bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Characterization of Fuel-Air Mixing in a Multi-Hole Tube
Authors: Zhang Chi , Xu Quanhong , Lin Yuzhen , Zhu Jing , Yuan Yixiang , Sung Chih-Jen
Published: May 2012

This paper reports our recent research work on the mixing of fuel and air in a multi-hole tube. The multi-hole tube is an important component used for Lean Premixed Prevaporized (LPP), low emission combustion in a micro gas turbine. A baseline configuration of the multi-hole tube is investigated herein. Mixing characterization experiments are conducted by mapping the distribution of fuel-air ratios at the tube exit with a gas analyzer. Experimental results indicate that the matching of fuel atomization and flow field is the primary factor affecting fuel-air mixture uniformity. Based on the experimental results of the baseline configuration, a systematic and parametric configuration optimization can be then attempted. Experimental results with a modified configuration demonstrate improved mixing uniformity at the tube exit as compared to the baseline configuration, thereby signifying the importance of developing multi-hole tube design rules.
Towards Large-Eddy Simulation of Turbulent Flow in a Centrifugal Impeller
Authors: Medic Gorazd , Feng Jinzhang , Chen Liwei , Sharma Om
Published: May 2012

Large-eddy simulation (LES) using wall-adapting local eddy-viscosity (WALE) subgrid scale model has been applied towards elucidating the complex turbulent flow physics in a centrifugal impeller. Several canonical cases of increased complexity were analyzed to better understand the advantages and challenges of applying the LES framework to the aforementioned target problem. These include turbulent flow in a rotating channel, a straight and a curved duct. Results obtained with LES are compared in detail with two-equation eddy-viscosity Reynolds Averaged Navier-Stokes (RANS) turbulence models widely used in industry, as well as, for some of the canonical cases, with hybrid RANS/LES approaches such as the detached eddy simulation (DES) and scale-adaptive simulation (SAS). Finally, LES has been applied to turbulent flow in NASA CC3 centrifugal impeller with grids of increased resolution (up to 100 million computational cells per passage).
Numerical Analysis of Biomass-Derived Gaseous Fuels Fired in a RQL Micro Gas Turbine Combustion Chamber: Preliminary Results
Authors: Laranci Paolo , Bursi Edoardo , Fantozzi Francesco
Published: May 2012

The economically sustainable availability of biomass residuals and the growing need to reduce carbon dioxide emissions from power generation facilities has driven the development of a series of processes that lead to the production of a variety of biomass-derived fuels gaseous fuels, such as syngas, pyrolysis gas, landfill gas and digester gas. These technologies can find an ideal coupling when used for fuelling micro gas turbines, especially for distributed power generation applications, in a range between 50 and 500 kWE. This paper features a report on numerical activity carried out at the University of Perugia on a 80 kWE micro gas turbine annular combustion chamber, featuring RQL technology, that has been numerically modeled in order to verify combustion requirements, principally in terms of air/fuel ratio and lower heating value, simulating mixtures with varying chemical composition. The use of CFD turbulence and combustion modeling, via both Eddy Break-up and non-adiabatic PPDF methods, allows us to evaluate flame temperatures and stability, NOx and unburnt hydrocarbons emissions, under various load conditions, for the different fuel mixtures taken into account.
Dynamic Simulation of Centrifugal Compressor Startup With Inlet Guide Vane
Authors: Ebisawa Naoto , Fukushima Yasuo , Orikasa Hideaki
Published: May 2012

To achieve safe and efficient operation of centrifugal compressors, understanding the transient behavior of the compression system and reflecting such characteristics into the design of compressors and peripheral equipment early in the plant engineering stage are important. Since such transient states cannot be completely studied by static analysis alone, additional analyses using plant’s dynamic model are desired. To utilize for compressor design and process verification in the engineering phase, a dynamic simulator specialized for compressor systems has been developed. The presented work demonstrates an example of the way the simulator was used for a preparatory investigation of the Mixed Refrigerant (MR) compressor start up in an LNG plant. The simulation results showed that motor acceleration could be successfully accomplished by using the throttled inlet guide vanes (IGVs) for lowering the load torque and that the compressor could generate the required liquefaction pressure at settle out condition.
Effect of Scaling of Blade Row Sectors on the Prediction of Aerodynamic Forcing in a Highly-Loaded Transonic Turbine Stage
Authors: Hosseini Seyed Mohammad , Fruth Florian , Vogt Damian M. , Fransson Torsten H.
Published: May 2012

The viability of a scaling technique in prediction of forced response of the stator and rotor blades in a turbine stage has been examined. Accordingly the so called parameter, generalized force, is defined which describes the excitation of a modeshape due to the unsteady flow forces at a certain frequency. The capability of this method to accurately predict the generalized forces serves as the viability criterion. The scaling technique modifies the geometry to obtain an integer stator, rotor blade count ratio in an annulus section while maintaining steady aerodynamic similarity. A non-scaled configuration is set up to serve as the reference case. Further configurations with different scaling ratios are also generated for accuracy comparison. Unsteady forces are calculated through 3D Navier-Stokes simulations by VolSol, which is based on an explicit, time-marching. A general purpose finite element model of blades is also provided to enable modal analysis with the harmonic forces. The generalized forces of stator and rotor blades revealed high sensitivity towards modification of stator blades while acceptable accuracy was obtained by moderate modifications of the rotor blades for first harmonic forces. Moreover the influence of variable blade’s structural characteristics proved to be remarkable.
Geometry Optimization of Textured 3-D Micro-Thrust Bearings
Authors: Papadopoulos C. I. , Efstathiou E. E. , Nikolakopoulos P. G. , Kaiktsis L.
Published: May 2012

The paper presents an optimization study of the geometry of three-dimensional micro-thrust bearings, in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as microchannels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of single-objective optimization problems at different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings.
Rotordynamic Evaluation of Centrifugal Compressor Using Electromagnetic Exciter
Authors: Takahashi Naohiko , Magara Yohei , Narita Mitsuhiro , Miura Haruo
Published: May 2012

Since heavier gases exert larger effects on rotordynamic stability, stability evaluation is important in developing or designing high-pressure compressors. To evaluate the rotor stability during operation, an excitation test using a magnetic bearing is the most practical method. In stability analysis, labyrinth seals can produce significant cross-coupling forces, which particularly reduce the damping ratio of the first forward mode. Therefore, forward modes should be distinguished from backward modes in the excitation test. One method that excites only the forward modes, not the backward modes (and vice versa), is the use of a rotating excitation. In this method, the force is simultaneously applied to two axes to excite the rotor in circular orbits. Two trigonometric functions, i.e., cosine and sine functions, are used to generate this rotation force. Another method is the use of a unidirectional excitation and a mathematical operation to distinguish the forward whirl from the backward whirl. In this method, a directional frequency response function that separates the two modes in the frequency domain is obtained from four frequency response functions by using a complex number expression for the rotor motion. In this study, the latter method was employed to evaluate the rotor stability of a high-pressure compressor. To obtain the frequencies and damping ratios of the eigenvalues, the curve fitting based on system identification methods, such as the prediction error method, was introduced for the derived frequency response functions. Firstly, these methods were applied to a base evaluation under a low-pressure gas operation, in which the stability mainly depends on the bearing property. Using the obtained results, the bearing coefficients were estimated. Next, the same methods were applied to stability evaluations under high-pressure gas operations. The destabilizing forces were also estimated from the test results and compared with the calculation results.
Performance Simulation of a Hybrid Micro Gas Turbine Fuel Cell System Based on Existing Components
Authors: Bakalis D. P. , Stamatis A. G.
Published: May 2012

The objective of this work is the development of a simulation model for a hybrid Solid Oxide Fuel Cell (SOFC)/Micro Gas Turbine (MGT) system, flexible and robust enough, capable to predict the system performance under various operating conditions. The hybrid system consists of a high temperature SOFC, based on a tubular configuration developed by Siemens Power Generation Inc, and a recuperated small gas turbine (GT) validated using data for the Capstone C30. The design and off-design performance of the system is examined by means of performance maps. Moreover, operating parameters such as fuel utilization factor, steam to carbon ratio and current density are varied over a wide range and the influence on system performance is studied. The optimum operating conditions are discussed with regard to overall system performance under part load operation. The results show that high electrical efficiencies can be achieved making these systems appropriate for distributed generation applications.
Time Resolved Measurements in the Durham Cascade
Authors: Fo¨rster Felix , Sims-Williams David , Ingram Grant , Dominy Robert
Published: May 2012

This paper describes investigations into unsteady flow phenomena in a high turning linear cascade with a nominal steady flow. Traditionally time averaged instrumentation is used in such a cascade. Detailed intermittency readings were taken inside the cascade using hot wires to highlight the detailed flow interactions of the passage vortex and the blade suction surface. A new fast response five hole probe was built and tested against a hot-wire. Time-accurate measurements taken using this probe allowed an evaluation of the error made by using a probe with limited frequency response for the cascade measurements. This evaluation showed significant deviations in loss for regions of high unsteadiness, for instance the passage vortex. The Reynolds stress tensor was measured at 101%, 115% and 128% axial chord and the deformation work was calculated for 126% axial chord. The deformation work shows regions of negative values and positive values. While negative values are associated with a production of turbulent k.e. from the mean kinetic energy, positive values may represent a gain of kinetic energy from the turbulence.
Stall Warning by Blade Pressure Signature Analysis
Authors: Young Anna , Day Ivor , Pullan Graham
Published: May 2012

At low mass flow rates axial compressors suffer from flow instabilities leading to stall and surge. The inception process of these instabilities has been widely researched in the past — primarily with the aim of predicting or averting stall onset. In recent times, attention has shifted to conditions well before stall and has focussed on the level of irregularity in the blade passing signature in the rotor tip region. In general, this irregularity increases in intensity as the flow rate through the compressor is reduced. Attempts have been made to develop stall warning/avoidance procedures based on the level of the flow irregularity, but little effort has been made to characterise the irregularity, or to understand its underlying causes. Work on this project has revealed for the first time that the increase in irregularity in the blade passing signature is highly dependent on both tip-clearance and eccentricity. In a compressor with small, uniform, tip-clearance, the increase in blade passing irregularity which accompanies a reduction in flow rate will be modest. If the tip-clearance is enlarged, however, there will be a sharp rise in irregularity at all circumferential locations. In a compressor with eccentric tip-clearance, the increase in irregularity will only occur in the part of the annulus where the tip-clearance is largest, regardless of the average clearance level. In this paper, some attention is also given to the question of whether this irregularity observed in the pre-stall flow field is due to random turbulence, or to some form of coherent flow structure. Detailed flow measurements reveal that the latter is the case. From these findings, it is clear that a stall warning system based on blade passing signature irregularity will not be viable in an aero-engine where tip-clearance size and eccentricity change during each flight cycle and over the life of the compressor.
A Hybrid EKF-Fuzzy Approach to Fault Detection and Isolation of Industrial Gas Turbines
Authors: Salar Amin , Sedigh Ali Khaki , Hosseini SeyedMehrdad , Khaledi Hiwa
Published: May 2012

Based on the Gas Path Analysis (GPA) method, nonlinear estimation and fuzzy classification theories, a comprehensive fault diagnosis system has been developed for an industrial Gas Turbine (GT). The hybrid method consists of two parts, in the first part noisy sensor output changes are translated to changes in the health parameters using an Extended Kalman Filter (EKF). In the second part the outputs of the EKF are used as the inputs of a fuzzy system. This system can isolate and evaluate the physical faults based on the predetermined rules obtained mostly from experimental data and aerothermodynamical simulations. The ratios of changes in different health parameters due to different faults and also the areas in the compressor most affected by these faults are the key factors for developing the rules. The Fuzzy Inference System (FIS) gives the fault locations in the compressor or turbine. Also, operator-friendly suggestions for the time of the compressor washing or components repair are provided. This leads to a hybrid fault detection and isolation solution for the GT, and with pre-filtering the data before use as input of fuzzy inference system, the accuracy of the fault diagnosis system is improved. Nonlinear simulation, estimation and classification results are provided to show the effectiveness of the proposed methodology.
The Effects of Blade Loading on Trailing Edge Vortex Formation on a Highly Loaded Stator Upstream of a Transonic Rotor
Authors: Clark Kenneth P. , Gorrell Steven E.
Published: May 2012

Multiple high-fidelity time-accurate computational fluid dynamics simulations were performed to investigate the effects of upstream stator loading and rotor shock strength on vortex shedding characteristics in a single stage transonic compressor. Three loadings on the upstream stator row of decreased, nominal, and increased were studied. The time-accurate URANS code TURBO was used to generate periodic, quarter annulus simulations of the Blade Row Interaction compressor rig. It was observed that vortex shedding was synchronized to the passing of a rotor bow shock. Results show that vortex size and strength increase with stator loading. “Normal” and “large” shock-induced vortices formed on the stator trailing edge immediately after the shock passing, but the “large” vortices were strengthened at the trailing edge due to a low velocity region at the suction surface. This low velocity region was generated upstream on the suction surface from a shock-induced thickening of the boundary layer or separation bubble. The circulation of the “large” vortices was greater than the “normal” vortices by a factor of 1.7, 1.9 and 2.1 for decreased, nominal and increased deswirler loadings. At decreased loading only 24% of the measured vortices were considered “large” while at nominal loading 58% were “large”. An understanding of the unsteady interactions associated with blade loading and rotor shock strength in transonic stages will help compressor designers account for unsteady flow physics at design and off-design operating conditions.
Pressure Side and Cutback Trailing Edge Film Cooling in a Linear Nozzle Vane Cascade at Different Mach Numbers
Authors: Barigozzi Giovanna , Perdichizzi Antonio , Ravelli Silvia
Published: May 2012

Tests on a specific designed linear nozzle guide vane cascade with trailing edge coolant ejection were carried out to investigate the influence of trailing edge bleeding on both aerodynamic and thermal performance. The cascade is composed of six vanes with a profile typical of a high pressure turbine stage. The trailing edge cooling features a pressure side cutback with film cooling slots, stiffened by evenly spaced ribs in an inline configuration. Cooling air is ejected not only through the slots but also through two rows of cooling holes placed on the pressure side, upstream of the cutback. The cascade was tested for different isentropic exit Mach numbers, ranging from M2is = 0.2 to M2is = 0.6, while varying the coolant to mainstream mass flow ratio MFR up to 2.8%. The momentum boundary layer behavior at a location close to the trailing edge, on the pressure side, was assessed by means of Laser Doppler measurements. Cases with and without coolant ejection allowed to identify the contribution of the coolant to the off the wall velocity profile. Thermochromic Liquid Crystals (TLC) were used to map adiabatic film cooling effectiveness on the pressure side cooled region. As expected, the cutback effect on cooling effectiveness, compared to the other cooling rows, was dominant.
Analysis of the Effects of Parallel and Angular Misalignment in Hyperstatic Rotors Equipped With Oil-Film Bearings
Authors: Pennacchi P. , Vania A. , Chatterton S.
Published: May 2012

Misalignment is one of the most common sources of trouble of rotating machinery having couplings between the shafts. Ideal alignment is a chimera and the coupling flanges of the shafts are never ideally aligned, presenting angular and/or parallel misalignment (defined also as radial misalignment or offset). In particular, during the shaft rotation, if coupling misalignment between the shafts of a statically aligned line is excessive, a periodical change, of the load on the bearings in hyperstatic shaft-lines, occurs. If the rotating machine is equipped with oil-film bearings, the change of the loads on the bearings causes also the variation of their oil-film dynamic characteristics, i.e. damping and stiffness, and the complete system cannot be considered as linear. In the paper, this phenomenon is modelled accurately and analyzed by considering the simulated response of a misaligned rotor train in the time domain. A finite element model is used for the hyperstatic rotor, while bearing characteristics are calculated by integrating Reynolds equation (considering the actual type and dimensions of the bearings) as a function of the instantaneous load acting on the bearings, caused by the coupling misalignment. Nonlinear effects are highlighted and the spectral components of system response are analyzed, in order to give pertinent diagnostic information.
Numerical Investigation of a Single Circumferential Groove Casing Treatment on Three Different Compressor Rotors
Authors: Heinichen F. , Gu¨mmer V. , Schiffer H.-P.
Published: May 2012

In axial compressors, casing treatments represent a passive method to increase the working range without the need to modify the blade geometry. The majority of the open literature on the topic considers one or several casing treatment variants on the same compressor. The question how one casing treatment and its basic mechanisms can be transferred to a different compressor is only covered in a small number of publications. This paper tries to fill this gap by applying a single circumferential groove type casing treatment to three different transonic compressor rotors. It is demonstrated numerically that the casing treatment is able to improve the aerodynamic performance of all three rotors. Detailed investigation of the flow field near the rotor tip shows that the single circumferential groove works by influencing the interaction between the tip clearance vortex and the shock. Hence, this type of casing treatment can be generalized to transonic rotors with a stall mechanism that is based on tip clearance vortex-shock interaction.
Investigation of Calculated Turbulence Parameters for Use in Hybrid Broadband Fan Noise Calculations
Authors: Maunus Jeremy , Grace Sheryl M. , Sondak Douglas L. , Yakhot Victor
Published: May 2012

The ability to predict the broadband noise due to fluid-structure interaction in the fan-stage of a turbofan engine could enhance engine design. Currently, fully computational hybrid schemes for coupling RANS flow simulations and linearized Euler acoustic simulations offer a potential broadband noise prediction methodology. The success of the hybrid method depends partly on the ability of RANS to accurately predict the turbulent kinetic energy and the integral length scale. The impact of the accuracy of a RANS simulation on the broadband noise prediction is explored. NASAs Source Diagnostic Test (SDT), a 1/5th scale model representation of the bypass stage of a turbofan engine provides the basis for the computations and validations. The RSI (rotor-stator interaction) code is utilized to compute the fan exit guide vane response and exhaust noise due to the interaction with inflow turbulence. The experimental data for the baseline vane SDT case at the approach condition are analyzed using structure functions to obtain the turbulent kinetic energy, dissipation rate, and integral length scale. These results are compared to the solutions provided by four proprietary CFD codes that employ two-equation turbulence models. The CFD simulations are shown to predict the turbulent kinetic energy well, over-predict mean dissipation rate, and capture the integral length scale moderately well. The broadband exhaust noise computed with RSI based on input derived from the various CFD simulations differ and it is shown that the differences are most strongly dependent upon the variation in the estimation of the integral length scale.
Modeling of the Dynamic Response of a Pelton Turbine Hydroelectric Plant
Authors: Pennacchi P. , Chatterton S. , Vania A.
Published: May 2012

The paper presents a detailed numerical model of the dynamics of a Pelton turbine installed in a hydroelectric plant. The model considers in detail the Pelton turbine with all the electromechanical subsystems, such as the main speed governor, the controller and the servoactuator of the turbine nozzle, and the electric generator. In particular it reproduces the effects of pipe elasticity in the penstock, the water inertia and the water compressibility on the turbine behaviour. The dynamics of the surge tank on low frequency pressure waves is also modeled together with the main governor speed loop and the position controllers of the nozzle needle actuators and of the hydraulic electrovalve. Model validation has been made by means of experimental data acquired during some starting tests after a partial revamping of a hydroelectric unit, which involved also the control system of the hydraulic actuators but not the nozzles. The model is used in order to identify the cause of the oscillations of the electric power mainly ascribed to the backlash of the nozzle needle system.
Qualification Testing of a Liquid CO2 Turbopump for Carbon Capture and Sequestration Applications
Authors: Moore J. Jeffrey , Delgado Hector , Allison Timothy
Published: May 2012

In order to reduce the amount of carbon dioxide (CO2) greenhouse gases released into the atmosphere, significant progress has been made in developing technology to sequester CO2 from power plants and other major producers of greenhouse gas emissions. The compression of the captured carbon dioxide stream requires a sizeable amount of power, which impacts plant availability, capital expenditures and operational cost. Preliminary analysis has estimated that the CO2 compression process reduces the plant efficiency by 8% to 12% for a typical power plant. The goal of the present research is to reduce this penalty through development of novel compression and pumping processes. The research supports the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) objectives of reducing the energy requirements for carbon capture and sequestration in electrical power production. The primary objective of this study is to boost the pressure of CO2 to pipeline pressures with the minimal amount of energy required. Previous thermodynamic analysis identified optimum processes for pressure rise in both liquid and gaseous states. At elevated pressures, CO2 assumes a liquid state at moderate temperatures. This liquefaction can be achieved through commercially available refrigeration schemes. However, liquid CO2 turbopumps of the size and pressure needed for a typical power plant were not available. This paper describes the design, construction, and qualification testing of a 150 bar cryogenic turbopump. Unique characteristics of liquid CO2 will be discussed.
Massively-Parallel DNS and LES of Turbine Vane Endwall Horseshoe Vortex Dynamics and Heat Transfer
Authors: Schwa¨nen Markus , Meador Michael , Camp Josh , Jagannathan Shriram , Duggleby Andrew
Published: May 2012

Higher turbine inlet temperatures enable increased gas turbine efficiency but significantly reduce component lifetimes through melting of the blade and endwall surfaces. This melting is exacerbated by the horseshoe vortex that forms as the boundary layer stagnates in front of the blade, driving hot gasses to the surface. Furthermore, this vortex exhibits significant dynamical motions that increase the surface heat transfer above that of a stationary vortex. To further understand this heat transfer augmentation, the dynamics of the horseshoe vortex must be characterized in a 3D time-resolved fashion which is difficult to obtain experimentally. In this paper, a 1st stage high pressure stator passage is examined using a spectral element direct numerical simulation at a Reynolds number Re = U∞C/v = 10,000. Although the Re is lower than engine conditions, the vortex already exhibits similar strong aperiodic motions and any uncertainty due to sub-grid scale modeling is avoided. The vortex dynamics are analyzed and their impact on the surface heat transfer is characterized. Results from a baseline case with a smooth endwall are also compared to a passage with film cooling holes. Higher Reynolds number simulations require a Large Eddy Simulation turbulent viscosity model that can handle the high accelerations around the blade. A high-pass-filter sub-grid scale model is tested at the same low Reynolds number to test its effectiveness by direct comparisons to the DNS. This resulted in a significant drop in turbulence intensity due to the high strain rate in the freestream, resulting in different dynamics of the vortex than observed in the DNS. Appropriate upstream engine conditions of high freestream turbulence and large integral length scales for all cases are generated via a novel inflow turbulence development domain using a periodic solution of Taylor vortices that are convected over a square grid. The size of the vortices and grid spacing is used to control the integral length scale, and the intensity of the vortices and upstream distance is used to control the turbulence intensity. The baseline DNS exhibits a bi-modal horseshoe vortex, and the presence of cooling-holes qualitatively increases the number of vortex cores resulting in more complex interactions.
Influence of Unsteady Wake With Trailing Edge Coolant Ejection on Turbine Blade Film Cooling
Authors: Li Shiou-Jiuan , Rallabandi Akhilesh P. , Han Je-Chin
Published: May 2012

Detailed film cooling effectiveness distributions along a modeled turbine rotor blade under combined effects of upstream trailing edge unsteady wake with coolant ejection are presented using the pressure sensitive paint (PSP) mass transfer analogy method. The experiment is conducted in a low speed wind tunnel facility with a five blade linear cascade. The exit Reynolds number based on the axial chord is 370,000. Unsteady wakes and trailing edge coolant jets are produced by a spoked wheel-type wake generator with hollow rods equipped with several coolant ejections from holes. The coolant-to-mainstream density ratios for both blade and trailing edge coolant ejection range from 1.5 to 2.0 for simulating realistic engine conditions. Blade blowing ratios studied are 0.5 and 1.0 on Suction surface and 1.0 and 2.0 on Pressure surface. Trailing edge jet blowing ratio and Strouhal number are 1.0 and 0.12, respectively. Results show the unsteady wake reduces overall film cooling effectiveness. However, the unsteady wake with trailing edge coolant ejection enhances overall effectiveness. Results also show that the overall filming cooling effectiveness increases by using heavier coolant for trailing edge ejection as well as for blade surface film cooling.
Ultra-Low Emission Hydrogen/Syngas Combustion With a 1.3 MW Injector Using a Micro-Mixing Lean-Premix System
Authors: Hollon Brian , Steinthorsson Erlendur , Mansour Adel , McDonell Vincent , Lee Howard
Published: May 2012

This paper discusses the development and testing of a full-scale micro-mixing lean-premix injector for hydrogen and syngas fuels that demonstrated ultra-low emissions and stable operation without flashback for high-hydrogen fuels at representative full-scale operating conditions. The injector was fabricated using Macrolamination technology, which is a process by which injectors are manufactured from bonded layers. The injector utilizes sixteen micro-mixing cups for effective and rapid mixing of fuel and air in a compact package. The full scale injector is rated at 1.3 MWth when operating on natural gas at 12.4 bar (180 psi) combustor pressure. The injector operated without flash back on fuel mixtures ranging from 100% natural gas to 100% hydrogen and emissions were shown to be insensitive to operating pressure. Ultra-low NOx emissions of 3 ppm were achieved at a flame temperature of 1750 K (2690 °F) using a fuel mixture containing 50% hydrogen and 50% natural gas by volume with 40% nitrogen dilution added to the fuel stream. NOx emissions of 1.5 ppm were demonstrated at a flame temperature over 1680 K (2564 °F) using the same fuel mixture with only 10% nitrogen dilution, and NOx emissions of 3.5 ppm were demonstrated at a flame temperature of 1730 K (2650 °F) with only 10% carbon dioxide dilution. Finally, using 100% hydrogen with 30% carbon dioxide dilution, 3.6 ppm NOx emissions were demonstrated at a flame temperature over 1600 K (2420 °F). Superior operability was achieved with the injector operating at temperatures below 1470 K (2186 °F) on a fuel mixture containing 87% hydrogen and 13% natural gas. The tests validated the micro-mixing fuel injector technology and the injectors show great promise for use in future gas turbine engines operating on hydrogen, syngas or other fuel mixtures of various compositions.
Multi-Blade Row Interactions in a Low Pressure Ratio Centrifugal Compressor Stage With a Vaned Diffuser
Authors: Ramakrishnan Kishore , Richards Simon K. , Moyroud Franc¸ois , Michelassi Vittorio
Published: May 2012

Previous experimental and CFD investigation of a GE Oil and Gas centrifugal compressor stage with a vaneless diffuser revealed a complex excitation mechanism caused by an aero-acoustic interaction between three blade rows. In stages with vaned diffusers, additional sources of aeromechanical excitation on the impeller can be expected. This unsteady CFD investigation is a follow-up from the previous vaneless diffuser study to identify any additional sources of excitation that arise in the presence of a vaned diffuser in preparation for aeromechanic tests to be conducted later. The study confirms that excitation from impeller-diffuser interaction generated acoustic modes can dominate the potential field excitation from the diffuser vanes. In addition, a significant aero-acoustic excitation to the impeller at a vane pass frequency corresponding to the sum of the vane counts in the two downstream vane rows is observed, and its origination is discussed. The latter excitation is different from that observed in the vaneless diffuser stage where the vane pass frequency observed by the impeller corresponds to the sum of the vane counts in the upstream and downstream vane rows.
ICR350: A Turbine Solution for Medium and Heavy Duty Vehicles
Authors: Dewis David W.
Published: May 2012

This paper briefly reviews automotive gas turbine history, examines the factors that influence engine selection, and introduces the ICR350 intercooled-recuperated gas turbine, an engine designed for Medium and Heavy Duty Vehicles, (MHDV). After turbines successfully displaced reciprocating engines from aircraft in the 1950’s, it was widely believed that they would rapidly penetrate the vehicular market. With the promise of low cost and simplicity all major automotive companies had aggressive turbine programs. But what began as a sprint became a marathon. Of the many that started, just a few managed to reach the finish line, only to be defeated by revised emissions legislation and the unforeseen energy crisis. The DOE continued funding automotive turbine development and transitioned from mechanical to hybrid drivetrain solutions. Ultimately, and somewhat serendipitously, microturbines were developed from range extender engines conceived as battery chargers in the Hybrid Vehicle program. Most recently, the Advanced Microturbine Systems program, AMTS, is responsible for technologies leveraged in ICRTec’s next generation vehicular turbine. Today battery technology has advanced sufficiently for low daily use vehicles and collection or delivery vehicles with regenerative braking. With its low power density, this same technology does not work for MHDV’s, a sector dominated by diesel engines. Emissions compliance is placing heavy cost and performance penalties on incumbent diesel engines, and the recently proposed MHDV efficiency legislation will only exacerbate the situation. After 40 years it appears that externalities, coupled with advances in turbomachinery, now favor a gas turbine solution.
CFD Analyses of HPT Blade Air Delivery System With and Without Impellers
Authors: Wu Charles , Vaisman Boris , McCusker Kevin
Published: May 2012

In the design of a HPT blade cooling air delivery system, sufficient supply pressure is required to guarantee HPT blades are working properly in the high temperature environment. A design goal is to set a pressure level at the blade inlet that will prevent the ingestion of gaspath air into the blades which is caused by pressure fluctuations under various operating conditions and other uncertainties. Traditional 1-D design tools are not sophisticated enough for detailed system analysis. Therefore, CFD (Computational Fluid Dynamics) analysis was utilized for designing HPT blade cooling air delivery system to guarantee meeting the supply pressure requirement. Two HPT blade air delivery systems were explored. The baseline is a cooling air delivery system without radial impellers. It provides a simplistic design at low manufacturing cost, however CFD analysis shows that the system has a larger pressure loss at the broach slot entrance and delivers low supply pressure. The alternative is a cooling air delivery system with radial impellers. CFD analysis shows that the system with impellers results in much better aerodynamic performance at the broach slots and provides high supply pressure, but comes with the price of high manufacturing cost and lower TSFC due to the parasitic drag induced by impellers. For the alternative approach, three high solidity impeller designs were analyzed. The alternative approaches analyzed had inlet angles of 0°, 30°, 90° and exit angles of 0°, respectively. Comparisons of detailed aerodynamic performance are presented in the paper. CFD simulation reveals that the source of pressure loss without impellers is caused by mismatch of the swirl ratio at broach slot entrance. CFD results show that a system with radial impellers produces a better matched swirl ratio at broach slot entrance. Radial impellers enhance aerodynamic performance and improve pressure distribution within broach slots.
Modeling and Control System Design of a Marine Condensing System
Authors: Sun Zhixin , Wang Jiangfeng , Dai Yiping , Xie Danmei
Published: May 2012

Rapid and frequent load changes bring a number of challenges to the control system of a marine condenser. However, few studies have been published in this area. In this paper, a whole condensing system, which includes condenser, ejector, cooling water pump and its driving turbine, was modeled based on three conservation laws. Propulsion steam turbine was also modeled to simulate the load changes. A proportional integral (PI) controller was developed to regulate the condenser pressure. Opening signal of the governing valve of the propulsion turbine was added to the controller as a feed forward signal, and to improve the performance further, fuzzy algorithm was adopted to tune the gains of PI controller. Numerical experiments were conducted to study the dynamic behavior and the control performance of the condensing system. The simulation results show that employing the valve opening signal of main turbine as feed forward signal and tuning the gains of conventional PI controller by fuzzy logic are both effectual approaches to enhance the control performance. The former is good at reducing maximum overshooting while the latter is good at decreasing settling time. The combination of these two methods can improve the performance of simple PI controller further.
Heat Transfer Characteristics of a Non-Rotating Two-Pass Rectangular Duct With Various Guide Vanes in the Tip Turn Region
Authors: Lee Dong Myeong , Park Jun Su , Lee Dong Hyun , Kim Beom Soo , Cho Hyung Hee
Published: May 2012

The present study investigated convective heat transfer inside a two-pass rectangular duct with guide vanes in the turning region. The objective was to determine the effect of the guide vanes on blade tip cooling. The duct had a hydraulic diameter (Dh) of 26.67 mm and an aspect ratio (AR) of 5. The duct inlet width was 80 mm, and the distance between the tip of the divider and the tip wall of the duct was also 80 mm. Various guide vane configurations were used in the turning region. The Reynolds number (Re), based on the hydraulic diameter, was held constant at 10,000. The naphthalene sublimation technique was used to determine the detailed local heat transfer coefficients, using the heat and mass transfer analogy. The results indicated that guide vanes in the turning region enhanced heat transfer in the blade tip region. The guide vane on the second-pass side of the turning region had higher heat transfer than the guide vane on the first-pass side. Strong secondary flow enhanced heat transfer in the blade tip region. Dean vortices induced by the guide vanes pushed the high-momentum core flow towards the tip wall, and heat transfer was increased in the turning region, but decreased in the second passage. Consequently, a guide vane on the second-pass side of the turning region generates high heat transfer rates on the tip surface, and can also increase the thermal performance factor in a two-pass duct.
Dynamic Characteristics of Dry Friction Damping at Bladed Disk Joints: Experiments
Authors: Hong Jie , Chen Lulu , Ma Yanhong , Zhang Dayi
Published: May 2012

An experimental system was designed to measure dynamic responses of non-rotating blade, in which the similar stress and strain fields can be recreated similar to a blade which is fixed to its disk by means of dovetail. During the experiments, the beam was subject to different tensile loads and excitation forces. The dynamic response was measured while the beam was vibrating as various modes. The effects of tensile load, excitation load and contact condition at bladed disk joints on the resonance frequency and resonance response level were analyzed from the test results. These results could be used to explain the measured dynamical response in view of the behavior at the interface.
A Quantitative Comparison Between a Low Order Model and a 3D FEM Code for the Study of Thermoacoustic Combustion Instabilities
Authors: Campa Giovanni , Camporeale Sergio Mario , Guaus Anai¨s , Favier Julien , Bargiacchi Matteo , Bottaro Alessandro , Cosatto Ezio , Mori Giulio
Published: May 2012

The study of thermoacoustic combustion instabilities has an important role for safety operation in modern gas turbines equipped with lean premixed dry low emission combustion systems. Gas turbine manufacturers often adopt simulation tools based on low order models for predicting the phenomenon of humming. These simulation codes provide fast responses and good physical insight, but only one-dimensional or two-dimensional simplified schemes can be generally examined. The finite element method can overcome such limitations, because it allows to examine three-dimensional geometries and to search the complex eigenfrequencies of the system. Large Eddy Simulation (LES) techniques are proposed in order to investigate the instability phenomenon, matching pressure fluctuations with turbulent combustion phenomena to study thermoacoustic combustion oscillations, even if they require large numerical resources. The finite element approach solves numerically the Helmholtz equation problem converted in a complex eigenvalue problem in the frequency domain. Complex eigenvalues of the system allow us to identify the complex eigenfrequencies of the combustion system analyzed, so that we can have a valid indication of the frequencies at which thermoacoustic instabilities are expected and of the growth rate of the pressure oscillations at the onset of instability. Through the collaboration among Ansaldo Energia, University of Genoa and Polytechnic University of Bari, a quantitative comparison between a low order model, called LOMTI, and the three-dimensional finite element method has been examined, in order to exploit the advantages of both the methodologies.
Experimental and Modelling Studies of the Oxidation of Surrogate Bio-Aviation Fuels
Authors: Shafagh Ida , Hughes Kevin J. , Catalanotti Elena , Liu Zhen , Pourkashanian Mohamed , Wilson Chris W.
Published: May 2012

Jet fuels currently in use in the aviation industry are exclusively kerosene-based. However, potential problems regarding security of supply, climate change and increasing cost are becoming more significant, exacerbated by the rapidly growing demand from the aviation sector. Biofuels are considered one of the most suitable alternatives to petrochemical-based fuels in the aviation industry in the short to medium term, since blends of biofuel and kerosene provide a good balance of properties currently required from an aviation fuel. Experimental studies at a variety of stoichiometries using a flat flame burner with kerosene and kerosene/biofuel blends have been performed with product analysis by gas sampling and laser induced fluorescence detection of OH, CO and CO2. These studies have been complemented by modelling using the PREMIX module of Chemkin to provide insights into and to validate combined models describing the oxidation chemistry of surrogate fuels depicting kerosene, fatty acid methyl ester biofuels and Fischer-Tropsch derived fuels. Sensitivity analysis has identified important reactions within these schemes which where appropriate have been investigated by molecular modelling techniques available within GAUSSIAN 03.
A Competitive Market Approach to Gas Turbine Technology Portfolio Selection
Authors: Justin Cedric Y. , Briceno Simon I. , Mavris Dimitri N. , Villeneuve Frederic
Published: May 2012

Heavy duty gas turbine developments are major endeavors which use significant resource for development. Optimization of the technology portfolio is critical to yield a competitive product-line which is robust enough to compete in a dynamic market where vantage positions bring large profits but quickly erode over time. The current research addresses some of these challenges by proposing a transparent and integrated method aimed at investigating technology portfolio selection for future gas turbine-based power plants. The value-driven methodology analyzes technology investments, and is the foundation for a strategic decision framework that facilitates the formulation of robust and competitive technology portfolio solutions. A three-step process is proposed in this paper. A market response analysis is first carried out to estimate market penetration. A technology impact and readiness level analysis is performed next and augmented with a portfolio optimization. Finally, “what-if” scenarios are investigated to assess the robustness of selected technology portfolio candidates against a set of market conditions.
Combined Cycle Inlet Air Cooling by Cold Thermal Storage: Aeroderivative vs. Heavy Duty GT Comparison
Authors: Barigozzi G. , Palestra N. , Perdichizzi A. , Salvitti G.
Published: May 2012

An assessment of energetic performance achievable by GT inlet air cooling through cold thermal storage is presented. Results have been obtained by a numerical code specifically developed to model the whole system behavior all over a year. Some cases with hot climatic condition have been compared and discussed in order to enlighten performance differences due to GT characteristics and possible enhancement strategies for different configurations. An existing 127 MWe combined cycle power plant with a twin GT configuration was assumed as a reference case. Two heavy-duty units with different technology levels have been compared with an advanced aero-derivative model, in the range of 40 MW power output. Aero-derivative unit provided a much better performance than the more advanced heavy-duty model; this was strictly related to the higher sensitivity to inlet air temperature of the aero derivative unit. The comparison between the two heavy-duty GTs has clearly shown that a high specific power is needed to obtain cost-effective solutions for inlet air cooling systems. The analysis for the considered GT units was then extended also to a plant configuration including an inlet air supercharging system. The boost fan head has been selected in order to only compensate all inlet pressure losses, i.e. inlet duct, filters and air coils pressure drops.