bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer and Thermal Mechanical Stress Distributions in Gas Turbine Blades
Authors: Sierra Fernando Z. , Narzary Diganta , Bolaina Candelario , Han Je Chin , Kubiak Janusz , Nebradt Jesu´s
Published: February 2010

In this paper the distributions of heat transfer and thermal mechanical stress in the metal blade surface are investigated. The stream that surrounds the blade was considered at the time that the cooling airflow runs through the blade interior. Cooling channel flow and gases were simulated using a finite volume program, Fluent. The conjugate problem was addressed using coupled domains solid-fluid. Beside the numerical approach, measurements of metal blade surface temperature distributions based on the temperature sensitive paint technique, TSP, were conducted. The cooling effectiveness was compared showing good agreement between computational/experimental results. Additionally to laboratory conditions, finite volume results were obtained for real engine operating conditions. These results were used to establish temperature boundary conditions into a second computational model programmed in ANSYS, based on finite elements. This second model allowed calculating the distribution of thermo-mechanical stress in the blade material. The results show the temperature distribution in the blade surface. Based on this, the heat transfer rate was calculated finding it as a strong function of position. The cooling effectiveness was also calculated, which in turn performs with less variation over the sections of the blade under investigation. Following, the thermal effects in the metal blade surface lead to calculate the stress distribution. Differences in stresses magnitude were also found, suggesting a strong correlation between heat transfer and stress in the metal blade surface.
Study of the Cold Flow Field of a Multi-Injection Combustor
Authors: Wang F. , Huang Y. , Deng T.
Published: February 2010

Multi-injection combustor (MIC) could extend the steady working range of the whole combustor and reduce emissions therefore, so it is one of the Gas Turbine Combustor (GTC) design direction of future. The cold flow character of MIC is the basic work for MIC designers. Because of the low cost nowadays, the CFD method is a very suitable tool for it. Thus, firstly realizable k-epsilon turbulent model (RKE) and Reynolds stress turbulent model (RSM) were used to simulate the downstream flow field of a double radial swirl-cup amongst a simple tube, and the prediction results are compared with the experimental data which are gained by another researcher in Beihang University. The comparison between the experimental data and the CFD prediction results are shown that in most regions, the prediction results quite agree with the experimental data, and the max error of RKE model and RSM model is about 5% and 3% respectively. So the RKE model can be used for swirl-cup combustor simulation for its low computing cost. Then the RKE model is applied in a single swirl-cup gas turbine combustor and two kinds of multi-injection GTC flow field simulation. In the comparison between one single swirl-cup and nine arranged swirl-cups which all are in the same lining structure, each swirl-cup in MIC has a recirculation zone after its exit. Gradually, the recirculation zones mixed and united together in the downstream region. Finally, the recirculation zones structure turns to be similar to the structure in the single swirl-cup GTC after the primary combustion holes. In the other comparison between two kinds of lining structures which all are fixed with the same multi-injection head, the primary combustion holes affect flow field obviously. All the recirculation zones finished before the former primary combustion holes of the MIC without the primary combustion holes, and the separated recirculation zones form a new recirculation zone close to the primary holes for the MIC with primary holes. So the MIC design should combine with the real combustor lining structure to make a high performance for the whole combustor.
The Fouling of Axial Flow Compressors: Causes, Effects, Susceptibility, and Sensitivity
Authors: Meher-Homji Cyrus B. , Chaker Mustapha , Bromley Andrew F.
Published: February 2010

Increased fuel costs have created a strong incentive for gas turbine operators to understand, minimize and control performance deterioration. The most prevalent deterioration problem faced by gas turbine operators is compressor fouling. Fouling causes a drop in airflow, pressure ratio and compressor efficiency, resulting in a “re-matching” of the gas turbine and compressor and a drop in power output and thermal efficiency. This paper addresses the causes and effects of fouling and provides a comprehensive treatment of the impact of salient gas turbine design parameters on the susceptibility and sensitivity to compressor fouling. Simulation analysis of ninety two (92) gas turbines of ranging from a few kW to large engines rated at greater than 300 MW has been conducted. It is hoped that this paper will provide practical information to gas turbine operators.
Effect of Tooth Height, Tooth Width and Shaft Diameter on Carry-Over Coefficient of Labyrinth Seals
Authors: Suryanarayanan Saikishan , Morrison Gerald L.
Published: February 2010

The accuracy of rotodynamic analysis of any turbomachinery is dependent upon the accuracy of seal leakage prediction. An expression for the leakage through a labyrinth seal can be developed by combining the coefficient of discharge under each tooth and a carryover coefficient to account for the dissipation of kinetic energy of the jet emerging from under each tooth in the subsequent cavity through turbulence viscosity interaction. While most popularly used leakage models consider the carry-over coefficient only as a function of clearance and pitch, it was established in our earlier work that Reynolds number and clearance/pitch ratio have a major effect on the carry-over coefficient. This work extends the carry-over coefficient model presented by Saikishan Suryanarayanan and G.L. Morrison [1] for incompressible, straight through, rectangular cavity, tooth on stator labyrinth seals by studying and incorporating the effect of tooth width, pitch, tooth height and shaft diameter in addition to Reynolds number and clearance on the carry-over coefficient. It is shown that the tooth width/pitch ratio has a significant effect upon the carry-over coefficient.
A Parametric Study on the Influence of the Lateral Ejection Angle of Double-Jet Holes on the Film Cooling Effectiveness for High Blowing Ratios
Authors: Kusterer Karsten , Elyas Anas , Bohn Dieter , Sugimoto Takao , Tanaka Ryozo , Kazari Masahide
Published: February 2010

The improvement of the thermal efficiency of modern gas turbines can be achieved by reducing the required cooling air amount. The reduction of the cooling air claims for an improved cooling technology, which assures the protection of the vane and blade airfoil from the hot mainstream flow. Consequently, it is required to increase the cooling efficiency of applied cooling technologies. Streamwise ejection from a cylindrical hole causes kidney vortices, which transport hot gas underneath the cooling jet and leads the cooling jet to lift off the surface. The double-jet film cooling technology represents a solution to establish an anti-kidney vortex, which prevents the double jet from lifting off the surface and raises the lateral spreading of the cooling air. This is achieved by a particular arrangement of simple cylindrical holes to each other. Additionally, the design of double-jet holes reduces significantly the effort of hole manufacturing compared to the effort of manufacturing a shaped hole design. Numerical investigations for blowing ratios from M = 0.5 up to M = 2 and experimental investigations in a test rig prove the proper film cooling ability of the double-jet film cooling technology. Furthermore, this paper presents a numerical parametric study of the double jet film cooling technology. The influence of the lateral ejection angle on the distribution of the cooling film is calculated and analyzed for the blowing ratios of M = 1, M = 1.5 and M = 2. It can be shown that an even higher film cooling effectiveness is reached with the use of the double-jet film cooling technology by an improvement of the hole positions and hole angles than in previous investigations.
Simulation of Vorticity Driven Flame Instability Using a Flame Surface Density Approach Including Markstein Number Effects
Authors: Voigt Torsten , Habisreuther Peter , Zarzalis Nikolaos
Published: February 2010

The combustion induced and vorticity driven instability behaviour of a lean flame within a premixed combustion system under typical gas turbine conditions is investigated numerically. Over a wide range of operation conditions, the flame is stabilised by the well known mechanisms of premixed confined combustion systems interacting with a turbulent swirled flow field. However, the behaviour of the flame changes drastically just as a critical equivalence ratio is reached: the flame moves upstream close to the rotational axis at positions of originally highest downstream velocities. This flashback behaviour is known as combustion induced vortex breakdown (CIVB) [1] since the upstream propagation results from a local breakdown of the swirled flow field caused by the heat release. A Reynolds-Stress turbulence approach is used as closure model for the three dimensional uRANS simulations to capture the highly turbulent and exceedingly anisotropic flow field. In addition, a flame surface density (FSD) formulation is utilised for combustion modelling. Hence, the essential process of flame vortex interaction is considered in particular. This process is expressed by the important effects of flame strain and curvature and is directly taken into account by means of solving the Favre averaged area of flame surface with the aid of a transport equation. The considered stretch effects do not only influence the production and destruction of the flame surface but moreover modify the local heat release by altering the pseudo-chemical parameter of flame speed. This effect is captured through the Markstein number that is determined by preliminary flamelet calculations. The numerical results lead to the conclusion that the strained and re-orientated vorticity filaments are mainly responsible for the formation of locally negative velocities close to the rotational axis. The re-orientation and straining of vortex filaments is in turn controlled by the local heat release. Finally, the overall occurrence of the simulated flashback is in good accordance with the experiments but does also demonstrate the importance of strain effects on global flame behaviour.
GasTurboLib: Simulink Library for Gas Turbine Engine Modelling
Authors: Panov V.
Published: February 2010

A new Simulink library, called GasTurboLib, containing blocks specialized for gas turbine modelling has been developed. Different engine configurations can be generated using GasTurboLib components and these models can be used for steady state and transient performance analysis. This paper describes the newly developed generic gas turbine simulation tool and presents experiences with modelling and simulation of single and twin shaft gas turbine engines. This library enables 0-D modelling, which is the simplest level of modelling but the most widely used in industry. This component-based modelling environment can be used to simulate start-up sequence, load change, control system design, power-system stability studies and real-time modelling. Traditionally, control method improvements are developed and validated through engine testing. The goal was to develop a functional engine model, which can be started, operated and shut down by a governor model, for the purposes of development of control methods and protection algorithms, thus providing considerable cost savings, as well as enabling better project progress through independence from the availability of test beds. It has been demonstrated that rapid model generation and reusability of components along with user-friendly graphical user interface make this simulation environment a valuable tool for gas turbine system performance analysis.
Augmented Heat Transfer of Internal Blade Tip Wall With Pin-Fins
Authors: Xie G. N. , Sunde´n B. , Wang L. , Utriainen E.
Published: February 2010

The heat transferred to the turbine blade is substantially increased as the turbine inlet temperature is increased. Cooling methods are therefore much needed for the turbine blades to ensure a long durability and safe operation. The blade tip region is exposed to the hot gas flows. A common way to cool the tip is to use serpentine passages with 180-deg turn under the blade tip cap taking advantage of the three-dimensional turning effect and impingement. Improving internal convective cooling is therefore required to increase the blade tip life. In this paper, augmented heat transfer of a blade tip has been investigated numerically. The computational models consist of a two-pass channel with 180-deg turn and an array of pin-fins mounted on the tip-cap, and a smooth two-pass channel. Inlet Reynolds numbers are ranging from 100,000 to 600,000. The computations are 3D, steady, incompressible and stationary. The detailed 3D fluid flow and heat transfer over the tip surfaces are presented. The overall performance of the two models is evaluated. It is found that the pin-fins make the counter-rotating vortices towards pin-fin surfaces, resulting in continuous turbulent mixing near the pin-finned tip. Due to the combination of turning, impingement and pin-fin crossflow, the heat transfer coefficient of the pin-finned tip is a factor of as much as 1.84 higher than that of a smooth tip. This augmentation is achieved at the expense of a penalty of pressure drop around 35%. It is suggested that the pin-fins could be used to enhance blade tip heat transfer and cooling.
Verification of a Neural Network Based Predictive Emission Monitoring Module for an RB211-24C Gas Turbine
Authors: Botros K. K. , Selinger C. , Siarkowski L.
Published: February 2010

This paper presents a verification of a Predictive Emission Monitoring (PEM) model developed for a non-DLE RB211-24C gas turbine used at a natural gas compressor station on the TransCanada Pipeline System in Alberta, Canada. The basis and methodology of the PEM model is first described, and its predictions were compared to recent Continuous Emission Monitoring (CEM) data obtained at different engine load conditions varying from 10 to 19 MW (site condition). The PEM model is based on an optimized Neural Network (NN) architecture which takes 6 fundamental engine parameters as input variables. The model predicts NOx (dry) as an output variable. The NN was trained using CEM measurements comprising four sets of actual emission data collected over four different dates in four different seasons during 2000, and at different operating conditions covering the range of the engine operating parameters. The PEM model was then implemented in the station Compressor Equipment Health Monitoring (CEHM) system and NOx predictions were reported online on a minutely basis for several months and NOx emission trends were captured and analyzed. Comparison between predictions and stack measurements shows a fairly good agreement between the PEM and CEM data within ±10 ppm (dry).
Prediction of Flow Features in Rotating Cavities With Axial Throughflow by RANS and LES
Authors: Tan Qinxue , Ren Jing , Jiang Hongde
Published: February 2010

Rotating cavities with axial throughflow are found inside the compressor rotors of turbomachines. The flow pattern and heat transfer in the cavities are known as sophisticated problems. In this paper, the 3D compressible flow field in a rotating cavity is investigated numerically using a steady RANS method, an unsteady RANS method and LES. The numerical results based on the three methods are analyzed in detail and compared with the available experimental data. For the LES method with a subgrid-scale model, the instantaneous flow structure and the heat transfer can be captured very well. For the unsteady RANS method with an appropriate turbulence model, the large-scale flow structure can be revealed acceptably, and the heat transfer solution agrees with the experimental data with a certain error. For the steady RANS method, a reasonable flow structure cannot be obtained, while the distribution of the heat transfer has a same tendency and uncertain error with the experiments. Therefore, it is suggested that the steady RANS method can still be a numerical tool in the quite preliminary design of the rotating cavities, while the LES is more advanced from an academic view. Moreover, the unsteady RANS method is most appropriate for industry. It should be valuable in the detailed design computations for selecting the optimized design.
New Model Based Gas Turbine Fault Diagnostics Using 1D Engine Model and Nonlinear Identification Algorithms
Authors: Hosseini Seyyed Hamid Reza , Khaledi Hiwa , Soltani Mohsen Reza
Published: February 2010

Gas turbine fault identification has been used worldwide in many aero and land engines. Model based techniques have improved isolation of faults in components and stages’ fault trend monitoring. In this paper a powerful nonlinear fault identification system is developed in order to predict the location and trend of faults in two major components: compressor and turbine. For this purpose Siemens V94.2 gas turbine engine is modeled one dimensionally. The compressor is simulated using stage stacking technique, while a stage by stage blade cooling model has been used in simulation of the turbine. New fault model has been used for turbine, in which a degradation distribution has been considered for turbine stages’ performance. In order to validate the identification system with a real case, a combined fault model (a combination of existing faults models) for compressor is used. Also the first stage of the turbine is degraded alone while keeping the other stages healthy. The target was to identify the faulty stages not faulty components. The imposed faults are one of the most common faults in a gas turbine engine and the problem is one of the most difficult cases. Results show that the fault diagnostic system could isolate faults between compressor and turbine. It also predicts the location of faulty stages of each component. The most interesting result is that the fault is predicted only in the first stage (faulty stage) of the turbine while other stages are identified as healthy. Also combined fault of compressor is well identified. However, the magnitude of degradation could not be well predicted but, using more detailed models as well as better data from gas turbine exhaust temperature, will enhance diagnostic results.
Experimental and Numerical Analysis of Gas Turbine Blades With Different Internal Cooling Geometries
Authors: Eifel M. , Caspary V. , Ho¨nen H. , Jeschke P.
Published: February 2010

This paper presents the effects of major geometrical modifications to the interior of a convection cooled gas turbine rotor blade. The analysis of the flow is performed experimentally with flow visualization via paint injection into water whereas the flow and the heat transfer are investigated numerically with Ansys CFX utilizing the SST turbulence model. Two sets of calculations are carried out, one under the same conditions as the experiments and another according to realistic hot gas conditions with conjugate heat transfer. The aim is to identify flow phenomena altering the heat transfer in the blade and to manipulate them in order to reduce the thermal load of the material. The operating point of the geometric base configuration is set to Re = 50,000 at the inlet while for the modified geometries the pressure ratio is held constant compared to the base. Flow structures and heat transfer conditions are evaluated and are linked to specific geometric features. Among several investigated configurations one could be identified that leads to a cooling effectiveness 15% larger compared to the base.
Producing Hydrogen and Power Using Chemical Looping Combustion and Water-Gas Shift
Authors: McGlashan Niall R. , Childs Peter R. N. , Heyes Andrew L. , Marquis Andrew J.
Published: February 2010

A cycle capable of generating both hydrogen and power with ‘inherent’ carbon capture is proposed and evaluated. The cycle uses chemical looping combustion (CLC) to perform the primary energy release from a hydrocarbon, producing an exhaust of CO. This CO is mixed with steam and converted to H2 and CO2 using the water-gas shift reaction (WGSR). Chemical looping uses two reactions with a re-circulating oxygen carrier to oxidise hydrocarbons. The resulting oxidation and reduction stages are preformed in separate reactors — the oxidiser and reducer respectively, and this partitioning facilitates CO2 capture. In addition, by careful selection of the oxygen carrier, the equilibrium temperature of both redox reactions can be reduced to values below the current industry standard metallurgical limit for gas turbines. This means that the irreversibility associated with the combustion process can be reduced significantly, leading to a system of enhanced overall efficiency. The choice of oxygen carrier also affects the ratio of CO vs. CO2 in the reducer’s flue gas, with some metal oxide reduction reactions generating almost pure CO. This last feature is desirable if the maximum H2 production is to be achieved using the WGSR reaction. Process flow diagrams of one possible embodiment using a zinc based oxygen carrier are presented. To generate power, the chemical looping system is operated as part of a gas turbine cycle, combined with a bottoming steam cycle to maximise efficiency. The WGSR supplies heat to the bottoming steam cycle, as well as helping to raise the steam necessary to complete the reaction. A mass and energy balance of the chemical looping system, the WGSR reactor, steam bottoming cycle and balance of plant, is presented and discussed. The results of this analysis show that the overall efficiency of the complete cycle is dependant on the operating pressure in the oxidiser, and under optimum conditions, exceeds 75%.
Modelling of Liquid Leakage Sprays in Crossflow
Authors: Hutcheson Paul S. , Chew John W. , Thorpe Rex B. , Young Colin , Regan Nicholas J.
Published: February 2010

The leakage and transport of oil within secondary air system cavities is of interest in oil and air system design, for which CFD can be used as a predictive tool. This paper focuses on the leakage of oil from cracks into a high speed crossflow, idealised as round nozzles at Weber numbers and momentum flux ratios relevant to those in an aero-engine. Simulations were performed using the Euler-Lagrangian approach implemented in a commercial CFD code (FLUENT), including sub-models for breakup, deforming droplet drag, collisions/coalescence and turbulent dispersion. CFD predictions were compared with experimental data from two independent studies. The calculated position of the centre-of-mass of the spray plume agreed well with experiment in all cases, but the penetration was found to be under-estimated. Differences in droplet sizes between experiments could not be explained by variations in the the gas Weber number alone, and a review of the literature has highlighted the importance of the liquid to gas viscosity ratio in determining droplet size trends. Experimental trends in droplet size with changing viscosity ratios were captured by CFD simulations, and droplet SMD was predicted within 20% of experiment. It is concluded that the sub-models used within an Euler-Lagrangian approach can be useful tools for the prediction of droplet size, although further improvements in breakup and coalescence modelling will be necessary if greater accuracy is required.
Numerical Study on Flat Plate and Leading Edge Film Cooling
Authors: Sakai Eiji , Takahashi Toshihiko , Funazaki Ken-ichi , Bin Salleh Hamidon , Watanabe Kazunori
Published: February 2010

This study describes a 3-D computation for film cooling effectiveness investigation using Fluent commercial code, version 6.2. Two configurations are examined: (1) Flat plate, and (2) Semi-cylindrical leading edge with a flat after-body. Three different RANS turbulence models and DES based on Spalart-Allmaras model are utilized to see the difference in accuracy between DES and RANS approaches. Similar to the previous RANS simulation, lateral spreading of film cooling is under-estimated in the RANS simulation, while in the DES, lateral spreading of film cooling is enhanced and shows adequate agreement with the previous experiments. The effects of velocity magnitude and orientation of plenum flow on film cooling effectiveness are also studied in the flat plate configuration. The plenum flow is eventually found to have a strong impact on the flow structure in the cooling pipe, and the distorted velocity profile in the pipe consequently lowers film cooling effectiveness, in particularly at high blowing ratio.
Detailed Numerical Simulations of the Primary Atomization of a Turbulent Liquid Jet in Crossflow
Authors: Herrmann Marcus
Published: February 2010

This paper presents numerical simulation results of the primary atomization of a turbulent liquid jet injected into a gaseous crossflow. Simulations are performed using the balanced force Refined Level Set Grid method. The phase interface during the initial breakup phase is tracked by a level set method on a separate refined grid. A balanced force finite volume algorithm together with an interface projected curvature evaluation is used to ensure the stable and accurate treatment of surface tension forces even on small scales. Broken off, small scale nearly spherical drops are transferred into a Lagrangian point particle description allowing for full two-way coupling and continued secondary atomization. The numerical method is applied to the simulation of the primary atomization region of a turbulent liquid jet (q = 6.6, We = 330, Re = 14,000) injected into a gaseous crossflow (Re = 570,000), analyzed experimentally by Brown and McDonell (2006). The simulations take the actual geometry of the injector into account. Grid converged simulation results of the jet penetration agree well with experimentally obtained correlations. Both column/bag breakup and shear/ligament breakup modes can be observed on the liquid jet. A grid refinement study shows that on the finest employed grids (flow solver 64 points per injector diameter, level set solver 128 points per injector diameter), grid converged drop sizes are achieved for drops as small as one-hundredth the size of the injector diameter.
Computational Analysis of Conjugate Heat Transfer and Particulate Deposition on a High Pressure Turbine Vane
Authors: Ai Weiguo , Fletcher Thomas H.
Published: February 2010

Numerical computations were conducted to simulate flyash deposition experiments on gas turbine disk samples with internal impingement and film cooling using a CFD code (FLUENT). The standard k-ω turbulence model and RANS were employed to compute the flow field and heat transfer. The boundary conditions were specified to be in agreement with the conditions measured in experiments performed in the BYU Turbine Accelerated Deposition Facility (TADF). A Lagrangian particle method was utilized to predict the ash particulate deposition. User-defined subroutines were linked with FLUENT to build the deposition model. The model includes particle sticking/rebounding and particle detachment, which are applied to the interaction of particles with the impinged wall surface to describe the particle behavior. Conjugate heat transfer calculations were performed to determine the temperature distribution and heat transfer coefficient in the region close to the film-cooling hole and in the regions further downstream of a row of film-cooling holes. Computational and experimental results were compared to understand the effect of film hole spacing, hole size and TBC on surface heat transfer. Calculated capture efficiencies compare well with experimental results.
A Numerical Investigation on Fluid-Thermal-Structure Coupling Characteristics of Laminated Film Cooling Configurations
Authors: Wang Jianhua , Xu Huazhao , Lv Xijia , Du Zhineng , Yang Shijie
Published: February 2010

This paper presents a numerical approach to study the fluid-thermal-structure coupling problems of laminated film cooling configurations. The SST k-ω turbulence model, T-grid technology, and SIMPLEC algorithm in the commercial tool Fluent 6.3 were employed to solve the coupling problems of flowing fluid and heat transfer within the solid configurations. The numerical method and program were validated with the experimental date obtained by an infrared thermal imaging system in the first part of this work. The validated method and program were applied to analyze the coupling effects of variant solid structure devices, and the influences of film-hole angles and rib-arrangements on cooling effectiveness were compared. The temperature fields obtained by the validated program were input into another commercial tool, Ansys 11, to estimate the thermal stress profiles within the configurations. The fluid-thermal-structure characteristics of the laminated cooling configurations were synthetically discussed.
Relevant Points for Thermodynamic Diagnosis Application Using the Reconciliation Method
Authors: Silva Julio Augusto , Venturini Osvaldo Jose´ , Lora Electo Eduardo , Santos Jose´ Joaquim , Pinho Alexandre Ferreira
Published: February 2010

After some hours of operation, every power plant’s equipment begins to show degraded performance. The amount of equipment degradation and the gain that can be achieved in plant heat rate and power generation by the replacement or repairing of each component is important information for proper plant maintenance management. This paper aims to show how diagnosis and prognosis of a power plant can be performed based on thermodynamic data measured by plant instrumentation on site. Some important points such as how to increase the accuracy of the prognostic by developing the complete Taylor series and how it affects the thermodynamic state are also explained. Practical considerations for implementing a thermodynamic diagnosis/prognosis system in a real plant are also discussed. The system receives thermodynamic data from the plant information system (PI) and after a filtering step, the performance factors (PFs) of each component are calculated based on the component’s performance curves. Thus, the current state can be modeled using these PFs. By replacing the calculated performance factors, component by component, with factors that represents no degradation, future cycle performance can be estimated. This work is a partial result of an ongoing research program that implements a thermodynamic diagnosis/prognosis system on a 130 MW combined cycle co-generation power plant.
Development of a Novel Flow Control Device for Limiting the Efflux of Air Through a Failed Pipe
Authors: Scanlon T. , Wilson P. , Priestman G. , Tippetts J.
Published: February 2010

The secondary air-systems of a gas turbine engine frequently incorporate pipes and ducts to transport air for duties such as cooling and sealing of the turbine components, pressurisation of the aircraft cabin and component de-icing. The engine must be capable of operating safely in the event of failure of a pipe or duct. The ducts typically pass through the low pressure ventilation zones outboard of the core engine and failure will result in a large mass flow of relatively high temperature air escaping from the secondary air system; the design of the engine must accommodate this potential escape so that no component is over-pressurised or over-heated as a result. A novel device is presented that will limit the flow that escapes in the event of a pipe failure. This device has been developed from a number of flow elements from Fluidic technology applications. It has no moving parts and is thus suitable for use as a high-reliability failure protection device. The device consists of a Coanda diverter that can switch the flow through a vortex throttle so that the device has high and low resistance states. The diverter is conditioned to default to the low resistance state unless a control flow extracted from the device exceeds a critical value whereupon it will switch the device to a high resistance state. The level of the control flow is determined by the pressure ratio acting across the device. This is achieved by contrasting the flow characteristics of a metering orifice that determines the control flow with that of a diffuser fitted to the device outlet. The device has been shown to half the flow that escapes from a failed duct compared with an unrestricted duct of the same flow capacity. Experimental and numerical results are presented that show that the device is effective at the high pressure ratios pertaining to gas turbine operation. With suitable modification the device could be adapted to fulfill a number of other functions within a secondary air-system that require variation of flow resistance in response to a change in pressure ratio combined with the high reliability and robustness of a no-moving-parts device.
Optimal Tuner Selection for Kalman Filter-Based Aircraft Engine Performance Estimation
Authors: Simon Donald L. , Garg Sanjay
Published: February 2010

A linear point design methodology for minimizing the error in on-line Kalman filter-based aircraft engine performance estimation applications is presented. This technique specifically addresses the underdetermined estimation problem, where there are more unknown parameters than available sensor measurements. A systematic approach is applied to produce a model tuning parameter vector of appropriate dimension to enable estimation by a Kalman filter, while minimizing the estimation error in the parameters of interest. Tuning parameter selection is performed using a multi-variable iterative search routine which seeks to minimize the theoretical mean-squared estimation error. This paper derives theoretical Kalman filter estimation error bias and variance values at steady-state operating conditions, and presents the tuner selection routine applied to minimize these values. Results from the application of the technique to an aircraft engine simulation are presented and compared to the conventional approach of tuner selection. Experimental simulation results are found to be in agreement with theoretical predictions. The new methodology is shown to yield a significant improvement in on-line engine performance estimation accuracy.
Numerical Analysis of a Multiple Jet Impingement System
Authors: Rao G. Arvind , Kitron-Belinkov Myra , Levy Yeshayahou
Published: February 2010

Jet impingement is known to provide higher heat transfer coefficients as compared to other conventional modes of single phase heat transfer. Jet impingement has been a subject of research for a long time. Single jets have been studied extensively for their heat transfer and flow characteristics. However, for practical usage, multiple jets (in the form of arrays) have to be used for increasing the total heat transfer over a given area. Most of the research on multiple impinging jets have focused on evaluating heat transfer correlations for such arrays in the turbulent regime (Re >2500). The focus of the present paper is on experimental investigation of a large array of impinging jets in the low Reynolds number regime (<1000) and subsequently numerically modeling the same array by using existing Computational Fluid Dynamics tools in order to study the physical phenomena within such a complex system. Different turbulence models were used for modeling the fluid flow within these impinging jets and it was found that the SST k-ω model is the most suitable. Results obtained from CFD analysis are in reasonable agreement with experimental values. It was observed that CFD simulations over predicted the Nusselt number and pressure drop when compared to the experimentally obtained values. It was also observed that the decrease in Nusselt number along the streamwise direction of the array was not monotonic. This could be due to the complex flow field resulting from interaction between the crossflow and the impinging jets in the wall jet region. It is anticipated that results obtained from the present work will provide greater insight into the flow behavior and the heat transfer mechanism occurring in multiple impinging jets.
Large Eddy Simulation of a Lean Gas Turbine Model Combustor
Authors: Staufer M. , Janicka J.
Published: February 2010

Partially premixed flames although common on many technical devices are difficult to model in numerical simulations. In this paper a Large Eddy Simulation of a lean combustor is presented. To account for mixing effects in case of partially premixed combustion, a suitable extension to the well known coherent flame model (CFM) is applied. The turbulent reaction rate of the partially premixed flame is approximated by solving an additional transport equation for the flame surface density which accounts for flame wrinkling effects as well as for the creation and destruction of flame surface due to stretch and strain effects. The variation of stoichiometry in the flame is accounted for by using a suitable presumed PDF methodology. The pdf-model represents finite rate, as well as non-equilibrium chemistry effects in the flame. The model has been validated against experimental data. The results show an overall reasonable agreement with experimental data, both in profile shapes as well as peak values.
Main Gas Ingestion in a Turbine Stage for Three Rim Cavity Configurations
Authors: Zhou D. W. , Roy R. P. , Wang C.-Z. , Glahn J. A.
Published: February 2010

Experiments were carried out in a model air turbine stage to study the influence of rotor-stator rim cavity configuration on the ingestion of mainstream gas into the cavity. The three rim cavity configurations differed in their aspect ratio (height / width), the rim seal geometry remained the same. The aspect ratio was changed from the baseline ratio by installing an inner shell on the stator at an appropriate radius; this effectively introduced an axial-gap seal between the rim cavity and the cavity radially inboard. The initial step in each experiment was the measurement of time-average static pressure distribution in the turbine stage to ascertain that proper flow condition had been established. Subsequently, tracer gas concentration and particle image velocimetry techniques were employed to measure, respectively, the time-average but spatially local main gas ingestion and the instantaneous velocity field in the rim cavity. At low purge air flow, regions of ingestion and egress could be identified by inspecting the radial velocity distribution near the rim seal obtained from cavity gas velocity maps close to the stator. While the tangential velocity tended to be slightly larger for the ingested gas, a more clear-cut indicator of ingestion was the strong inward gas radial velocity. Information provided by ensemble-average velocity maps was not sufficient for identifying ingestion because the averaging smeared out flow details which varied from instant to instant. Velocity fields obtained from three-dimensional, time-dependent numerical simulation of a rim seal–cavity with the same dimensions qualitatively showed similar characteristics in the outer part of the cavity and provided insight into the complex flow in the seal region.
Research and Development of Staging Fuel Nozzle for Aeroengine
Authors: Yamamoto Takeshi , Shimodaira Kazuo , Kurosawa Yoji , Mastuura Kazuaki , Iino Jun , Yoshida Seiji
Published: February 2010

Research and development of combustion technologies to reduce NOx emission of aero-engines to 20% of ICAO CAEP4 is progressing as a part of a project of JAXA (Japan Aerospace Exploration Agency), the Technology Development for Clean Engine (TechCLEAN). To realize such low NOx level on aero-engines, it is necessary to use not conventional combustion system such as rich-lean combustion but advanced one such as premixed combustion. We are conducting research and development of staging fuel nozzles that use diffusion combustion for the pilot nozzle and premixed combustion for the main nozzle. As the first step, five fuel nozzles were tested experimentally in the form of single-sector combustor. Test conditions were selected as the LTO cycle of presumed small-class engines. From the result of tests, to combine the combustion efficiency in low engine power condition and low NOx emission in high power one, fuel nozzle models that have triple contrary swirler are suitable. However, the combustion efficiency in 7%MTO is lower than that of current engines. It is necessary to decrease the emission of CO.
Operation of Micro Gas Turbine System Employing Two Stage Combustion of Biomass Gas
Authors: Yamasaki Yudai , Okada Yukinori , Iijima Kazuki , Kaneko Shigehiko
Published: February 2010

A two-axis, recuperated cycle micro-gas turbine (MGT) system for biomass gas is developed. The rated specifications of the MGT are as follows, pressure ratio of 2.7, turbine inlet temperature of 1120K, and output power of 5kW. The system consists of three components: the MGT power-generating system, control system and mock biomass gas supply system. The original two-stage combustor and H infinity system controller used in this system are discriminative. Since the gaseous fuel converted from biomass has a low heat quantity, the combustor is designed to achieve both high combustion efficiency and low NOx emission for lower calorific fuel. In the combustor, a stable tubular flame combustion of city gas in the first stage supplies burned gas, which has enthalpy and activated radicals, to the second stage and enables stable ignition and combustion of biomass gas and air premixture. In addition, because the gas composition of biomass gas is also affected by the sources, the gasification method, and the gasifying condition, the system controller is required to absorb fuel fluctuation while meeting the demanded output. Hence, the H infinity algorithm is employed as a system controller because of its robustness against disturbances from the unpredictable fuel component fluctuation. Using this MGT system, an operation test was carried out with mock biomass gases. The rotational speed of the power turbine could be kept almost constant with both mock fermentation gas and pyrolysis gas as the second-stage fuel, and NOx emission was 50ppm when load was increased to a rated power of 5kW. When the second-stage fuel composition changed from 100% methane to 50% methane and 50% CO2 at a certain speed, the power turbine speed could also be kept constant. The H infinity controller is compared with the 2-DOF PID controller for secondary fuel concerning the response to varying load. The former shows slightly better performance than the 2-DOF PID controller.
Planar Investigation of Outlet Boundary Conditions Effect on Isothermal Flow Fields of a Swirl-Stabilized Burner
Authors: Emara Ahmed , Lacarelle Arnaud , Paschereit Christian Oliver
Published: February 2010

The swirling flow velocity profiles can be strongly influenced by the outlet conditions of the combustion chamber especially at subcritical flow conditions. The effect of such changes on the mean flow or coherent structures is still unclear. It is investigated in the present work in an industrial swirl inducing burner in cold flow conditions with help of PIV. Proper orthogonal decomposition (POD) as well as acoustic measurements were used to characterize the coherent structures shed from the burner mouth. The combustor length (670, and 2020mm) and the outlet area contraction ratio (1, 0.56, 0.27, and 0.09) are varied. Major changes in the flow field are achieved when using a short combustor and the smallest contraction ratio. For this case, a central jet with streamwise velocity is added to the typical central recirculation zone. The POD analysis of the contraction ratios 1 and 0.09 for the long combustor shows that the first helical mode as well as Kelvin Helmholtz vortices are present with minor changes for both cases. At a contraction ratio of 0.09, some new structures at the jet location and near the combustor wall appear.
An Assessment of a Turbofan Engine Using Catalytic Interturbine Combustion
Authors: Avella´n Richard , Gro¨nstedt Tomas
Published: February 2010

The potential for using catalytic combustion in aero engines is discussed. Some preliminaries relating to NOx formation and material capabilities are analyzed. Various means to integrate catalytic combustors in aero engines are described. In particular, catalytic interturbine combustion is investigated both in terms of technical feasibility and through a preliminary design exercise. A thermodynamic design point study is presented analyzing a configuration with a combustor located concentrically around the engine core receiving pressurized air through an interstage high pressure compressor bleed. A parameter study of the compressor bleed ratio is presented for the configuration. A substantial reduction in NOx emissions at the expense of an increase in mission fuel consumption is observed.
Investigation of Flow Instabilities Near the Rim Cavity of a 1.5 Stage Gas Turbine
Authors: Rabs M. , Benra F.-K. , Dohmen H. J. , Schneider O.
Published: February 2010

The present paper gives a contribution to a better understanding of the flow at the rim and in the wheel space of gas turbines. Steady state and time-accurate numerical simulations with a commercial Navier-Stokes solver for a 1.5 stage turbine similar to the model treated in the European Research Project ICAS-GT were conducted. In the framework of a numerical analysis, a validation with experimental results of the test rig at the Technical University of Aachen will be given. In preceding numerical investigations of realistic gas turbine rim cavities with a simplified treatment of the hot gas path (modelling of the main flow path without blades and vanes), so called Kelvin-Helmholtz vortices were found in the area of the gap when using appropriate boundary conditions. The present work shows that these flow instabilities also occur in a 1.5 stage gas turbine model with consideration of the blades and vanes. Therefore, several simulations with different sealing air mass flow rates (CW 7000, 20000, 30000) have been conducted. The results show, that for high sealing air mass flow rates Kelvin-Helmholtz Instabilities are developing. These vortices significantly coin the flow at the rim.
Measurement of Detailed Heat Transfer Coefficient and Film Cooling Effectiveness Distributions Using PSP and TSP
Authors: Russin Rebekah A. , Alfred Daniel , Wright Lesley M.
Published: February 2010

This paper presents the development of a novel experimental technique utilizing both temperature and pressure sensitive paints (TSP and PSP). Through the combination of these paints, both detailed heat transfer coefficient and film cooling effectiveness distributions can be obtained from two short experiments. Using a mass transfer analogy, PSP has proven to be a powerful technique for measurement of film cooling effectiveness. This benefit is exploited to obtain detailed film cooling effectiveness distributions from a steady state flow experiment. This measured film cooling effectiveness is combined with transient temperature distributions obtained from a transient TSP experiment to produce detailed heat transfer coefficient distributions. Optical filters are used to differentiate the light emission from the florescent molecules comprising the PSP and TSP. Although two separate tests are needed to obtain the heat transfer coefficient distributions, the two tests can be performed in succession to minimize setup time and variability. The detailed film effectiveness and heat transfer enhancement ratios have been obtained for a generic, inclined angle (θ = 35°) hole geometry on a flat plate. Distinctive flow features over a wide range of blowing ratios have been captured with the proposed technique. In addition, the measured results have compared favorably to previous studies (both qualitatively and quantitatively), thus substantiating the use of the combined PSP / TSP technique for experimental investigations of three temperature mixing problems.