabilized combustor, in which the acoustic boundary conditions were modified to obtain combustion instability. Several axisymmetric and helical unstable modes were identified for fully premixed conditions. The combustion structure associated with the different unstable modes was visualized by phase locked images of OH chemiluminescence. The axisymmetric mode showed large variation of the heat release during one cycle, while the helical mode showed variation in the radial location of maximal heat release. The helical and axisymmetric unstable modes were associated with flow instabilities related to the recirculating flow in the wakelike legion on the combustor axis and shear layer instabilities at the sudden expansion (dump plane), respectively. A closed loop active control system was employed to suppress the thermoacoustic pressure oscillations and to reduce undesired emissions of pollutants during premixed combustion. Microphone and OH emission detection sensors were utilized to monitor the combustion process and provide input to the control system. High frequency valves were employed to modulate the fuel injection. The specific design of the investigated experimental burner allowed testing the effect of different modulated fuel injection concepts on the different combustion instability modes. Symmetric and antisymmetric fuel injection schemes were tested. Suppression levels of up to 12 dB in the pressure oscillations were observed. In some cases a concomitant reductions of NOx and CO emissions were obtained, however, in other instances increased emissions were recorded at reduced pressure oscillations. The effect of the various pulsed fuel injection methods on the combustion structure was investigated.
Up-Rated Reheat Gas Turbine for the Repowering of Steam Power Plants
Authors: Negri di Montenegro G. , Peretto A. , Mantino E.
Published: December 2014

In the present paper, a thermoeconomic analysis of combined cycles derived from existing steam power plants is performed. The gas turbine employed is a reheat gas turbine. The increase of the two combustor outlet temperatures was also investigated.

The study reveals that the transformation of old conventional fossil fuel power plants in combined cycle power plants with reheat gas turbine supplies a cost per kWh lower than that of a new combined cycle power plant, also equipped with reheat gas turbine. This occurs for all the repowered plants analyzed.

Moreover, the solution of increasing the two combustor outlet temperatures resulted a strategy to pursue, leading, in particular, to a lower cost per kWh, Pay Back Period and to a greater Internal Rate of Return.
Detailed Analysis of the Thermal Wall Heat Load in Annular Combustors
Authors: Krebs Werner , Walz Günther , Hoffmann Stefan , Judith Hans
Published: December 2014

A detailed thermal analysis involving both measurements and calculations has been carried out in order to determine the wall heal load and to optimize the amount of cooling air for an annular combustor. In calculations, the convective wall heat flux has been detemined by application of a 3D Navier-Stokes Code. Furthermore, the radiation exchange between the hot combustion gases and the liner has been calculated using a multidimensional spectral approach.

Although a quite high thermal power density is found within the combustion chamber the wall heat load is at a low level. Values are well below 80 kW/m2, due to the application of ceramic tiles which have a low thermal conductivity. The wall heat load is dominated by radiation emitted in the lower gas radiation bands (λ < 2.9 μm). The convective wall heat flux is nearly balanced out by the sealing air which is discharged through gaps between the ceramic tiles. The cooling effect of the sealing air, however, is strongly influenced by the 3D near wall flow field in the combustion chamber.
Formation of Cyclic Compounds in Cracking Reactions for Hydrocarbon-Fueled High Speed Vehicles
Authors: Striebich R. C. , Maurice L. Q. , Edwards T.
Published: December 2014

An endothermic fuel pyrolytic reactor may favor the formation of benzene and polynuclear aromatic hydrocarbon (PAH) soot precursors which degrade fuel system performance. Both experimental and computational studies are in progress which verify the formation of multi-ring aromatic compounds in endothermic thermal cracking processes. Classic gas phase pyrolytic soot mechanisms may be effective for the prediction of soot precursor concentrations. Hence, a need exists to examine thermal molecular growth processes in a versatile experimental apparatus which can help guide modeling efforts and increase basic understanding (and mitigation) of growth mechanisms. In the present work, cyclic formation experimental data are presented for three mixtures: n-decane, 90 volume % n-decane/10 volume % toluene, and 80 volume % n-decane/20 volume % toluene pyrolysis in a System for Thermal Diagnostic Studies (STDS). The data are qualitatively and quantitatively compared to computations at temperatures, pressures and residence times commensurate with those encountered in endothermic fuel reactor systems. These computations are an attempt to assess the applicability of gas-phase kinetic mechanisms to predict the chemistry of thermal decomposition in the fuel system. Preliminary results show the prominence of molecular growth reactions similar to gas phase pyrolysis mechanisms, starting with hydrocarbon unsaturation, cyclization, and finally, benzene, toluene and heavier PAH formation. Experimental results to date show general qualitative agreement to computational models. However, it is clear that molecular growth mechanisms found to be unimportant at the high temperatures generally associated with combustion can play a significant role in fuel systems.
A New Procedure and Equipment for Exciting and Measuring Gas Turbine Blade Vibrations
Authors: Voloshchenko Anatoly P. , Rovkov Victor A.
Published: December 2014

A procedure and experimental equipment for exciting and measuring gas turbine blade vibrations by their main and higher-order vibration modes within the range from 150 to 20,000 Hz at a normal temperatures are described. The above equipment was used to advantage in fast determining the influence of a wide variety of design, technology and other factors on the frequency and vibration modes.
Effect of Film-Cooling Hole Location on Turbulator Heat Transfer Enhancement in Turbine Blade Internal Air-Cooling Circuits
Authors: McDonough J. M. , Garzón V. E. , Schulte D. E.
Published: December 2014

Numerical results demonstrating the effect of film-cooling hole placement on turbulator heat transfer effectiveness in internal convective cooling air circuits of turbine blades in high-performance gas turbine engines is presented for a two-dimensional model problem. Of particular interest will be the performance of a new turbulence modeling formalism similar to large-eddy simulation (LES) but employing subgrid-scale models constructed from nonlinear discrete dynamical systems, and not requiring filtering of the resolved-scale governing equations. Computed results for temperature distribution, flow streamlines, pressure coefficient and heat transfer Stanton number are compared for three different cooling hole/turbulator configurations, and turbulence kinetic energy is compared with results from a standard k-ε model.
Mist/Steam Cooling in a Heated Horizontal Tube: Part 2 — Results and Modeling
Authors: Guo T. , Wang T. , Gaddis J. L.
Published: December 2014

Experimental studies on mist/steam cooling in a heated horizontal tube have been performed. Wall temperature distributions have been measured under various main steam flow rates, droplet mass ratios, and wall heat fluxes. Generally, the heat transfer performance of steam can be significantly improved by adding mist into the main flow. An average enhancement of 100% with the highest local heat transfer enhancement of 200% is achieved with 5% mist. When the test section is mildly heated, an interesting wall temperature distribution is observed: the wall temperature increases first, then decreases, and finally increases again. A three-stage heat transfer model with transition boiling, unstable liquid fragment evaporation, and dry-wall mist cooling, has been proposed and has shown some success in predicting the wall temperature of the mist/steam flow. The PDPA measurements have facilitated better understanding and interpreting of the droplet dynamics and heat transfer mechanisms. Furthermore, this study has shed light on how to generate appropriate droplet sizes to achieve effective droplet transportation, and has shown that it is promising to extend present results to a higher temperature and higher pressure environment.
Feasibility of Contact Elimination of a Mechanical Face Seal Through Clearance Adjustment
Authors: Zou Min , Dayan Joshua , Green Itzhak
Published: December 2014

The feasibility of eliminating contact in a noncontacting flexibly mounted rotor (FMR) mechanical face seal is studied. The approach for contact elimination is based on a parametric study using FMR seal dynamics. Through clearance adjustment it is possible to reduce the maximum normalized relative misalignment between seal faces and, therefore, eliminate seal face contact Clearance is measured by proximity probes and varied through a pneumatic adjustment mechanism. Contact is determined phenomenologically from pattern recognition of probe signals and their power spectrum densities as well as angular misalignment orbit plots, all calculated and displayed in real-time. The contact elimination strategy is experimentally investigated for various values of stator misalignment and initial rotor misalignment Contrary to intuition but compliant with the parametric study, the experimental results show that for the seal under consideration contact can be eliminated through clearance reduction.
Prediction of Acoustic, Vorticity and Entropy Waves Generated by Short-Duration Acoustic Pulses Incident on a Blade Row
Authors: Sajben Miklos
Published: December 2014

Some long-standing questions concerning the dynamic behavior of coupled inlet/compressor systems have been answered by analyzing data from recent experiments in which the reflections of intense, short-duration acoustic pulses from an operating compressor were documented. The present paper offers a simple, one-dimensional integral theory as a background for these experiments. The arrival of an acoustic pulse (or an acoustic step change) to a single row of stationary blades gives rise to two acoustic waves (one upstream and one downstream), one vorticity wave, and possibly also an entropy wave. Pulses are characterized by integrals of spatial distributions of pressure, temperature or tangential velocity, while steps are defined by the jump of these flow properties at the wave. Simple expressions are given for the strength of each wave type, in terms of the blade stagger angle and the axial Mach number. The results help in interpreting, scaling and extrapolating experimental data. The work is a step towards an ability to specify realistic outflow boundary conditions in unsteady inlet flow computations, as appropriate for the compressor geometry and the operating conditions.
Influence of Turbulence Intensity on Annular Turbine Stator Aerodynamics at Low Reynolds Numbers
Authors: Matsunuma Takayuki , Abe Hiroyuki , Tsutsui Yasukata
Published: December 2014

The aerodynamic characteristics of turbine cascades are thought to be relatively satisfactory due to the favorable pressure of the accelerating flow. But within the low Reynolds number region of 6×104 where the 300kW ceramic gas turbines which are being developed under the New Sunshine project of Japan operate, the characteristics such as boundary layer separation, reattachment and secondary flow which lead to prominent power losses can not be easily predicted.

In this research, experiments have been conducted to evaluate the performance of an annular turbine stator cascade, especially focused on the influence of inlet turbulence intensity at low Reynolds numbers. The Reynolds number, based on inlet condition, was varied from 2×104 to 12×104. The turbulence intensity was changed between 0.5% and 8.9% by setting turbulence generation sheets. The wake of the cascade was measured using a 5-hole pressure probe and a single element hot-wire anemometry.

The Reynolds number was a determinative important parameter, while the turbulence intensity was found to have an insignificant effect on the overall total pressure loss of annular turbine stator at low Reynolds numbers. However, the increase in separation zone on suction surface and the decrease of passage vortices near the endwalls were observed locally with the increase in the inlet turbulence intensity. Instantaneous velocity signals proved the transformation of the flow structure in separation zone. The increase in profile loss (separation) and the decrease in net secondary loss (passage vonices) offset each other. Therefore, the net overall loss remains almost constant.
On the Development and Application of the FRAP® (Fast-Response Aerodynamic Probe) System in Turbomachines: Part 2 — Flow, Surge and Stall in a Centrifugal Compressor
Authors: Roduner Christian , Kupferschmied Peter , Köppel Pascal , Gyarmathy George
Published: December 2014

The present paper, Part 2 of a trilogy, is primarily focussed on demonstrating the capabilities of a FRAP® system configuration based on the simplest type of fast-response probe. A single cylindrical probe equipped with a single pressure sensor is used to measure absolute pressure and both velocity components in an essentially two-dimensional flow field. The probe is used in the pseudo-3-sensor mode (see Part 1). It is demonstrated that such a 1-sensor probe is able to measure high-frequency rotor-governed systematic fluctuations (like blade-to-blade phenomena) alone or in combination with flow-governed low-frequency fluctuations as rotating stall (RS) and mild surge (MS). However 3-sensor probes would be needed to measure stochastic (turbulence-related) or other aperiodic velocity transients.

The data shown refer to the impeller exit and the vaned diffuser of a single-stage high-subsonic centrifugal compressor. Wall-to-wall probe traverses were performed at the impeller exit and different positions along the vaned diffuser for different running conditions. The centrifugal compressor was operated under stable as well as under unstable (pulsating or stalled) running conditions. The turbomachinery oriented interpretation of these unsteady flow data is a second focus of the paper. A refined analysis of the time-resolved data will be done in Part 3 where different spatial/temporal averaging methods are compared.

Two different averaging methods were used for the data evaluation. Impeller based ensemble averaging for blade-to-blade systematic fluctuations (with constant period length at a constant shaft speed) and flow-based class averaging for the relatively slow MS and RS with slightly variable period length.

Due to the ability of fast-response probes to simultaneously measure velocity components as well as total and static pressure, interesting insights can be obtained into impeller and diffuser channel flow structures as well as into the time behavior of large-domain phenomena as RS and MS.
Effect of Two-Scale Roughness on Boundary Layer Transition Over a Heated Flat Plate: Part 2 — Boundary Layer Structure
Authors: Pinson Mark W. , Wang Ting
Published: December 2014

Velocity and temperature measurements made within transitional boundary layers over a surface roughened by two roughness scales were examined. The variation of intermittency through the transition region was shown to be consistent with a smooth-wall model of transition, but the prediction of transition onset was not well represented by momentum thickness for cases with strong surface disturbances. During transition, distributed roughness was shown to reduce the growth of velocity fluctuation possibly through stronger dissipation and to significantly enhance wall-ward transport of momentum without a corresponding increase in thermal transport. The step-change between the two roughness scales was shown to notably affect boundary layer behavior. Spectral analysis supported the hypothesis in part 1 that the separated region downstream of the step shed vortices into the downstream flow. The wavelet analysis suggested that transition over rough surfaces may be in bypass mode because the disturbances were shown to be amplified in a broad spectral band.
Effects of Hole Shape on Film Cooling With Large Angle Injection
Authors: Kohil Atui , Bogard David G.
Published: December 2014

In this study the film cooling performance of a single row of discrete holes inclined at an injection angle of 55° is investigated at a density ratio of DR = 1.6. Three different hole geometries were used in this study, a round hole and two shaped holes. One shaped hole had forward and lateral expansions of 15°, and the other a 15° lateral with a 25° forward expansion. For reference, a round hole with an injection angle of 35° was also tested. The film cooling performance of each hole shape was evaluated using adiabatic effectiveness, thermal field, and velocity field measurements.

The shaped holes showed higher spatially averaged adiabatic effectiveness than the round hole over the whole range of momentum flux ratios (I) investigated. The effectiveness values for the shaped holes were only marginally better than the round hole at the low I, but at the high I, the shaped holes performed much better than the round hole. The temperature and velocity field measurements near the hole exit suggest that there is a slight detachment of the jet from the wall for the round hole, while the jets remain attached for the two shaped holes. The shaped hole with the larger forward expansion had a warmer jet with a higher trajectory at the hole exit suggesting ingestion of mainstream fluid and flow separation within the hole.
Experimental Investigation of Adaptive Control Applied to HSFD Supported Rotors
Authors: El-Shafei A. , El-Hakim M.
Published: December 2014

This paper describes the experimental application of adaptive control to Hybrid Squeeze Film Damper (HSFD) supported rotors. The HSFD has been shown to be an adaptive damper capable of providing infinite damper configurations between short and long damper configurations. Previously, theoretical investigations of the adaptive control of HSFD concentrated on the development of the model reference adaptive control (MRAC) method, as well as development of a nonlinear reference model. Simulations of the performance of the adaptive controller during run-up and coast-down indicated the superior performance of the adaptive controller. In this paper, the adaptive controller is tested on a multi-mode rotor. A test rig is designed and developed using computer control. A simple reference model is investigated consisting of a second order system. Three forms for adaptation gain are studied. The results of the experimental investigation illustrated the performance capabilities of the adaptive controller applied to the HSFD, and moreover indicated the possibility of simple design for the adaptive controller.
A 35,000 RPM Test Rig for Magnetic, Hybrid and Back-Up Bearings
Authors: Swanson Erik E. , Walton James F. , Heshmat Hooshang
Published: December 2014

Magnetic bearings have long offered the potential for significant turbomachinery system improvements due to their oil-free, non-contact, low loss nature and their ability to actively control shaft dynamic motion. However, end-users and many designers are hesitant to apply this technology. There are two basic stumbling blocks: active magnetic bearings (AMBs) have little overload capacity, and failure of any portion of the AMB system could result in catastrophic damage to the machine. To cope with both of these problems, a secondary back-up bearing must be included in the system. This paper describes a new full scale, high speed test rig which has the capability to test a variety of back-up bearings at speeds of up to 35,000 RPM, and bearing loads of up to 6.7 kN. Preliminary data for two novel back-up bearings are presented as a demonstration of the test rig’s capabilities.
Overshoot of the Rankine Vortex Formed in the Flow Field Behind the Inlet Guide Vane of Centrifugal Compressors
Authors: Chen Y. N. , Hagelstein D. , Kassens I. , Hasemann H. , Haupt U. , Rautenberg M.
Published: December 2014

This paper is aimed to analyze the experimental results obtained by Kassens and Rautenberg (1998) and Kassens (1997) concerning the overshoot of the rotating velocity field behind the IGV. Since the IGV used in the present investigation has the form of a disc in the closed condition of the blades, the vorticity field of the rotating flow behind the outlet edge of the IGV can be determined by means of the streamline deflection in this IGV, whose function as an actuator disc does not need to be used. The potential-vortex field generated by these streamlines out of the IGV is calculated with good accuracy compared with the experimental results.

The further development of the vorticity field mentioned into the distribution of the tangential velocities can be derived from the diffusion of the vorticity, but with an inaccuracy caused by the overshoot of the Rankine vortex. This overshoot originates from the potential vortex field and travels towards the vortex core, which acts as a rigid body rotation.

The overshoot degenerates downstream from the outlet of the IGV due to strong damping incorporated in its unusual velocity field. Its disappearance introduces the formation of the orderly Lamb-Oseen vortices, whose theoretical property coincides well with the experimental result. Thus, the overshoot plays an active role for the loss in the total pressure in the central region of the rotating flow generated by the IGV.
Part Load Operation of a Combined Plant Using a Closed Circuit Blade Cooled Gas Turbine
Authors: Marushima Shin’ya , Higuchi Shin’ichi , Ikeguchi Takashi
Published: December 2014

Closed circuit blade cooled gas turbines are drawing attention because of their efficiency compared with that of a conventional air cooled gas turbine. In a closed circuit blade cooled gas turbine, coolant is not discharged into the gas path, so dilution of the hot gas stream, rotor blade pumping loss and pressure loss due to mixing of coolant with the stream are drastically reduced.

In this paper, two types of combined cycles, a closed circuit steam cooled gas turbine combined cycle CCSC, and a closed circuit air cooled gas turbine combined cycle CCAC are analyzed to verify the part load performance.

The blade temperatures of both combined cycles are lower than at full load, that is, the blades are sufficiently cooled. Under 30% load in the CCSC, the coolant steam pressure is lower than the main gas stream because of a shortage of coolant steam.
Flowfield Measurements in the Endwall Region of a Stator Vane
Authors: Kang M. B. , Thole K. A.
Published: December 2014

A first stage stator vane experiences high heat transfer rates particularly near the end wall where strong secondary flows occur. In order to improve numerical predictions of the complex endwall flow at low speed conditions, benchmark quality experimental data are required. This study documents the flowfield in the endwall region of a stator vane that has been scaled up by a factor of nine while matching an engine exit Reynolds number of Reex = 1.2·106. Laser Doppler velocimeter (LDV) measurements of all three components of the mean and fluctuating velocities are presented for several flow planes normal to the turbine vane. Measurements indicate that downstream of the minimum static pressure location on the suction surface of the vane, an attenuated suction side leg of the horseshoe vortex still exists. At this location, the peak turbulent kinetic energy coincides with the center of the passage vortex location. These flowfield measurements were also related to previously reported convective heat transfer coefficients on the endwall showing that high Stanton numbers occur where the passage vortex brings mainstream fluid towards the vane surface.
Advances in Oxide-Oxide CMC
Authors: Jurf Robert A. , Butner Steven C.
Published: December 2014

Recent advances in COI’s oxide-oxide CMC materials will be presented including basic processing steps, updated material properties, and fabrication techniques. Material properties of COI’s alumino-silicate system reinforced with various oxide fabrics will be compared, along with progress in developing a 1200°C oxide matrix system for future turbine system applications. Examples of fabricated hardware, including a subscale combustion liner, will be shown. Recent test and evaluation data will be provided.
Performance of Pre-Swirl Rotating-Disc Systems
Authors: Karabay Hasan , Pilbrow Robert , Wilson Michael , Owen J. Michael
Published: December 2014

This paper summarises and extends recent theoretical, computational and experimental research into the fluid mechanics, thermodynamics and heat transfer characteristics of the so-called cover-plate pre-swirl system. Experiments were carried out in a purpose-built rotating-disc rig, and the Reynolds-averaged Navier-Stokes equations were solved using 2D (axisymmetric) and 3D computational codes, both of which incorporated low-Reynolds-number k-ε turbulence models. The free-vortex flow, which occurs inside the rotating cavity between the disc and cover-plate, is controlled principally by the pre-swirl ratio, βp: this is the ratio of the tangential velocity of the air leaving the nozzles to that of the rotating disc. Computed values of the tangential velocity are in good agreement with measurements, and computed distributions of pressure are in close agreement with those predicted by a one-dimensional theoretical model.

It is shown theoretically and computationally that there is a critical pre-swirl ratio, βp,crit, for which the frictional moment on the rotating discs is zero, and there is an optimal pre-swirl ratio, βp,opt, where the average Nusselt number is a minimum. Computations show that, for βp < βp,opt, the temperature of the blade-cooling air decreases as βp increases; for βp > βp,opt, whether the temperature of the cooling air increases or decreases as βp increases depends on the flow conditions and on the temperature difference between the disc and the air. Owing to the three-dimensional flow and heat transfer near the blade-cooling holes, and to unquantifiable uncertainties in the experimental measurements, there were significant differences between the computed and measured temperatures of the blade-cooling air. In the main, the 3D computations produced smaller differences than the 2D computations.
Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge
Authors: Bohn Dieter E. , Kusterer Karsten A.
Published: December 2014

A leading edge cooling configuration is investigated numerically by application of a 3-D conjugate fluid flow and heat transfer solver, CHT-Flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multi-block technique.

The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row is on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45°. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena.

The numerical domain includes the internal cooling fluid supply, the radially inclined holes and the complete external flow field of the turbine vane in a high resolution grid. Periodic boundary conditions have been used in the radial direction. Thus, end wall effects have been excluded. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three dimensional and asymmetric jet flow field. Within a secondary flow analysis it can be shown that complex vortex systems are formed in the ejection holes and in the cooling fluid jets. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a good agreement concerning the vortex development. The phenomena on the suction side and the pressure side are principally the same. It can be found that the jets are barely touching the blade surface as the dominating vortex transports hot gas under the jets. Thus, the cooling efficiency is reduced.
Experimental and Numerical Conjugate Flow and Heat Transfer Investigation of the Influence of Density Ratio and Blowing Ratio on the Film-Cooling Efficiency of a First Stage Turbine Guide Vane
Authors: Bohn Dieter E. , Becker Volker J. , Rungen Agnes U.
Published: December 2014

A modem nozzle guide vane with showerhead cooling is investigated. The showerhead design consists of four rows of ejection holes at the leading edge in the stagnation region and has been worked out on the basis of a former design with only two rows.

The experimental analysis is performed in a cold-air test turbine by means of LDV. In order to overcome the thermal limitations of the test rig, the heat transfer analysis is performed with CHT-Flow, a numerical method that has been developed at the Institute of Steam and Gas Turbines and that works in a conjugate manner. This means that no thermal boundary conditions such as heat transfer coefficients have to be described on the vane surface for thermal analysis.

The first part of the investigation deals with the aerodynamics. At first, air is used as a cooling fluid leading to a density ratio of Πρ = 1.2. Then, in order to take density effects into account in the experiments. CO2 is used as a cooling gas providing a density ratio Πρ = 1.8 representative for modern engine operating conditions. The results are compared to the simulations.

It is shown that the cooling gas does not penetrate the main flow as far under realistic density ratios. Thus, the aerodynamic losses are reduced and there is better attachment of the cooling film to the airfoil.

The second part analyses the heat transfer. It is shown that lowering the blowing ratio has different influences on the material temperature locally. On the suction side, the cooling gas film attachment is enhanced and the surface temperature is lowered. In contrast, the surface temperature rises slightly on the pressure side.
Aerodynamic Damping Predictions Using a Linearized Navier-Stokes Analysis
Authors: Hoyniak Daniel , Clark William S.
Published: December 2014

A recently developed two dimensional, linearized Navier-Stokes algorithm, capable of modeling the unsteady flows encountered in turbomachinery applications, has been benchmarked and validated for use in the prediction of the aerodynamic damping. Benchmarking was accomplished by comparing numerical simulations with experimental data for two geometries. The first geometry investigated is a high turning turbine cascade. For this configuration, two different steady operating conditions were considered. The exit flow for one operating condition is subsonic whereas the exit flow for the other operating condition is supersonic. The second geometry investigated is a tip section from a high speed fan. Again, two separate steady operating conditions were examined. For this fan geometry, one operating condition falls within an experimentally observed flutter region whereas the other operating condition was observed experimentally to be flutter free. For both geometries considered, experimental measurements of the unsteady blade surface pressures were acquired for a linear cascade subjected to small amplitude torsional vibrations. Comparisons between the numerical calculations and the experimental data demonstrate the ability of the present computational model to predict accurately the steady and unsteady blade loading, and hence the aerodynamic damping, for each configuration presented.
Development of an Oil Injection System Optimised to the ABB Double Cone Burner
Authors: Aigner Manfred , Engelbrecht E. Geoffrey , Eroglu Adnan , Hellat Jaan , Syed Khawar J.
Published: December 2014

Present day land-based gas turbine combustors, operating on oil, must meet strict requirements for emissions (CO, unburned hydrocarbons, particulates, smoke and NOx) and burn stabily without pulsations over a wide range of operating conditions. In addition many engines, such as those produced by ABB, operate with both oil and natural gas fuels either together or independently. This paper concentrates on the development of an oil injection system which is optimised for ABB’s double cone burner (Figure 1) and which does not affect the operation of this burner on natural gas. The development procedure, which involved a coupling of numerical and experimental techniques, is described. The results of the application of this procedure indicate that a simple plain jet atomiser in conjunction with a small quantity of unswirling air admitted at the head of the burner is the best option for this burner.
The Requirements for a Modern Marine Gas Turbine and the Development of the WR21
Authors: Butler Brian , Wright Nigel
Published: December 2014

The maritime engine test facility at the Defence Evaluation and Research Agency (DERA) Pyestock in the United Kingdom has been involved with the testing of gas turbine engines for the Royal Navy since 1952. This testing has been aimed at proving that the already developed gas turbine can operate in the maritime environment, perform the expected duty cycles, and reach the required levels of availability, reliability, and maintainability as required. To this end, the vast amount of testing at DERA has been the endurance style where the engine is run over extended periods in arduous conditions to test the life of components and with only a minimum amount of data collection. This dramatically changed in 1994 with the beginning of the WR21 Intercooled Recuperated gas turbine (WR21 ICR) development program.

The paper describes the benefits of the WR21 ICR over a simple cycle gas turbine, the methodology behind the current development testing, and the evolution of the DERA Pyestock facility. In particular facility designs, instrumentation, data handling, and testing operations to meet the growing needs of the customer to develop this complex cycle gas turbine.
Workshop Testing of GT140P: Part 1 — Test Program and Test Arrangement
Authors: Knudsen Knud , Larsson Jonas , Nilsson Ulf , Thörnblad Per
Published: December 2014

Based on the experience from operation of 75 MW PFBC power plants in Sweden, Spain and USA, development of a gas turbine for a larger PFBC plant started in 1990. Before delivery to its user in Japan the first machine underwent extensive testing. A special test rig was built in one of ABB STAL’s workshops in Finspong Sweden. In the absence of the regular coal-fired PFBC combustor a silo-type gas turbine combustor was installed to supply power. Permanent and temporary instrumentation, together more than 1200 gauges, were installed and data was displayed for on-line monitoring and recorded for analysis. This paper describes the design of GT140P, the test program and the test arrangements.
A Study of the Flow Field in a Model Rotor-Stator Disk Cavity
Authors: Roy R. P. , Devasenathipathy S. , Xu G. , Zhao Y.
Published: December 2014

Experimental and computational studies of the turbulent flow field in a model gas turbine disk cavity have been carried out. The experiments were performed in a rig which features a rotor disk-stator disk configuration with stator vanes, rotor blades, and rim discouragers with axial overlap. Particle Image Velocimetry was used to map the flow field in the cavity at three positions along the axial gap between the disks for various mainstream and secondary air flow rates, and rotor speeds. Static pressure distribution in the cavity at the stator disk and the circumferential distribution of the same at the mainstream passage outer shroud were measured.

A recirculation region developed radially inboard in the disk cavity where a strong radial outflow was found close to the rotor disk and a weak radial inflow near the stator disk. This is the source region where the rotation of the core fluid is minimal, its radial extent increasing with the secondary air flow rate. Radially outboard, in the core region, the flow was rotation-dominated except when the secondary air flow rate was high.

The peak-to-peak amplitude of the circumferential pressure asymmetry in the mainstream flow path increased as the square of the main air flow rate, attained its maximum value at the stator vane exit, and decreased rapidly downstream. For the experiments performed, no circumferential pressure asymmetry could be found in the disk cavity, even near its rim. The rotating fluid in the core region of the cavity gave rise to an adverse radial pressure gradient, its magnitude increasing as the secondary air flow rate decreased. This feature can facilitate ingress of mainstream gas into the cavity.

Concurrently with the experiments, the flow field was simulated numerically using the commercial CFD code FLUENT/UNS. The agreement between the measurements and the computed results is generally good.
Influence of Rim Seal Geometry on Hot Gas Ingestion Into the Upstream Cavity of an Axial Turbine Stage
Authors: Bohn Dieter , Rudzinski Bernd , Sürken Norbert , Gärtner Wolfgang
Published: December 2014

The ingestion of hot gas at the rim seal of a turbine has been investigated for a complete stage with nozzle guide vanes and rotor blades for two types of geometry: 1. the simple axial gap between a flat rotor disk and a flat stator disk, commonly used for industrial gas turbines and 2. an axial lip of the rim seal on the stator combined with a flat rotor disk, often found in aero engine applications. The clearance of the axial gap has been varied for the second type. The efficiency of the rim seal has been examined for different seal flow rates, rotational Reynolds numbers and Mach numbers in the main flow.

For the determination of the sealing effectiveness carbon dioxide gas concentration measurements have been carried out in the wheelspace. The distribution of the static pressure in the vicinity of the seal and inside the wheelspace has been measured by means of pressure taps at the stator disk.

It is shown that the external flow Mach number in the main flow has a significant effect on the sealing efficiency. As Mach number increases sealing efficiency goes down. The rotational Reynolds number has a distinct effect on the rim seal efficiency depending on the examined configuration. Even for high seal flow rates the ingestion of hot gas can not be fully avoided.

The experimental results were the motivation for a three-dimensional CFD approach neglecting the influence of the rotor blades. The results give further insight into aerodynamic features of the ingestion phenomenon.
Calculation of Flow Losses in Rotating Passages of Gas Turbine Cooling Systems
Authors: Brillert D. , Reichert A. W. , Simon H.
Published: December 2014

The continuous improvement in thermal efficiency of gas turbines is primarily achieved by increasing the turbine inlet temperatures without, however, affecting the thermal stability and the fatigue strength of the blades which must be guaranteed for their entire service life. The precise analysis of secondary air systems is therefore of crucial importance for the design of gas turbines.

Stationary and rotating passages constitute important elements of secondary air systems, and this paper focuses on the calculation of the characteristics of fluid flow through stationary and rotating passages (or bores) as a function of passage length, asymmetric inflow (i.e. crossflow at the inlet) and inlet edge geometry (i.e. rounded or sharp–edged inlets). A simple physical model is developed on the basis of the simple and thoroughly investigated passage flow. The model is then matched to a large number of test results taken from the literature. The result is a versatile tool for calculating flow losses in rotating and stationary passages.