bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Microturbocharger and Microcombustor for a Three-Dimensional Gas Turbine at Microscale
Authors: Isomura Kousuke , Murayama Motohide , Tanaka Shuji , Yamaguchi Hiroshi , Ijichi Nobuaki , Genda Takashi , Asakura Hiroshi , Saji Nobuyoshi , Esashi Masayoshi , Shiga Osamu , Takahashi Katsuyoshi
Published: February 2009

A microscale gas turbine is under development at Tohoku University in Japan. Current objective of the project is to reveal the performance of the gas turbine at microscale with optimum aerodynamic shape. Therefore the engine to be tested will be fabricated by machining using a micro-5-axis end mill to realize three-dimensional modeling. The first step of the development has been split into the development of microturbocharger and microcombustor, to prevent the problem of the heat flow effect pointed out in the previous study [1]. The heat flow from the combustor to compressor will become relatively large at microscale, and this will degrade the performance of the compressor. The goal of the first step of the development is to achieve the required performance of the components to realize the gas turbine cycle, without the heat effect. Those are, 62% compressor efficiency, 870,000 rpm shaft rotating speed, and the self sustained combustion. A microscale turbocharger has been designed. The compressor impeller of diameter 10mm is expected to produce a pressure ratio of 3, and 68% compressor adiabatic efficiency. The bearings to realize the design rotational speed are hydrodynamic type gas bearing. Fabrication of the herring-bone grooves have been attempted, and successfully formed on a cylindrical surface by new etching procedure. A technique to fabricate three-dimensional turbine impellers at microscale by powder sintering of ceramics has been demonstrated. A semi-microcombustor has been fabricated and shown successful performance by burning hydrogen fuel.
CFD Analysis of Industrial Gas Turbine Exhaust Diffusers
Authors: Vassiliev V. , Irmisch S. , Florjancic S.
Published: February 2009

The key aspects for the reliable CFD modelling of exhaust diffusers are addressed in this paper. In order to identify adequate turbulence models a number of 2D diffuser configurations have been simulated using different turbulence models and results have been compared with measurements. An automated procedure for a time- and resource-efficient and accurate prediction of complex diffuser configuration is presented. The adequate definitions of boundary conditions for the diffuser simulation using this procedure are discussed. In the second part of this paper, the CFD procedure is being applied to investigate the role of secondary flow on axial diffusers. Prediction results are discussed and compared with available measurement data.
Evolution of a Turbine Engine Test Facility to Meet the Test Needs of Future Aircraft Systems
Authors: Montgomery Peter , Burdette Rick , Klepper Jason , Milhoan Al
Published: February 2009

Meeting the test needs of future aircraft systems is the driving goal behind Arnold Engineering Development Center’s (AEDC) ongoing programs of turbine engine test facility modernization, improvement, consolidation, and streamlining. This paper will discuss the evolution of the AEDC J2 turbine engine test cell, its conditioned air supply system, and other related systems with emphasis on how modeling and simulation played a vital role throughout the evolutionary process. Modeling and simulation was used for the analysis of potential design changes, the coding and checkout of control system changes, as well as to improve control system performance and increase overall facility capabilities. These changes began under the Test Operations Modernization and Improvement Program (TOMIP) and continue today in the Propulsion Consolidation and Streamlining Program (PC&S). Already significant improvements have been made in facility capability, and these along with the steps still to come in the near future will be discussed as a turbine engine test facility continues to evolve to meet the test needs of tomorrow’s aircraft systems.
Conjugate Heat Transfer Analysis of Turbine Rotor-Stator System
Authors: Okita Yoji , Yamawaki Shigemichi
Published: February 2009

A fluid-solid conjugate solver has been newly developed and applied to an actual engine disk system. Most of the currently available conjugate solvers lack the special thermal modeling for turbomachinery disk system applications. In the present new code, these special models are implemented to expand the applicability of the conjugate method and to reduce the required computational resources. Most of the conjugate analysis work so far were limited to the axisymmetric framework. However, the actual disk system includes several non-axisymmetric components which inevitably affect the local heat transfer phenomena. This paper presents 3D conjugate analysis of a single stage high pressure turbine rotor-stator disk system to assess these three-dimensional effects. The predicted temperatures shows good agreement with measured data. The calculated results revealed the three-dimensional analysis is crucial to predict the correct heat transfer field which is especially important in transient situations.
Sensitivity of Optimum Design of Rotor System With Magnetic Bearing Via Multilevel Technique
Authors: Shiau T. N. , Wu M. D. , Chang J. R. , Yang T. H.
Published: February 2009

There are many nonlinear factors in the optimization process. The objective of this study is to determine some effects of these nonlinear factors on the sensitivity of optimum design. A rotor-bearing system is composed of rigid disks, shaft elements with distributed mass and stiffness, and magnetic bearings. To obtain an optimum design, the objectives including shaft weight and amplitude of shaft lateral response as well as the constraints including critical speeds and bending stresses are considered. The inner radii of shaft elements, the bias currents of magnetic bearings, and the axial positions of bearings and disks are chosen as the design variables. The single objective method, the multi-objective method and the multilevel technique are employed to deal with the problem of optimality. Optimum results obtained by applying these methods are compared and discussed in this study. Finally, the sensitivity of optimum design is analyzed to determine what nonlinear effects the position of magnetic bearings have on different initial designs.
Experimental Research Into Aerodynamic Forces Leading to Self-Excited Vibrations of Turbine Rotors
Authors: Kosowski Krzysztof , Piwowarski Marian
Published: February 2009

The experimental investigation into pressure field in the shroud clearance and rotor trajectory were performed on an one-stage air model turbine of impulse type. Basing on the pressure distribution, the aerodynamic forces and moments were investigated as a function of rotor eccentricity, axial gap, rotor-stator misalignment, rotor speed and turbine load. We obtained the following results: 1. confirmation of the linear correlation between the rotor eccentricity (or rotor-stator misalignment angle) and aerodynamic forces, 2. proof that radial eccentricity influences the average location of the rotor, while the general shape of rotor trajectory remains unchanged, 3. proof that although the axial component of the pressure force is relatively low, the moments exerted by this force should be take into account when total aerodynamic moments are determined.
Prediction of Combustion Dynamics in a Staged Premixed Combustor
Authors: Lovett Jeffery A. , Uznanski Kevin T.
Published: February 2009

Combustion instabilities are a major challenge in the development of low-emissions premixed gas turbine combustors. The development and demonstration of predictive capabilities for instabilities has progressed considerably. One of the major fundamental mechanisms demonstrated in several instances is the convection of fuel concentration fluctuations from the fuel injector to the reaction zone. A one-dimensional model has been developed which captures this mechanism coupled to solutions for standing acoustic waves. Since many real combustion systems include multiple flow paths for mixing and/or staged fuel injection, the model has been extended to include a parallel acoustic path and two fuel injection locations. Splitting of fuel between two injection positions is a common method to influence combustion dynamics toward a more operable system. A relatively simple model which only partially couples acoustics and heat release was applied to an axially staged combustor and the predictions are compared with the experimental behavior. The results from this model successfully predict the overall dynamics behavior as a function of the fuel split between the two injection locations.
Extrapolation of Compressor Characteristics to the Low-Speed Region for Sub-Idle Performance Modelling
Authors: Jones Geoff , Pilidis Pericles , Curnock Barry
Published: February 2009

In order to model the performance of a gas-turbine engine in the sub-idle region, particularly for starting and windmilling, it is necessary to use compressor characteristics which describe their operation and low speeds. As most compressor tests are conducted only in the range of operating speeds normally encountered, the resultant characteristics must be extrapolated in order to define the low speed compressor maps. In this paper, a variety of techniques for the extrapolation of axial-flow compressor characteristics are presented and evaluated. These include those presented by De-You & Zhong-Fan [4], Agrawal & Yunis [1] and Converse & Giffen [3]. The ease and reliability of the extrapolation methods are compared. Problems associated with the prediction of losses within the turbomachinery are highlighted, particularly in respect of compressor operation at high flows and low rotational speeds. This is due to the creation of highly off-design values of incidence which are not encountered during above-idle running, but which may be found during windmilling.
Application of Reduced-Order Aerodynamic Modeling to the Analysis of Structural Uncertainty in Bladed Disks
Authors: Willcox K. , Peraire J.
Published: February 2009

Blade-to-blade variations can significantly impact the operation of bladed disks. In this paper, a method is presented for assessing the effects of these variations using a high-fidelity aerodynamic analysis. Systematic model reduction is applied to a high-order computational fluid dynamics code using the proper orthogonal decomposition technique. This results in a low-order model suitable for time domain computations of mistuning effects. The model is shown to capture the dynamics of the aeroelastic system more accurately than with a traditional influence coefficient approach. Results are presented for a bladed disk with structural uncertainty, where the blade frequencies exhibit random variations about a nominal state. Finally, the concept of a robust design is explored, in which intentional variation is introduced to the system in an attempt to alleviate the ill-effects of random variations. The approach can also be extended to consider aerodynamic uncertainty, which may arise from geometric variations.
A Novel Approach to the Optimisation of Reaction Rate Parameters for Methane Combustion Using Multi-Objective Genetic Algorithms
Authors: Elliott L. , Ingham D. B. , Kyne A. G. , Mera N. S. , Pourkashanian M. , Wilson C. W.
Published: February 2009

This study uses a multi-objective genetic algorithm to determine new reaction rate parameters (A’s, β’s and Ea’s in the non-Arrhenius expressions) for the combustion of a methane/air mixture. The multi-objective structure of the genetic algorithm employed allows for the incorporation of both perfectly stirred reactor and laminar premixed flames data in the inversion process, thus enabling a greater confidence in the predictive capabilities of the reaction mechanisms obtained. Various inversion procedures based on reduced sets of data are investigated and tested on methane/air combustion in order to generate efficient inversion schemes for future investigations concerning complex hydrocarbon fuels. The inversion algorithms developed are first tested on numerically simulated data. In addition, the increased flexibility offered by this novel multi-objective GA has now, for the first time, allowed experimental data to be incorporated into our reaction mechanism development. A GA optimised methane air reaction mechanism is presented which offers a remarkable improvement over a previously validated starting mechanism in modelling the flame structure in a stoichiometric methane-air premixed flame (http://www.leeds.ac.uk/ERRI/research/res.html). In addition, the mechanism outperforms the predictions of more detailed schemes and is still capable of modelling combustion phenomena that were not part of the optimisation process. Therefore, the results of this study demonstrate that the genetic algorithm inversion process promises the ability to assess combustion behaviour for fuels where the reaction rate coefficients are not known with any confidence and, subsequently, accurately predict emission characteristics, stable species concentrations and flame characterisation. Such predictive capabilities will be of paramount importance within the gas turbine industry.
A Receptivity Based Transition Model
Authors: Johnson Mark W.
Published: February 2009

A numerical procedure for predicting the receptivity of laminar boundary layers to freestream turbulence, consisting of vortex arrays with arbitrary orientation, has been developed previously. In the current paper this method is refined to improve accuracy using an unstructured computational grid. Results show that boundary layers only have high receptivity to a narrow band of normal and spanwise frequencies. The computed near wall gains have similar values to those obtained by experiment for zero pressure gradient boundary layers. Near wall gains are also obtained for a wide range of favourable and adverse pressure gradients for both attached and separated boundary layers. The gain values are used to predict start of transition values which are in reasonable agreement with Reθ values which are in reasonable agreement with the Abu-Ghannam and Shaw correlations. The current results extend transition inception prediction into the separated flow regime.
Optical Sensing of Lean Blowout Precursors in a Premixed Swirl Stabilized Dump Combustor
Authors: Muruganandam Thiruchengode M. , Seitzman Jerry M.
Published: February 2009

The work described here is part of an effort to detect and prevent lean blowout in turbine engine combustors. The approach uses optical emission, primarily chemiluminescence, to identify blowout precursor events, and is demonstrated in a premixed, swirl-stabilized dump combustor. The results show that the transient behavior of the flame as lean blowout is approached is characterized by short duration, localized extinction and reignition events. These events increase in frequency and duration, and spatial extent, as LBO is approached. Several methods can be used to detect these events in the raw sensor output, including signal thresholding and frequency analysis. The paper describes examples of how these analysis techniques can be used to calculate a simple LBO proximity measure that would be ideally suited for use in an active (closed-loop) control system. The LBO proximity sensing is also demonstrated using sensor technology that is close to what would be required in a realistic turbine engine environment, specifically, optical fibers to collect the chemiluminescence and miniature, metal package PMTs for detection. Possible detection locations within the combustor are discussed and various locations are compared, based on their practicality and sensitivity to LBO precursor detection. It was found that the best detection was from fiber that was mounted on the head end and viewed downstream.
Technology Update on Gas Turbine Dual Fuel, Dry Low Emission Combustion Systems
Authors: Ro̸kke Petter Egil , Hustad Johan E. , Ro̸kke Nils A. , Svendsgaard Ole Birger
Published: February 2009

A challenging issue in the gas turbine industry is to develop a practical dual fuel (DF), dry low emission (DLE) combustion system. Especially for the onshore-based power generation systems, and liquid DLE for aeroderivative engines used for marine propulsion. A novel mid-size (3MW) gas turbine is being developed mainly targeted for marine propulsion, where a dual fuel DLE combustion system aiming at single digit NOx emission figures has been explored. As a part of this development, the present technology available from different gas turbine manufacturers has been surveyed. Status of the different techniques applied in dual fuel DLE combustors today and their achievements are presented, including the available information on fuel injectors, cooling schemes, combustion air distribution, noise control and combustor performance. The techniques utilized and explained are such as flame temperature control (water/steam injection), staged combustion, lean premixing and lean prevaporized premixing, rich-quench-lean-burning (RQLB) and catalytic combustion. These are also documented for the different concepts commercially available, describing both advantages and drawbacks. Conclusions are made towards the dominating trends for the different parameters mentioned above, and how they affect the final combustor design. A survey of the dominating parameters for low emission combustion systems is presented.
Experimental and Numerical Investigation of Impingement on a Rib-Roughened Leading-Edge Wall
Authors: Taslim M. E. , Bakhtari K. , Liu H.
Published: February 2009

Effective cooling of the airfoil leading-edge is imperative in gas turbine designs. Amongst several methods of cooling the leading edge, impingement cooling has been utilized in many modern designs. In this method, the cooling air enters the leading edge cavity from the adjacent cavity through a series of crossover holes on the partition wall between the two cavities. The crossover jets impinge on a smooth leading-edge wall and exit through the film holes, and, in some cases, form a crossflow in the leading-edge cavity and move toward the end of the cavity. It was the main objective of this investigation to measure the heat transfer coefficient on a smooth as well as rib-roughened leading-edge wall. Experimental data for impingement on a leading edge surface roughened with different conical bumps and radial ribs are reported by the same authors, previously. This investigation, however, deals with impingement on different horseshoe ribs and makes a comparison between the experimental and numerical results. Three geometries representing the leading-edge cooling cavity of a modern gas turbine airfoil with crossover jets impinging on 1) a smooth wall, 2) a wall roughened with horseshoe ribs, and 3) a wall roughened with notched-horseshoe ribs were investigated. The tests were run for a range of flow arrangements and jet Reynolds numbers. The major conclusions of this study were: a) Impingement on the smooth target surface produced the highest overall heat transfer coefficients followed by the notched-horseshoe and horseshoe geometries. b) There is, however, a heat transfer enhancement benefit in roughening the target surface. Amongst the three target surface geometries, the notched-horseshoe ribs produced the highest heat removal from the target surface which was attributed entirely to the area increase of the target surface. c) CFD could be considered as a viable tool for the prediction of impingement heat transfer coefficients on an airfoil leading-edge wall.
Heat Transfer Measurements Using Liquid Crystal in a Pre-Swirl Rotating-Disc System
Authors: Lock Gary D. , Yan Youyou , Newton Paul J. , Wilson Michael , Owen J. Michael
Published: February 2009

Pre-swirl nozzles are often used in gas turbines to deliver the cooling air to the turbine blades through receiver holes in a rotating disc. The distribution of the local Nusselt number, Nu, on the rotating disc is governed by three non-dimensional fluid-dynamic parameters: pre-swirl ratio, βp, rotational Reynolds number, Reφ, and turbulent flow parameter, λT. A scaled model of a gas turbine rotor-stator cavity, based on the geometry of current engine designs, has been used to create appropriate flow conditions. This paper describes how thermochromic liquid crystal (TLC), in conjunction with a stroboscopic light and digital camera, is used in a transient experiment to obtain contour maps of Nu on the rotating disc. The thermal boundary conditions for the transient technique are such that an exponential-series solution to Fourier’s one-dimensional conduction equation is necessary. A method to assess the uncertainty in the measurements is discussed and these uncertainties are quantified. The experiments reveal that Nu on the rotating disc is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations have been measured. At the higher coolant flow rates studied, there is a peak in heat transfer at the radius of the pre-swirl nozzles. The heat transfer is governed by two flow regimes: one dominated by inertial effects associated with the impinging jets from the pre-swirl nozzles, and another dominated by viscous effects at lower flow rates. The Nusselt number is observed to increase as either Reφ or λT increases.
Film Cooling Analysis Using DES Turbulence Model
Authors: Roy Subrata , Kapadia Sagar , Heidmann James D.
Published: February 2009

The complex dynamic nature of the spanwise vortices in film cooling of turbine blades makes it necessary to accurately model the flow field temporally and spatially using detailed simulation techniques like direct numerical simulation or large eddy simulation of turbulence. Although, the later requires less computational effort and thus can simulate flows at higher Reynolds number than direct simulation, both these methods remain very expensive. As a viable alternative, this paper presents a Spalart-Allamaras based detached eddy simulation (DES) that is applied to a film cooled flat plate for the first time. The numerical model uses an unstructured grid system to resolve the dynamic flow structures on both sides of the plate as well as inside the hole itself. Detailed computation of a single row of 35 degree round holes on a flat plate has been obtained for blowing ratio of 1.0, and a density ratio of 2.0. The DES solution is also benchmarked with Reynolds averaged Navier-Stokes formulation for the same blade-hole configuration. The comparison shows that the DES simulation, which makes no assumption of isotropy downstream of the hole, greatly enhances the realistic description of the dynamic mixing processes.
Centrifugal Compressor of a 100 kW Microturbine: Part 1 — Experimental and Numerical Investigations on Overall Performance
Authors: Benini E. , Toffolo A. , Lazzaretto A.
Published: February 2009

This paper describes on/off design performance of a centrifugal compressor of a 100 kW turbogenerator gas turbine engine used for small scale power generation. The compressor stage is made up of a radial impeller and a two-stage diffuser (radial and deswirl). Part 1 deals with the experimental and numerical tests on overall compressor and diffuser performance: An extensive test series with steady probe measurements at impeller exit and diffuser exit is performed at different operating points and rotational speeds. This makes it possible to characterize both overall compressor and diffuser. The numerical model is based on a mixing plane at impeller-diffuser interface and therefore neglects the effect of unsteadiness due to rotor-stator interaction. Then, in part 2 the true time-dependent interaction is investigated by means of a numerical model where a sliding mesh technique is adopted. The unsteady results are then processed and compared with the steady ones regarding the flow in the diffuser. Finally, in part 3 the geometry of the compressor diffuser is optimized using an evolutionary algorithm coupled with a CFD code in order to improve compressor performance.
Centrifugal Compressor of a 100 kW Microturbine: Part 2 — Numerical Study of Impeller-Diffuser Interaction
Authors: Benini E. , Toffolo A.
Published: February 2009

The interaction between impeller and diffuser blades in high-speed centrifugal compressors is thought to have a significant influence on the flow within the diffuser. In this part, Computational Fluid Dynamics is exploited to simulate, visualize and analyze the complex flow generated by the interaction, with particular emphasis on the unsteady behavior of the vaned diffuser of the microturbine compressor studied in part 1. For this purpose, the 3D geometry of the compressor stage is studied by performing a fully unsteady simulation of rotor-stator interaction. The results of the unsteady calculation regarding the diffuser performance are then averaged in time and compared with those obtained with a fully steady and decoupled computation in order to highlight the main difference between the two approaches.
Steady-State and Transient Simulation of Turbodrop Engine Using SIMULINK® Model
Authors: Kong Changduk , Roh Hongsuk , Lim Kangtaek
Published: February 2009

A performance simulation model of the PT6A-62 turboprop engine using the SIMULINK® was proposed to predict transient and steady state behaviors. This SIMULINK has some advantages such as user-friendly circumstance due to the GUI (Graphic User Interfaces) and ease in modification of the computer program. The SIMULINK model consists of subsystems to represent engine gas path components such as flight initial subsystem, compressor subsystem, burner subsystem, compressor turbine subsystem, power turbine, exhaust nozzle subsystem and integrator subsystem. In addition to these subsystems, there are search subsystems to search an appropriate operating point by scaling from the 2-D components look-up table, error matching subsystem to calculate the gas property precisely. In case of steady state validation, performance parameters analyzed by the proposed SIMULINK model were compared with the analysis results by commercial GASTURB program. In the validation of the transient model, the produced dynamic simulation results were compared with analysis results produced by a well-proved computer program using FORTRAN. In performance analysis of the PT6A-62 turboprop engine by the developed SIMULINK model, the steady state simulation was performed at off design points with altitude variation and part throttle, and the transient simulations with step fuel increases for accelerating the engine were carried out from 64% rpm (idle speed) to 94%rpm. In this investigation, the maximum error in all steady state off-design points in part load cases was within 7.33%. In case of transient analysis with different step fuel increases, the acceleration times using the SIMULINK model were well agreed with experimental values, and also the times calculated by the well proven FORTRAN program.
Reduction of NOx and CO to Below 2ppm in a Diffusion Flame
Authors: Sahai Vivek , Cheng Dah-Yu
Published: February 2009

The so-called “sudden death reaction” theory, for a diffusion flame, assumes that the fuel and oxidizer diffuse toward a stoichiometric concentration surface, and then suddenly disappear, due to their combustion which produces water and carbon dioxide. The presence of NOx and CO in the combustion products cannot be explained by the “sudden death” theory. NOx, due to its high activation energy may not be formed prior to the formation of H2O and CO2. NOx is created when both oxygen and nitrogen are present in a high temperature volume; after all the combustible species are consumed. Appearance of CO indicates a lack of oxygen or a low gaseous temperature. Traditionally, when steam is injected into the combustion air, its high heat capacity reduces the flame temperature, which then reduces NOx formation, and this is usually accompanied by high CO formation. This phenomenon is caused by the dilution of oxygen as a quenching effect. This paper describes a novel approach that reverses the traditional wisdom of using steam to control NOx and CO formation, by accelerating the combustion process. This new approach begins with (1) shrinking the flame envelope, (2) enhancing the oxygen diffusion rate, and (3) suppressing the nitrogen concentration diffusion rate. Test results showed that (1) a high temperature volume could form NOx after the combustion of fuel is reduced to a minimum, and (2) that a very high fuel jet momentum increases the oxygen diffusion rate, thus reducing the flame envelope. Also due to the inward movement of the flame envelope, the residential time for NOx formation is also reduced and with the presence of a diluent, the nitrogen penetration rate into the flame is controlled. When all three phenomena are working together, total NOx was reduced downward to below 2 ppm without losing flame stability. Since this process generates enhanced oxygen diffusion, CO has always been seen to be below 2ppm, which indicates extremely high combustion efficiency. The above theory was first simulated by numerical methods using a 3-step reaction for nitrogen and oxygen, and was further expanded to a 28-step chemical kinetic model. The simulation used gas turbine compressor discharge temperatures to produce real adiabatic flame temperatures. Atmospheric tests of real full-scale gas turbine combustors were used with appropriate air temperatures, to simulate adiabatic flame temperatures. Below 2ppm NOx and CO were consistently obtained, independent of turbine types. Actual turbine tests on GE 6B and W501D5A turbines consistently indicated pressure dependent exponents of 0.1.
Auto-Ignition in a Gas Turbine Burner at Elevated Temperature
Authors: Brandt Martin , Polifke Wolfgang , Ivancic Blazenko , Flohr Peter , Paikert Bettina
Published: February 2009

Many facilities, e.g. reheat gas turbines or internal combustion engines, are operated with hydrocarbon fuels at elevated preheat temperatures such that conditions may be encountered where the flame is not stabilized by flame propagation, but by self-ignition. A model for turbulent reacting flow in this combustion regime has been developed, based on an ignition indicator representing the evolution of a pool of chemical intermediates. Interactions between turbulence and chemistry are taken into account using a new Monte-Carlo joint PDF approach. The joint PDF is not approximated by an analytical function, but by representative ensembles of particles, which are generated with a biased random number generator. Mean reaction rates are computed from the first and second moments — including co-variances — of those variables which describe the thermochemical state of the mixture. It is possible to calculate mean reaction rates in a pre-processing step and store them in a lookup-table table for use in a subsequent CFD simulation, making the approach very efficient. The model has been implemented in a CFD code and validated against an industrial gas turbine burner configuration. It has been found that the model describes the combustion process for a range of operating conditions with good accuracy.
Numerical Prediction of Partially Premixed Flames Based on Extended BML Model Coupled With Mixing Transport and ILDM Chemical Model
Authors: Maltsev Alexander , Sadiki Amsini , Janicka Johannes
Published: February 2009

To improve the numerical prediction of partially premixed flames occurring in gas turbine combustors the extension of the well-known Bray-Moss-Libby model for premixed combustion is presented. The model modification based on the algebraic closure for a mean chemical source term is coupled to the mixing transport model providing variable equivalence ratio distinguishing partially premixed flames. Finite rate chemistry is incorporated by means of ILDM model solving transport equations for two reaction progress variables conditioned on the flame front. Multivariate presumed PDF model is used for the turbulence chemistry interaction treatment. Turbulence models of two levels of complexity are applied in order to investigate the influence of non-gradient turbulent transport phenomenon. Redistribution terms in second moment transport equations are extended to take into account strongly variable density effects. Model combinations considered are assessed simulating piloted partially premixed flame. The obtained results agree well with experimental data.
Unsteady Flow Interactions Within the Inlet Cavity of a Turbine Rotor Tip Labyrinth Seal
Authors: Pfau A. , Schlienger J. , Rusch D. , Kalfas A. I. , Abhari R. S.
Published: February 2009

This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth seal of a 2 stage axial research turbine. Highly resolved, steady and unsteady 3-dimensional flow data are presented. The probes used here are a miniature 5 hole probe of 0.9mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth seal configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focussing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.
Technical and Tariff Scenarios Effect on Microturbine Trigenerative Applications
Authors: Campanari Stefano , Macchi Ennio
Published: February 2009

The paper considers the use of gas fired Micro Turbine Generators (MTG) for tri-generation (combined production of electricity, heating and cooling) applications in tertiary buildings. The importance of the adopted MTG technology is investigated, showing that the high electrical efficiency levels achievable by future advanced ceramic MTGs would improve dramatically the economic competitiveness of the application, as well as the primary energy savings and environmental benefits. Calculations are performed by the simulation code TRIGEN, capable of optimizing the plant operating mode in each time step and integrating the results over the entire year. The requirement of a “target” energy saving index on the optimization procedure is also addressed.
Investigations of Dust Separation in the Internal Cooling Air System of Gas Turbines
Authors: Schneider O. , Dohmen H. J. , Benra F.-K. , Brillert D.
Published: February 2009

Improvements in efficiency and performance of gas turbines require a better understanding of the internal cooling air system which provides the turbine blades with cooling air. With the increase of cooling air passing through the internal air system, a greater amount of air borne particles is transported to the film cooling holes at the turbine blade surface. In spite of their small size, these holes are critical for blockage. Blockage of only a few holes could have harmful effects on the cooling film surrounding the blade. As a result, a reduced mean time between maintenance or even unexpected operation faults of the gas turbine during operation could occure. Experience showed a complex interaction of cooling air under different flow conditions and its particle load. To get more familiar with all these influences and the system itself, a test rig has been built. With this test rig, the behaviour of particles in the internal cooling air system could be studied at realistic flow conditions compared to a modern, heavy duty gas turbine. It is possible to simulate different particle sizes and dust concentrations in the coolant air. The test rig has been designed to give information about the quantity of separated particles at various critical areas of the internal air system [1]. The operation of the test rig as well as analysis of particles in such a complex flow system bear many problems, addressed in the previous paper [1]. New measurements and analysis methods give new and more accurate results, which will be shown in this paper. Furthermore the inspection of the test rig shows dust deposits at unexpected positions of the flow path. Theoretical studies to characterize the flow behaviour of the disperse phase in a continuous fluid using Lagrangian Tracking were also performed. A comparison between the numerical solution and the measurements will be shown in the paper.
Thermodynamic Property Models for the Simulation of Advanced Wet Cycles
Authors: Yan J. , Ji X. , Jonsson M.
Published: February 2009

Advanced gas turbine cycles with water or steam addition (i.e., wet cycles) have attracted much interest in recent years and some commercial systems are available. Because water is added into different points of a gas turbine depending on the methods of water addition, the working fluid of gas turbine has been changed to air-water (humid air) mixture at elevated pressure. Thus, the thermodynamic properties of working fluid are different as conventional gas turbines. Accurate calculation models for thermodynamic properties of air-water mixture are of importance for process simulation, and traceable performance test of turbomachinery and heat exchangers in the wet cycle systems. However, the impacts of thermodynamic properties on the simulation of systems and their components have been overlooked. This paper is to present our study and provide a comprehensive comparison of exiting thermodynamic models of air-water mixtures. Different models including ours have been used to calculate some components including compressor, humidification tower, heat exchanger etc. in wet cycles for investigating the impacts of thermodynamic properties on the system performance. It reveals that a careful selection of thermodynamic property model is crucial for the design of cycles. This paper will provide a useful tool for predicting the performance of the system and design of the wet cycle components and systems.
Industrial Gas Turbine Exciters: Design Considerations for More Effective Products
Authors: Tozzi Luigi , Petruska Dave , Emergy John
Published: February 2009

Ignition systems for industrial gas turbines, in use for decades, continue to evolve with improving technology. A recent development is the use of microprocessors and solid-state semiconductor power switching devices (digital systems). Extensive testing of digital systems has demonstrated excellent ignitability, reliability, and plug life compared to traditional analog systems. Furthermore, digital systems demonstrate a potential for combustion feedback.
Fault Diagnosis of a Two Spool Turbo-Fan Engine Using Transient Data: A Genetic Algorithm Approach
Authors: Sampath Suresh , Li Y. G. , Ogaji S. O. T. , Singh Riti
Published: February 2009

Traditionally engine fault diagnosis has been performed at steady state conditions. There are several problems which can only be detected by transient data analysis like bearing fault, some control problems etc.. In addition, gas turbine performance deviation due to a component fault is more likely to be magnified during transients, when compared with the same parameter deviations at steady states. The specific approach used in this paper is to compare model-based information with measured data obtained from the engine during a slam acceleration. The measured transient data (from actual engine) is compared with a set of simulated data from the engine transient model, under similar operating conditions and known faults through a Cumulative Deviation. The Cumulative Deviations obtained from the comparisons are minimized for the best match using Genetic Algorithm. The Genetic Algorithm has been tailored to use real coding [1] method and to meet the requirements of the new procedure. The paper describes the application of the approach to a 2-spool turbofan engine and discusses the preliminary studies conducted.
Design, Test and Analysis of a High-Pressure-Ratio Transonic Fan
Authors: Calvert W. John , Emmerson Paul R. , Moore Jon M.
Published: February 2009

Aircraft gas turbine engines require compression systems with high performance and low weight and cost. There is therefore a continuing drive to increase compressor stage pressure ratios, particularly for military fans. To meet this need, a technology acquisition programme has been carried out by QinetiQ and Rolls-Royce. Firstly, the stage matching issues for an advanced two-stage military fan were investigated, including the effects of employing variable inlet guide vanes. From this, the requirements for the first stage together with key operating conditions for the blading were defined. The blade profiles were then designed to satisfy the range of aerodynamic conditions using a quasi-3D calculation system. A satisfactory compromise between the aerodynamic and mechanical design requirements was reached in which a blisk construction was employed for the rotor, machined from a single piece of titanium. The new stage was manufactured and tested successfully, and it achieved its target flow, pressure ratio and efficiency on the first build. Detailed measurements of the internal flows using laser anemometry and high response pressure transducers were taken. Finally, these data have been analysed and used to calibrate current 3D multi-row CFD methods.
Unsteady Surface Pressures Due to Wake Induced Transition in a Laminar Separation Bubble on a LP Turbine Cascade
Authors: Stieger Rory , Hollis David , Hodson Howard
Published: February 2009

This paper presents unsteady surface pressures measured on the suction surface of a LP turbine cascade that was subject to wake passing from a moving bar wake generator. The surface pressures measured under the laminar boundary layer upstream of the steady flow separation point were found to respond to the wake passing as expected from the kinematics of wake convection. In the region where a separation bubble formed in steady flow, the arrival of the convecting wake produced high frequency, short wavelength, fluctuations in the ensemble averaged blade surface pressure. The peak-to-peak magnitude was 30% of the exit dynamic head. The existence of fluctuations in the ensemble averaged pressure traces indicates that they are deterministic and that they are produced by coherent structures. The onset of the pressure fluctuations was found to lie beneath the convecting wake and the fluctuations were found to convect along the blade surface at half of the local freestream velocity. Measurements performed with the boundary layer tripped ahead of the separation point showed no oscillations in the ensemble average pressure traces indicating that a separating boundary layer is necessary for the generation of the pressure fluctuations. The coherent structures responsible for the large amplitude pressure fluctuations were identified using PIV to be vortices embedded in the boundary layer. It is proposed that these vortices form in the boundary layer as the wake passes over the inflexional velocity profiles of the separating boundary layer and that the rollup of the separated shear layer occurs by an inviscid Kelvin-Helmholtz mechanism.
The Transition Mechanism of Highly-Loaded LP Turbine Blades
Authors: Stieger R. D. , Hodson H. P.
Published: February 2009

A detailed experimental investigation was conducted into the interaction of a convected wake and a separation bubble on the rear suction surface of a highly loaded low-pressure (LP) turbine blade. Boundary layer measurements, made with 2D LDA, revealed a new transition mechanism resulting from this interaction. Prior to the arrival of the wake, the boundary layer profiles in the separation region are inflexional. The perturbation of the separated shear layer caused by the convecting wake causes an inviscid Kelvin-Helmholtz rollup of the shear layer. This results in the breakdown of the laminar shear layer and a rapid wake-induced transition in the separated shear layer.
Micro Humid Air Cycle: Part B — Thermoeconomic Analysis
Authors: Parente J. , Traverso A. , Massardo A. F.
Published: February 2009

Part A of this paper demonstrated that the HAT cycle, when applied to small-size gas turbines, can significantly enhance the efficiency and specific work of simple and recuperated cycles without the drastic changes to plant layout necessary in medium- and large-size plants. In this part B a complete thermoeconomic analysis is performed for microturbines operating in a Humid Air cycle. The capital cost and internal rate of return for both new machines and existing microturbines working in an mHAT-optimised cycle are presented and analysed. Three different scenarios are considered. The first scenario reflects a distributed electrical power generation application where cogeneration is not taken into account. Instead, the other two scenarios deal with CHP civil applications for different heat demands. The thermoeconomic results of the integrated mHAT cycle, based on a preliminary design of the saturator, demonstrate that microturbine performance can be greatly enhanced, while specific capital costs, in some cases, can be reduced up to 14%, without significant increase in layout complexity. Moreover, thanks to its operational flexibility (able to operate in dry and wet cycles), the mHAT is financially attractive for distributed power and heat generation (micro-cogeneration), particularly when heat demand is commutated in short period.
Study on Crack Propagation Tendencies of Non-Repaired and Repaired Nozzles
Authors: Fujii Tomoharu , Takahashi Takeshi
Published: February 2009

A system designed to control and predict the length of cracks that generate in the first-stage nozzles of E and F class gas turbines was developed. This system consists of three programs for (1) inputting cracks, (2) displaying cracks, and (3) predicting cracks, and a database consisting of approximately 350,000 cracks generated in first-stage nozzles taken from past repair records of five power plants operating in Japan. The database also contains data on operating time and number of starts of gas turbines. The distinctive features of this system are described below. 1) The crack data can be entered on the nozzle drawing as a picture by using the mouse. 2) The accumulated data allows the sections of nozzles in which cracks have generated most frequently to be identified. 3) The correlation formula of cracks and operating time or number of starts can be obtained simply. 4) By entering the scheduled operating time or number of start-ups to the time of the next scheduled inspection in the correlation formula, the length of cracks in optional sections and propagating in optional directions can be predicted. Using this system, the statuses of cracks generated in nonrepaired and repaired nozzles of E class gas turbines were compared. The comparison focused on 11 patterns with comparatively long cracks selected from the cracks propagating together with the increase in operating time or number of starts. The propagation of cracks covering a period of approximately two years, which corresponds to the inspection interval of power plants in Japan, was also compared. The results showed that the extent of crack propagation tends to increase with the increase in the number of repairs. Furthermore, the propagation of cracks in repair nozzles is about two times greater than that in non-repair nozzles. It was also found that the system could identify the sections in which the longest cracks are generated.