bluuebunny/crossref_metadata_2025 huggingface dataset:
A Combined Numerical and Experimental Study of the Effect of Non-Axisymmetric Contouring on Performance and Film Cooling Behavior of a Rotating Turbine Endwall
Authors: Lu K. , Rezasoltani M. , Schobeiri M. T. , Han J. C.
Published: September 2014

Applying a new non-axisymmetric endwall contouring technology introduced by Turbomachinery Performance and Flow Research Laboratory (TPFL) at Texas A&M University to the second rotor row of a three-stage research turbine, has shown that for a single rotor row a major turbine efficiency improvement can be achieved [1]. Motivated by these results, comprehensive numerical and experimental investigations on the TPFL research turbine were conducted to determine the impact of the endwall contouring on film cooling effectiveness. For this investigation, the first rotor row directly subjected to the purge flow injection was chosen to which the new contouring technology was applied. Performing an extensive RANS simulation by using the boundary conditions from the experiments, aerodynamics, performance and film cooling effectiveness studies were performed by varying the injection blowing ratio and turbine rotational speed. Performance measurements were carried out within a rotational speed range of 1800 to 3000 RPM. The corresponding CFD simulations were carried out for four rotational speeds, 2000, 2400, 2600, and 3000 rpm. Comparison of the RANS aerodynamics simulation with experiments reveals noticeable differences. Considering the film cooling effectiveness, major differences between experiment and numerical results were observed and discussed in the paper.
Experimentally Verified Study of Regeneration-Induced Forced Response in Axial Turbines
Authors: Aschenbruck Jens , Seume Joerg R.
Published: September 2014

Geometrical variations occur in highly loaded turbine blades due to operation and regeneration. To determine the influence of such regeneration-induced variances of turbine blades on the aerodynamic excitation, a typical stagger angle variation of overhauled turbine blades is applied to stator vanes of an air turbine. This varied turbine stage is numerically and experimentally investigated.

For the aerodynamic investigation of the vane wake, CFD simulations are conducted. It is shown that the wake is changed due to the stagger angle variation. These results are confirmed by aerodynamic probe measurements in the air turbine.

The vibration amplitude of the downstream rotor blades has been determined by a computational forced response analysis using a uni-directional fluid-structure interaction approach and is experimentally verified here by tip-timing measurements. The results of the simulations and the measurements both show significantly higher amplitudes at certain operating points due to the additional wake excitation. For typical regeneration-induced variations in stagger angle, the vibration amplitude is up to five times higher than in the reference case of uniform upstream stators. Based upon the present results, the influence of these variations and of the vane patterns on the vibration amplitude of the downstream rotor blade can and should be estimated in the regeneration process to minimize the dynamic stresses of the blades.
Conjectural Bifurcation Analysis of an Aircraft Engine Blade Undergoing 3D Unilateral Contact Constraints
Authors: Batailly Alain , Legrand Mathias
Published: September 2014

Prediction of rotor/stator interaction phenomena between a blade-tip and the surrounding abradable coating deposited on the casing has seen recent promising numerical developments that revealed consistency with several experimental set-up. In particular, the location of critical rotational frequencies, damaged blade areas as well as the wear pattern along the casing circumference were accurately predicted for an interaction scenario involving a low-pressure compressor blade and the surrounding abradable coating deposited on a perfectly rigid casing. The structural behaviour of the blade in the vicinity of a critical rotational frequency however remains unclear as brutal amplitude variations observed experimentally could not be numerically captured without assuming contact loss or an improbable drastic and sudden change of the abradable coating mechanical properties during the interaction. In this paper, attention is paid to the structural behaviour of a high-pressure compressor blade at the neighbourhood of a critical rotational frequency. The interaction scenarios for two close rotational frequencies: Ωc and Ωc* are analyzed using empirical mode decomposition based on an adjusted B-spline interpolation of the time responses. The obtained results are compared to the interaction scenario dictated by the abradable coating removal history and the location of contact areas. The unstable nature of the blade vibratory response when the rotational frequency exceeds a critical rotational frequency is underlined and a plausible scenario arises for explaining a sudden and significant decrease of the blade amplitude of vibration without contact separation.
Numerical Investigation of Swirl Cooling Heat Transfer Enhancement on Blade Leading Edge by Adding Water Mist
Authors: Jiang Yuting , Zheng Qun , Yue Guoqiang , Dong Ping , Jiang Yu
Published: September 2014

In this paper, the idea of utilizing finely dispersed water-in-air mixture in the swirl channel to cool the leading edge of a turbine blade is proposed and investigated. The computational techniques are verified and the results are compared with dry air experimental data. Heat transfer enhancement is achieved by application of mist injection to the swirl cooling configuration that is modified from the well-known C3X airfoil. The results indicate that swirl cooling can take full advantage of mist addition. The effects of parameters, such as mist concentration, diameters, inlet temperature and inject velocity etc. are simulated and analyzed in this study.
Effect of Radiative Heat Transfer Factor on the Temperature Distribution of a First Stage Vane
Authors: Yin Hong , Li Mingfei , Chi Zhongran , Ren Jing , Jiang Hongde
Published: September 2014

As the advanced heavy-duty gas turbine develops, the turbine inlet temperature and pressure have increased quite significantly to achieve better performance. The flow and heat transfer conditions of hot components including combustor and turbine become even more extreme than ever which need corresponding aerodynamic and cooling design development. The issue of combustor-turbine interaction has been proposed as a complicated research topic. Currently the hot streak, turbulence intensity, swirling flow, radiation are the four important factors for combustor-turbine interaction research according to the literature. Especially as the turbine inlet temperature increases, the radiative heat transfer plays a more and more important role.

In this paper, a first stage vane is selected for the conjugate heat transfer simulation including radiative heat transfer since it is almost impossible to identify the radiative effect in experiment. The goal is to examine the effects of radiative heat flux and temperature increment caused by radiation. Several radiative factors including the inlet radiation, gas composition, vane surface emissivity and outlet reflection are investigated. The temperature distribution and heat flux enhancement under different conditions are compared, which can provide reference to the turbine heat transfer design. The general information of radiative effect can be summarized by quantitative analysis.

Results show that the temperature increases obviously when considering the radiation effect as expected. However, these factors show distinct influence on the vane temperature distribution. The inlet radiation has significant impact on the vane leading edge and pressure side. Besides the gas radiation plays quite uniform on the whole vane surface.
Study of Particle Ingestion Through Two-Stage Gas Turbine
Authors: Ghenaiet Adel
Published: September 2014

This paper presents a numerical study of particle laden gas flow through a two-stage hp axial turbine, by means of an in-house code based on the Lagrangian tracking model and the finite element method. As fly-ash solid particles trajectories and locations of impacts are predicted, the local erosion rates and the deteriorations of blades are assessed. The computed trajectories provide a detailed description of particles behaviors and reveal that particle impacts on the aft of vane pressure side usually lead to significant variations in the directions of particles to the next rotor blade, and subsequently particles impact the suction side. The plots of equivalent erosion rates indicate the vanes and blades locations which suffer more erosion. The first vane pressure surface is impacted more than any other component, but higher rates are seen at the top corner from trailing edge. The critical regions of erosion wear in the first rotor are observed over the top of blade leading edge extending along the tip as well as a rounding of the top corner from trailing edge. In the second vane, the regions of higher erosion are revealed over the last third of leading edge and the top corner extending along tip. The erosion in the second rotor is over a large area of suction side till the tip corner. The predicted areas of extreme erosion, also shown by the deteriorated profiles, are indicators for anticipated vanes and blades failures.
Cycle Optimization of Mixed High Bypass Turbofan
Authors: Ghenaiet Adel
Published: September 2014

This paper presents a parametric study and an optimization approach, targeting the design of optimum mixed turbofan engines employed by long-range passenger aircraft. The first part of this paper concerns a parametric analysis carried out with the aim of highlighting the effects of principal design criteria on engine performance in terms of specific thrust and specific fuel consumption. The second part deals with the optimization to find the design parameters concurrently minimizing the specific fuel consumption at cruise. The backbone of the optimization approach consists of a genetic algorithm and a developed engine performance analysis method for both design point and off-design operations. This latter employs closed form analytical expressions instead of numerical solution using pre-defined components’ maps. This approach is deemed sufficient for simple feasibility studies carried out during the course of conceptual and preliminary designs. The strong coupling between the core and bypass streams has constrained the range of physical properties and reduced the space of search for the optimum. The results show possible benefits from utilizing the mixing of gases and a common propelling nozzle, which in some cases may increase the propulsive efficiency.
Simultaneous Optimization of Rotor Blade and Wind-Lens for Aerodynamic Design of Wind-Lens Turbine
Authors: Oka Nobuhito , Furukawa Masato , Yamada Kazutoyo , Kawamitsu Kenta , Kido Kota , Oka Akihiro
Published: September 2014

An optimum aerodynamic design method for the new type of wind turbine called “wind-lens turbine” has been developed. The wind-lens turbine has a diffuser with brim called “wind-lens”, by which the wind concentration on the turbine rotor and the significant enhancement of the turbine output can be achieved. In order to design efficient wind-lens turbines, an aerodynamic design method for the simultaneous optimization of rotor blade and wind-lens has been developed. The present optimum design method is based on a genetic algorithm (GA) and a quasi-three-dimensional design of turbine rotor. In the GA procedure, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) is used as evaluation and selection model. The Real-coded Ensemble Crossover (REX) is used as crossover model. The quasi-three-dimensional design consists of two parts: meridional viscous flow calculation and two-dimensional blade element design. In the meridional viscous flow calculation, an axisymmetric viscous flow is numerically analyzed on a meridional plane to determine the wind flow rate through the wind-lens and the spanwise distribution of the rotor inlet flow. In the two-dimensional rotor blade element design, the turbine rotor blade profile is determined by a one-dimensional through flow modeling for the wind-lens turbine and a two-dimensional blade element theory based on the momentum theorem of the ducted turbine. Total performances and three-dimensional flow fields of the optimized wind-lens turbines have been investigated by Reynolds averaged Navier-Stokes (RANS) simulations, in order to verify the present design method. The RANS simulations and the flow visualization have been applied to conventional and optimum design cases of the wind-lens turbine, in order to elucidate the relation between their aerodynamic performances and the flow fields around them. The numerical results show that separation vortices behind the wind-lens brim play a major role in the wind concentration and the diffuser performance of the wind-lens. As a result, it is found that the aerodynamic performance of wind-lens turbine is significantly affected by the interrelationship between the internal and external flow fields around the wind-lens.
Numerical Study of Unsteady Flow-Field and Flame Dynamics in a Gas Turbine Model Combustor
Authors: Wankhede Moresh J. , Tap Ferry A. , Schapotschnikow Philipp , Ramaekers Wilhelmus J. S.
Published: September 2014

In swirl-stabilized gas turbine combustors, interaction between unsteady flow-field and flame dynamics play a key role in driving several types of combustion instabilities, establishing flame location and its structure and influencing heat release rates. This is challenging to understand and computationally expensive to resolve in detail. In this study, a highly turbulent and swirling flow-flame dynamics in a gas turbine model combustor is characterized numerically using unsteady Reynolds-averaged Navier Stokes (URANS) and detached eddy simulation (DES) based computational fluid dynamics (CFD) methods. From flame representation point of view, the Flamelet Generated Manifold (FGM) method is used to reduce combustion chemistry (which still includes detailed reaction kinetics and species diffusion in reaction layers) and hence computational requirements. The helical precessing vortex core (PVC) instability and its influence on downstream flow/flame dynamics is captured. Further insight is gained into URANS and DES methods capabilities in simulating various coherent swirl flow structures such as central toroidal recirculation zone (CTRZ) and outer recirculation zones (ORZ) as well as fuel-air mixing patterns. NOx emission, which is currently a high-priority design objective due to stringent pollutant regulations, is also computed. The results show that the numerically captured swirling flow-flame dynamics is in accordance with the experimental observations and measurements.
Aerodynamic Optimization of the Diffuser Towards Improving the Performance of Turbine and Exhaust Hood
Authors: Fu Jing-Lun , Liu Jian-Jun , Zhou Si-Jing
Published: September 2014

Exhaust hood of large steam turbines is designed to recover the leaving kinetic energy of the last stage turbine while guiding the flow from the turbine to the condenser, which is of great importance to the overall performance of the steam turbine. The influences imposed by the strong flow interactions between the last stage turbine and the non-axisymmetric exhaust hood have not been taken into account properly in the current exhaust hood design approaches. The purpose of this paper is to optimize the diffuser in order to guarantee the aerodynamic performance of the turbine and the exhaust hood under the operational conditions. Considering the flow interactions between the turbine and the exhaust hood, the profiles of the diffuser end-wall were improved. The coupled turbine and exhaust hood calculations and the experiments were carried out to validate the effects of the optimization. It’s found that the redesigned diffuser can enhance the pressure recovery ability of the exhaust hood and increase the power output of the last stage turbine.
Performance Increase of Steam Turbine Condensers by CFD Analysis
Authors: Hecker Simon , Auge Andreas , Ellsel Tobias , Flegler Johan , Musch Christian , Graßmann Arne
Published: September 2014

An effective measure to increase the performance of turbine power plants is to minimize flow losses in the condenser resulting in a smaller terminal temperature difference (TTD) — the more the TTD of the condenser can be reduced in an optimization process of a given power plant configuration, the more the exhaust pressure will decrease. With an optimized condenser tube bundle design the TTD can be improved.

This study presents the modification of a commercial CFD code to simulate the three-dimensional flow field around and within tube bundles. Additionally the temperature distribution of the cooling water is part of the numerical solution without modeling each individual condenser tube.

To show the accuracy of the CFD code the flow in a large scale power plant condenser is simulated and compared to measurements of local heat transfer coefficients in the bundles. The comparison shows that the presented CFD tool is valid to predict the performance of such condensers.

Based on the results of the study, areas with low cooling performance are identified and suggestions are made for the increase of the overall condenser efficiency.
Off-Design Analysis and Flow Control of Centrifugal Compressor for Vehicle Engine Turbocharger
Authors: Wang Chenfang , Zhang Yangjun , Zheng Xinqian , Chen Jinke , Wang Zengquan , Xing Weidong
Published: September 2014

To improve vehicle engine overall performance, an off-design analysis method of centrifugal compressor is presented. Mismatching degree is involved in the off-design analysis method. The mismatching degree of compressor flow fields of different working conditions is investigated, and flow control method of the compressor is proposed to decrease the mismatching degree and improve performance of the off-design point of the compressor. As an example, a diesel engine turbocharger centrifugal compressor is analyzed and optimized. The maximum mismatching degree of different working conditions locates at the leading edge of the main blades near shroud, and vaned shroud is presented to decrease the mismatching degree. Simulation shows that the maximum mismatching degree of the centrifugal compressor with vaned shroud decreases significantly, and experimental results show that the performance of the centrifugal compressor with vaned shroud is improved and pressure ratio is increased by 3.1% and efficiency by 1.7% at 80,000 RPM near surge.
Residual Stress Modelling and Inverse Heat Transfer Coefficients Estimation of a Nickel-Based Superalloy Disc Forging
Authors: Rauer Georg , Kühhorn Arnold , Springmann Marcel
Published: September 2014

Aero engine disc forgings are subjected to heat treatment operations, i.e., solution treatment followed by quenching and artificial aging, with the aim of achieving improved mechanical material properties. During heat treatment high inhomogeneous temperature gradients and long loading times at elevated temperatures occur and lead to the development and partial relaxation of bulk residual stresses. The intention of this paper is to describe the residual stress modelling of a nickel-based ATI 718Plus® superalloy disc forging. For this purpose, an uncoupled thermomechanical finite element problem is solved consisting of a thermal model based on transient, spatially varying heat transfer coefficients (HTCs) and a stress model incorporating the nonlinear material behaviour to account for thermal induced inelastic deformations. A graphical user interface based application has been created for the automatic estimation of the a priori unknown HTCs by using a serial solution procedure for the two dimensional inverse heat conduction problem (IHCP) based on the function specification method. The estimated temperature fields have been compared at the thermocouple positions with the corresponding measurement data and confirm the suitability of the inverse algorithm to this problem. A rate-independent elasto-plastic constitutive model is used to simulate the residual stress formation while quenching the disc forging. Two creep models have been adjusted to uniaxial tensile test data and applied to simulate the stress relaxation during aging. Finally, this paper presents the numerical results of the stress analysis.
Dynamic Modeling and Simulation of Gasifier Based on Volume-Resistance Characteristics Method
Authors: Huang Di , Zhang Huisheng , Weng Shilie , Su Ming
Published: September 2014

Gasifier is one of core parts of Integrated Gasification Combined Cycle, which combines clean coal technology with combined cycle through the gasification of solid coal. The conventional lumped parameters simulation model cannot reflect the distribution characteristics in the gasifier.

In order to obtain a more realistic model which can depict the dynamic response as well as the distribution characteristics, this paper utilizes the volume-resistance modeling technique and modular modeling method for the gasifier modeling. The gasifier will be divided into several compartments. The parameters in each compartment are uniform, while it has distribution characteristics for a whole gasifier. Thus the pressure and temperature distribution in the gasifier will be incorporated into the gasification process.

The gasifier model in this paper can not only be used for the system performance analysis, but also for the control system design and debugging.
Nekomimi Film Cooling Holes Configuration Under Conjugate Heat Transfer Conditions
Authors: Kusterer Karsten , Tekin Nurettin , Wüllner Tobias , Bohn Dieter , Sugimoto Takao , Tanaka Ryozo , Kazari Masahide
Published: September 2014

In modern gas turbines, the film cooling technology is essential for the protection of the hot parts, in particular of the first stage vanes and blades of the turbine, against the hot gases from the combustion process in order to reach an acceptable life span of the components. As the cooling air is usually extracted from the compressor, the reduction of the cooling effort would directly result in increased thermal efficiency of the gas turbine. Understanding of the fundamental physics of film cooling is necessary for the improvement of the state-of-the-art. Thus, huge research efforts by industry as well as research organizations have been undertaken to establish high efficient film cooling technologies. Today it is common knowledge that film cooling effectiveness degradation is caused by secondary flows inside the cooling jets, i.e. the Counter-Rotating Vortices (CRV) or sometimes also called kidney-vortices, which induce a lift-off of the jet. Further understanding of the secondary flow development inside the jet and how this could be influenced, has led to hole configurations, which can induce Anti-Counter-Rotating Vortices (ACRV) in the cooling jets. As a result, the cooling air remains close to the wall and is additionally distributed flatly along the surface. Beside different other technologies, the NEKOMIMI cooling technology is a promising approach to establish the desired ACRVs. It consists of a combination of two holes in just one configuration so that the air is distributed mainly on two cooling air streaks following the special shape of the generated geometry.

The NEKOMIMI configuration and two conventional cooling hole configurations (cylindrical and shaped holes) has been investigated numerically under adiabatic and conjugate heat transfer conditions. The influence of the conjugate heat transfer on the secondary flow structure has been analysed.

In conjugate heat transfer calculations, it cannot directly derived from the surface temperature distribution if the reached cooling effectiveness values are due to the improved hole configuration with improved secondary flow structure or due to the heat conduction in the material. Therefore, a methodology has been developed, to distinguish between cooling effectiveness due to heat conduction in the material and film cooling flow over the surface. The numerical results shows that for the NEKOMIMI configuration, 77% of the reached overall cooling effectiveness is due to film cooling with improved flow structure in the secondary flow (ACRV) and 23% due to heat conduction in the material. For the cylindrical hole configuration, 10% of the reached overall cooling effectiveness is due to the film cooling flow structure and 90% due to heat conduction in the material.
Effects of Mechanical Preloads on the Rotordynamic Performance of a Rotor Supported on 3 Pad Gas Foil Journal Bearings
Authors: Sim Kyuho , Koo Bonjin , Lee Jong Sung , Kim Tae Ho
Published: September 2014

The paper presents the rotordynamic performance measurements and model predictions of a rotor supported on three-pad gas foil journal bearings (GFJBs) with various mechanical preloads. The rotor with its length of 240 mm, diameter of 40 mm, and weight of 19.6 N is supported on two GFJBs and one pair of gas foil thrust bearings (GFTBs), being a permanent magnet rotor of a high speed electric motor. Each bearing pad consisting of a top foil and a bump strip layer is installed on a lobed bearing housing surface over the arc length of 120 deg along the circumference. Test three-pad GFJBs have four different mechanical preloads, i.e., 0 μm, 50 μm, 70 μm, 100 μm with a common radial nominal clearance of 150 μm. A series of speed-up tests are conducted up to 93 krpm to evaluate the effects of increasing mechanical preloads on the rotordynamic performance. Two sets of orthogonally positioned displacement sensors record the rotor horizontal and vertical motions at the thrust collar and the other end. Test results show that the filtered synchronous amplitudes change little, but the onset speed of sub-synchronous motions (OSS) increases dramatically for the increasing mechanical preloads. In addition, test bearings with the 100 μm preload show a higher OSS in load-on-pad (LOP) condition than that in load-between-pads (LBP) condition. A comparison to test results for a one-pad GFJB with a single top foil and bump strip layer reveals that three-pad GFJB has superior rotordynamic performance to the one-pad one. Finally, the test data benchmark against linear rotordynamic predictions to validate a rotor-GFJB model. In general, predicted natural frequencies of the rotor-bearing system and synchronous rotor motions agree well with test data. However, stability analyses underestimate OSSs recorded during the experimental tests.
Leading Edge Cooling of a Gas Turbine Blade With Double Swirl Chambers
Authors: Kusterer Karsten , Lin Gang , Bohn Dieter , Sugimoto Takao , Tanaka Ryozo , Kazari Masahide
Published: September 2014

The gas turbine blade leading edge area has locally extremely high thermal loads, which restrict the further increase of turbine inlet temperature or the decrease of the amount of coolant mass flow to improve the thermal efficiency. Jet impingement heat transfer is the state of the art cooling configuration, which has long been used in this area. In the present study, a modified double swirl chambers cooling configuration has been developed for the gas turbine blade leading edge. The double swirl chambers cooling (DSC) technology is introduced by the authors and comprises a significant enhancement of heat transfer due to the generation of two anti-rotating swirls. In DSC cooling the reattachment of the swirl flows with the maximum velocity at the middle of the chamber leads to a linear impingement effect, which is most suitable for the leading edge cooling for a gas turbine blade. In addition, because of the two swirls both suction side and pressure side of the blade near the leading edge can be very well cooled. In this work, a comparison among three different internal cooling configurations for the leading edge (impingement cooling, swirl chamber and double swirl chambers) has been investigated numerically. With the same inlet slots and the same Reynolds number based on hydraulic diameter of channel the DSC cooling shows overall higher Nusselt number ratio than that in the other two cooling configurations. Downstream of the impingement point, due to the linear impingement effect, the DSC cooling has twice the heat flux in the leading edge area than the standard impingement cooling channel.
Meanline Modelling of Inlet Recirculation in Automotive Turbocharger Centrifugal Compressors
Authors: Harley Peter , Spence Stephen , Filsinger Dietmar , Dietrich Michael , Early Juliana
Published: September 2014

This study provides a novel meanline modelling approach for centrifugal compressors. All compressors analysed are of the automotive turbocharger variety and have typical upstream geometry with no casing treatments or pre-swirl vanes. Past experience dictates that inducer recirculation is prevalent toward surge in designs with high inlet shroud to outlet radius ratios; such designs are found in turbocharger compressors due to the demand for operating range. The aim of the paper is to provide further understanding of impeller inducer flow paths when operating with significant inducer recirculation. Using 3D Computational Fluid Dynamics (CFD) and a single-passage model, the flow coefficient at which the recirculating flow begins to develop and the rate at which it grows are used to assess and correlate work and angular momentum delivered to the incoming flow. All numerical modelling has been fully validated using measurements taken from hot gas stand tests for all compressor stages.

The new modelling approach links the inlet recirculating flow and the pressure ratio characteristic of the compressor. Typically for a fixed rotational speed, between choke and the onset of impeller inlet recirculation the pressure ratio rises gradually at a rate dominated by the aerodynamic losses. However, in modern automotive turbocharger compressors where operating range is paramount, the pressure ratio no longer changes significantly between the onset of recirculation and surge. Instead the pressure ratio remains relatively constant for reducing mass flow rates until surge occurs.

Existing meanline modelling techniques predict that the pressure ratio continues to gradually rise toward surge, which when compared to test data is not accurate. A new meanline method is presented here which tackles this issue by modelling the direct effects of the recirculation. The result is a meanline model that better represents the actual fluid flow seen in the CFD results and more accurately predicts the pressure ratio and efficiency characteristics in the region of the compressor map affected by inlet recirculation.
Research on Multidisciplinary Design Optimization of Aeroengine Turbine Flow Path in the Preliminary Design Phase
Authors: Shen Xiuli , Long Dan
Published: September 2014

The design of an aero-engine is traditionally divided into three levels: conceptual design, preliminary design and detailed design. This three-step design process is inherently iterative, which can slow the design process and overall productivity. Additionally, as an integrated systems engineering analysis, aero-engine design involves multiple-disciplines. The complex coupled-relationship among multiple-disciplines and multiple-components gives rise to severe conflict with performance requirements when designing, especially when it comes to high-performance aero-engine. Traditionally, designers need to empirically balance all kinds of requirements, which lead to a longer design cycle. So it is necessary to apply Multidisciplinary Design Optimization (MDO) to organize and manage the process of design system which sufficiently utilizes the effect of interaction of multidisciplines for the optimal solution. The MDO of a turbine flow path is one of the key multidisciplinary optimization technologies in aeroengine overall design. The problem studied and presented in this paper consists in optimizing a turbine modeled by a multidisciplinary system of two coupled disciplines: turbine aerodynamics and structural strength, with temperature limited by the materials. In the present work, three modules are established to conduct the MDO research of turbine flow path: flow path design, turbine strength calculation and MDO. The aeroengine turbine flow path, including high and low pressure turbine flow path, is designed in the first module, with its efficiency estimated. In the second module, turbine rotors consisting of blades, discs and the low spool shaft are parametric modeled so as to analyze the structural aspects of turbine rotors, such as weight and stresses. MDO is conducted using multi-island genetic algorithm optimization (MIGA) optimization algorithm provided in iSIGHT software. Fully Integrated Optimization (FIO) strategy is studied to deal with the multidisciplinary analysis. The complex coupling relations between aerodynamic performance and turbine strength are analyzed to establish turbine multidisciplinary optimization system. The optimal values of loading coefficient, rotational speed, bore diameter of rotor discs defined by the shaft size, and other independent design variables are obtained in order to achieve minimum weight of turbine rotors while simultaneously meeting the strength and aerodynamics efficiency requirements. This method presented in this paper can greatly shorten turbine design cycle, improve aeroengine design ability, and is prospective to be widely applied to engineering field.
Heat Transfer Enhancement Using Wedge-Shaped Detached Ribs With Grooves in Internal Cooling Channel
Authors: Lin Gang , Kusterer Karsten , Merkel Viktor , Bohn Dieter
Published: September 2014

As the state of the art internal cooling configuration the serpentine passage with angled ribs has been developed for many decades and is now widely used in almost all the blade internal cooling applications. To further increase the thermal efficiency of gas turbine, the development of new internal cooling configurations is necessary. In the present study, a new internal cooling configuration, which is characterized by placing modified wedge-shaped detached ribs above the grooves, has been obtained and investigated. Under this new cooling configuration, the main effect for enhancement of heat transfer in standard ribbed channel, the separation and reattachment of the main flow, has been retained. Additional improvements can be found in several areas as follows: (1) flow near rib corner is not stagnant anymore and both corner vortexes near the rib have been eliminated, (2) the increased velocity in groove leads to locally high heat flux. With the same channel dimension, ribs pitch-height ratio, boundary conditions and the Reynolds number based on hydraulic diameter the new cooling configuration shows higher Nusselt number ratio at the ribbed wall by approximately 25–32%. The globally-averaged thermal performance parameter shows a 19–25% better heat performance by this kind of cooling configuration.
Large-Scale Simulation of the Clocking Impact of 2D Combustor Profile on a Two Stage High Pressure Turbine
Authors: Dyson Thomas E. , Helmer David B. , Tallman James A.
Published: September 2014

This paper presents sliding-mesh unsteady CFD simulations of high-pressure turbine sections of a modern aviation engine in an extension of previously presented work [1]. The simulation included both the first and second stages of a two-stage high-pressure turbine. Half-wheel domains were used, with source terms representing purge and film flows. The end-wall flow-path cavities were incorporated in the domain to a limited extent. The passage-to-passage variation in thermal predictions was compared for a 1D and 2D turbine inlet boundary condition. Substantial impact was observed on both first and second stage vanes despite the mixing from the first stage blade. Qualitative and quantitative differences in surface temperature distributions were observed due to different ratios between airfoil counts in the two domains.
Prometheus: A Geometry-Centric Optimization System for Combustor Design
Authors: Zhang Xu , Toal David J. J. , Bressloff Neil W. , Keane Andy J. , Witham Frederic , Gregory Jonathan , Stow Simon , Goddard Christopher , Zedda Marco , Rogers Mark
Published: September 2014

The following paper presents an overview of the Prometheus design system and its applications to gas turbine combustor design. Unlike a traditional “optimizer-centric” method, Prometheus aims to reduce both the level of workflow complexity and rework by taking a more “geometry-centric” approach to design optimization by shifting the control of script generation away from the optimization program to the computer aided design (CAD) package. Prometheus therefore enables significant geometry changes to be automatically reflected in all subsequent scripts necessary for the analysis of a combustor. Prometheus’ current capabilities include automatic fluid volume generation and aero-thermal and thermo-acoustic network generation as well as automatic mesh and computational fluid dynamics (CFD) script generation.
Shock, Leakage Flow and Wake Interactions in a Radial Turbine With Variable Guide Vanes
Authors: Liu Yinhong , Yang Ce , Qi Mingxu , Zhang Hanzhi , Zhao Ben
Published: September 2014

The clearances of the nozzle and volute have significant influences on the unsteady flow, blade load distribution and thermodynamic performance of downstream radial turbine. The unsteady flow and blade loads are intensified due to the interactions among shock, leakage flow and nozzle wake. Few studies have been conducted to date to investigate these effects in detail. This work focuses on the tip leakage flow effects on the nozzle wake and shock. Furthermore, the blade loads of the downstream rotor are considered by evaluating the effects of shock, leakage flow and nozzle wake, and the fluctuating pressures are presented in a novel space-time diagram. To reveal the flow mechanism in a variable radial turbine, two nozzle clearance sizes were chosen for investigation via numerical simulation of the unsteady flow and the interactions among the shock, leakage flow and wake, and the turbine performance was verified with test data. The results show that the interactions between leakage flow and nozzle wake are intensified with increasing nozzle clearances, and the nozzle wake deformations also become more severe. Additionally, the gas mixing speed between the nozzle wake and leakage flow is enhanced, thus inhibiting the gas from expanding in the nozzle channel and weakening the shock at the nozzle outlet. When the nozzle clearance leakage enters the downstream rotor channel, it interacts with the rotor tip clearance leakage in the blade tip region. These interactions have significant impacts on the formation of leakage vortexes and the distribution of the inlet flow angles. With the increase in tip clearances at both sides, the load fluctuation increases at the root and the tip of rotor leading edge, whereas the fluctuation decreases due to the weakening of the upstream shock in the middle span region of the blades.
Investigation of Variated Unsteady Inflow Boundary Conditions on the Transition Behavior of a Low Pressure Turbine Cascade Family
Authors: Blaim Franz F. , Brachmanski Roland E. , Niehuis Reinhard
Published: September 2014

The objective of this paper is to analyze the influence of incoming periodic wakes, considering the variable width, on the integral total pressure loss for two low pressure turbine (LPT) airfoils.

In order to reduce the overall weight of a LPT, the pitch to chord ratio was continuously increased, during the past decades. However, this increase encourages the development of the transition phenomena or even flow separation on the suction side of the blade. At low Reynolds numbers, large separation bubbles can occur there, which are linked with high total pressure losses.

The incoming wakes of the upstream blades are known to trigger early transition, leading to a reduced risk of flow separation and hence minor integral total pressure losses caused by separation. For the further investigation of these effects, different widths of the incoming wakes will be examined in detail, here. This variation is carried out by using the numerical Unsteady Reynolds Averaged Solver TRACE developed by the DLR Cologne in collaboration with MTU Aero Engines AG. For the variation of the width of the wakes, a variable boundary condition was modeled, which includes the wake vorticity parameters. The width of the incoming wakes was used as the relevant variable parameter. The implemented boundary condition models the unsteady behavior of the incoming wakes by the variation of the velocity profile, using a prescribed frequenc. TRACE can use two different transition models; the main focus here is set to the γ–Reθt transition model, which uses local variables in a transport equation, to trigger the transition within the turbulence transport equation system.

The experimental results were conducted at the high speed cascade open loop test facility at the Institute for Jet Propulsion at the University of the German Federal Armed Forces in Munich.

For the investigation presented here, two LPT profiles — which were designed with a similar inlet angle, turning, and pitch are analyzed. However, with a common exit Mach number and a similar Reynolds number range between 40k and 400k, one profile is front loaded and the other one is aft loaded.

Numerical unsteady results are in good agreement with the conducted measurements. The influence of the width of the wake on the time resolved transition behavior, represented by friction coefficient plots and momentum loss thickness will be analyzed in this paper.
Gas Temperature Field Measurement Using Thin-Filament Pyrometry
Authors: Wang Guanghua , Bonilla Carlos , Kalitan Danielle
Published: September 2014

Thin Filament Pyrometry (TFP) has been proven to be a useful approach to measure hot gas temperature. The TFP technique involves suspending a thin filament (typically a SiC fiber) in hot gas flow path and calculating the gas temperature from the measured thermal radiance of the filament. Comparing to most optical and laser based non-intrusive techniques, the TFP approach offers significant simplicity, reduced cost and relative ease of applicability, especially at high-pressure gas-turbine type conditions.

In this study, TFP was employed to measure combustor exit gas temperature distributions in an atmospheric combustion rig simulating a model aero-engine combustor burning Jet-A fuel. Hot gas from the combustor was accelerated through a converging nozzle to achieve high exit velocities. The thermal radiation signal from the glowing fiber was collected by a Near Infrared (NIR) camera outfitted with a band pass filter. The gas temperature profile was calculated by an intensity ratio technique. Two-Dimensional temperature maps were obtained via spatially and temporally scanning the TFP system. Temperature measurements at the combustor exit are reported for various fuel-air ratios at Mach numbers around 0.38. A type-B thermocouple stationed at the centerline of the combustor exit was corrected for radiation effects and used to infer the flame temperature for TFP measurement.

The major contributions of the current study to the advancement of the TFP technique for measuring hot gas temperatures are: (1) To the authors’ knowledge, this is the first time that the TFP technique has been used in a liquid fueled combustion system, and (2) The data presented herein were obtained at greater Mach numbers than all previous studies (Ma = 0.38).
Numerical Study of Effects of AJVG on Aerodynamic Performance and Speed Control of Small-Scale Fixed-Pitch HAWT
Authors: Gao Xiang , Hu Jun , Wang Zhiqiang , Zhang Chenkai
Published: September 2014

Due to the feature of structure simplicity, lower production cost and maintenance ease, fixed pitch variable speed wind turbine has been widely used in non-grid-connected wind power systems. The calculation of wind turbine performance plays an important part in the design of wind turbines. Aerodynamic performance calculation is particularly significant in the fixed pitch stall-regulated wind turbine aerodynamic design process. To enhance the output power and power coefficient of wind turbine, active flow control technologies such as vortex generator are adopted in recent years. In this paper, a small wind turbine with air jet vortex generator (AJVG) on the blade tip is designed, and the output power of the wind turbine gets changed by operating the air jet. Computational Fluid Dynamics method is chosen to obtain aerodynamic characteristics of the wind turbine with/without AJVG and these features are furtherly integrated with speed control method to get speed control strategy under full-speed circumstance. It can be found after complete comparison that through setting AJVG at the blade tip, the new speed control features can help make it operate more stably in a wide range of wind speed without changing the existing wind turbine blades profiles and pitch angle. Also details of the flow field are obtained when solving the three-dimensional Navier-Stokes Equations. By analyzing the flow field of wind turbine with/without AJVG, the influence mechanism of the AJVG is demonstrated in this paper.
Conjugate Heat Transfer Analysis for Gas Turbine Cooled Blade
Authors: Ho Kuo-San , Urwiller Christopher , Konan S. Murthy , Liu Jong S. , Aguilar Bruno
Published: September 2014

This paper explores the conjugate heat transfer (CHT) numerical simulation approach to calculate the metal temperature for a cooled gas turbine blade. ANSYS CFX14.0 code was selected as the computational fluid dynamic (CFD) tool to perform the CHT simulation. The two-equation SST turbulence model with automatic wall treatment was employed. A full engine test with Silicon Carbide (SiC) chip measurements was performed and used to validate the CHT results.

Metal temperatures calculated with the CHT model were compared to engine test data. The results demonstrated good agreement between predicted and measured airfoil metal temperatures. The blade cooling flow prediction was matched to the flow network analysis.

This paper describes a process to calculate convection heat transfer coefficients (HTC) for cooling passages and airfoil surfaces using CHT results. This process was made possible because local wall heat flux and fluid temperatures were known. This approach assisted in calibrating an in-house conduction thermal model for steady state thermal analyses.