bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow and Thermal Field Measurements in a Combustor Simulator Relevant to a Gas Turbine Aero-Engine
Authors: Vakil S. S. , Thole K. A.
Published: February 2009

The current demands for high performance gas turbine engines can be reached by raising combustion temperatures to increase power output. Predicting the performance of a combustor is quite challenging, particularly the turbulence levels that are generated as a result of injection from high momentum dilution jets. Prior to predicting reactions in a combustor, it is imperative that these turbulence levels can be accurately predicted. The measurements presented in this paper are of flow and thermal fields produced in a large-scale combustor simulator, which is representative of an aero-engine. Three-component laser Doppler velocimeter measurements were made to quantify the velocity field while a rake of thermocouples was used to quantify the thermal field. The results indicate large penetration depths for the high momentum dilution jets, which result in a highly turbulent flow field. As these dilution jets interact with the mainstream flow, kidney shaped thermal fields result due to counter-rotating vortices that develop.
Measurements and Prediction of Free-Stream Turbulence and Pressure-Gradient Effects on Attached-Flow Boundary-Layer Transition
Authors: Roberts S. K. , Yaras M. I.
Published: February 2009

This paper presents measurements of free-stream turbulence, streamwise pressure gradients and flow Reynolds number effects on attached-flow transition. The measurements were performed on a flat plate, at free-stream turbulence intensities ranging from 0.5% to 9.0%, four Reynolds numbers, and several streamwise pressure distributions, including ones that are typical of the suction side pressures of axial turbine blades. Based on the results, the extent of upstream movement of transition location with free-stream turbulence, the changes in transition length with variations in the streamwise pressure gradients, and the sensitivity of these trends to flow Reynolds number are quantified. Interpretation of the measurements is based primarily on streamwise and cross-stream intermittency distributions extracted from the velocity traces of hot-wire traverses. The measured transition inception locations and transition lengths are used to evaluate mathematical models available in the published literature. A modification is proposed to a transition length model to improve the prediction of the streamwise intermittency distribution.
An Experimental and Theoretical Study of Brush Seal and Shaft Thermal Interaction
Authors: Owen Andrew K. , Jones Terry V. , Guo S. M. , Hogg Simon
Published: February 2009

This paper presents a detailed experimental study and theoretical analysis of the thermal interactions of brush seal, shaft and airflow. The tests were performed in the Oxford University Brush Seal Test Facility. The facility, which was originally designed for the brush seal aerodynamic study, has been enhanced for thermal measurements. A variety of brush seals, typically applicable to aero and power generation gas and steam turbines, have been tested. The thermal interaction caused by changes in rotor and housing alignment was also studied. In the tests, in addition to the conventional aerodynamic parameters, such as the pressure, mass flow and torque, the temperatures of the rotor were measured and heat generated in the bristle/rotor contact were deduced using the finite element analysis. A theoretical analysis of the system was developed which predicts the heat transfer to the airflow from the bristle pack. This analysis is used to give a correlation to predict heat input to the rotor. The study provides valuable design information for the use of brush seals.
Biomass Gasification Combined Cycle Opportunities Using the Future Energy SilvaGas® Gasifier Coupled to Alstom’s Industrial Gas Turbines
Authors: Paisley Mark A. , Welch Mike J.
Published: February 2009

The last two decades have seen a rapid increase in the use of land based gas turbines. To a large extent, this use has been a result of the availability of natural gas at low prices which has in turn facilitated the development of high efficiency low-cost turbines designed to utilize this high value, clean energy source. Recent fluctuations in fuel prices, however, have rekindled interest in alternatives to these natural gas based systems. Transforming solid fuels such as biomass into gas so that they can substitute for natural gas provides the opportunity to enhance the efficiency of biomass based power systems by allowing the solid fuels to be used in high efficiency power generation cycles such as Integrated Gasification Combined Cycle (IGCC) processes. This paper discusses the use of Future Energy Resources’s (FERCO’s) SilvaGas® biomass gasification process as the key element in an advanced biomass power system based integrated with Alstom’s small industrial gas turbines in an advanced gas turbine combined cycle system. Operating experience with the SilvaGas process at commercial scale is discussed along with projected IGCC process efficiencies utilizing a range of biomass materials.
Advanced Technology Biomass-Fueled Combined Cycle
Authors: Liscinsky D. S. , Sangiovanni J. J. , Robson R. L. , Tuthill R. S. , Foyt A. G. , Swanson M.
Published: February 2009

Under the sponsorship of the U.S. Department of Energy/National Energy Technology Laboratory, a multidisciplinary team led by the United Technologies Research Center (UTRC) has identified a high performance biomass gasification/combined cycle system using Refuse Derived Fuel (RDF) as the major fuel resource. The system consists of fuel receiving/preparation/feed, advanced transport gasifier, high temperature gas cleanup and Pratt & Whitney Power Systems FT8 aero-derivative gas turbine with heat recovery steam generator and steam turbine. One of the team members, Connecticut Resource Recovery Agency (CRRA), currently processes approximately 2200 tons/day of municipal solid waste and delivers 1825 tons/day of RDF “across the fence” to a nominal 65 MWe steam plant. Based on the characteristics of the RDF from this plant, an 80 MWe combined cycle system having an estimated efficiency of 45% (RDF in/kW out) was identified. Other advanced cycle variations had even greater performance potential. The resulting cost of electricity for the biomass integrated gasification combined cycle (BIGCC) is competitive with that of natural gas fueled combined cycles, and the plant is projected to meet or exceed all environmental requirements.
Micro Humid Air Cycle: Part A — Thermodynamic and Technical Aspects
Authors: Parente J. , Traverso A. , Massardo A. F.
Published: February 2009

With the increasing interest in distributed power and heat generation, microturbines (mGT) have come to play an important role in small-size energy plants as the most competitive alternative to piston engines, due to their low environmental impact and reduced O&M costs. The Humid Air Turbine (HAT), which has received special attention over the last ten years, can be exploited to enhance thermal efficiency for power generation, although it is still not able to provide more than 30% efficiency for a regenerated cycle. For this reason a micro HAT cycle seems to offer an interesting way to significantly increase thermal efficiency and specific work and easily reduce NOx emissions. This paper presents a general thermodynamic assessment of a micro Humid Air cycle (mHAT), in the range of 100–500 kWe, with cycle optimisation, and a preliminary attempt to integrate existing microturbines and the humid air cycle: the results show that a remarkable increase in efficiency (up to 3–5 percentage points) and specific work (up to 50–70%) can be achieved without any major re-design of the machine, with the exception of the combustion chamber. Moreover, the detailed analysis and design of the saturation tower demonstrates its compactness, one of the overriding requirements for a system for distributed power generation.
Aerodesign and Testing of an Aero-Mechanically Highly Loaded LP Turbine
Authors: Malzacher F. J. , Gier J. , Lippl F.
Published: February 2009

Future turbo systems for aircraft engines need very compact geometry, low weight and high efficiency components. The geared turbofan enables the engine designer to decouple the speed of the fan and the LP turbine to combine a low speed fan with a high speed LP turbine. The low pressure turbine is a key component for this concept. The technological challenge is very much driven by the very high low-spool speed. Resulting from also high inlet temperatures the LP turbine needs cooling of the first stage. A new MTU LPT concept for such a high speed turbine has been developed and tested in a turbine rig. The concept consists of a 2 stage turbine for extremely high speed and high stage pressure ratio (ER 2.3). This leads to extra high mechanical loading and an exotic combination of high Mach Numbers (transonic) and very low Reynolds Numbers. In this paper some design features are described. Some elements of the airfoil design were also tested in additional cascade tests. The 2 stage turbine was tested at the Altitude Test Facility of the ILA, Stuttgart. The test setup is described including details of the instrumentation. Test data shows a good turbine performance. Measurements are also compared to 3D CFD, which is used to analyse local effects.
Experimental and Numerical Study of Stall Flutter in a Transonic Low-Aspect Ratio Fan Blisk
Authors: Sanders A. J. , Hassan K. K. , Rabe D. C.
Published: February 2009

Experiments are performed on a modern design transonic shroudless low-aspect ratio fan blisk that experienced both subsonic/transonic and supersonic stall-side flutter. High-response flush mounted miniature pressure transducers are utilized to measure the unsteady aerodynamic loading distribution in the tip region of the fan for both flutter regimes, with strain gages utilized to measure the vibratory response at incipient and deep flutter operating conditions. Numerical simulations are performed and compared with the benchmark data using an unsteady three-dimensional nonlinear viscous computational fluid dynamic (CFD) analysis, with the effects of tip clearance, vibration amplitude, and the number of time steps-per-cycle investigated. The benchmark data are used to guide the validation of the code and establish best practices that ensure accurate flutter predictions.
Vortex Transport and Blade Interactions in High Pressure Turbines
Authors: Chaluvadi V. S. P. , Kalfas A. I. , Hodson H. P.
Published: February 2009

This paper presents a study of the three-dimensional flow field within the blade rows of a high-pressure axial flow steam turbine stage. Half-delta wings were fixed to a rotating hub to simulate an upstream rotor passage vortex. The flow field is investigated in a Low-Speed Research Turbine using pneumatic and hot-wire probes downstream of the blade row. The paper examines the impact of the delta wing vortex transport on the performance of the downstream blade row. Steady and unsteady numerical simulations were performed using structured 3D Navier-Stokes solver to further understand the flow field. The loss measurements at the exit of the stator blade showed an increase in stagnation pressure loss due to the delta wing vortex transport. The increase in loss was 21% of the datum stator loss, demonstrating the importance of this vortex interaction. The transport of the stator viscous flow through the rotor blade row is also described. The rotor exit flow was affected by the interaction between the enhanced stator passage vortex and the rotor blade row. Flow underturning near the hub and overturning towards the mid-span was observed, contrary to the classical model of overturning near the hub and underturning towards the mid-span. The unsteady numerical simulation results were further analysed to identify the entropy producing regions in the unsteady flow field.
Experimental Investigation of High Temperature Wear Resistant Coatings for Industrial Gas Turbine
Authors: Matsuoka Hideyuki , Shinohara Nobuo , Sugita Yuji , Ichikawa Kunihiro , Arikawa Hideyuki , Nishi Kazuya
Published: February 2009

In the contact section of industrial gas turbine parts, wear can be observed after normal operations. Especially, in the contact area of combustors and their fittings, such as a transition piece and a seal plate, the severe wear may occur owing to combustion vibration under high temperature. If such severe wear occurs, some inspections or repair of the combustor parts may be needed. The short cycle of inspection and repair will decrease the performance of the gas turbine. Though combustors and their fittings are subjected to high temperature condition without any lubricant, any relevant prevention has not been developed yet. In this paper, wear resistance of ceramic hard coating materials, i.e. titanium nitride (TiN), titanium aluminum nitride (TiaAIN), chromium nitride (CrN), titanium carbide (TiC), silicon carbide (SiC), aluminum oxide (Al2O3) against various metals was tested under the condition similar to that in a gas turbines. These coatings were deposited by physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes. It was concluded that, the combination of Al2O3 coating and stellite #6B had excellent high temperature wear resistance.
Automated Design Optimization of Compressor Blades for Stationary, Large-Scale Turbomachinery
Authors: Bu¨che Dirk , Guidati Gianfranco , Stoll Peter
Published: February 2009

An automated, multi-disciplinary optimization procedure for sub-sonic gas turbine compressor blades is presented. Evolutionary optimization algorithms are coupled with existing tools for geometry generation, mechanical integrity analysis and Q3D flow analysis for design and off-design conditions. Aerodynamic and mechanical objectives and constraints are formulated based on the standard design criteria. The feasibility of the approach is tested by automatically designing different rotor blades for the subsonic compressor region. First results are promising. All rotor blades show similar profile shapes, which underlines the robustness of the optimization procedure. The blades are characterized by a pronounced front loading which leads to a large (predicted) operating range. A special focus in this paper is on a 3D-blade parameterization, which by default leads to smooth blades, and on the assessment of the off-design behavior. The considered optimization algorithm shows a fast and robust convergence even from randomly initialized blades.
Gas Path Fault Diagnosis of a Turbofan Engine From Transient Data Using Artificial Neural Networks
Authors: Ogaji S. O. T. , Li Y. G. , Sampath S. , Singh R.
Published: February 2009

Transient and steady state data may contain the same essential fault information but some faults have been shown to be more easily detectable from transient data because the transient records provide significant diagnostic content especially as the fault effects are magnified under transient. Various traditional and conventional techniques such as fault trees, fault matrixes, gas path analysis and its variants have been applied to gas path fault diagnosis of gas turbines. Recently, artificial intelligence techniques such as artificial neural networks (ANN) as well as optimization techniques such as genetic algorithm (GA) are being explored for fault diagnosis activities. In this paper, a novel approach to gas path fault diagnosis is proposed. The method involves the use of ANN with engine transient data. A set of nested neural networks designed to estimate independent parameter (efficiencies and flow capacities) changes due to faults within single or multiple components of a turbofan engine are presented. The approach involves classification and approximation type networks. Measurements from the engine are first assessed by a trained network and if a fault is diagnosed, are then classified into two groups — those originating from sensor faults and those from component faults, by another trained network. Other trained networks continue the fault isolation process and finally the magnitude of the fault(s) is quantified. A computer simulation of the process shows that results from a batched process of these networks can be obtained in less than three seconds. Four of the gas path components — intermediate pressure compressor (IPC), high pressure compressor (HPC), high pressure turbine (HPT) and low pressure turbine (LPT) — and measurements from eight sensors are considered. Sensor noise and bias are also considered in this analysis. The comparison of fault signatures from a steady state and transient process show that diagnosis with transient data can improve the accuracy of gas turbine fault diagnosis.
Advanced Zero Emissions Gas Turbine Power Plant
Authors: Griffin Timothy , Sundkvist Sven Gunnar , A˚sen Knut , Bruun Tor
Published: February 2009

The AZEP (Advanced Zero Emissions Power Plant) project addresses the development of a novel “zero emissions,” gas turbine-based, power generation process to reduce local and global CO2 emissions in the most cost-effective way. Preliminary process calculations indicate that the AZEP concept will result only in a loss of 2–5% efficiency, as compared to approximately 10% loss using conventional tail-end CO2 capture methods. Additionally, the concept allows the use of air-based gas turbine equipment and thus, eliminates the need for expensive development of new turbomachinery. The key to achieving these targets is the development of an integrated MCM-reactor, in which a) O2 is separated from air by use of a mixed-conductive membrane (MCM), b) combustion of natural gas occurs in an N2-free environment and c) the heat of combustion is transferred to the oxygen depleted air by a high temperature heat exchanger. This MCM reactor replaces the combustion chamber in a standard gas turbine power plant. The cost of removing CO2 from the combustion exhaust gas is significantly reduced, since this contains only CO2 and water vapor. The initial project phase is focused on the research and development of the major components of the MCM-reactor (air separation membrane, combustor and high temperature heat exchanger), the combination of these components into an integrated reactor, and subsequent scale-up for future integration in a gas turbine. Within the AZEP process combustion is carried out in a nearly stoichiometric natural gas/O2 mixture heavily diluted in CO2 and water vapor. The influence of this high exhaust gas dilution on the stability of natural gas combustion has been investigated, using lean-premix combustion technologies. Experiments have been performed both at atmospheric and high pressures (up to 15 bar), simulating the conditions found in the AZEP process. Preliminary tests have been performed on MCM modules under simulated gas turbine conditions. Additionally, preliminary reactor designs, incorporating MCM, heat exchanger and combustor have been made, based on the results of initial component testing. Techno-economic process calculations have been performed indicating the advantages of the AZEP process as compared to other proposed CO2-free gas turbine processes.
Critical Analysis of Advanced H2/O2 Cycles Based on Steam-Methane Reforming
Authors: Gambini M. , Guizzi G. L. , Vellini M.
Published: February 2009

In this paper a critical analysis of H2/O2 cycles is presented. They seem to have great thermodynamic potentialities, but in these analyses it is very important to adopt reasonable assumptions. In fact choosing very high values of the maximum pressure and temperature and neglecting the energy requirements for oxygen and hydrogen compression and production, these cycles can attain very high efficiency: from 65 to 69%, depending on the typology of the thermodynamic cycle. In the present paper the H2/O2 cycles, one typology proposed by authors and another by other ones [1], have been analysed under realistic assumptions (with respect to the currently available technology) of the cycle parameters — TIT and maximum pressure — and taking into account the overall energetic requirements (H2 and O2 production and compression). The cycles, suitable for these assumptions, have been investigated by means of a parametric analysis as a function of the main cycle parameters. Summarizing, the results of the developed analysis show that the H2/O2 cycles, investigated here, yield very poor performance if all energetic requirements are taken into account.
Conjugate Flow and Heat Transfer Investigation of a Turbo Charger: Part II — Experimental Results
Authors: Bohn Dieter , Moritz Norbert , Wolff Michael
Published: February 2009

In this paper the results of experimental investigations are presented that were performed at the institute’s turbo charger test stand to determine the heat flux between the turbine and the compressor of a passenger car turbo charger. A parametric study has been performed varying the turbine inlet temperature and the mass flow rate. The aim of the analysis is to provide a relation of the Reynolds number at the compressor inlet and the heat flux from the turbine to the compressor with the turbine inlet temperature as the parameter. Thereto, the analysis of the local heat fluxes is necessary which is performed in a numerical conjugate heat transfer and flow analysis which is presented in part I of the paper. Beyond the measurements necessary to determine the operating point of compressor and turbine, the surface temperature of the casings were measured by resistance thermometers at different positions and by thermography. All measurement results were used as boundary conditions for the numerical simulation, i.e. the inlet and outlet flow conditions for compressor and turbine, the rotational speed, the oil temperatures and the temperature distribution on the outer casing surface of the turbo charger. The experimental results show that the total heat flux from turbine to compressor is mainly influenced by the turbine inlet temperature. The increase of the mass flow rate leads to a higher pressure ratio in the compressor so that the compressor casing temperature is increased. Due to the turbo charger’s geometry heat radiation has a small influence on the total heat flux.
Comparison of Neural Network Architectures for Machinery Fault Diagnosis
Authors: Hassan T. A. F. , El-Shafei A. , Zeyada Y. , Rieger N.
Published: February 2009

This paper provides a comparison of the performance of five different neural network architectures in diagnosing machinery faults. The network architectures include perceptrons, linear filters, feed-forward, self-organizing, and LVQ. The study provides a critical analysis of the performance of each network on a test rig with different faults. The comparison discusses the success rate in network training and identification of faults including: unbalance and looseness. It is shown that the perceptron and LVQ architectures were superior and achieved 100% diagnosis on the cases presented.
Improved Formulation to Determine Minimum Sealing Flow – Cw, min – for Different Sealing Configurations
Authors: Bohn Dieter , Wolff Michael
Published: February 2009

Steadily increasing HP turbine inlet temperatures underline the need for effective sealing and cooling technologies. This paper presents a new approximation to determine the minimum sealing air flow Cw,min for sealing efficiencies of different rim seal geometries in the upstream cavity of an axial turbine stage. In contrast to the iteration method of Phadke and Owen the approximation does not require the knowledge of Cw,min. Only with information about the main stream and the geometry of the sealing configuration the minimum sealing air can be estimated. The approximation is based on experimental results performed in a 1.5 stage axial turbine at rotating speeds up to 9000 rpm with different Reynolds numbers 8·105 < Rec1 < 1.5·106 and 4.5·105 < Reu < 8·105 as well as different cooling gas mass flows. In order to get results, regarding the physical phenomena connected to hot gas ingestion, different measurement techniques were applied. Results of CO2 concentration measurements as well as steady pressure measurements are used for the approximation. Different sealing geometries were investigated: 1st a simple axial gap between a flat rotor disk and a flat stator disk, commonly used for industrial gas turbines, 2nd an axial lip of the rim seal on the stator combined with flat rotor disk, often found in aero engine applications, 3rd an axial lip of the rim seal on each stator and rotor and 4th a double lip on stator and single lip on rotor side. The results of Cw,min show very well the linear behavior as in the equation given by Phadke and Owen. Nevertheless the results of the approximation show a strong dependency of the gradient of the Cw,min due to the seal geometry. The gradient of Cw,min of the first geometrical configuration without any sealing lips is about 10 times higher than the gradient of configuration four with altogether 3 sealing lips. The other two configurations are in between these extremes. The result of the 2D–3D approximation with a polynomial equation η=exp∑i=02∑j=02∑k=01(Pi,j,k·(1/Cw)i·Cp1j·Gck) extend the rule of Phadke and Owen. This formulation gives the capability to optimize the sealing mass flow for different sealing configurations.
Surface-Stabilized Fuel Injectors With Sub-Three ppm NOx Emissions for a 5.5 MW Gas Turbine Engine
Authors: Greenberg Steven J. , McDougald Neil K. , Weakley Christopher K. , Kendall Robert M. , Arellano Leonel O.
Published: February 2009

ALZETA Corporation has developed surface-stabilized fuel injectors for use with lean premixed combustors which provide extended turndown and ultra-low NOx emission performance. These injectors use a patented technique to form interacting radiant and blue-flame zones immediately above a selectively-perforated porous metal surface. This allows stable operation at low reaction temperatures. A previous ASME paper (IJPGC2002-26088) described the development of this technology from the proof-of-concept stage to prototype testing. In 2002 development of these fuel injectors for the 5.5 MW turbine accelerated. Additional single-injector rig tests were performed which also demonstrated ultra-low emissions of NOX and CO at pressures up to 1.68 MPa (16.6 atm) and inlet temperatures up to 670 °K (750 °F). A pressurized multi injector ‘sector rig’ test was conducted in which two injectors were operated simultaneously in the same geometric configuration as that expected in the engine combustor liner. The multi-injector package was operated with various combinations of fired and unfired injectors, which resulted in low emissions performance and no adverse affects due to injector proximity. To date sub-3 ppm NOx emissions with sub-10 ppm CO emissions have been obtained over an operating range of 0.18 to 1.68 MPa (1.8 to 16.6 atm), inlet temperatures from 340 to 670 °K (186 to 750 °F), and adiabatic flame temperatures from 1740 to 1840 °K (2670 to 2850 °F). A full scale multi-injector engine simulation is scheduled for the beginning of 2003, with engine tests beginning later that year.
Design of Aspirated Compressor Blades Using Three-Dimensional Inverse Method
Authors: Dang T. Q. , van Rooij M. P. C. , Larosiliere L. M.
Published: February 2009

A three-dimensional viscous inverse method is extended to allow blading design with full interaction between the prescribed pressure-loading distribution and a specified transpiration scheme. Transpiration on blade surfaces and endwalls is implemented as inflow/outflow boundary conditions, and the basic modifications to the method are outlined. This paper focuses on a discussion concerning an application of the method to the design and analysis of a supersonic rotor with aspiration. Results show that an optimum combination of pressure-loading tailoring with surface aspiration can lead to a minimization of the amount of sucked flow required for a net performance improvement at design and off-design operations.
3D Inverse Design Loading Strategy for Transonic Axial Compressor Blading
Authors: Medd A. J. , Dang T. Q. , Larosiliere L. M.
Published: February 2009

A pressure-loading tailoring scheme for transonic axial compressor blading is developed with the goal of managing the passage shock in order to reduce loss and enhance stability. This loading distribution along with other prescribed quantities is employed in a 3-D viscous inverse design procedure to refine initial rotor blade geometries of an advanced 2-stage transonic compressor. Key features of this loading strategy are discussed in the context of their impact on flow structure and performance. Results are presented showing the merits of this scheme.
Experimental Investigation of Centrifugal Compressor Stabilization Techniques
Authors: Skoch Gary J.
Published: February 2009

Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection vs. bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 9.3 points of additional surge margin over the baseline surge margin of 11.7 points.
The Unsteady Effect of Passing Shocks on Pressure Surface Versus Suction Surface Heat Transfer in Film-Cooled Transonic Turbine Blades
Authors: Smith A. C. , Nix A. C. , Diller T. E. , Ng W. F.
Published: February 2009

This paper documents the measurement of the unsteady effects of passing shock waves on film cooling heat transfer on both the pressure and suction surfaces of first stage transonic turbine blades with leading edge showerhead film cooling. Experiments were performed for several cooling blowing ratios with an emphasis on time-resolved pressure and heat flux measurements on the pressure surface. Results without film cooling on the pressure surface demonstrated that increases in heat flux were a result of shock heating (the increase in temperature across the shock wave) rather than shock interaction with the boundary layer or film layer. Time-resolved measurements with film cooling demonstrated that the relatively strong shock wave along the suction surface appears to retard coolant ejection there and causes excess coolant to be ejected from pressure surface holes. This actually causes a decrease in heat transfer on the pressure surface during a large portion of the shock passing event. The magnitude of the decrease is almost as large as the increase in heat transfer without film cooling. The decrease in coolant ejection from the suction surface holes did not appear to have any effects on suction surface heat transfer.
Numerical Simulation of Combustion Instabilities in a Lean Premixed Combustor With Finite Rate Chemistry
Authors: Cook David J. , Pitsch Heinz , Peters Norbert
Published: February 2009

Combustion instabilities in lean premixed gas turbine combustors remain a major limitation in decreasing NOx emissions. Computational Fluid Dynamics (CFD) has become an important design and analysis tool that is often used to predict thermoacoustic oscillations caused by these instabilities. Limitations to prediction accuracy are imposed by the choice of chemistry and combustion model. The focus of this study is to compare CFD calculations using Eddy Dissipation and Finite Rate Chemistry models to experimental data reported by Richards and Janus (1997) on the single-injector lean premixed DOE-NETL combustor. The computational domain consists of an annular swirl inlet, fuel injection, a can combustor, a plug for reduced flow area, and an exhaust plenum. The numerical calculations were done using a RANS solver. A 2D axisymmetric-swirl model with RANS turbulence model was employed. The Eddy Dissipation Model has become popular largely because of its robust performance. It is shown that this model does not predict combustion instabilities for the present case. On the other hand, the Finite Rate Chemistry Model is numerically stiff, but is capable of capturing the onset of combustion instabilities.
Performance Comparison of Internal Reforming Against External Reforming in a SOFC, Gas Turbine Hybrid System
Authors: Liese Eric A. , Gemmen Randall S.
Published: February 2009

Solid Oxide Fuel Cell (SOFC) manufacturers are presently considering both internal and external reforming fuel cell designs. Generally, the endothermic reforming reaction and excess air through the cathode provide the cooling needed to remove waste heat from the fuel cell. Current information suggests that external reforming fuel cells will require a flow rate twice the amount necessary for internal reforming fuel cells. The increased airflow could negatively impact system performance. This paper compares the performance among various external reforming hybrid configurations and an internal reforming hybrid configuration. A system configuration is introduced that uses interstage external reforming. Results show that that the thermodynamic performance of an interstage reforming system is an improvement over a base-concept external approach, and may be slightly better than the hybrid with an internal reforming fuel cell.
Measurements and Predictions of Surface Roughness Effects on the Turbine Vane Aerodynamics
Authors: Boyle R. J. , Senyitko R. G.
Published: February 2009

The aerodynamic performance of a turbine vane was measured in a linear cascade. These measurements were conducted for exit-true chord Reynolds numbers between 150,000 and 1,800,000. The vane surface rms roughness-to-true chord ratio was approximately 2 × 10−4. Measurements were made for exit Mach numbers between 0.3 and 0.9 to achieve different loading distributions. Measurements were made at three different inlet turbulence levels. High and intermediate turbulence levels were generated using two different blown grids. The turbulence was low when no grid was present. The wide range of Reynolds numbers was chosen so that, at the lower Reynolds numbers the rough surfaces would be hydraulically smooth. The primary purpose of the tests was to provide data to verify CFD predictions of surface roughness effects on aerodynamic performance. Data comparisons are made using a two-dimensional Navier-Stokes analysis. Both two-equation and algebraic roughness turbulence models were used. A model is proposed to account for the increase in loss due to roughness as the Reynolds number increases.
Effect of Film Cooling on Low Temperature Hot Corrosion in a Coal Fired Gas Turbine
Authors: Krishnan Vaidyanathan , Kapat J. S. , Sohn Y. H. , Desai V. H.
Published: February 2009

In recent times, the use of coal gas in gas turbines has gained a lot of interest, as coal is quite abundant as a primary source of energy. However, use of coal gas produces a few detrimental effects that need closer attention. This paper concentrates on one such effect, namely hot corrosion, where trace amounts of sulfur can cause corrosion (or sulfidation) of hot and exposed surfaces, thereby reducing the life of the material. In low temperature hot corrosion, which is the focus of this paper, transport of SO2 from the hot gas stream is the primary process that leads to a chain of events, ultimately causing hot corrosion. The corrosion rate depends on SO2 mass flux to the wall as well as wall surface temperature, both of which are affected in the presence of any film cooling. An analytical model is developed to describe the associated transport phenomena of both heat and mass in the presence of film cooling The model predicts how corrosion rates may be affected under operating conditions. It is found that although use of film cooling typically leads to lower corrosion rate, there are combinations of operating parameters under which corrosion rate can actually increase in the presence of film cooling.
Incorporating Data Uncertainty in Rotordynamic Model Reconciliation
Authors: Wang Qingyu , Maslen Eric H. , Ahn Hyeong-Joon
Published: February 2009

A method called model reconciliation (MR) has previously been reported which modifies analytic rotordynamic models to make them match experimental data. An identified model derived from the experimental data and a nominal model from the engineering analysis are needed; an auxiliary dynamic system is then synthesized to modify the dynamics of the nominal model to match the identified model. The combination of the engineering model and the auxiliary dynamic system is the reconciled model. Due to numerous experimental uncertainties, the identified model may contain significant errors. These errors are then embedded by the reconciliation process so that the reconciled model is incorrect, and sometimes quite poor. A robust control synthesis method is presented here which accounts for model error bounds in generating the auxiliary dynamics to minimize their impact on the final model. To examine the validity of the process, extra data as a reference are used to compare with the data produced by the reconciled model. Both simulated data and experimental data are used to demonstrate the results of the method. The error model permits the synthesis to ignore spurious features of the identified model, thereby producing more reasonable results.
On the Flow and Turbulence Within the Wake and Boundary Layer of a Rotor Blade Located Downstream of an IGV
Authors: Chow Yi-Chih , Uzol Oguz , Katz Joseph
Published: February 2009

This paper presents detailed experimental data on the flow and turbulence within the wake and boundary layer of a rotor blade operating behind a row of Inlet Guide Vanes (IGVs). The experiments are performed in a refractive index matched facility that provides an unobstructed view of the entire flow field. Results of the high-resolution 2D Particle Image Velocimetry (PIV) measurements are used for characterizing the mean flow, Reynolds stresses, turbulent kinetic energy as well as dissipation and production rates. Dissipation and production rates are high and of the same order of magnitude near the trailing edge, and decrease rapidly with increasing distance from the blade. The trend is reversed in the wake kinking region, resulting in elevated turbulence levels, i.e. a turbulent hot spot. One-dimensional spectral analysis shows that, except for the very near wake and hot-spot regions, the turbulence within the rotor wake can be assumed to be isotropic. Also the directions of the maximum shear strain and shear stress are aligned in that region, i.e. consistent with eddy viscosity type Reynolds stress models. The rotor near wake mainly consists of two parallel layers experiencing planar shear with opposite signs as one would expect to find in a 2D wake. However, orientation differences can extend up to 45° near the trailing edge and the hot-spot. Furthermore, there is substantial mismatch in the location of the local maxima of stresses and strains. The values of S33 are also large there, indicating that the flow is three-dimensional. Rotor boundary layer measurements focus on a region where the IGV wake intersects with the rotor blade. The impingement of the increased axial velocity region in between the IGV wakes causes the thinning of the boundary layer. This is similar to the effect of a turbulent jet impinging on a flat surface. When viewed in the frame of reference of “non-wake” flow regions, the boundary layer thinning can also be attributed to the suction (or “negative jet”) effect of the “slip velocity” present in the IGV wake segments. Spectral analysis shows that the turbulence in the rotor boundary layer is highly anisotropic. As a result, the spectra cannot be used for estimating the dissipation rate.
Development of High-Speed Industrial Turbo Blowers With Foil Air Bearings
Authors: Oh JongSik , Lee HeonSeok
Published: February 2009

In the paper, the development of high-speed industrial turbo blowers with foil air bearings is presented as a first successful commercialization in the world. Their target market is various from wastewater treatment to cement factory processes which require compressed air ranging between 0.6 and 0.8 bar gauge. Employing the state-of-the-art technology of the high-speed BLDC motors, the bump-type foil air bearings and the high-efficient turbo impellers/diffusers, so much compact, efficient and silent blower machines of a single stage are now available in the market, aiming to replace the existing inefficient, bulky and noisy ones, such as roots blowers. The first production lines are established for 75 and 150 hp class blowers. Rotational speeds up to 40,000 rpm are realized directly from the high-speed BLDC motors without any gear boxes, and no lubrication oil is required. A brief introduction of design, manufacture and test results is presented for mechanical, electrical and aerodynamic performance.
Film Cooling and Thermal Field Measurements for Staggered Rows of Rectangular-Shaped Film Cooling Holes
Authors: Rhee Dong Ho , Lee Youn Seok , Kim Young Bong , Cho Hyung Hee
Published: February 2009

An experimental study has been conducted to measure the temperature fields and the local film cooling effectiveness for two and three staggered rows of the rectangular-shaped film cooling holes with various blowing rates. Three different cooling hole shapes such as a straight rectangular hole, a rectangular hole with laterally expanded exit and a circular hole are tested. The rectangular cross-section has the aspect ratio of 2 at the hole inlet with the hydraulic diameter of 10 mm. The area ratio of the exit to the hole inlet is 1.8 for the rectangular hole with expanded exit, which is similar to a two-dimensional slot. The holes are spaced 3d apart in the spanwise direction and 4d apart in the streamwise direction with a staggered arrangement. Temperature fields are acquired using a three-axis traversing system equipped with a thermocouple rake. A thermochromic liquid crystals technique is applied to determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. The results show that the rectangular-shaped holes provide better performance than the cylindrical holes because the penetration of coolant is reduced and the lateral spreading of coolant is promoted. For rows of film cooling holes, the film cooling performance decreases with increasing blowing rate. However, the difference of hole shapes and blowing rates for film cooling performance is reduced with increasing the row of cooling holes.
Experimental Investigation of the Interaction of Unsteady Flow With Combustion
Authors: Schildmacher K.-U. , Koch R.
Published: February 2009

In order to reduce the dimensions of the combustor, swirl stabilized flames are used in heavy duty gas turbines. In our recent investigation of the swirling flow at a single heavy duty gas turbine burner under non-reacting conditions typical instabilities like precessing vortex cores and vortex shedding have been found (Schildmacher et al., 2002). In the present paper the experimental investigations will be discussed. Combustion instabilities have been analyzed by phase-locked Laser Doppler Anemometer (LDA) measurements. For the reacting flow, also combustion instabilities could be detected. The amplitude increases strongly with the equivalence ratio. The frequency of the oscillations for reacting conditions has been found to be slightly shifted towards lower frequencies compared to those of the corresponding non-reacting flow. In addition, for the reacting flow a linear and non-linear range of oscillations could be discriminated.
Effect of Various Injection Hole Shapes on Film Cooling of Turbine Blade
Authors: Kim S.-M. , Kim Youn J.
Published: February 2009

Dispersion of coolant jets in a film cooling flow field is the result of a highly complex interaction between the film cooling jets and the mainstream. In order to investigate the effects of injection hole shapes and injection angle on the film cooling of turbine blade, four models having cylindrical and laterally-diffused holes were used. Three-dimensional Navier-Stokes code with k – ε model was used to compute the film cooling coefficient on the turbine blade. A multi-block grid system was generated that was nearly orthogonal to the various surfaces. Mainstream Reynolds number based on the cylinder diameter was 7.1 × 104. The turbulence intensity kept at 5.0% for all inlets. The effect of coolant flow rates was studied for blowing ratios of 0.9, 1.3 and 1.6, respectively. The temperature distribution of the cylindrical body surface is visualized by infrared thermography (IRT) and compared with computational results. Results show that the effects of injection hole shape and injection angle increase as the blowing ratio increases. As lateral injection angle increases, the adiabatic film cooling effectiveness is more broadly distributed and the area protected by coolant increases. The mass flow rate of the coolant through the first-row holes is less than that through the second-row holes due to the pressure distribution around the cylinder surface.
Evaluation of the MKS On-Line FTIR MultiGas™ Analyzer for Gas Turbine Applications
Authors: Oliver William , Marran David F. , Spartz Martin L. , Lee John C. Y. , Nazeer Waseem
Published: February 2009

A side-by-side comparison between the MKS On-Line MultiGas™ analyzer (MGA) and conventional continuous emissions monitoring systems (CEMS) was performed under various test rig operating conditions at Solar Turbines Incorporated (Solar). The CEMS used an array of single gas analyzers (SGA’s) to measure NOX, CO, CO2, O2 and UHC (unburned hydrocarbons). The MGA, which uses Fourier transform infrared (FTIR) spectrometry to make its measurements, simultaneously analyzed the exhaust stream for ten compounds: NO, NO2, CO, CO2, H2O, CH4, H2CO (formaldehyde), N2O, SO2, and NH3. Both dry and wet samples were collected using the MGA. The only calibration grade gas required was nitrogen, which was used as a zero (or purge) gas. Overall, the comparison between the CEMS and the MGA was very favorable, with the NO emissions within 0.1 ppmV (∼5%) and CO2 emissions within about 6% of each other. Larger differences were observed for NO2 and CO, but were most likely caused by sensor sensitivity range and sample handling problems with the in-house conventional CEMS.