bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel EFHAT System With Low Temperature Heat Utilization
Authors: Jin Hongguang , Zhao Hongbin , Liu Zelong , Cai Ruixian
Published: February 2009

In this paper the low-temperature heat utilization was developed based on the externally fired humid air turbine (EFHAT) system with latent heat utilization. In the EFHAT, the exhaust temperature of gas turbine is not limited by dew point, so that the latent heat can be utilized to increase ability of humidification of air. Additionally, thermal efficiency of low temperature heat is usually quite low. In this paper, the low temperature heat is introduced and utilized in a saturator not only to enhance the air humidification but also to effectively use the latent heat. As a result, the thermal efficiency of the low temperature heat (200°C) can attain 20% or so, higher about 6∼8 percent points than conventional instance, while the latent heat utilization ratio is increased by about 10 percent points compared to usual EFHAT system with latent heat utilization. The novel EFHAT system combined with low temperature heat utilization will be a new orientation not only for the clean coal power generation system, but also for low-temperature heat utilization.
Heat Transfer and Friction in Channels With Very High Blockage 45° Staggered Turbulators
Authors: Bailey Jeremy C. , Bunker Ronald S.
Published: February 2009

Heat transfer and friction coefficients have been measured within a rectangular passage of aspect ratio 0.4 containing 45-degree staggered turbulators of very high blockage. Using a constant pitch-to-height ratio of 10 for all geometries, turbulator height-to-channel hydraulic diameter ratios from 0.193 to 0.333 were investigated. This range of e/D creates actual channel blockage ratios e/H from 0.275 to 0.475, presenting significant flow area restrictions. A liquid crystal test technique is used to obtain both detailed heat transfer behavior on the surfaces between turbulators, as well as averaged fully developed heat transfer coefficients. Reynolds numbers from 20000 to 100000 were tested. Nusselt number enhancements of up to 3.6 were obtained over that of a smooth channel, with friction coefficient enhancements of as much as 65. In contrast to low-blockage turbulated channels, the 45-degree turbulated Nu is found to be lower than that at 90-degree orientation, given very similar e/D and e/H values.
Heat/Mass Transfer in 1:4 Rectangular Passages With Rotation
Authors: Agarwal Peeyush , Acharya Sumanta , Nikitopoulos D. E.
Published: February 2009

The paper presents an experimental study of heat/mass transfer coefficient in 1:4 rectangular channel with smooth or ribbed walls for Reynolds number in the range of 5000 to 40000 and Rotation numbers in the range of 0–0.12. Such passages are encountered close to the mid-chord sections of the turbine blade. Normal ribs (e/Dh = 0.3125, and P/e = 8) are placed on the leading and the trailing sides only. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. For purposes of comparison, selected measurements are also performed in a 1:1 cross-section. The local mass-transfer data in the fully developed region is averaged to study the effect of the Reynolds and the Rotation numbers. The span-wise mass transfer distributions in the smooth and the ribbed cases are also examined.
Flow and Heat Transfer in an Internally Ribbed Duct With Rotation: An Assessment of LES and URANS
Authors: Saha A. K. , Acharya Sumanta
Published: February 2009

Large Eddy Simulations (LES) and Unsteady Reynolds Averaged Navier-Stokes (URANS) simulations have been performed for flow and heat transfer in a rotating ribbed duct. The ribs are oriented normal to the flow and arranged in a staggered configuration on the leading and trailing surfaces. The LES results are based on a higher-order accurate finite difference scheme with a dynamic Smagorinsky model for the subgrid stresses. The URANS procedure utilizes a two equation k-ε model for the turbulent stresses. Both Coriolis and centrifugal buoyancy effects are included in the simulations. The URANS computations have been carried out for a wide range of Reynolds number (Re = 12,500–100,000), rotation number (Ro = 0–0.5) and density ratio (Δρ/ρ = 0–0.5), while LES results are reported for a single Reynolds number of 12,500 without and with rotation (Ro = 0.12, Δρ/ρ = 0.13). Comparison is made between the LES and URANS results, and the effects of various parameters on the flow field and surface heat transfer are explored. The LES results clearly reflect the importance of coherent structures in the flow, and the unsteady dynamics associated with these structures. The heat transfer results from both LES and URANS are found to be in reasonable agreement with measurements. LES is found to give higher heat transfer predictions (5–10% higher) than URANS. The Nusselt number ratio (Nu/Nu0) is found to decrease with increasing Reynolds number on all walls, while they increase with the density ratio along the leading and trailing walls. The Nusselt number ratio on the trailing and side walls also increases with rotation. However, the leading wall Nusselt number ratio shows an initial decrease with rotation (till Ro = 0.12) due to the stabilizing effect of rotation on the leading wall. However, beyond Ro = 0.12, the Nusselt number ratio increases with rotation due to the importance of centrifugal-buoyancy at high rotation.
Blade Tip Leakage Flow and Heat Transfer With Pressure-Side Winglet
Authors: Saha Arun K. , Acharya Sumanta , Prakash Chander , Bunker Ron
Published: February 2009

A numerical study has been conducted to explore the effect of a pressure-side winglet on the flow and heat transfer over a blade tip. Calculations are performed for both a flat tip and a squealer tip. The winglet is in the form of a flat extension, and is shaped in the axial chord direction to have the maximum thickness at the chord location where the pressure difference is the largest between the pressure and suction sides. For the flat tip, the pressure side winglet exhibits a significant reduction in the leakage flow strength and an associated reduction in the aerodynamic loss. The low heat transfer coefficient “sweet-spot” region is larger with the pressure-side winglet, and lower heat transfer coefficients are also observed along the pressure side of the blade. The winglet reduces the average heat transfer coefficient by about 7%. In the presence of a squealer, the role of the winglet decreases significantly, and only a 0.5% reduction in the pressure ratio is achieved with the winglet with virtually no reduction in the average heat transfer coefficient.
Effects of Duct Aspect Ratios on Heat/Mass Transfer With Discrete V-Shaped Ribs
Authors: Rhee Dong Ho , Lee Dong Hyun , Cho Hyung Hee , Moon Hee Koo
Published: February 2009

The present study investigates the effects of rib arrangements and aspect ratios of a rectangular duct simulating the cooling passage of a gas turbine blade. Two different V-shaped rib configurations are tested in a rectangular duct with the aspect ratios (W/H) of 3 to 6.82. One is the continuous V-shaped rib configuration with 60° attack angle, and the other is the discrete V-shaped rib configuration with 45° attack angle. The designed aspect ratio of the duct is obtained by changing the height with a fixed width of 150 mm. The square ribs (3 mm) with the pitch to height ratio of 10.0 are installed on the test section in a parallel arrangement for both rib configurations. Reynolds numbers based on the hydraulic diameter are changed from 10,000 to 30,000 in this study to investigate the variation of duct Reynolds number. A naphthalene sublimation method is used to measure local heat/mass transfer coefficients. For the continuous V-shaped rib configuration, two pairs of counter-rotating vortices are generated in a duct, and high transfer region is formed at the center of the ribbed walls of the duct. However, for the discrete V-shaped rib configuration with 45° attack angle, complex secondary flow patterns are generated in the duct due to its geometric feature, and more uniform heat/mass transfer distributions are obtained for all tested cases.
Experimentally Verified Numerical Optimisation of a 3D-Parametrized Turbine Vane With Non-Axisymmetric End Walls
Authors: Nagel Marc G. , Baier Ralf-D.
Published: February 2009

A 3D optimisation procedure on the basis of a transitional Navier-Stokes code has been developed and tested. It allows complete three-dimensional parameterisation of the flow channel for improved engine component design. Both the aerofoils and the end walls are three-dimensionally parameterised to permit full design control over the wetted surface. The end wall curvature is in fact controlled by the superposition of an axisymmetric and a non-axisymmetric parameterisation. The target comprises profile and secondary losses. The optimisation procedure was applied to a low-loss turbine vane and resulted in an aerodynamic design with considerably reduced losses. Vanes and end walls were then manufactured according to this optimisation. The high-speed cascade wind tunnel measurements performed on these parts confirm the computational results.
Optimum Aero-Thermal Design of Turbomachinery Blading Systems Accounting for Variable Operating Conditions
Authors: Manna Marcello , Tuccillo Raffaele
Published: February 2009

The paper presents further developments to a recently proposed innovative procedure specifically conceived for the aero-thermal design of high performance turbomachinery cascades. The method, applied to an existing nozzle guide vane for which extensive and detailed experimental data are available, is demonstrated capable of increasing in an integral sense the overall blade performance. The latter are generalized to account for part and over load flow conditions. This is accomplished by formulating the design objectives in terms of a multiple point minimization procedure whose associated cost function includes the flatness of the overall blade performance. The results confirm that, despite the excellence of the initial design, there is room for improvements.
Resistance Reduction in Pulsating Turbulent Pipe Flows
Authors: Manna Marcello , Vacca Andrea
Published: February 2009

The paper describes the effects of a forced harmonic oscillations of fixed frequency and amplitudes in the range Λ = Um/Ub = 1 ÷ 11 on the characteristics of a turbulent pipe flow with a bulk Reynolds number of 5900. The resulting Stokes layer δ is a fraction of the pipe radius (χ = R/δ = 53) so that the vorticity associated to the oscillating motion is generated in a small near wall region. The analysis is carried out processing a set of statistically independent samples obtained from wall resolved Large Eddy Simulations; time and space averaged global quantities, extracted for the sake of comparison with recent experimental data, confirm the presence of a non negligible drag reduction phenomenon. Phase averaged profiles of the Reynolds stress tensor components provide valuable material for the comprehension of the effects of the time varying mean shear upon the near wall turbulent flow structures. The large scale of motion are directly computed through numerical integration of the space filtered three dimensional Navier-Stokes equations with a spectrally accurate code; the subgrid scale terms are parametrized with a dynamic procedure.
Prediction of Low Speed Compressor Rotor Flowfields With Large Tip Clearances
Authors: Gupta Anurag , Khalid S. Arif , McNulty G. Scott , Dailey Lyle
Published: February 2009

Rotor tip modeling fidelity, grid resolution, and near wall modeling have been examined to determine the requirements for an accurate prediction of the effects of large tip clearance in a low-speed axial compressor rotor. The effort, using a Reynolds-Averaged Navier-Stokes (RANS) solver, aimed to obtain the most accurate predictions from a three-dimensional, steady, single blade row simulation. A recently tested, modern low speed rotor, was used as the test geometry; the measured pressure rise characteristic as well as detailed data near stall was used to evaluate the ability of different modeling strategies to capture the correct flow structure. The leakage flow was quantified to show that a wide range of tip blockage could be obtained for different simulations of the same geometry and conditions. The results show that using a square tip and gridding to fully resolve the real tip gap was better able to capture the effects of loading on the leakage flow than either of the approximate models studied. Sufficient clustering near the casing to capture the shear layers was also found to be critical. While wall integration provided the best results in simultaneously improving the prediction of pressure rise characteristics and flow range, higher fidelity wall modeling and a casing y+ of approximately 3 were found to provide similar benefits.
Ability of a Popular Turbulence Model to Capture Curvature Effects: A Film Cooling Test Case
Authors: Undapalli Satish , Leylek James H.
Published: February 2009

Computations are performed in conjunction with code validation quality experiments found in the open literature to specifically address the usage of popular two-equation eddy viscosity models in day-to-day gas turbine applications. In such simulations many features such as pressure gradients, curvature effects are present. The present work is focused on testing a popular turbulence model to resolve film cooling on curved surfaces. A systematic computational methodology has been employed in order to minimize numerical errors and evaluate the performance of a popular turbulence model. The test cases were examined for a single row of holes, blowing rates ranging from 1 to 2.5, isolated effects of convex and concave curvature on film cooling, density ratio close to 2, and an injection angle of 35°. Key aspects of the study include: (1) extremely dense, high quality, multi-block, multi-topology grid involving over 3 million finite volumes; (2) higher order discretization; (3) turbulence model with two-layer near-wall treatment; (4) strict convergence criteria; and (5) grid independence. A fully-implicit, pressure-correction Navier-Stokes solver is used to obtain all the solutions. Results for adiabatic cooling effectiveness are compared with measurements in order to document the: (1) Range of applicability of the present modeling capability; and (2) Possible reasons for discrepancies. The data shows that the computations predicted the effects of curvature on mean flow, however effect on turbulence field is not captured. A clear set of recommendations is provided for future treatments of this class of problems.
Bifurcation of Nonlinear Hydrodynamic Thrust Bearing-Mounted Rotor Subjected to Parametric Excitations With Unbalance
Authors: Shiau T. N. , Hsu K. S. , Chang J. R.
Published: February 2009

The purpose of this study is to investigate the dynamics of a nonlinear hydrodynamic thrust bearing-mounted rigid rotor subjected to an unbalance force and parametric excitations. The parametric excitations include hydrodynamic forces and momenta of the thrust bearing when the rotor is subjected to an axial harmonic excitation. The effect of an eccentric axial excitation is also considered and the associated equations of motion are derived. Nonlinear phenomena including periodic response, hysteresis cycle, chaotic motion, etc. are investigated. The bifurcation values of parametric and unbalance excitation for steady state response are determined. The solutions of lateral response are dominated by the magnitude and frequency of axial excitation under light unbalance. The results show that the effect of axial excitation on bifurcation phenomenon of lateral vibration is significant as the eccentricity of axial force is enlarged.
Blade Forced Response Prediction for Industrial Gas Turbines: Part 2 — Verification and Application
Authors: Ning Wei , Moffatt Stuart , Li Yansheng , Wells Roger G.
Published: February 2009

This is part two of a two-part paper. Part One describes the methodologies of a blade forced response prediction system. The emphasis of this part is to demonstrate the capability and computational efficiency of the system for predicting blade forced response. Part two firstly presents verification of the multistage time-linearized unsteady flow solver through comparison of predicted blade surface pressure distributions with data measured on a VKI transonic turbine stage. It concludes with presentation of the results of an analysis carried out on the last stage rotor blade of an ALSTOM three-stage transonic test compressor. In the analysis, strain gauge results together with Finite Element (FE) modal analysis identify the resonant crossings. The mode shape of the blade vibration is used in the CFD code to predict the blade aerodynamic damping. The aerodynamic damping is compared with the blade system damping obtained from the strain gauge tests. The variation is shown of aerodynamic and mechanical damping with blade mode shape. The blade unsteady modal forces induced by the upstream stators are derived from the calculated unsteady flows. The blade vibration at three resonant crossings is compared with those given by strain gauge measurements. Good comparisons and high computational efficiency demonstrate that the forced response methodologies described in Part One can be used in the blade design process to tackle blade aeromechanical issues.
Adapting the Micro-Gas Turbine Operation to Variable Thermal and Electrical Requirements
Authors: Bozza Fabio , Cameretti Maria Cristina , Tuccillo Raffaele
Published: February 2009

This paper examines the possibilities for a micro-gas turbine operation under a wide range of thermal and mechanical load requirements. The authors focus the attention on a partially recuperated thermal cycle based on a by-pass option towards the heat recovery boiler, in order to adapt the gas turbine operation to increasing needs of thermal output. In addition, a variable speed operation is considered as a more reliable method for decreasing the mechanical output without producing an excess in efficiency decay. The actual possibilities of the above named regulation tools are examined by an integrated procedure which involves, besides an accurate thermodynamic preliminary analysis, the component matching study and the CFD based simulation of the combustion chamber.
IPRP: Integrated Pyrolysis Combined Plant — An Efficient and Scalable Concept for Gas Turbine Based Energy Conversion From Biomass and Waste
Authors: Fantozzi Francesco , D’Alessandro Bruno , Desideri Umberto
Published: February 2009

A massive effort towards sustainability is necessary to prevent global warming and energy sources impoverishment: both biomass and waste to energy conversion may represent key actions to reach this goal. At the present State Of the Art (SOA) available technologies for biomass and waste to energy conversion are similar and include low to mid efficiency grate incineration or fluidised bed combustion with steam power cycles or mid to high efficiency Gas Turbine based cycles through integrated gasification technology. Nevertheless these plants are all available from mid-to-high scale range that can be highly intrusive on protected areas and socially unacceptable. This paper proposes an innovative, low cost, high efficiency plant in which the residue is gasified in absence of oxygen (pyrolysis), in a rotary kiln, by means of a highly regenerative gas turbine based cycle. Pyrolysis is preferred to gasification, because the syngas obtained has a higher LHV and produces char or tar as a by-product with an interesting energy content to be re-utilized inside the cycle. Different plant configurations are proposed and discussed through principal thermodynamic variables parametric analysis. Results show that very interesting efficiencies are obtainable in the 30%–40% range, at every scale range therefore presenting an interesting alternative especially to small size (below 5 MW) grate incineration and steam power plant technology. Moreover, the IPRP plant provides a unique solution for micro-scale (below 500 kW) power plants, opening a new and competitive possibility for distributed biomass or waste to energy conversion systems where low environmental and social impact turns into higher interest and positive dissemination effect.
Coupled Analysis of Cooled Gas Turbine Blades
Authors: Chmielniak Tadeusz , Wro´blewski Włodzimierz , Nowak Grzegorz , Wec˛el Daniel
Published: February 2009

The paper presents solution aspects of the heat transfer modeling and fluid flow prediction of the convective cooled gas turbine blade. The heat transfer problem within the blade material is solved using finite element method whereas the flow problem employs the finite volume method. The flow field is calculated by solving the Navier-Stokes (NS) equations. The problem can be faced in two ways which are presented in this work. The first one is the uncoupled field method which does not take into consideration the interaction between the flowing medium and the blade. This way of solution is simpler and computationally cheap but has limited accuracy. The other one is the coupled field method (conjugate heat transfer CHT), which resolves iteratively the thermal interaction between the fluid and the blade material. The coupled method is much more accurate but one has to pay for it with longer computations as well as the algorithm stability control. As the fluid flow schemes are very sensitive to boundary condition changes, a fine time stepping with relaxation as well as an adequate mesh were required. The calculations showed another very important problem occurring in the analyses carried out. This is the laminar-turbulent transition which can significantly affect the accuracy of the results. The change of the flow character influences the heat exchange intensity and consequently the temperature distribution within the blade. Nevertheless, the problem is not yet satisfactorily worked out and the criteria of the laminar-turbulent transition are very difficult to build. The problem becomes simpler if the location of the transition point is known (i.e. from experimental data). On the basis of experimental data authors solved the problem of a blade cooling for both uncoupled and coupled method and different flow characters in order to obtain numerical results best matching the real phenomena.
Crack Detection in a Rotor Dynamic System by Vibration Monitoring: Part I — Analysis
Authors: Green Itzhak , Casey Cody
Published: February 2009

Many practical rotor dynamic systems contain shaft/rotor elements that are highly susceptible to transverse cross-sectional cracks due to fatigue. The early detection of mechanical malfunction that can be provided by an effective vibration monitoring system is essential. Two theoretical analyses, global and local asymmetry crack models, are utilized to identify characteristics of the system response that may be directly attributed to the presence of a transverse crack in a rotating shaft. A model consisting of an overhung whirling rotor is utilized to match an experimental test rig. A 2X harmonic component of the system response is shown to be the primary response characteristic resulting from the introduction of a crack. Once the unique characteristics of the system response are identified, they serve then as target observations for the monitoring system.
Large-Eddy Simulation of Atomizing Spray With Stochastic Modeling of Secondary Breakup
Authors: Apte Sourabh V. , Gorokhovski Mikhael , Moin Parviz
Published: February 2009

Large-eddy simulation (LES) of reacting multi-phase flows in practical combustor geometries is essential to accurately predict complex physical phenomena of turbulent mixing and combustion dynamics. This necessitates use of Lagrangian particle-tracking methodology for liquid phase in order to correctly capture the droplet evaporation rates in the sparse-liquid regime away from the fuel injector. Our goal in the present work is to develop a spray-atomization methodology which can be used in conjuction with the standard particle-tracking schemes and predict the droplet-size distribution accurately. The intricate process of primary atomization and lack of detailed experimental observations close to the injector requires us to model its global effects and focus on secondary breakup to capture the evolution of droplet sizes. Accordingly, a stochastic model for LES of atomizing spray is developed. Following Kolmogorov’s idea of viewing solid particle-breakup as a discrete random process, atomization of liquid blobs at high relative liquid-to-gas velocity is considered in the framework of uncorrelated breakup events, independent of the initial droplet size. Kolmogorov’s discrete model of breakup is represented by Fokker-Planck equation for the temporal and spatial evolution of droplet radius distribution. The parameters of the model are obtained dynamically by relating them to the local Weber number. A novel hybrid-approach involving tracking of individual droplets and a group of like-droplets known as parcels is developed to reduce the computational cost and maintain the essential features and dynamics of spray evolution. The present approach is shown to capture the complex fragmentary process of liquid atomization in idealized and realistic Diesel and gas-turbine combustors.
Characterisation of the Instantaneous Velocity and Mixture Field Issuing From a Lean Premixed Module (LPM)
Authors: Carrotte J. F. , Batchelor-Wylam C.
Published: February 2009

Measurements have been made on the non-reacting flow field issuing from a Lean Premixed module (LPM) that incorporates a radial swirler, mixing duct section and nozzle. The geometry contains many features that are thought typical of LPM systems in which gaseous fuel is introduced into a swirling flow at a discrete number of locations. Hot wire anemometry measurements have been used to define the velocity field issuing from the module whilst additional experiments have utilised heated air to simulate gaseous fuel. In this way temperature measurements, using Constant Current Anemometry, have been used to infer the fuel-air mixture field issuing from the module. The velocity data indicates a highly turbulent flow field and the basic spectral characteristics of this velocity field are defined. In addition, within certain regions a strong periodic flow component is observed and is indicative of the instabilities typically associated with swirling flows. The spectral characteristics of the mixture field are also presented and the method by which the mixture and velocity spectra should be compared is outlined. Using this method the measurements indicate the basic spectral characteristics are virtually identical and, furthermore, a periodic fluctuation in the mixture field is also observed. For these types of LPM systems fluctuations in the mixture and velocity fields are therefore strongly correlated. In addition it is shown that the flow fields are dominated by the relatively large time and length scales associated with the main velocity field rather than, say, the much smaller velocity and mixing scales associated with the individual fuel jets.
A New Approach to Gas Turbine Systems in the All Electric Warship Era
Authors: Boughner Abe
Published: February 2009

This paper will focus on discussions of new concepts for integration of gas turbines into advanced warship designs. The advancement of the electric warship creates several revolutionary opportunities in ship design concepts. The Integrated Power System (IPS) combines propulsion and auxiliary loads such that any electric generator can supply any load including electric propulsion, combat and hotel loads with light areo derivative gas turbines serving as prime movers for power generation. A combination of small and large gas turbine generators are fitted so that the operator can match the on-line generation capacity to the demand thereby keeping the gas turbines loaded to efficient levels. The IPS, or All Electric Warship concept, although a matter of much interest and study, will not be discussed in this paper. This paper will discuss how the light aero engine coupled with the IPS concept allows greater flexibility in overall design of the machinery plant as well as several new concepts for gas turbine systems in warships.
Optimum Gain-Scheduling PID Controllers for Gas Turbine Engines Based on NARMAX and Neural Network Models
Authors: Mu Junxia , Rees David , Chiras Neophytos
Published: February 2009

This paper presents PID controller designs based on NARMAX and feedforward neural network models of a Spey gas turbine engine. Both models represent the dynamic relationship between the fuel flow and shaft speed. Due to the engine non-linearity, a single set of PID controller parameters is not sufficient to control the gas turbine throughout the operating range. Gain-scheduling PID controllers are therefore used in order to obtain optimum control. A comparison between the controller designs based on the two model representations is also made.
A CFD Study of Wake-Induced Transition on a Compressor-Like Flat Plate
Authors: Walters D. Keith , Leylek James H.
Published: February 2009

Recent experimental work has documented the importance of wake passing on the behavior of transitional boundary layers on the suction surface of axial compressor blades. This paper documents computational fluid dynamics (CFD) simulations using a commercially-available general-purpose CFD solver, performed on a representative case with unsteady transitional behavior. The study implements a new, advanced version of a three-equation eddy-viscosity model previously developed and documented by the authors, which is capable of resolving boundary-layer transition. It is applied to the test cases of steady and unsteady boundary-layer transition on a 2-D flat plate geometry with a freestream velocity distribution representative of the suction side of a compressor airfoil. The CFD results are analyzed and compared to a similar experimental test case from the open literature. Results with the new model show a dramatic improvement over more typical RANS-based modeling approaches, and highlight the importance of resolving transition in both steady and unsteady compressor aero simulations.
Temperature Measurement System for Low Pressure Ratio Turbine Testing
Authors: Va´zquez R. , Sa´nchez J. M.
Published: February 2009

In 1999, ITP (Industria de Turbopropulsores, S.A.) launched a wide on-going research program focusing on new technologies to provide significant improvements in Low Pressure Turbines cost and weight. As consequence of the new technologies the experience limits are exceeded and new unknown concepts, like high stage loading turbines, must be explored and then a wide experimental work is required for validation purposes. Cold flow single stage rigs in high-speed facilities were selected by ITP as main vehicle to carry out the experimental validation. Single stage Low Pressure Turbine rigs have low-pressure ratio and power consumption, therefore efficiency predictions based on temperature drop require high accuracy thermocouple measurement systems (precision uncertainties lower than ±50 mK), if small efficiency variations must be captured. In this paper, a detailed uncertainty analysis is introduced and a temperature measurement system that allows achieving such high measurement accuracy is evaluated and described. Type T thermocouples are proposed for use in the range 0°C to 80°C, which are individually calibrated. The procedure followed for this calibration is presented and how is possible to achieve a precision of 30 mK. It is also shown as conventional UTR based on metal plates can behave as good as thermal baths in terms of temperature uniformity and errors, with the adequate isolation and temperature reference calibration. The conventional data recording and voltage measurement systems are experimentally evaluated, and they are found as main source of temperature errors. Although following some recommendations the precision of those systems can be improved, it is experimentally probed and therefore suggested the use of high accuracy voltmeter with a commutation unit to reduce significantly the temperature uncertainty. Finally a miniature Kiel Shroud is proposed and aerodynamically characterised in a high-speed facility. Mach, Reynolds number, yaw, blockage and manufacturing tolerance impact on recovery factor can be inferred from those results.
Thermoacoustic Modeling and Control of Multi Burner Combustion Systems
Authors: Schuermans Bruno , Bellucci Valter , Paschereit Christian Oliver
Published: February 2009

Thermoacoustic interactions in industrial combustion systems are difficult to model because they involve complex interactions between several physical mechanisms. In order to obtain dynamic models of such systems, a hybrid approach is used: numerical, experimental and analytical techniques are combined to describe the system. The system is modeled as a modular network, where the input–output relation of the modules can be based on analytic models, experimental data or numerical analysis. The modules are represented as state-space realizations. A modal expansion technique is used to obtain a state-space representation of the acoustic propagation through complex 3-dimensional geometries. The modal expansion can be based on an analytic model (for relatively simple volumes), or on a finite element analysis (for geometries of any complexity). Modules that are very complex, such as the acoustic behavior of the combustion process itself, are modeled using a combined experimental and analytic approach. The method is not restricted to symmetries of any kind: configurations with geometrically or operationally different burners are simulated. The state-space network approach allows for time domain simulations, including non-linearities. An active controller has been synthesized for an (hypothetical) annular multi burner combustion system. The controller uses spatial filtering to decompose the acoustic field to its individual modes. The modes are then controlled using an H∞ control algorithm. Time domain simulations of this control system demonstrate the effectiveness of this method, even in the presence of non-linear saturation and parametric errors.
Effect of Showerhead Injection on Superposition of Multi-Row Pressure Side Film Cooling With Fan Shaped Holes
Authors: Schneider Martin , Parneix Sacha , von Wolfersdorf Jens
Published: February 2009

In the present study the effect of approach boundary layer conditions on film cooling effectiveness superposition for pressure side fan shaped holes on a first stage vane is investigated. More particularly, the effect of showerhead cooling on the film effectiveness of downstream pressure side rows is addressed. The experimental test facility used is a continuously running , two passage, linear cascade wind tunnel equipped with a central vane and contoured side walls. Main stream stagnation conditions and pressure measurements on the vane external surface were taken to determine the isentropic Mach number distribution. The turbulence level generated with a bar grid is around 15%. Film cooling effectiveness has been determined with the narrow banded thermochromic liquid crystal steady state technique. Mainstream as well as coolant flow could be heated to shift the iso-temperature contours across the vane. Carbon dioxide was used as coolant gas to better match the density ratio in the experimental facility to engine conditions. The test model is a research vane equipped with four rows of cylindrical holes showerhead and three rows of fan shaped holes along the pressure side at typical inclination angles to the surface. The study incorporates single row blowing with the following row approach conditions: 1) no showerhead injection, 2) boundary layer trip, 3) isothermal showerhead blowing, and multi-row blowing with and without showerhead blowing. The results are used to investigate the applicability of the single row results superposition approach for multiple-row injection. Simulating the appropriate aerodynamic conditions during individual row measurements improves the superposition prediction in comparison to the multi-row results.
Flutter of Low Pressure Turbine Blades With Cyclic Symmetric Modes: A Preliminary Design Method
Authors: Kielb Robert , Barter John , Chernysheva Olga , Fransson Torsten
Published: February 2009

A current preliminary design method for flutter of low pressure turbine blades and vanes only requires knowledge of the reduced frequency and mode shape (real). However, many low pressure turbine (LPT) blade designs include a tip shroud, that mechanically connects the blades together in a structure exhibiting cyclic symmetry. A proper vibration analysis produces a frequency and complex mode shape that represents two real modes phase shifted by 90 degrees. This paper describes an extension to the current design method to consider these complex mode shapes. As in the current method, baseline unsteady aerodynamic analyses must be performed for the 3 fundamental motions, two translations and a rotation. Unlike the current method work matrices must be saved for a range of reduced frequencies and interblade phase angles. These work matrices are used to generate the total work for the complex mode shape. Since it still only requires knowledge of the reduced frequency and mode shape (complex), this new method is still very quick and easy to use. Theory and an example application are presented.
Temperature and Temperature Profile Measurements in the Combustor Flowpath Using Structured Emission Thermography
Authors: Goldstein Neil , Adler-Golden Steven , Jin Xuemin , Lee Jamine , Richtsmeier Steven , Arana Carlos A.
Published: February 2009

Structured Emission Thermometry (SET) is a new optical technique for deriving temperature and species concentrations in high-temperature regions of a combustor flow-path from measurements of water and soot emission spectra in the 1 micron region. A prototype instrument has been built for gas- and liquid-fuel combustors with temperatures ranging from 1400–2500K (2100–4000F). This instrument can be used for test stand instrumentation and routine monitoring in fixed installations. With further evolution, the technique may be suitable for an aircraft engine control system. The emissions are measured along narrow lines of sight using small, simple passive fiber probes placed at a short standoff distance from the hot gas flow-path. With proper placement of multiple probes, data may be collected over overlapping lines of sight and inverted to produce a low-resolution spatial map of the temperature and emitter density in the flow-path. In this work, we describe a series of combustor measurements, including cross-validation measurements in a well-controlled laboratory flame and measurements in combustor test stands. Both line-of-sight measurements and reconstructed temperature profiles are presented and discussed.
Emission Performance of a Micro Gas Turbine LPP-Combustor With Fuel Film Evaporation
Authors: Liedtke O. , Schulz A. , Wittig S.
Published: February 2009

The present paper describes the emission performance of a newly designed liquid fuelled micro gas turbine combustor. In order to reduce pollutant emissions, in particular nitrogen oxides NOx, lean premixed pre-vaporized combustion is utilized. Both, combustor inlet pressure and temperature are very low due to the thermodynamic cycle conditions chosen. As a consequence, the heat available for fuel spray evaporation is not sufficient. The present combustor concept therefore uses fuel film evaporation on the hot inner surface of a premix tube. The heat for evaporating the liquid fuel film is provided by the outer counter flow of hot exhaust gases. To establish almost adiabatic conditions within the reaction zone the flame tube features a multi-layered design, consisting of ceramic rings forming the inner wall, an insulation compliant layer, and the outer metal casing. To demonstrate the potential for reducing pollutant emissions overall NOx and CO concentrations of the exhaust gases have been measured and analyzed. The impact of combustor loading parameter, equivalence ratio, staging of the combustion, and ratio between calculated reaction times and mean residence times on the formation of pollutant emissions is investigated in detail. Furthermore, the impact of the flame tube volume on pollutant emissions and combustion stability is considered at various operating conditions. Measured pollutant emissions indicate the great potential for pollutant reduction that is associated with the specific geometry of the combustor.
Multi-Objective Design and Optimisation of Bypass Outlet-Guide Vanes
Authors: Shahpar Shahrokh , Giacche David , Lapworth Leigh
Published: February 2009

This paper describes the development of an automated design optimization system that makes use of a high fidelity Reynolds-Averaged CFD analysis procedure to minimize the fan forcing and fan BOGV (bypass outlet guide vane) losses simultaneously taking into the account the down-stream pylon and RDF (radial drive fairing) distortions. The design space consists of the OGV’s stagger angle, trailing-edge recambering, axial and circumferential positions leading to a variable pitch optimum design. An advanced optimization system called SOFT (Smart Optimisation for Turbomachinery) was used to integrate a number of pre-processor, simulation and in-house grid generation codes and postprocessor programs. A number of multi-objective, multi-point optimiztion were carried out by SOFT on a cluster of workstations and are reported herein.
Flow Effects on the Bend Region Heat Transfer Distribution of 2-Pass Internal Coolant Passages of Gas Turbine Airfoils: Influence of Film Cooling Extraction
Authors: Chanteloup D. , Bo¨lcs A.
Published: February 2009

A study of the flow and heat transfer in stationary models of a two-pass internal coolant passage is presented, which focuses on the flow characteristic effects on the wall heat transfer distribution. Results are given in the sharp 180deg bend region of the channel. The transient thermochromic liquid crystal technique was used. The technique allows full surface heat transfer coefficient measurements on all the walls, in the region of interest. Flow measurements were also conducted with a stereoscopic digital PIV system. The system measures all three-velocity components simultaneously. 3D-streamlines are extracted from the full data set. The coolant passage model consists of two square ducts, each having a 20 hydraulic diameter length. The ducts are connected by a sharp 180deg bend with a rectangular outer wall. 45deg ribs are mounted in a staggered arrangement on the bottom and top walls of both legs. The height of the ribs is equal to 0.1 hydraulic diameters. They are spaced 10 rib heights apart. One geometry is also equipped with extraction holes to simulate holes for film cooling. Two series of holes are placed solely in the bottom wall; four holes are located in the bend, and twelve in the downstream leg. The global extraction through the holes was set to 50% of the inlet massflow. The flow measurements were obtained at one flow condition with an inlet flow Reynolds number, based on the hydraulic diameter, of 50,000. The heat transfer measurements were obtained at the same flow conditions. The paper presents detailed measurement results of the heat transfer distribution on all the channel outer walls in the bend region. It describes how the main and secondary flows govern the heat transfer coefficient in the bend region. It relates the flow recirculating cell structures and the heat transfer distribution on the bend walls. It also shows how the film cooling extraction influences both the recirculating cells and the heat transfer distribution.
Comparison of Various Tube to Header Attachment Details Under Cyclic Service
Authors: Douglas Lewis R. , Thomson Kerstin H. , Komora George B. , Gremaud Paul D. , Diab Raafat
Published: February 2009

Heat recovery steam generator (HRSG) superheater outlet headers are exposed to cyclic stresses under varying transient operating conditions. Three different tube to header connections are analyzed. Cold, warm, and hot startup cycles are defined along with a load change cycle. These cycles are used to develop boundary conditions for a transient three dimensional finite element analysis of each detail. The results show that the highest stresses are away from the tube to header weld area. For the startup cycles analyzed, equations are presented for cycle life determination.
An Improved Method for Evaluating Market Value of Turbine Gaspath Component Alternatives
Authors: Willett Fred T. , Pothier Michael R.
Published: February 2009

The large installed base of large frame industrial gas turbines has prompted a number of replacement part offerings, in addition to the replacement parts offered by the OEM. Willett [1] proposed an economic model developed to evaluate gas turbine component alternatives for base load and cyclic duty operation. The improved method expands the capability of the earlier model by including risk level as a variable. Power plant operator value of alternative replacement turbine components for a popular large frame industrial gas turbines is evaluated. A baseline case is established to represent the current component repair and replacement situation, assuming no risk. Each of the modes of power plant operation is evaluated from a long-term financial focus. A short-term financial focus is evaluated for contrast and discussed briefly. Long-term focus is characterized by a nine-year evaluation period, while short-term focus is based on first year benefit only. Four factors are varied: part price, output increase, simple cycle efficiency increase, and additional risk. Natural gas fuel is considered at two different gas prices. Peak, off-peak, and spot market electricity prices are considered. Results are calculated and compared using net present value (NPV) criteria. A case study is presented to demonstrate the method’s applicability to a range of different risk scenarios, from ill-fitting replacement parts to catastrophic turbine failure.
Fuel Composition Effects on the Velocity Field in a Lean Premixed Swirl-Stabilized Combustor
Authors: Wicksall Donald M. , Agrawal Ajay K. , Schefer Robert W. , Keller Jay O.
Published: February 2009

Fuel composition effects on the flow-field of a lean premixed swirl-stabilized burner were studied. Methane (CH4) was enriched with hydrogen (H2) to vary the fuel composition. The burner inlet had 28-degree swirl vanes located in the annulus around a centerbody. Combustion occurred in an air-cooled quartz chamber at atmospheric pressure. The measurements were obtained, using the particle image velocimetry (PIV) technique, which allowed the 2-D velocity and vorticity fields to be examined for different fuels. The average velocity field was significantly altered, including the shape of the central and corner recirculation zones in the H2 enriched flames. The instantaneous velocity fields showed corresponding differences as well. The length scales and vorticity levels of the time-averaged velocity field differed from those for the instantaneous fields, indicating the importance of temporally resolved measurements.