bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Simulated Combustor Temperature Nonuniformity on HP Vane and Endwall Heat Transfer: An Experimental and Computational Investigation
Authors: Qureshi Imran , Beretta Arrigo , Povey Thomas
Published: January 2011

This paper presents experimental measurements and computational predictions of surface and endwall heat transfer for a high-pressure (HP) nozzle guide vane (NGV) operating as part of a full HP turbine stage in an annular rotating turbine facility, with and without inlet temperature distortion (hot-streaks). A detailed aerodynamic survey of the vane surface is also presented. The test turbine was the unshrouded MT1 turbine, installed in the Turbine Test Facility (previously called Isentropic Light Piston Facility) at QinetiQ, Farnborough UK. This is a short duration facility, which simulates engine representative M, Re, non-dimensional speed and gas-to-wall temperature ratio at the turbine inlet. The facility has recently been upgraded to incorporate an advanced second-generation combustor simulator, capable of simulating well-defined, aggressive temperature profiles in both the radial and circumferential directions. This work forms part of the pan-European research programme, TATEF II. Measurements of HP vane and endwall heat transfer obtained with inlet temperature distortion are compared with results for uniform inlet conditions. Steady and unsteady CFD predictions have also been conducted on vane and endwall surfaces, using the Rolls-Royce CFD code HYDRA to complement the analysis of experimental results. The heat transfer measurements presented in this paper are the first of their kind in the respect that the temperature distortion is representative of an extreme cycle point measured in the engine situation, and was simulated with good periodicity and with well defined boundary conditions in the test turbine.
Experimental and Numerical Analysis of Hub-Corner Stall in Compressor Cascades
Authors: Lewin Eugen , Kozˇulovic´ Dragan , Stark Udo
Published: January 2011

The development of a corner stall has been investigated experimentally and numerically in a rotor hub equivalent compressor cascade operated at increasing loadings (inlet angles). The paper presents some of the experimental and numerical results, including midspan results, contour plots of the total pressure losses, pitchwise averaged total pressure losses and turning angles, flow visualization and, numerically only, visualization of so-called ribbons. These results have been analysed to finally identify an endwall separation vortex, increasing in pitchwise and spanwise direction with increasing loading in a highly complicated and permanently changing endwall topology, as the dominating feature of a developed corner stall.
Probabilistic Property Prediction of Aero-Engine Components for Fatigue
Authors: Brooks J. W. , Basoalto H. C. , Sahota R. , Tranter P.
Published: January 2011

Service lives for critical rotating parts in aero engine gas turbines are declared using deterministic lifing calculations based on fixed point values of key mechanical properties and factors to allow for the scatter. However, novel probabilistic lifing algorithms have been developed, which are able to take into account the degree of scatter in the material properties throughout the component. Process simulation software has been developed to predict the material flow, residual stresses, microstructure and properties in components during the disc forging operations to ensure robust manufacturing routes. This allows the changes in the materials microstructure, and the mechanical property variation throughout the component, to be predicted as the crack initiation and propagation properties are significantly dependent on the grain structure. These two strains of research have been combined in an attempt to increase the reliability of service life predictions through modelling the scatter in the mechanical properties resulting from manufacturing variation. Results will be presented which indicate that significant life benefits can be obtained by adopting a location specific lifing method based on this approach.
Measurement and Simulation of Turbulent Mixing in a Jet in Crossflow
Authors: Galeazzo Flavio Cesar Cunha , Donnert Georg , Habisreuther Peter , Zarzalis Nikolaos , Valdes Richard J. , Krebs Werner
Published: January 2011

Computational Fluid Dynamics (CFD) has an important role in current research. While Large Eddy Simulations (LES) are now common practice in academia, Reynolds-averaged Navier-Stokes (RANS) simulations are still very common in industry. Using RANS allows faster simulations, however the choice of the turbulence model has a bigger impact on the results. An important influence of the turbulence modeling is the description of turbulent mixing. Experience has shown that often inaccurate simulations of combustion processes originate from an inadequate description of the mixing field. A simple turbulent flow and mixing configuration of major theoretical and practical importance is the jet in crossflow (JIC). Due to its good fuel-air mixing capability over a small distance JIC is favored by gas turbine manufacturers. As the design of the mixing process is the key to creating stable low NOx combustion systems, reliable predictive tools and detailed understanding of this basic system are still demanded. Therefore the current study has re-investigated the JIC configuration under engine relevant conditions both experimentally and numerically using the most sophisticated tools available today. The combination of planar Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF) was used to measure the turbulent velocity and concentration fields as well as to determine the correlations of the Reynolds stress tensor ui′uj′ and the Reynolds flux vector ui′c′. Boundary conditions were determined using Laser Doppler Velocimetry. The comparisons between the measurements and simulation using RANS and LES showed that the mean velocity field was well described using the SST turbulence model. However, the Reynolds stresses and more so the Reynolds fluxes deviate substantially from the measured data. The systematic variation of the turbulent Schmidt number reveals the limited influence of this parameter indicating that the basic modeling is amiss. The results of the LES simulation using the standard Smagorinsky model were found to provide much better agreement with experiments also in the description of turbulent mixing.
CFD-FE Automation and Thermo-Fluid Characterisation of an IP Turbine Cavity
Authors: Bagshaw David , Alizadeh Sohail , Mabilat Christophe , Lewis Leo
Published: January 2011

This paper shows a method by which the combined CFD-FE analysis process for prediction of aero engine disc temperatures and thermal growths is sped up, with relatively small computational power requirements. The method, known as the temperature influence coefficients method (Lewis et al. (2004)) is further developed into an integrated/automated system, providing a complete thermo-mechanical solution with minimal user input and which fits within aero engine design timescales. 3-D CFD solutions are produced, adiabatically and diabatically, at three key engine operating conditions, for a turbine rotor-stator cavity in a large-scale aero-engine. A standardised method is developed for characterisation of the surface and near-wall coefficients. The variation of these parameters along the disc surface is presented, showing the nature of the flow field adjacent to the disc. The paper describes the development of the automated transfer process of the coefficients into the separate axisymmetric FE model, which can then be run through any cycle. The temperature results and the process time results from the temperature influence coefficients method are compared with existing methods for a 13000 second flight cycle.
Heat Transfer for the Blade of a Cooled Stage and One-Half High-Pressure Turbine: Part I—Influence of Cooling Variation
Authors: Mathison R. M. , Haldeman C. W. , Dunn M. G.
Published: January 2011

Heat-flux measurements are presented for a one-and-one-half stage high-pressure turbine operating at design corrected conditions with modulated cooling flows in the presence of different inlet temperature profiles. Coolant is supplied from a heavily film cooled vane and the purge cavity (between the rotor disk and the upstream vane) but not from the rotor blades, which are solid metal. Thin-film heat-flux gauges are located on the un-cooled blade pressure and suction surface (at multiple span locations), on the blade tip, on the blade platform, and on the disk and vane sides of the purge cavity. These measurements provide a comprehensive picture of the effect of varying cooling flow rates on surface heat transfer to the turbine blade for uniform and radial inlet temperature profiles. Part I of this paper examines the macroscopic influence of varying all cooling flows together, while Part II investigates the individual regions of influence of the vane outer and purge cooling circuits in more detail. The heat-flux gauges are able to track the cooling flow over the suction surface of the airfoil as it wraps upwards along the base of the airfoil for the uniform vane inlet temperature profile. A similar comparison for the radial profile shows the same coolant behavior but with less pronounced changes. From these comparisons, it is clear that cooling impacts each temperature profile similarly. Nearly all of the cooling influence is limited to the blade suction surface, but small changes are observed for the pressure surface. In addition to the cooling study, a novel method of calculating the adiabatic wall temperature is demonstrated. The derived adiabatic wall temperature distribution shows very similar trends to the Stanton Number distribution on the blade.
Heat Transfer for the Blade of a Cooled Stage and One-Half High-Pressure Turbine: Part II—Independent Influences of Vane Trailing Edge and Purge Cooling
Authors: Mathison R. M. , Haldeman C. W. , Dunn M. G.
Published: January 2011

The independent influences of vane trailing edge and purge cooling are studied in detail for a one-and-one-half stage transonic high-pressure turbine operating at design corrected conditions. This paper builds on the conclusions of Part I, which investigated the combined influence of all cooling circuits. Heat-flux measurements for the airfoil, platform, tip, and root of the turbine blade as well as the shroud and the vane side of the purge cavity are used to track the influence of cooling flow. By independently varying the coolant flow rate through the vane trailing edge or purge circuit, the region of influence of each circuit can be isolated. Vane trailing edge cooling is found to create the largest reductions in blade heat transfer. However, much of the coolant accumulates on the blade suction surface and little influence is observed for the pressure surface. In contrast, the purge cooling is able to cause small reductions in heat transfer on both the suction and pressure surfaces of the airfoil. Its region of influence is limited to near the hub, but given that the purge coolant mass flow rate is 1/8th that of the vane trailing edge, it is impressive that any impact is observed at all. The cooling contributions of these two circuits account for nearly all of the cooling reductions observed for all three circuits in Part I, indicating that the vane inner cooling circuit that feeds most of the vane film-cooling holes has little impact on the downstream blade heat transfer. Time-accurate pressure measurements provide further insight into the complex interactions in the purge region that govern purge coolant injection. While the pressures supplying the purge coolant and the overall coolant flow rate remain fairly constant, the interactions of the vane pressure field and the rotor pressure field create moving regions of high pressure and low pressure at the exit of the cavity. This results in pulsing regions of injection and ingestion.
Heat Transfer Investigations in Multiple Impinging Jets at Low Reynolds Number
Authors: Rao Arvind G. , Kitron-Belinkov Myra , Krapp Vladimir , Levy Yeshayahou
Published: January 2011

Jet impingement is a well established cooling methodology used for cooling turbine blades in gas turbine engines. Jet impingement results in high heat transfer coefficients as compared to other conventional modes of single phase heat transfer. Most of the research in jet impingement has been confined to high Reynolds number regime. In order to increase the applicability of this technique to non conventional applications like in a low pressure micro turbine combustors or turbine blades, the behavior of such systems in the low Reynolds number regime should be understood. The present paper is a continuation of earlier investigations on the heat transfer behavior of a large jet impingement array in the low Reynolds number regime, especially in the laminar and transitional region. More experiments have been conducted with different geometrical parameters of the array to analyze the effect of these parameters on the average heat transfer coefficient. Numerical simulations with existing CFD tools were carried out in order to understand the fluid mechanics inside such a complex system. The CFD model was validated with the experiments. Different turbulence models were used and it was found that the SST-k-ω model was the best for modeling jet impingement phenomena. It is anticipated that the results obtained from the present exercise will give better insights in optimizing the design of multiple jet impingement cooling systems for high heat density applications.
Reduced Order Model of a Multistage Bladed Rotor With Geometric Mistuning via Modal Analyses of Finite Element Sectors
Authors: Bhartiya Yasharth , Sinha Alok
Published: January 2011

An algorithm to generate a reduced order model of a multi-stage rotor in which each stage has a different number of blades has been developed. It is shown that a reduced order model can be developed on the basis of tuned modes of certain bladed disks which can be easily obtained via sector analyses. Further, it is shown that reduced order model can also be obtained when blades are geometrically mistuned. This algorithm is similar to the modified modal domain analysis, which has been recently developed for a single-stage bladed rotor with geometric mistuning. The validity of this algorithm is shown for the finite element model of a two-stage bladed rotor. In addition, the statistical distributions of peak maximum amplitudes and natural frequencies of a two-stage rotor are generated via Monte Carlo simulations for different patterns of geometric mistuning.
Measurements of Losses and Reynolds Stresses in the Secondary Flow Downstream of a Low-Speed Linear Turbine Cascade
Authors: MacIsaac G. D. , Sjolander S. A. , Praisner T. J.
Published: January 2011

Experimental measurements of the mean and turbulent flow field were preformed downstream of a low-speed linear turbine cascade. The influence of turbulence on the production of secondary losses is examined. Steady pressure measurements were collected using a seven-hole pressure probe and the turbulent flow quantities were measured using a rotatable x-type hotwire probe. Each probe was traversed downstream of the cascade along planes positioned at three axial locations: 100%, 120% and 140% of the axial chord (Cx) downstream of the leading edge. The seven-hole pressure probe was used to determine the local total and static pressure as well as the three mean velocity components. The rotatable x-type hotwire probe, in addition to the mean velocity components, provided the local Reynolds stresses and the turbulent kinetic energy. The axial development of the secondary losses is examined in relation to the rate at which mean kinetic energy is transferred to turbulent kinetic energy. In general, losses are generated as a result of the mean flow dissipating kinetic energy through the action of viscosity. The production of turbulence can be considered a preliminary step in this process. The measured total pressure contours from the three axial locations (1.00, 1.20 and 1.40Cx) demonstrate the development of the secondary losses. The peak loss core in each plane consists mainly of low momentum fluid that originates from the inlet endwall boundary layer. There are, however, additional losses generated as the flow mixes with downstream distance. These losses have been found to relate to the turbulent Reynolds stresses. An examination of the turbulent deformation work term demonstrates a mechanism of loss generation in the secondary flow region. The importance of the Reynolds shear stress to this process is explored in detail.
Low Fidelity Turbomachinery Disk Design Studies
Authors: Gutzwiller David P. , Turner Mark G.
Published: January 2011

Turbomachinery disks are highly stressed, heavy components used in virtually all axially configured gas turbines. Historically, simple plane stress models have primarily been used to quickly analyze the thickness profiles of thin compressor disks. The application of a plane stress model to a more complex system including large thermal gradients or composite materials is much less common. This paper will focus on low fidelity design studies of complex disk systems using a plane stress model. The automated design of a thick, high pressure turbine (HPT) disk with a large radial thermal gradient will be explored. This system clearly shows the limitations of a plane stress model. Discussion will focus on ways to identify and account for inaccuracies in the low fidelity turbine disk results. This paper will also explore the use of a low fidelity stress model in a fan disk design study including both isotropic and composite disk materials. This study shows that with proper assumptions, a plane stress model may be used to investigate a wide range of disk loading and geometry configurations in much less time than would be needed with higher fidelity tools. As examples, hardware from the GE E3 HPT and GE90 fan will be investigated using the disk design program T-Axi Disk. With proper assumptions and an understanding of the stress model, complex disk systems can be designed and optimized accurately at a low fidelity level. The time savings from using a low fidelity tool allows the designer to perform design studies that would be much more difficult or expensive using higher fidelity tools.
Performance Analysis on the Hybrid Power Plant of SOFC and Steam Injected Gas Turbine
Authors: Zhang Wenshu , Zhang Huisheng , Lu Zhenhua
Published: January 2011

This paper presents performance analysis of a hybrid power generation system consisting of a solid oxide fuel cell (SOFC) and a steam injected gas turbine (GT) based on the commercial software Easy5. The steam is produced by using the hot exhaust gases heat in the heat recovery steam generator (HRSG) and is injected into the afterburner. Compared with the system without HRSG, the exhaust gas temperature decreases slightly and the power output of the gas turbine is higher because of the increase of the inlet mass flow rate. In addition, the heat exchanger reformer is used in the hybrid system to reduce space and cost. Simulation results show that the hybrid system could achieve a system efficiency of 62.6% under full load operation. And the part load and the dynamic performance of the hybrid system was presented and analyzed.
Investigation of Unsteady Impeller-Diffuser Interaction in a Transonic Centrifugal Compressor Stage
Authors: Liu Yangwei , Liu Baojie , Lu Lipeng
Published: January 2011

In this paper, unsteady impeller-diffuser interaction in a transonic centrifugal compressor stage, which is composed of an impeller with splitter blade and a vaned diffuser, was studied numerically. The unsteady interaction has a significant impact on the time-averaged flow, which are presented by the so-called deterministic correlations in the average-passage equation system (APES) proposed by Adamczyk. Both steady and unsteady simulations were carried out at the design and off-design conditions. Results from the steady and unsteady simulations were compared to highlight the importance of the unsteady interactions and to help assess the shortcomings of simple mixing-plane methods. The comparisons indicate that the unsteady interactions should be considered in the simulations since the differences between the time averaged unsteady results and steady simulation results are significant especially at off-design conditions. Then the interactions between impeller and diffuser were studied in detail to advance the understanding of the flow physics involved. The results show that the impeller/diffuser interaction can affect a range of 30% impeller chord from impeller trailing edge on impeller performance, while whole chord length on diffuser performance. The potential effects of the diffuser cause an unsteady pressure disturbance at the impeller exit, leading to the unsteadiness of impeller load, tip leakage flow and losses. While the unsteadiness of impeller exit flow cause period varieties of inlet flow conditions for the diffuser and have large impacts on diffuser performance. Based on the unsteady results, deterministic correlations in the APES framework were computed and analyzed in order to reveal some shortcomings of present deterministic correlations models and to make some contributions to the modeling development. The distribution characteristics of deterministic correlations were studied. The study indicates that the deterministic correlations in the impeller and diffuser have the similar magnitudes, and that the correlations in the passages have large gradients in circumferential direction and decrease rapidly in flow direction especially in the vaneless space. The deterministic correlations at the impeller/diffuser interface were compared with their spatial correlations using the framework of the deterministic decomposition. The comparisons show that the spatial correlations have some discrepancies with the total deterministic correlations at the impeller/diffuser interface.
Loss Coefficient Dependence of Turbine Blade Cascade
Authors: Mateˇjka Milan , Sˇafarˇi´k Pavel , Luxa Martin , Sˇimurda David , Syna´c´ Jaroslav
Published: January 2011

This paper presents the experimental results of aerodynamic research performed on a blade cascade representing the midsection of 1220 mm long rotor blades of the last stage of a large output steam turbine. The operational regime of the blade cascade is characterized by supersonic exit velocity. Isentropic exit Mach number M2is = 1.323. The experimental data analysis concerns pneumatic measurements to calculate the total pressure and the kinetic energy loss coefficients, and to evaluate them mainly with respect to the aperiodicity of the flow field. The flow structure is also studied on the basis of results obtained by means of optical methods, such as schlieren and interferometric methods.
Numerical Investigation of Leakage and Power Loss for Different Seal Types in Turbine Stage Environment
Authors: Yang Rui , Yang Jiandao , Qi Mingxu , Shi Liqun , Peng Zeying
Published: January 2011

In this study, a turbine stage together with diaphragm seals and shroud seals were chosen for numerical investigation. As the baseline design, labyrinth seals’ leakage and blade stage efficiency were analyzed firstly. The results illustrates that as a custom seal, although simplicity, reliableness, and easy replacement make labyrinth seals widely used in steam and gas turbine, but additional power loss caused by excessive leakage flow affects the efficiency of turbine. In order to enhance the efficiency of the turbine stage by leakage reduction, the labyrinth seals at diaphragm and shroud were replaced by brush seals and honeycomb seals respectively. Porous medium method was used to simulate the flow in bristle pack of brush seals, and the pressure drop in bristle was explored by Darcy law. Pressure distribution and flow field details of honeycomb seals were also researched by CFD method. Radial clearance has a direct influence on leakage, so the clearance effect was analyzed in this paper. Lastly, for the stage together with brush seals and honeycomb seals researched, results show that comparing to custom labyrinth seals, the reduction leakage was approximate 30% and the improvement of stage efficiency was 0.6%.
The Development of Long Last Stage Steam Turbine Blades
Authors: McBean Ivan , Havakechian Said , Masserey Pierre-Alain
Published: January 2011

In steam turbine power plants, the appropriate design of the last stage blades is critical in determining the plant efficiency and reliability and competitiveness. A high level of technical expertise combined with many years of operating experience are required for the improvement of last stage designs that increases performance, without sacrificing mechanical reliability. This paper focuses on three main development areas that are key for the development of last stage blades, namely the aerodynamic design, the mechanical design and the validation process. The three different lengths of last stage blade (LSB) were developed of 41in, 45in and 49in (and a number of scaled variants). The aerodynamic design process involves 3D CFD and flow path analysis, considerations such as last stage blade flutter and water droplet erosion, and last stage guide design. The mechanical design includes finite element stress and dynamic analysis, appropriate selection of the blade material, the coupling of the LSB with the rotor and the design of the LSB snubber and shroud. Experimental measurements form a key part of the product validation, from both the mechanical reliability and performance points of view.
Measurements of Endwall Flows in Transonic Linear Turbine Cascades: Part II—High Flow Turning
Authors: Taremi F. , Sjolander S. A. , Praisner T. J.
Published: January 2011

An experimental investigation of two low-turning (90°) transonic linear turbine cascades was presented in Part I of the paper. Part II examines two high-turning (112°) turbine cascades. The experimental results include total pressure losses, streamwise vorticity and secondary kinetic energy distributions. The measurements were made using a seven-hole pressure probe downstream of the cascades. In addition to the measurements, surface flow visualization was conducted to assist in the interpretation of the flow physics. The turbine cascades in Part II, referred to as SL1F and SL2F, have the same inlet and outlet design flow angles, but different aerodynamic loading levels: SL2F is more highly loaded than SL1F. The surface flow visualization results show evidence of small flow separation on the suction side of both airfoils. At the design conditions (outlet Mach number ≈ 0.8), SL2F exhibits stronger vortical structures and larger secondary velocities than SL1F. The two cascades, however, produce similar row losses based on the measurements at 40% axial chord lengths downstream of the trailing edge. Additional data were collected at off-design outlet Mach numbers of 0.65 and 0.91. As the Mach number is raised, the cascades become more aft-loaded. The absolute blade loadings increase, but the Zweifel coefficients decrease due to higher outlet dynamic pressures. Both profile and secondary losses decrease at higher Mach numbers; the main vortical structures and the corresponding peak losses migrate towards the endwall, and there are reductions in secondary kinetic energy and exit flow angle variations. The streamwise vorticity distributions show smaller peak vorticities associated with the passage and the counter vortices at higher exit Mach numbers. The corner vortex, on the other hand, becomes more intensified, resulting in reduction of flow overturning near the endwall. The results for SL1F and SL2F are compared and contrasted with the results for the lower turning cascades presented in Part I. The possible effects of suction-surface flow separation on profile and secondary losses are discussed in this context. The current research project is part of a larger study concerning the effects of endwall contouring on secondary losses, which will be presented in the near future.
Development of a 125KW AMB Expander/Generator for Waste Heat Recovery
Authors: Hawkins Lawrence A. , Zhu Lei , Blumber Eric J.
Published: January 2011

Development and field testing of a low cost expander/generator system that incorporates a high performance, high-speed permanent magnet generator and low loss magnetic bearings is described. The expander/generator is part of a waste heat recovery system based on the Organic Rankine Cycle. The waste heat system can recover energy from a wide variety of heat sources including: landfill gas, reciprocating engine exhaust, solar, geothermal, boilers, and other industrial processes. The varying frequency voltage supplied by the generator is connected to the grid using an active/active power electronics package that can deliver power at 400–480 VAC (50 or 60 Hz). Active magnetic bearings (AMB) were chosen for the application because they can operate directly in the working fluid, have low losses, and provide high reliability and remote monitoring capabilities. The expander operates between 20,000 and 26,500 rpm depending on the energy available from the heat source. The first field unit was installed in April, 2009 at a biogas site. The system design, test results, and magnetic bearing operating experience are discussed.
Computational Modelling of Turbulent Mixing of a Transverse Jet
Authors: Ivanova Elizaveta , Noll Berthold , Aigner Manfred
Published: January 2011

This paper presents numerical simulations of turbulent mixing of a jet in crossflow. The test case is chosen to resemble scalar mixing processes in the premixing zones of gas turbine combustion chambers. Steady and unsteady simulations employing three different computational approaches are presented: steady Reynolds-Averaged Navier-Stokes (RANS), unsteady Reynolds-Averaged Navier-Stokes (URANS), and Scale-Adaptive Simulations (SAS). Presented results comprise the (time-averaged) profiles of flow velocities, turbulent kinetic energy of the flow, Reynolds stresses, passive scalar distribution, turbulent scalar fluxes, and the turbulent variance of the passive scalar. All presented results are directly validated against experimental data. Additionally two parameter studies are presented. Both studies are related to the accuracy of the turbulent scalar mixing predictions for all used simulation methods. In the first study the dependence of the scalar mixing predictions on the value of the turbulent Schmidt number is considered. In the second study the dependence of the predicted turbulent scalar variance on the used modelling approach is analysed.
Gas Turbine Online Waterwash for DDG-51 Class U.S. Navy Ships
Authors: Caguiat Daniel E.
Published: January 2011

Currently, the U.S. Navy DDG-51 class ships employ a system of piping, tanks, and nozzles for washing the four Gas Turbine Main (GTM) engines and three Ship Service Gas Turbine Generator (SSGTG) engines. The wash system employed, referred to as the crankwash system, allows the user to wash the compressor section of a gas turbine only when the turbine in question is not operating. On a DDG-51 class ship, it is possible to utilize the existing crankwash piping, tank, and overall architecture to supply water to an online water wash system. An online water wash system allows the compressor section to be cleaned while the gas turbine is in operation. This is intended to reduce the periodicity of crankwashing and associated starter cycling costs. Online water wash is also intended to maintain compressor cleanliness in the interval between crankwashes. NAVSEA Philadelphia researched appropriate online water wash system designs, methods for collecting data to address fuel savings and engine performance issues, and installation methods. GTM and SSGTG Online Water Wash Systems were then installed on USS PREBLE (DDG-88) in late 2008. USS PREBLE subsequently deployed for a period of six months beginning January 2009. During the deployment, data was collected as the systems were operated. This paper will discuss the system design, provide data analysis results, and discuss lessons learned.
Enhanced Film Cooling Effectiveness With New Shaped Holes
Authors: Liu Jong S. , Malak Malak F. , Tapia Luis A. , Crites Daniel C. , Ramachandran Dhinagaran , Srinivasan Balamurugan , Muthiah Gopalsamy , Venkataramanan Jyothishkumar
Published: January 2011

Gas Turbine Engines operate at temperatures higher than current material temperature limits. This necessitates cooling the metal through internal or external means and/ or protecting the metal with coatings that have higher material limits. Film cooling is one of the major technologies allowing today’s gas turbines to operate at extremely high turbine inlet temperatures, consequently higher power density, and extend the cooled components life. Film cooling is a technique where a coolant is blown over the surface exposed to hot gas and a film of low temperature gas is maintained that protects the metal surface from the hot gas. The application of effective film-cooling techniques provides the first and best line of defense for hot gas path surfaces against the onslaught of extreme heat fluxes, serving to directly reduce the incident convective heat flux on the surface. The effectiveness of film cooling methods depends on the blowing ratio, shape of the cooling holes, and geometrical parameters such as the area ratio and diffusion angle. Film cooling is performed almost exclusively through the use of discrete holes. The holes can be of round or other shaped. A detailed study of the literature shows that the fan shaped has higher effectiveness when compared to other shapes. In this study a number of cooling hole shapes are evaluated numerically using the Computational Fluid Dynamics (CFD) tool ANSYS-CFX-11.0 with the objective of improving cooling effectiveness under a favorable pressure gradient main flow. In order to delineate the effects of shape from that of diffusion, a constant area ratio is assumed first. In the next set of analyses the effect of hole exit diffusion is considered. Results are presented in terms of surface temperatures and adiabatic effectiveness at three different blowing ratios for the different film cooling hole shapes analyzed. Comparison is made with reference to the fan shaped film cooling hole with forward and lateral angles of 10/10/10 degree respectively. Hole shapes that show improvement over the fan shaped hole are identified and optimized.
Transonic Turbine Blade Tip Aero-Thermal Performance With Different Tip Gaps: Part II—Tip Aerodynamic Loss
Authors: O’Dowd D. O. , Zhang Q. , Usandizaga I. , He L. , Ligrani P. M.
Published: January 2011

Blade tip aerodynamic loss results from experimental and numerical investigations are presented for engine representative conditions downstream of a blade row with an exit Mach number Mexit of 1.0, and an exit Reynolds number Reexit of 1.27×106 (based on axial chord). These results are presented for three different tip gaps of 0.5, 1.0, and 1.5 percent relative to engine-equivalent blade span. Experimental data are obtained by traversing a specially-made and calibrated three-hole pressure probe as well as a single-hole probe one axial chord downstream of the blade within the Oxford High Speed Linear Cascade research facility. Three-dimensional RANS CFD numerical predictions are conducted using the Rolls-Royce HYDRA numerical prediction code for steady flow with the Spalart-Allmaras (SA) turbulence model. Included are detailed distributions of stagnation pressure losses, and pitch-wise flow angle. Local total pressure data and mass-averaged total pressure loss coefficients show that the strength of the tip leakage vortex decreases as the tip gap decreases. Magnitudes of the pitch-wise flow angle increase within over-tip leakage vortices, as these vortices become stronger and the tip leakage flow increases. The most important difference between experimental and numerical results is in relation to the passage vortex signatures, which are more apparent for all three tip gap values within the numerical results. The effects of relative casing motion and tip clearance are also examined and discussed, and show that the relative casing movement has a relatively small impact on the size of the over-tip leakage vortex at the medium (1.0% of span) and large (1.5% of span) tip gaps, with more noticeable impact at the smallest tip gap (0.5% of span).
A Model for Cylindrical Hole Film Cooling: Part I—A Correlation for Jet-Flow With Application to Film Cooling
Authors: auf dem Kampe Tilman , Vo¨lker Stefan , Zehe Frank
Published: January 2011

This paper presents a model to predict the flow structure of cooling flows emanating from cylindrical holes. It is based on a correlation of the flow field with characteristic film cooling parameters. In a previous paper, auf dem Kampe and Vo¨lker [1] reported on the dependence of the film-jet on flow parameters, such as blowing ratio, density ratio, free stream Mach number and turbulence intensity. The present paper extends these results by including the effect of geometry parameters, namely length-to-diameter ratio and inclination angle. All correlations are derived based on a numerical parameter study using a validated 3D-CFD model of a flat plate, scaled to engine conditions. To investigate the effects of the geometry parameters as well as their interaction with the aforementioned flow parameters, a DOE varying all parameters was performed. Results from these numerical investigations are used to correlate the flow-field in the film-jet with the underlying film cooling parameters. The focus of this paper is to demonstrate the predictive capability of the proposed correlations. It provides the basis for a model to simulate film cooling flows in 3D-CFD without meshing the cooling hole geometry, which is presented in the second part of this paper [2].
Numerical Simulation of Biomass Derived Syngas Combustion in a Swirl Flame Combustor
Authors: De Pascale Andrea , Fussi Marco , Peretto Antonio
Published: January 2011

In this work a numerical investigation is carried out on a model combustor characterized by swirl flow conditions, fed with a biomass derived syngas fuel (which incorporates CH4, CO and H2) and operated in laboratory at atmospheric pressure. The combustor internal aerodynamics and heat release in case of syngas combustion have been simulated in the framework of CFD-RANS techniques, by means of different available models and by adopting different levels of kinetic mechanism complexity. In particular, the applicability of reduced mechanisms involving CO and H2 species and also of detailed kinetic mechanisms are assessed. The results obtained by means of the CFD simulations on the model combustor and a comparison with available experimental data on flow field and thermal field are presented in the paper. In the test-case of syngas-air swirled flames, the turbulent non premixed combustion “flamelet” model with detailed non-equilibrium chemistry, originally developed for methane-air combustion, provides encouraging results in terms of temperature distribution. Nevertheless, a simpler chemical path including the main fuel species integrated in a general purpose, widely used in industry, turbulent combustion model still provides acceptable results.
Advanced Numerical Simulation Dedicated to the Prediction of Heat Transfer in a Highly Loaded Turbine Guide Vane
Authors: Gourdain Nicolas , Duchaine Florent , Gicquel Laurent Y. M. , Collado Elena
Published: January 2011

This paper proposes to investigate the capacity of numerical simulation to estimate wall heat fluxes in a highly loaded turbine guide vane (with both structured and unstructured flow solvers). Different numerical approaches are assessed, from steady-state methods based on the Reynolds Averaged Navier-Stokes (RANS) equations to more sophisticated methods such as the Large Eddy Simulation (LES) technique. As expected steady flow simulations fail to predict the wall heat transfer, mainly because unsteady flows and laminar-to turbulent transition are not taken into account. The results underline the role of the vortex shedding, mainly through the emission of acoustic waves that interact with the suction side boundary layer. Only the LES (partially) succeeds to estimate wall heat fluxes since this method considerably improves the level of physical description (including boundary layer transition). However, the LES still requires validation and developments for such complex flows. This study also points out the dependency of results to the freestream turbulence intensity, which is a difficult parameter to manage with LES. Structured and unstructured flow solvers predict a different behaviour of the boundary layer (natural or by-passed transition), depending on the external turbulence intensity.
Numerical and Experimental Investigations of Unsteady 3-D Wet-Steam Flows Through Two-Stage Stator-Rotor Cascade Channels
Authors: Yamamoto Satoru , Sasao Yasuhiro , Kato Hiroto , Satsuki Hiroshi , Ooyama Hiroharu , Ishizaka Kouichi
Published: January 2011

Unsteady 3-D flows through two-stage stator-rotor cascade channels in a low-pressure steam turbine model developed by Mitsubishi Heavy Industry (MHI) are numerically and experimentally investigated assuming dry and wet-steam conditions. The fundamental equations for condensate flows derived by the authors are applied to the present flow computations. The high-order high-resolution finite-difference method based on the fourth-order compact MUSCL TVD (Compact MUSCL) scheme and the Roe’s approximate Riemann solver are used for the space discretization of convection terms. The pipelined LU-SGS scheme optimized for the parallel-implicit time-integration is also employed. MHI measured the total pressures, static pressures and yaw angles of flow velocity vectors at the outlet of first-stage rotor, second-stage stator, and second-stage rotor. The calculated results are compared with the experimental results. In addition, unsteady condensate mass fractions are numerically visualized and the influence of wakes and secondary vortices to the condensation is discussed.
Experimental Characterization of a Micro Gas Turbine Test Rig
Authors: Hohloch Martina , Zanger Jan , Widenhorn Axel , Aigner Manfred
Published: January 2011

For the development of efficient and fuel flexible decentralized power plant concepts a test rig based on the Turbec T100 micro gas turbine is operated at the DLR Institute of Combustion Technology. This paper reports the characterization of the transient operating performance of the micro gas turbine by selected transient maneuvers like start-up, load change and shut-down. The transient maneuvers can be affected by specifying either the electrical power output or the turbine speed. The impact of the two different operation strategies on the behavior of the engine is explained. At selected stationary load points the performance of the gas turbine components is characterized by using the measured thermodynamic and fluid dynamic quantities. In addition the impact of different turbine outlet temperatures on the performance of the gas turbine is worked out. The resulting data set can be used for validation of numerical simulation and as a base for further investigations on micro gas turbines.
A Computational Parametric Analysis of the Vibration of a Three-Spool Aero-Engine Under Multi-Frequency Unbalance Excitation
Authors: Hai Pham Minh , Bonello Philip
Published: January 2011

The integration of squeeze-film dampers (SFDs) in aero-engine assemblies is a highly cost-effective means of introducing damping in an otherwise lightly damped structure. However, their deployment requires careful unbalance response calculations that take due account of the SFDs’ nonlinearity, particularly when they are unsupported by a centralising spring. Until recently, such calculations were prohibitive due to the large number of assembly modes that typically need to be considered. This problem has been overcome by the authors through the novel Impulsive Receptance Method (IRM) and the Receptance Harmonic Balance Method (RHBM), which efficiently solve the nonlinear problem in the time and frequency domains respectively. These methods have been illustrated on a realistic twin-spool engine and have been shown to be effective for both single frequency unbalance (SFU) excitation (unbalance on a single rotor) and multi-frequency unbalance (MFU) excitation (unbalance on both rotors). In the present paper, the methods are applied to a realistic three-spool engine and the aims are two fold: i) to present some preliminary results of a parametric study into a three-spool aero-engine assembly; ii) to propose a technique that makes use of both IRM and RHBM in producing the speed responses under MFU excitation (from all three rotors), with a realistic speed relation between the rotors. The latter technique is necessary since the speed ratio will vary along a realistic speed characteristic and the authors have previously solved the twin-spool MFU problem under a constant speed ratio condition. The approach used here is to approximate the speed characteristic by one in which the speed ratios are ratios of low integers, enabling the use of RHBM to finish off (to steady state) time-transient solutions obtained through IRM. The parameter study shows that the application of simple bump-spring supports to selected, otherwise unsupported, SFDs, along with slight sealing, should have a beneficial effect on the dynamic response of aero-engines with heavy rotors.
Multistage Coupling of Eight Bladed Discs on a Solid Shaft
Authors: Rza˛dkowski Romuald , Drewczynski Marcin
Published: January 2011

Considered here is the effect of multistage coupling on the dynamics of a rotor consisting of eight bladed discs on a solid shaft. Each bladed disc had a different number of rotor blades. Free vibrations were examined using finite element representations of rotating single blades, bladed discs, and the entire rotor. In this study, the global rotating mode shapes of flexible tuned bladed discs-shaft assemblies were calculated, taking into account rotational effects, such as centrifugal stiffening. The thus obtained natural frequencies of the blade, the shaft, the bladed disc, and the entire shaft with discs were carefully examined to discover resonance conditions and coupling effects. This study found that the flexible modes of the tuned bladed discs affected by shaft motion were those with zero, one and two nodal diameters. In these modes shaft deflection was clearly visible. In forced vibration analysis a different EO excitation was applied for each stage. The importance of using models with different numbers of blades on each disc is apparent when compared with earlier results concerning discs with identical numbers of blades. Here the model of 8 discs with an equal number of blades on each disc is referred to as (Model 1), and the model of 8 discs with a different number of blades on each disc is referred to as (Model 2).