bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring of HRSG Performance in Large Size Combined Cycle Power Plants
Authors: Cafaro Silvio , Traverso Alberto , Massardo Aristide F.
Published: August 2009

Monitoring of all components of large size combined cycle power plants (gas turbine, HRSG, steam turbine, auxiliaries) plays a determinant role in improving plant availability, profitability and maintenance scheduling. This paper presents a research project carried out by TPG (Thermochemical Power Group) of University of Genoa in collaboration with Ansaldo Energia S.p.A. to improve existing monitoring and diagnostics procedures and to develop innovative software tools for software-aided maintenance and customer support: the first part of research is concerned with the monitoring of a three pressure level HRSG (Heat Recovery Steam Generator), which is presented in this paper. A procedure for estimating HRSG performance in large size combined cycle power plants is presented. The work consists of the development of an original Matlab code which calculates heat exchangers’ performance, at different power plant operating conditions. The Matlab code uses some parameters (areas of heat exchangers, heat transfer coefficient, heat loss, pressure drop) coming from a detailed on-design model necessary to set some parameters for the calculation. The original Matlab code was developed with a twofold objective: to calculate the actual gas path inside the HRSG starting from the available measurements, thus obtaining the current effectiveness of all the heat exchangers in the HRSG; to estimate the expected performance of each heat exchanger to be compared with the actual ones. Once the actual effectiveness and the expected effectiveness of the heat exchanger are defined, non-dimensional performance parameters suitable for degradation assessment can be defined. Such parameters will be used to monitor plant degradation, to support plant maintenance, and to assist on-line troubleshooting. As a result of the sensitivity analysis, each performance parameter is coupled with an accuracy factor. The accuracy of each performance parameter is estimated through the sensitivity analysis, which allows to determine the best parameters to be monitored and to define the related tolerance due to measurement errors. The methodology developed has been successfully applied to historical logged data (2 years) of an existing large size (400 MW) combined cycle, showing the capabilities in estimating the degradation of the HRSG throughout plant life.
A Rim Seal Orifice Model With 2 Cds and Effects of Swirl in Seals
Authors: Johnson Bruce V. , Wang Cheng-Zhang , Roy Ramendra P.
Published: August 2009

Rim seal ingestion models for gas turbines are formulated to estimate the amount of hot fluid ingested through “clearance” seals into the disk cavity. Previous numerical and experimental studies showed the complex time-dependent, three-dimensional characteristics of the flow through the seals and in the outer region of the disk cavity. The present model is developed for estimating ingress and egress flow through the seal that is driven by the azimuthal variation in gas path pressure near the vane and blade platforms. Most published rim seal orifice models have used one “lumped parameter” Cd for both ingress and egress across the seal. However, the flow path from the gas path through the seal is often more convoluted than the flow returning to the gas path. The present Rim Seal Orifice Model includes (i) a Cd value for ingress from the gas path into the disk cavity, (ii) a Cd value for egress from the disk cavity to the gas path and (iii) an estimate for effects of swirl from the seal outer radius to the inner radius of the seal mixing region. The use of two Cd values provides two parameters for characterizing the flow through the seal. The ingress and egress Cd values for a turbine rim seal configuration and flow condition are estimated by comparing the modeled seal effectiveness for a parametric range of ingress and egress Cd values with experimental stator wall measurements. The combination of Cd values, which best matches experimental data over a range of coolant flow ratios, characterizes the seal and flow condition. Arizona State University experimental data were used to estimate the Cd values for an overlap seal configuration.
An Innovative Gas Turbine Cycle With Methanol Fuelled Chemical-Looping Combustion
Authors: Jin Hongguang , Zhang Xiaosong , Hong Hui , Han Wei
Published: August 2009

In this paper, a novel gas turbine cycle integrating methanol decomposition and the chemical-looping combustion (CLC) is proposed. The system study on two methanol-fuelled power plants, the new gas turbine cycle with CLC combustion, and a chemically intercooled gas turbine cycle, has been investigated with the aid of the exergy analysis (EUD methodology). In the proposed system, methanol fuel is decomposed into syngas mainly containing H2 and CO by recovering low-temperature thermal energy from an intercooler of the air compressor. After the decomposition of methanol, the resulting product of syngas is divided into two parts: the most part reacting with Fe2O3, is sent into the CLC subsystem, and the other part is introduced into a supplement combustor to enhance the inlet temperatures of turbine to 1100–1500°C. As a result, the new methanol-fuelled gas turbine cycle with CLC had a breakthrough in performance, with at least about 10.7 percentage points higher efficiency compared to the chemically intercooled gas turbine cycle with recovery of CO2 and is environmentally superior due to the recovery of CO2. This new system can achieve 60.6% net thermal efficiency with CO2 separation. The promising results obtained here indicated that this novel gas turbine cycle with methanol-fuelled chemical looping combustion could provide a promising approach of both effective use of alternative fuel and recovering low-grade waste heat, and offer a technical probability for CLC in applying into the advanced gas turbine with high temperatures above 1300°C.
Development, Characterization and Testing of MCrAlY HVOF Coating Used as Bond Coat for YPSZ Top Coat
Authors: Scrivani Andrea , Lanzi Alessandro , Giolli Carlo , Rizzi Gabriele , Russo Dario , Spagnoli Marco
Published: August 2009

MCrAlY coatings (where M stands for Co, Ni, or CoNi) are used as a single overlay coating or as bond coat for thermal barrier coating (TBC) systems. Low Pressure Plasma Spray (LPPS) or Vacuum Plasma Spray (VPS) MCrAlY coatings are considered nowadays the state of the art, nevertheless High Velocity Oxygen Fuel (HVOF) MCrAlY coating is gaining more and more importance due to its quality and to the possible cost reduction in comparison to the state of the art LPPS/VPS coatings. On the other hand the HVOF process tends to have a relatively low surface roughness, which hinders the possibility to act as bond coat for a TBC coating layer. In this work, a HVOF deposition process was developed to obtain a rough MCrAlY coating which can be used as bond coat for yttria partially stabilized zirconia (YPSZ) top coat. Developed parameters were used to apply a TBC system on a stage 2 blade. TBC sections on the same blade have successfully passed thermal fatigue testing according to the specification of an important OEM.
Simulation for a New Cascade of Helium Compressor With Enhanced Pressure Ratio
Authors: Long Yanli , Xu Limin , Xie Chunling , Sun Yufeng
Published: August 2009

The High Temperature Gas-cooled Reactor (HTGR) and external-combustion heat engine firing with non-traditional fuel bring Brayton-cycle helium turbine a very good prospect. If the helium compressor is designed according to conventional air-compressor rule, the compression ratio of single stage will be smaller and the number of stages will be excessive. These problems present a topic which must be solved in further development. Therefore a new velocity triangle of helium compressor is presented and analyzed. It can increase severalfold stage loading. The test data and experiences of air cascade are used to estimate the profile losses and stage efficiency of the new helium cascade. On the basis of validation for selected turbulence model and mesh division, fluid analysis software FLUENT6.3 is used to simulate the flow of new helium cascade. Simulation results show that, comparing with the conventional design, the new stage loading can be increased by 2 to 4 times when inlet Mach number is 0.466 to 0.7013. Therefore the stage number of helium compressor is reduced severalfold, while profile efficiency can reach 0.939 to 0.894; The air turning angle reaches 38.75° to 49.43°, while the outlet angle reaches 0.78° to −12.45°; There is basically no separating phenomenon in flow field. Because the experimental data are lacking to support the new cascade structural parameters and air cascade test is a kind of low-speed test, there is some deviation to estimate helium cascade performance at the higher Mach number by use of air cascade experiences. In this cascade simulation, traditional original profile thickness distribution (C-4 blade profile) is applied, therefore the optimizing for the profile thickness distribution and the shape of flow field are expected to be a greater potential for enhancing performance.
An Analysis of the Motion of a Centrifugal Impeller in Overspeed Test
Authors: Gozdawa Richard J. , Crook Alfred W.
Published: August 2009

This paper arose from the experience in overspeeding the impellers of centrifugal compressors. The industry had information that the ratio of certain moments of inertia of the impeller (about axis to about a diameter through the mass centre) should be outside a range from 0.7 to 1.5, but the basis for this prohibition was unknown. The tests provided confirmation of it in that impellers were spun successfully to overspeed. The observation was consistent with a conical precession of the impeller at an angular velocity, which was a small fraction of the angular velocity of the drive. The purpose of the investigation was to search for the dynamical basis of the prohibition.
An Advanced Optimization Procedure for the Thermodynamic Selection of Centrifugal Compressors Stages
Authors: Pazzi Simone , Giachi Marco , Al Musleh Ashraf , Pusceddu Massimo , Ghizawi Nidal
Published: August 2009

The present paper deals with the application of optimization algorithms to the selection of centrifugal stages for industrial compressors. The optimization procedure has been developed allowing an automatic stage selection to meet a mathematically stated target including the most relevant performance parameters and machine operating and size constraints. The thermodynamic selection is assessed by means of an internal-use CCS (Centrifugal Compressors Selector) that computes compressor flange-to-flange performance with a given sequence of stages. The CCS has been coupled to an internally used optimization code (“PEZ”, Perl Version of Easy Optimizer) using the CCS as the performance evaluator. The user indicates which flange variables must be matched as well as the stages parameters that the optimizer is allowed to alter, with their respective ranges of acceptable variation. The optimization objective reflects the job specifications and can be stated as a combination of several performance parameters. Constraints are enforced through appropriate penalty terms added to the objective function. The performance optimization process includes an automatic rotordynamic analysis that checks the rotor mechanical acceptability. The optimization of two different in-line barrel compressors, originally configured manually, brought a remarkable 2% flange-to-flange performance increase and a 5% gain in operating range respectively. Each case required about 10 hours windows desktop workstation.
Are Advanced Large Gas Turbine Ready for Use in Captive Applications?
Authors: Zachary Justin
Published: August 2009

Industrial facilities are applications where the majority of electricity and steam productions are devoted to internal consumption rather than being exported. Oil refineries, smelters, and chemical and desalinization plants are typical examples. In the case of aluminum smelters, the vast quantities of electricity required by the process cannot be supplied by utilities from the grid and therefore cogeneration is required. Since power and/or steam supply interruptions might have catastrophic effects on the facility processes, the paramount requirement for “dedicated power plants’ is availability and reliability rather than high performance. It is common to find older D and E gas turbines used as the prime mover. In recent years, however, advanced gas turbines (GTs) successfully demonstrated close to 60% efficiency in combined cycle applications. The G and H technology classes, using steam to perform GT cooling duty, accumulated thousands of operating hours. Many improvements from G and H were also implemented into FX Class (latest variants of the air-cooled F technology class). Firstly, the paper addresses the strategies for incorporation of advanced GTs in captive applications where the equipment must cope with rapid changes in power demand, such as load swings, load rejection, harmonic currents, etc. Further, it examines a variety of designs, where there is a high and low process steam demand for process. The discussion encompasses plant optimization aiming at a high level of redundancy: multi-shaft arrangements, common steam headers, and heavy supplementary firing. The selection of an optimum steam turbine (ST) is also discussed, including steam extraction locations and the ability to operate efficiently with steam extraction on and off. Issues dealing with steam purity requirements and water treatment sizing will also be addressed. Since the amount and quality of the condensate return vary substantially, maintaining the water chemistry is essential. In continuation, the article will describe the challenges for the control system design and in particular, the requirements to maintain tight process conditions during transients. Finally, the paper will present the experience of an engineering, procurement, and construction (EPC) contractor for several “captive applications” projects.
Ground-Based Vibration Response of a Spinning, Cyclic Symmetric Rotor With Gyroscopic and Centrifugal Softening Effects
Authors: Shen I. Y. , Kim Hyunchul
Published: August 2009

This paper is to study ground-based vibration response of a spinning, cyclic symmetric rotor through a theoretical analysis and an experimental study. The theoretical analysis consists of three steps. The first step is to analyze vibration characteristics of a stationary cyclic symmetric rotor with N identical substructures. For each vibration mode, we identify a phase index n and derive a Fourier expansion of the mode shape in terms of the phase index n. The second step is to predict rotor-based vibration response of the spinning, cyclic symmetric rotor based on the Fourier expansion of the mode shapes and the phase indices. The rotor-based formulation includes gyroscopic and centrifugal softening terms. Moreover, rotor-based response of repeated modes and distinct modes is obtained analytically. The third step is to transform the rotor-based response to ground-based response using the Fourier expansion of the stationary mode shapes. The theoretical analysis leads to the following conclusions. First, gyroscopic effects have no significant effects on distinct modes. Second, the presence of gyroscopic and centrifugal softening effects cause the repeated modes to split into two modes with distinct frequencies ω1 and ω2 in the rotor-based coordinates. Third, the transformation to ground-based observers leads to primary and secondary resonances. In general, the ground-based response presents resonance branches in the Campbell diagram at ω1 ± kω3 and ω2 ± kω3, where k is phase index n plus an integer multiple of cyclic symmetry N. When the gyroscopic effect is significantly greater than the centrifugal softening effect, two of the four resonance branches disappear. The remaining resonances take the form of either ω1 + kω3 and ω2 − kω3 or ω1 − kω3 and ω2 + kω3. To verify these predictions, we also conduct a modal testing on a spinning disk carrying 4 pairs of brackets evenly spaced in the circumferential direction with ground-based excitations and responses. The disk-bracket system is mounted on a high-speed, air-bearing spindle. An automatic hammer excites the spinning disk-bracket system and a laser Doppler vibrometer measures its vibration response. A spectrum analyzer processes the hammer excitation force and the vibrometer measurements to obtain waterfall plots at various spin speeds. The measured primary and secondary resonances from the waterfall plots agree well with those predicted analytically.
Numerical Analysis of Temperature Distribution of a Film-Cooled and TBC Coated Blade
Authors: Takahashi Toshihiko , Watanabe Kazunori , Fujii Tomoharu , Fujioka Terutaka
Published: August 2009

In order to contribute to assessment of structural integrity of a gas turbine cooled-blade, numerical estimation of temperature distributions of the blade was conducted. Steady-state simulations by means of one-way coupling of a CFD calculation with thermal conduction analysis were developed and executed to estimate the temperature distributions with using a realistic blade model. Thermal protection schemes applied to the target blade analyzed are external surface film cooling, internal convective cooling and thermal barrier coating (TBC). Non-conformal multi-block meshes were adopted in the analyses for the purpose of reducing turnarounds required in the simulations of real blades, so as to cope with a compound domain including film-cooling holes of various directions. The CFD was applied to flow fields inside and outside of the blade in order to estimate thermal loads imposed on the blade. The temperature distribution of the blade was calculated with the thermal conduction analysis under the conditions based on the CFD calculation. The calculated temperature profiles are in reasonable agreement with local temperature which was estimated on the basis of micro-structural observations of an ex-service blade. The present calculations can also predict influence of lower internal cooling performance on the temperature distribution of the blade.
Design and Testing of a Vibrating Test Object for Investigating Fluid-Structure Interaction
Authors: Andrinopoulos Nikos , Vogt Damian , Hu Jiasen , Fransson Torsten H.
Published: August 2009

In this study the vibration properties of a deforming test object are presented. The test object is bump shaped and is integrated into the wall of a transonic wind tunnel. The purpose for using such a test object is to study, in a generic manner, the unsteady aerodynamic phenomena occurring due to the presence of a vibrating structure in the flow. The setup is part of an ongoing study to address the phenomena of fluid-structure interaction and shock-boundary layer interaction. The design objective for the test object is to assimilate a 1F vibration mode at a given section of a typical compressor blade. Finite element (FE) analyses have been used to predict the frequency response of the test object prior to manufacturing. The design objectives have been verified experimentally by time-resolved laser measurements. It has been found that the FE predictions are in good agreement with experimental data. Furthermore it has been shown that the present test object allows for the achievement of the targeted vibration properties up to a frequency of 250Hz, corresponding to a reduced frequency above 0.8.
Unsteady CFD Investigation on Inlet Distortion in a Centrifugal Compressor
Authors: Zemp Armin , Kammerer Albert , Abhari Reza S.
Published: August 2009

Blade failure in turbomachinery is frequently caused by an excessive resonant response. Forced response of the blades originates from unsteady fluid structure interactions as conditioned in the inlet section by duct bends, struts or inlet guide vanes. This paper presents the computational part of a research effort that focuses on the blade forced response in a centrifugal compressor. Unsteady fluid flow simulations are used to quantify the forcing function acting on the compressor blades due to inlet flow distortion. The measured inlet flow distribution is applied as inlet boundary conditions in the computation. The unsteady investigation provided the temporal evolution of the distorted flow through the compressor. The time-resolved blade pressure distribution showed the temporal evolution of the dynamic load on the blade surface caused by the inlet distortion. The results suggest that the forcing function is most sensitive in the leading edge region due to inlet angle variations. Towards the impeller stability line the increase in incidence caused separation on the suction side of the main blade and therefore considerably altered the amplitude and the phase angle of the unsteadiness. The investigation of the effect of idealizing the inlet flow distribution on the forcing function showed an increase of the peak amplitude of approximately 30% compared to the actual inlet flow distribution.
Comparison Between Hot Wire and 5-Hole Pressure Probe Traverse Data in a Variable Density Two-Stages Air Turbine
Authors: D’Ovidio Alberto , Littlewood Lucy , Congiu F. , Ruffino P. , Mokulys Thomas
Published: August 2009

This paper presents the comparison between hot wire and 5-hole pressure radial traverses carried out in a variable density two stages air turbine, available at the Alstom Power test facility in Rugby, UK. In this centre accurate and innovative measurement techniques are employed in support of the product validation process. Hot wire anemometry has been extensively used in environments were the flow density is constant, such as in open circuit wind tunnels or water tunnels. One of the intents in this series of tests was to derive a suitable hot wire calibration in a flow where the density could be two to four times higher than that at standard ambient conditions. This works analyses the traverse data performed at turbine inlet and exit planes by means of the two measuring techniques. The mean velocity profiles obtained with the 5-hole pressure probe are compared with those derived from a single hot wire. This is done by means of both two-dimensional and contour plots. The traverse data are also compared with the CFD results determined during the design of the blade being tested.
Axial Load Control on High-Speed Turbochargers: Test and Prediction
Authors: Gjika Kostandin , LaRue Gerald D.
Published: August 2009

This paper deals with axial thrust load control in high-speed turbochargers. A specific test facility was developed to demonstrate the feasibility of axial load measurement and control. A special turbocharger was developed and instrumented to measure axial load and other test parameters. The axial load was controlled by throttling the compressor inlet and/or outlet flow. Extensive testing and analysis during both steady state and transient behavior conditions were completed on a special test bench. A thrust load map was developed and superimposed on the compressor map, and the relationship between turbocharger aerodynamics performance and axial thrust load was identified. During testing, the interaction between axial load, rotating group lateral motion and radial vibrations on the turbocharger housing was also identified. Running the turbocharger with low axial load shows no major problems on rotating group lateral motion or oil leakage. An analytical approach using a control volume type fluid dynamic model and a prediction code for axial thrust load has been developed. It shows good agreement between measured and predicted thrust load.
Design and Off-Design Numerical Investigation of a Transonic Double-Splitter Centrifugal Compressor
Authors: Marconcini Michele , Rubechini Filippo , Arnone Andrea , Ibaraki Seiichi
Published: August 2009

The flow field of a high pressure ratio centrifugal compressor for turbocharger applications is investigated using a three-dimensional Navier-Stokes solver. The compressor is composed of a double-splitter impeller followed by a vaned diffuser. The flow field of the transonic open-shrouded impeller is highly three-dimensional, and it is influenced by shock waves, tip leakage vortices and secondary flows. Their interactions generate complex flow structures which are convected and distorted through the impeller blades. Both steady and unsteady computations are performed in order to understand the physical mechanisms which govern the impeller flow field while the operation ranges from choke to surge. Detailed Laser Doppler Velocimetry (LDV) flow measurements are available at various cross-sections inside the impeller blades at both design and off-design operating conditions.
Optimizing the Swiss-Roll Recuperator of an Innovative Micro Gas Turbine by a Surrogate Neural Network and the Multi-Objective DIRECT Algorithm
Authors: Chang Yau-Zen , Hung Kao-Tin , Shih Hsin-Yi
Published: August 2009

Micro-turbines are promising high power-density engines for distributed generation. In this paper, an optimization process is proposed to design a Swiss-roll type recuperator used to recover the exhaust heat of a micro gas turbine. The recuperator is a counter-flow spiral plate heat exchanger, composed of two flat plates wrapped around each other. There are several design parameters to be optimized, including the number of turns, channel width, plate thickness, and mass flow rate. The complex interconnections of these design parameters make it difficult to analyze the process and select adequate parameter combination to build a recuperator with the highest effectiveness and lowest pressure drop. In order to reduce the number of numerical analysis in the optimization process, a neural network is employed as surrogate model, and a multi-objective DIRECT (DIviding RECTangle) algorithm, named as MO-DIRECT, is developed. After merely 5 iterations, with 3 representative sets selected from the Pareto front for convergence test during each iteration, we were able to find a min-max solution with prediction error lower than 4%. Also, only 24 numerical simulations are required to achieve the results, and only 2,313 steps were conducted in the MO-DIRECT search, rather than 35,343 required in an exhaustive search.
Experimental and Numerical Investigation of Interactions Between Axial Turbine and Non-Axisymmetric Exhaust Hood
Authors: Fu Jing-Lun , Zhou Si-Jing , Liu Jian-Jun
Published: August 2009

This paper describes experimental and numerical studies on the coupled flow field in a single turbine stage and exhaust hood model. The turbine stage with 22 stator blades and 30 rotor blades is especially designed for the hood model, which is a typical design for Westinghouse model 300/600 MW steam turbine. Unsteady pressure at the rotor blade, hood outer casing, unsteady total pressure at the stage outlet and velocity distributions at the turbine outlet and hood exit, in addition to static pressure distributions at the diffuser tip and hub end-walls and at hood outer casing, are measured and compared with numerical predictions. The flow details in the exhaust system with the whole annulus stator and rotor blade rows are simulated by employing CFD software CFX-5. It is found that the swirl angle profile and total pressure profile caused by the upstream turbine at the diffuser inlet have an unfavorable effect on the exhaust hood performance. The non-axisymmetric back-pressure generated by the downstream exhaust hood leads to the local flow varying for each stator and rotor blades and low frequency fluctuation in the aerodynamic force on the blade.
Determination and Comparison of the Dynamic Characteristics of a Perfectly Premixed Flame in Both Single and Annular Combustion Chambers
Authors: Fanaca Dan , Alemela Panduranga Reddy , Ettner Florian , Hirsch Christoph , Sattelmayer Thomas , Schuermans Bruno
Published: August 2009

In this paper we apply a new method to obtain the dynamical characteristics of premixed flames in acoustically complex systems like an annular combustor. For this a novel model based reduction method was applied which describes the acoustic field as a superposition of a discrete number of eigenmodes. The measured dynamic signals are decomposed into modal components which are then used to fit the model parameters. With this approach the complete characterisation of the annular test rig requires significantly less experimental effort, i.e. simultaneous pressure measurements, than before. After describing the new procedure, we show the validation of the acoustical model. Using this model, we were able to obtain the characteristics of the flame in the annular combustor with a much smaller number of pressure sensors as the model provides physical constraints that would otherwise have to be measured. The comparison of the characteristic flame parameters between the single burner and the annular combustor configurations for the same operating conditions shows that in the annular combustor slightly longer convective time delays are found which are consistent with the static flame characterisation showing longer flames in the annular combustor than in the single burner test rig.
Enhanced Cooling Effectiveness in Full-Coverage Film Cooling System With Impingement Jets
Authors: Oh Sang Hyun , Lee Dong Hyun , Kim Kyung Min , Kim Moon Young , Cho Hyung Hee
Published: August 2009

An experimental investigation is conducted on the cooling effectiveness of full-coverage film cooled wall with impingement jets. Film cooling plate is made of stainless steel, thus the adiabatic film cooling effectiveness and the cooling effect of impingement jet underneath the film cooling plate are comprised in the cooling effectiveness. Infra-red camera is used to measure the temperature of film cooled surfaces. Experiments are conducted with different film cooling hole angles, such as 35° and 90°. Diameters of both film cooling holes and impinging jet holes are 5 mm. The jet Reynolds number base on the hole diameter (Red) ranges from 3,000 to 5,000 and equivalent blowing ratios (M) varies from 0.3 to 0.5, respectively. The distance between the injection plate and the film cooling plate is 1, 3 and 5 times of the hole diameter. The streamwise and spanwise hole spacing to the hole diameter ratio (p/d) are 3 for both the film cooling hole plate and the impingement jet hole plate. The 35° angled film cooling hole arrangement shows higher film cooling effectiveness than the 90° film cooling hole arrangement. As the blowing ratio increases, the cooling effectiveness is enhanced for both the 35° almost constant regardless of H/d, while H/d = 1 shows a minimum value for the angled film cooling hole.
Development of a Tip Leakage Control Device for an Axial Flow Fan
Authors: Akturk Ali , Camci Cengiz
Published: August 2009

Performance of an axial fan unit used in ducted fan based propulsion systems is closely related to its tip leakage mass flow rate and the level of tip/casing interactions. The present experimental study uses a stereoscopic Particle Image Velocimeter to quantify the three dimensional mean flow observed at just downstream of a ducted fan unit. After a comprehensive description of the baseline fan exit flow, a number of novel tip treatments based on pressure side extensions are introduced. Various tip leakage mitigation schemes are introduced by varying the chordwise location and the width of the extension in the circumferential direction. The current study shows that a proper selection of the pressure side bump location and width are the two critical parameters influencing the success of each tip leakage mitigation approach. Significant gains in axial mean velocity component are observed when a proper pressure side tip extension is used. It is also observed that a proper tip leakage mitigation scheme significantly reduces the tangential velocity component near the tip of the axial fan blade. Reduced tip clearance interactions are essential in improving the energy efficiency of ducted fan systems. A reduction or elimination of the momentum deficit in tip vortices are also expected to reduce the adverse performance effects originating from the unsteady and highly turbulent tip leakage vortical flows rotating against a stationary casing.
The Use of Eddy Current Sensor Based Blade Tip Timing for FOD Detection
Authors: Chana K. S. , Cardwell D. N.
Published: August 2009

Deterioration of rotor blades due to foreign object damage (FOD), erosion by sand/water, low cycle fatigue (LCF) and high cycle fatigue (HCF) all limit blade life, but cannot always be detected before a failure. The advent of tip-timing systems makes it possible to assess turbomachinery blade vibration using non-contact systems. However, these systems are still largely optical based and therefore suffer from contamination problems, further development of these systems is difficult due to problems associated with keeping the sensors clean. Experimental measurements have been carried out using an alternative eddy current sensor that has been validated in a series of laboratory and engine tests to measure rotor blade arrival times. A series of engine trials have been conducted to assess their capability for detection of pre-existing damage and the capture of dynamic foreign object damage (FOD) events. The results show that it is possible to acquire high quality blade timing data for use in engine condition monitoring. In addition for the detection of FOD created damage and FOD damage as it occurs.
Transition Prediction on Turbine Blade Profile With Intermittency Transport Equation
Authors: Piotrowski Wladyslaw , Elsner Witold , Drobniak Stanisław
Published: August 2009

The paper presents the results of tests and validations of γ-Reθ model proposed by Menter at al [10], which was extended by in-house correlations on onset location and transition length. The tests performed were based on experimental data on the flat plate Test Cases available at ERCOFTAC Data Base as well as on experimental data of turbine blade profile investigated at Czestochowa University of Technology. Further on, the model was applied for unsteady calculations of the blade profile test case, where chosen inlet conditions (turbulent intensity, wake parameters) were applied. For the selected case numerical results were compared not only with the experimental data, but also with the results obtained with other transition models. It was shown that the applied model was able to reproduce some essential flow features related to the bypass and wake-induced transitions and the simulations reveal good agreement with the experimental results in terms of localisation and extent of wake-induced transition.
Suction-Side Gill-Region Film Cooling: Effects of Hole Shape and Orientation on Adiabatic Effectiveness and Heat Transfer Coefficient
Authors: Chappell Justin , Ligrani Phil , Sreekanth Sri , Lucas Terry
Published: August 2009

The performance of suction-side gill region film cooling is investigated using the University of Utah Transonic Wind Tunnel and a simulated turbine vane in a two-dimensional cascade. The effects of film cooling hole orientation, shape, and number of rows, and their resulting effects on thermal film cooling characteristics are considered for four different hole configurations: round axial (RA), shaped axial (SA), round radial (RR), and round compound (RC). The mainstream Reynolds number based on axial chord is 500,000, exit Mach number is 0.35, and the tests are conducted using the first row of holes only, second row of holes only, or both rows of holes at blowing ratios of 0.6 and 1.2. Carbon dioxide is used as the injectant to achieve density ratios of 1.73 to 1.92 similar to values present in operating gas turbine engines. A mesh grid is used to give a magnitude of longitudinal turbulence intensity of 5.7 percent at the inlet of the test section. Results show that the best overall protection over the widest range of blowing ratios and streamwise locations is provided by either the RC holes, or the RR holes. This result is particularly significant because the RR hole arrangement, which has lower manufacturing costs compared with the RC and SA arrangements, produces better or equivalent levels of performance in terms of magnitudes of adiabatic film cooling effectiveness and heat transfer coefficient. Such improved performance (relative to RA and SA holes) is likely mostly a result of compound angles, which increases lateral spreading. As such, the present results indicate that compound angle appears to be more effective than hole shaping in improving thermal protection relative to that given by RA holes.
Impact of Time-Resolved Entropy Measurement on a One-and-1/2-Stage Axial Turbine Performance
Authors: Mansour M. , Chokani N. , Kalfas A. I. , Abhari R. S.
Published: August 2009

An accurate assessment of unsteady interactions in turbines is required, so that this may be taken into account in the design of the turbine. This assessment is required since the efficiency of the turbine is directly related to the contribution of unsteady loss mechanisms. This paper presents unsteady entropy measurements in an axial turbine. The measurements are conducted at the rotor exit of a one-and-1/2-stage, unshrouded turbine that is representative of a highly loaded, high-pressure stage of an aero-engine. The unsteady entropy measurements are obtained using a novel miniature fast-response probe, which has been developed at ETH Zurich. The entropy probe has two components: a one-sensor fast response aerodynamic probe and a pair of thin-film gauges. The probe allows the simultaneous measurement of total temperature and total pressure from which the time-resolved entropy field can be derived. The measurements of the time resolved entropy provide a new insight into the unsteady loss mechanisms that are associated with the unsteady interaction between rotor and stator blade rows. A particular attention is paid to the interaction effects of the stator wake interaction, the secondary flow interaction and the potential field interaction on the unsteady loss generation at the rotor exit. Furthermore, the impact on turbine design of quantifying the loss in terms of the entropy loss coefficient, rather than the more familiar pressure loss coefficient, is discussed in detail.
High-Fidelity Numerical Analysis of Per-Rev-Type Inlet Distortion Transfer in Multistage Fans: Part II—Entire Component Simulation and Investigation
Authors: Yao Jixian , Gorrell Steven E. , Wadia Aspi R.
Published: August 2009

Part I of the paper validated the ability of the Unsteady RANS solve Pturbo to accurately simulate distortion transfer and generation through selected blade rows of two multistage fans. In part II, unsteady RANS calculations were successfully applied to predict the one-per-rev inlet total pressure distortion transfer in the entirety of two differently designed multistage fans. This paper demonstrates that Hi-Fi CFD can be used early in the design process for verification purposes before hardware is built, and can be used to reduce the number of distortion tests, hence reducing engine development cost. The unsteady RANS code Pturbo demonstrated remarkable agreement with data, accurately capturing both the magnitude and profile of total pressure and total temperature measurements. Detailed analysis of the flow physics identified from the CFD results has led to a thorough understanding of the total temperature distortion generation and transfer mechanism, especially for the spatial phase difference of total pressure and total temperature profiles. The analysis illustrates that the static parameters are more revealing than their stagnation counterpart and that pressure and temperature rise are more revealing while the pressure and temperature ratio could be misleading. The last stage is effectively throttled by the inlet distortion even though the overall engine throttle remains unchanged. The total temperature distortion generally grows as flow passes through the fan stages.
Performance Optimization of a Modified Wells Turbine Using Non-Symmetric Airfoil Blades
Authors: Mohamed M. H. , Janiga G. , The´venin D.
Published: August 2009

A Wells turbine is a self-rectifying air flow turbine employed to convert the pneumatic power of the air stream induced by an Oscillating Water Column into mechanical energy. Standard Wells turbines have several well-known disadvantages: a very low tangential force, leading to a low power output from the turbine; a high undesired axial force; usually a low aerodynamic efficiency and a limited range of operation due to stall. In the present work we investigate extensively the potential of non-symmetric airfoil blades to improve the tangential force induced by a two-stage modified Wells turbine. Since these two stages are mirrored, the system stays globally symmetric. Non-symmetric blades allow to increase considerably power output from the turbine and the global efficiency of the system. The optimization of the gap between the two stages as well as of the shape of the airfoils is considered. The automatic optimization procedure is carried out by coupling an in-house optimization library (OPAL) with an industrial CFD code (ANSYS-Fluent). The multi-objective optimization taking into account both tangential force coefficient and efficiency relies on Evolutionary Algorithms. Detailed comparisons are finally presented between the optimized design performance and the classical monoplane Wells turbine using symmetric airfoils, demonstrating the superiority of the proposed solution.
Reduction of Fan and Compressor Wake Defect Using Plasma Actuation for Tonal Noise Reduction
Authors: Lemire Se´bastien , Vo Huu Duc
Published: August 2009

This paper proposes a new technique to reduce the noise generated by rotor-stator interaction (tonal noise) in fans and compressors. The method involves the use of single dielectric barrier discharge (plasma) actuators near the blade trailing edge to reduce blade wakes. Plasma actuators are a new and simple type of active flow control device consisting of two parallel and offset electrodes separated by a layer of dielectric material. The application of a high AC voltage at high frequency to the electrodes generates a body force on the flow in the vicinity of the electrodes to inject momentum without mass addition. A preliminary assessment of the proposed concept is performed with a computational study on a modern low-speed compressor rotor geometry. A plasma actuator model is implemented in an established turbomachinery CFD code. Simulations are carried out to evaluate the effect of the actuator strength, location and actuation method (continuous versus pulsed) on the rotor wake. Results show that plasma actuators operated in continuous mode near the trailing edge can significantly influence the wake of the rotor with relatively little power consumption. The effectiveness of the actuation is proportional to actuator strength (induced body force). The exact position of the actuator in the trailing edge region has little effect on the effectiveness of the actuation. The results from simulations for pulsed actuation show very low time-averaged influence on the wake and are not fully conclusive, due possibly to the frequencies simulated and the limitations of the RANS CFD tool.
Low Emissions Combustion System Development for the GE Energy High Hydrogen Turbine Program
Authors: Lacy Ben , Ziminsky Willy , Lipinski John , Varatharajan Bala , Yilmaz Ertan , Brumberg Justin
Published: August 2009

Progress on the joint GE Energy/US Department of Energy (DOE) High Hydrogen Turbine Program is presented. A summary of GE’s current integrated gasification combined cycle (IGCC) experience is provided. The Phase I approach is discussed with selected results included. The program follows the well-established GE approach to introducing new technology through: fundamental laboratory testing and analysis; subscale demonstration; full-scale development; full-scale verification. Advancements towards the ultimate goal of ultralow NOx emissions with coal derived pre-combustion carbon capture fuels are presented. Feasibility of diluent-free low NOx combustion is demonstrated experimentally at gas turbine conditions with representative fuel compositions. Phase II design challenges are highlighted within the framework of Phase I results.
Tip-Timing Data Analysis for Mistuned Bladed Discs Assemblies
Authors: Ste´phan Cyrille , Berthillier Marc , Lardie`s Joseph , Talon Arnaud
Published: August 2009

In turbomachine industry, bladed assembly vibration measurements are very important for blades behaviour estimation. These measurements are generally obtained from strain gauges. However, one of the most promising methods for the analysis of blade vibrations in rotating bladed assemblies is the Blade Tip Timing or Optical Blade Vibration Measurement method. A set of optical sensors is mounted on an engine casing, in front of a disc, and measures the times of arrival of each blade. These timings are then used to compute the vibrations of the blades. However the fundamental problem for spectral analysis of blade tip timing data is that the signals are undersampled and aliased. We propose here a new method for spectral estimation of blades responses from tip timing data that overcome these difficulties. The method proposed in this communication is based on the use of a minimum variance filter associated with an iterative updating of the autocorrelation matrix. That allows to process correctly a signal even if the number of known signal samples is less than equivalent Nyquist criterion. This approach is suitable for spectral analysis of undersampled and aliased signals. Perfomances of the spectral estimator have been evaluated for one simulated and one experimental test cases. The method seems very promising for the monitoring of mistuned bladed discs.
Aeroderivative Gas Turbines for LNG Liquefaction Plants: Part 1—The Importance of Thermal Efficiency
Authors: Meher-Homji Cyrus , Messersmith Dave , Hattenbach Tim , Rockwell Jim , Weyermann Hans , Masani Karl
Published: August 2009

The trade in Liquefied Natural Gas (LNG) is expanding rapidly with projects being proposed worldwide to meet the industry forecasted growth rate of 12% by the end of the decade. This paper will cover the importance of thermal efficiency in base load LNG liquefaction facilities and delineate the underlying factors as to why it is becoming more important today. Advantages of the use of aeroderivative engines include lower greenhouse gas emissions, enhanced LNG production and the ability to startup without the use of helper motors. This paper presents for the first time, a comprehensive overview of the thermal efficiency considerations for LNG liquefaction plants and the value of the use of aeroderivative engines. Part 2 of this paper covers the world’s first implementation and operational experience of aeroderivative engines in a LNG liquefaction plant.