bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of a Ceramic Microchannel Heat Exchanger on a Micro Turbine
Authors: Carman B. G. , Kapat J. S. , Chow L. C. , An L.
Published: February 2009

A highly effective recuperator with low-pressure drop is a key enabling technology to increase the efficiency of a micro turbine. To achieve a cycle efficiency above 40%, the average micro turbine would require a recuperator that achieves close to 99% effectiveness with a pressure drop as low as 2%. This paper presents the design and analysis of a microchannel heat exchanger that could be used as a recuperator in a micro turbine as an alternative to the currently used metallic primary surface recuperators that achieve an effectiveness of 90% at most. In the proposed design, the recuperator will be a counter flow, multi-layer design of parallel ducts with wall thickness of 50 μm and will be constructed with SiCN or a similar polymer derived ceramics, and fabricated using micro-stereolithography technology. Two designs, one having ducts with square cross-sections and the other with equilateral triangle cross-sections, are proposed and compared. For each design, the geometric parameters are optimized to provide the highest overall cycle efficiency while the volume of the heat exchanger is kept limited to 0.125 m3 and other cycle parameters are kept constant at typical values. For the square cross section design, the optimization process provides a design with an effectiveness of 0.961 and pressure loss of 2.86% that correspond to a cycle efficiency of 39.4%. The corresponding values for the triangle cross-section design are 0.983, 2.4% and 42.2%, respectively. Both designs are expected to withstand temperatures up to 1300°C in combustion gases. Special strategy is needed to fabricate any of these two microchannel designs by existing or proposed micro-stereolithography systems. One possible option is to make the complete heat exchanger as a bundle of identical smaller segments so that overall performance is not affected.
Preliminary Design of Ceramic Components for the ST5+ Advanced Microturbine Engine
Authors: Shi Jun , Vedula Venkata R. , Holowczak John , Bird Connie E. , Ochs S. Scott , Bertuccioli Luca , Bombara David J.
Published: February 2009

Progress in the preliminary design of an axial vane ring and axial turbine rotor composed of silicon nitride structural ceramics is presented. The silicon nitride components allow for significantly increased turbine inlet temperature in the ST5+, an advanced version of the Pratt & Whitney Canada’s ST5, which powers the DTE Technologies ENT400 Distributed Energy Generator. Preliminary aerodynamic and mechanical design, steady state thermal and stress analysis, and life prediction results will be reviewed. Foreign object damage resistance will be compared between ceramic versions of the baseline rotor blade geometry and that developed for the ST5+ engine.
Feasibility of a High-Temperature Polymer-Derived-Ceramic Turbine Fabricated Through Micro-Stereolithography
Authors: Walsh C. , An L. , Kapat J. S. , Chow L. C.
Published: February 2009

Efficient micro turbines are expected to play a major role in power generation in the coming years. One of the biggest challenges in significantly increasing the system efficiency from the currently achievable values is the availability of high temperature materials that can be micro-fabricated with a low value of relative tolerance. This paper suggests a possible solution for both the material and the fabrication technique by which this goal can be achieved. Thermodynamic analysis shows that high turbine inlet temperatures, high isentropic efficiencies, and a recuperator with high effectiveness and low pressure losses are imperative to improve system efficiency, particularly in a micro turbine. An excellent relative tolerance with a high temperature ceramics is one way to achieve these improvements. The paper introduces new polymer-derived-ceramics (PDC), which could be used in turbine and recuperator designs. These materials can be used in micro-fabrication techniques to produce absolute tolerances of a few microns, and some of them are thermally stable up to 1800°C in air. The paper presents an enhancement to the typical micro-stereolithography technique, by which PDC can be micro-fabricated to form parts up to a few centimeters in overall linear dimensions and yet to have a relative tolerance that is comparable to or better than that in large-sized conventional parts. It is projected that for a turbine with 10 cm rotor outside diameter and 5 mm blade height, a tip-gap-to-blade-height ratio of better than 0.28% can be achieved by this proposed enhancement. This technique appears to be quite promising for next generation micro turbines, and hence requires further investigation and development.
Comparison of Blade Cooling Performance Using Alternative Fluids
Authors: Carcasci Carlo , Zecchi Stefano , Oteri Gianpaolo
Published: February 2009

CO2 emissions reduction has become an important topic, especially after Kyoto protocol. There are several ways to reduce the overall amount of CO2 discharged into the atmosphere, for example using alternative fluids such as steam or CO2. It is therefore interesting to analyze the consequences of their usage on overall performances of gas turbine and blade cooling systems. The presence of steam can be associated with combined or STIG cycle, whereas pure carbon dioxide or air-carbon dioxide mixtures are present in innovative cycles, where the exhaust gas is recirculated partially or even totally. In this paper we will analyze a commercial gas turbine, comparing different fluids used as working and cooling fluids. The different nature of the fluids involved determines different external heat transfer coefficients (external blade surface), different internal heat transfer coefficients (cooling cavities) and affects film cooling effectiveness, resulting in a change of the blade temperature distribution. Results show that the presence of steam and CO2 could determine a non negligible effect on blade temperature. This means that cooling systems need a deep investigation. A redesign of the cooling system could be required. In particular, results show that steam is well suited for internal cooling, whereas CO2 is better used in film cooling systems.
Film Cooling: A Comparative Study of Different Heater-Foil Configurations for Liquid Crystals Experiments
Authors: Vogel G. , Graf A. , Weigand B.
Published: February 2009

A new measurement technique for the determination of the heat transfer coefficient and the film cooling effectiveness is presented. It is based on a regression of multiple transient liquid crystals experiments using an electrical heater-foil producing a non-homogeneous surface heat flux. This is particularly interesting for film-cooled surfaces where each cooling hole in the heater-foil leads to a non-homogeneous heat flux distribution. The method and its theoretical basis are described. Results on two different heater-foil configurations for one row of film cooling holes are presented. The first heater-foil configuration deals with a longitudinal electrical current relatively to the main flow direction, while the second one is considering a transversal electrical current.
Heat Transfer Coefficient and Film-Cooling Effectiveness on the Squealer Tip of a Gas Turbine Blade
Authors: Kwak Jae Su , Han Je-Chin
Published: February 2009

Experimental investigations were performed to measure the detailed heat transfer coefficients and film-cooling effectiveness on the squealer tip of a gas turbine blade in a five-bladed linear cascade. The blade was a 2-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The test blade had a squealer (recessed) tip with a 4.22% recess. The blade model was equipped with a single row of film-cooling holes on the pressure-side near the tip region and the tip surface along the camber line. A hue detection based transient liquid crystal technique was used to measure heat transfer coefficients and film-cooling effectiveness. All measurements were done for the tip gap clearances of 1.0%,1.5%, and 2.5% of blade span at the two blowing ratios of 1.0 and 2.0. The Reynolds number based on cascade exit velocity and axial chord length was 1.1 × 106 and the overall pressure ratio was 1.32. The turbulence intensity level at the cascade inlet was 9.7%. Results showed that the overall heat transfer coefficients increased with increasing tip gap clearance, but decreased with increasing blowing ratio. However, the overall film-cooling effectiveness increased with increasing blowing ratio. Results also showed that the overall film-cooling effectiveness increased but heat transfer coefficients decreased for the squealer tip when compared to the plane tip at the same tip gap clearance and blowing ratio conditions.
Cogenerative BAGT Performance With Variable Thermal Power
Authors: Bianchi M. , Negri di Montenegro G. , Peretto A.
Published: February 2009

The use of gas turbine and combined cycle power plants for thermal and electric power generation is, nowadays, a consolidated technology. Moreover the employment of combined heat and power production, especially for low power requirements, is constantly increasing. In this scenario, Below Ambient pressure discharge Gas Turbine (BAGT) is an innovative and interesting application; the hot gases discharged from a gas turbine may be expanded below ambient pressure to obtain an increase in electric power generation. The gases are then cooled to supply heat to the thermal utility and finally recompressed to the ambient pressure. The power plant cogenerative performance depends on the heat and electric demand that usually varies during the year (for residential heating the heat to electric power ratio may range from 0.3 to 9). In this paper, the thermal load variation influence on the BAGT performance will be investigated and compared with those of gas turbine and combined cycle power plants.
A Feasibility Study of Existing Gas Turbines for Recuperated, Intercooled and Reheat Cycle
Authors: Bhargava R. , Bianchi M. , Peretto A. , Spina P. R.
Published: February 2009

In the present paper, a comprehensive and simple in application design methodology to obtain a gas turbine working on recuperated, intercooled and reheat cycle utilizing existing gas turbines is presented. Applications of the proposed design steps have been implemented on the three existing gas turbines, with wide ranging design complexities. The results of evaluated aero-thermodynamic performance for these existing gas turbines with the proposed modifications are presented and compared in this paper. Sample calculations of the analysis procedures discussed, including stage-by-stage analysis of the compressor and turbine sections of the modified gas turbines, have been also included. All the three modified gas turbines were found to have higher performance, with cycle efficiency increase of 9% to 26%, in comparison to their original values.
Thermo-Economic Analysis of Inlet Air Conditioning Methods of a Cogeneration Gas Turbine Plant
Authors: Nixdorf M. , Prelipceanu A. , Hein D.
Published: February 2009

The purpose of this work is to investigate the benefits of some different ambient air conditioning methods for reducing the gas turbine intake air temperature in order to enhance the gas turbine power. As a reference case the combined heat and power plant of the campus area of the Technische Universita¨t Mu¨nchen in Garching is considered, which is equipped with an Allison KH501 Cheng Cycle gas turbine. Three novel technical possibilities of ambient air cooling and power augmentation are shown in detail (desiccant dehumidification and evaporative cooling, absorption chiller unit with air cooler, evaporative cooling at increased inlet air pressure). Based on site ambient conditions and measured yearly load lines for heat and electrical power connected with actual cost functions, the potential economic savings are worked out for the different technical modifications using ambient air cooling for power augmentation of the gas turbine plant. The economic operation lines for power and heat, supplied by the modified gas turbine plant, are calculated by a cost optimization system. The results are compared based on investment costs and economic savings by the extended annual electrical and thermal power production of the modified gas turbine plant.
Inlet Fogging of Gas Turbine Engines: Part A — Fog Droplet Thermodynamics, Heat Transfer and Practical Considerations
Authors: Chaker Mustapha , Meher-Homji Cyrus B. , Mee Thomas
Published: February 2009

The inlet fogging of gas turbine engines for power augmentation has seen increasing application over the past decade yet not a single technical paper treating the physics and engineering of the fogging process, droplet size measurement, droplet kinetics, or the duct behavior of droplets, from a gas turbine perspective, is available. This paper provides the results of extensive experimental and theoretical studies conducted over several years coupled with practical aspects learned in the implementation of nearly 500 inlet fogging systems on gas turbines ranging in power from 5 to 250 MW. Part A of the paper covers the underlying theory of droplet thermodynamics and heat transfer, and provides several practical pointers relating to the implementation and application of inlet fogging to gas turbine engines.
Economic and Performance Evaluation of Combined Cycle Repowering Options
Authors: Tawney Rattan K. , Bonner James A. , Elgawhary Asem M.
Published: February 2009

The majority of fossil units in many countries including the United States were built from 1950 through the 1970s, and these older plants are now approaching the end of their useful operating design life. Faced with continued demand growth and compliance with stringent emissions requirements, the power industry may choose building new replacement units, extending the operating life of existing units, or repowering these existing units. Repowering has been demonstrated to be an attractive alternative that incorporates state-of-the-art technologies into an existing unit to achieve higher performance and thermal efficiency, lower emissions, higher reliability and usefulness, and the potential for a shorter execution permitting schedule. Combined cycle technology has become desirable and has matured for the repowering existing plants because of its high thermal efficiency, low emissions, low installed and operation cost, short installation time, high reliability and availability, excellent cycling capability, and operating flexibility. Various options are available for repowering applications on existing plants with combined cycle technology. The options include hot windbox repowering, feedwater heater repowering, and combustion turbine (CT) with heat recovery steam generator (HRSG) repowering. This paper examines the performance benefits of these combined cycle repowering options and analyzes associated costs.
Flow Accelerated Corrosion in HRSGs: A Method to Quantify the Probability of FAC Occurrence
Authors: Pasha Akber , Ahmad Syed F. , Baxter Stephen
Published: February 2009

Flow-Accelerated Corrosion (FAC) has become a source of failures in Low pressure units of HRSGs. Research in past 20 years has indicated that FAC is a very complex phenomenon. It is influenced by many variables, some among them are : pressure, temperature, pH of the water, Chrome content of the metal, the dissolved oxygen content in water, the velocity of steam and water etc. The matter of FAC was discussed in detail in a joint publication by Electric Power research Institute (EPRI), Electricite´ de France (EDF) and Siemens. However the methodologies presented to understand the phenomena and to find the solution are very complex. Considerable expertise is needed to arrive at a good solution. This paper combines the work done both empirically and experimentally and gives a simpler method to estimate the metal loss due to FAC in an HRSG given the design and operating conditions. The user should then be able to decide whether to proceed further with more complex and comprehensive investigations, install a monitoring system or make some changes in the design or the operating methodology. Since the most prevalent occurrence of FAC in an HRSG is in Low pressure (LP) evaporators, the discussion and solutions are focussed on LP evaporators only. At the end of the paper a tentative action plan is also described to handle the FAC related issues in HRSGs.
Blade Row Interaction in a High Pressure Steam Turbine
Authors: Chaluvadi V. S. P. , Kalfas A. I. , Hodson H. P. , Ohyama H. , Watanabe E.
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. Compound lean angles have been employed to achieve relatively low blade loading for hub and tip sections and so reduce the secondary losses. The flow field is investigated in a Low-Speed Research Turbine using pneumatic and hot-wire probes downstream of the blade row. Steady and unsteady numerical simulations were performed using structured 3D Navier-Stokes solver to further understand the flow field. Agreement between the simulations and the measurements has been found. The unsteady measurements indicate that there is a significant effect of the stator flow interaction in the downstream rotor blade. The transport of the stator viscous flow through the rotor blade row is described. Unsteady numerical simulations were found to be successful in predicting accurately the flow near the secondary flow interaction regions compared to steady simulations. A method to calculate the unsteady loss generated inside the blade row was developed from the unsteady numerical simulations. The contribution of various regions in the blade to the unsteady loss generation was evaluated. This method can assist the designer in identifying and optimizing the features of the flow that are responsible for the majority of the unsteady loss production. An analytical model was developed to quantify this effect for the vortex transport inside the downstream blade.
Blade Row Interaction Effects on the Performance of a Moderately Loaded NASA Transonic Compressor Stage
Authors: Van Zante Dale E. , To Wai-Ming , Chen Jen-Ping
Published: February 2009

Blade row interaction effects on loss generation in compressors have received increased attention as compressor work-per-stage and blade loading have increased. Two dimensional Laser Doppler Velocimeter measurements of the velocity field in a NASA transonic compressor stage show the magnitude of interactions in the velocity field at the peak efficiency and near stall operating conditions. The experimental data are presented along with an assessment of the velocity field interactions. In the present study the experimental data are used to confirm the fidelity of a three-dimensional, time-accurate, Navier Stokes calculation of the stage using the MSU-TURBO code at the peak efficiency and near stall operating conditions. The simulations are used to quantify the loss generation associated with interaction phenomena. At the design point the stator pressure field has minimal effect of the rotor performance. The rotor wakes do have an impact on loss production in the stator passage at both operating conditions. A method for determining the potential importance of blade row interactions on performance is presented.
A Unified Approach for Designing a Radial Flow Gas Turbine
Authors: Ebaid M. S. Y. , Bhinder F. S. , Khdairi G. H. , El-Hasan T. S.
Published: February 2009

Radial flow turbo machines have been used for a long time in a variety of applications such as turbochargers, cryogenics, auxiliary power units, and air conditioning of aircraft cabins. Hence numerous papers have been written on the design and performance of these machines. The only justification for yet another paper is that it would describe a unified approach for designing a single stage inward flow radial turbine comprising a rotor and the casing. The current turbine is designed to drive a direct-coupled permanent magnet high-speed alternator running at 60000 rpm and developing a maximum of 60 kW electrical power. The freedom of choice of the tip diameter and the tip width of the rotor that would be necessary for optimum isentropic efficiency of the turbine stage was restricted by the specified rotational speed and power output. Hence, an optimisation procedure was developed to determine the principal dimension of the rotor. The mean relative velocity in the rotor passages in the direction of the flow would be accelerated but flow velocity on the blade surfaces experiences a significant space rate of deceleration. The rate of deceleration can be controlled by means of a proper choice of the axial length of the rotor. A prescribed mean stream velocity distribution procedure was used to spread the rate of deceleration of the mean flow velocity along the meridional length of the flow passages. The nozzle-less volute casing was designed to satisfy the mass flow rate, energy and angular momentum equations simultaneously. This paper describes the work undertaken to design both the rotor and the casing. The work was motivated by the growing interest in developing gas turbine based hybrid power plant for road vehicles. The authors believe that the paper would lead to a stimulating discussion.
Test Facility for Screening and Evaluating Candidate Materials for Advanced Microturbine Recuperators
Authors: Lara-Curzio Edgar , Maziasz P. J. , Pint B. A. , Stewart Matt , Hamrin Doug , Lipovich Nathan , DeMore Dan
Published: February 2009

A test facility for screening and evaluating candidate materials for advanced microturbine recuperators is described. The central piece of the test facility is a modified 60 kW Capstone microturbine that serves as a test bed for subjecting test specimens to conditions of stress, environment and temperature that are representative of those experienced by the recuperator during microturbine operation. Special provisions have been incorporated into the design of this test facility for controlling the magnitude of the applied mechanical stress and the surface temperature of the test specimens with the objective of carrying out accelerated testing. Candidate materials for evaluation in this test facility are identified.
Low Emission Combustion Turbine Experiments With Supercritical Fuels™
Authors: Haldeman Charles W. , O’Brien Joseph P. , Opdyke George , Valbert Jon R. , Tester Jefferson W. , Cataldo Robert M. , Ahern Brian S. , White Arthur W.
Published: February 2009

Research conducted at the supercritical (SC) facility of MIT’s Energy Laboratory provided visual confirmation of a single phase, homogeneous water/fuel mixture near the critical temperature and pressure of water. This mixture was subsequently burned under atmospheric spray conditions with very low NOx, smoke, CO, and HC. Larger supercritical fuel systems were developed and tested in a 300 hp combustion turbine combustor simulator, and a 30 kW microturbine. Early results comparing combustion of this water/fuel mixture with standard #2 fuel operation in the 30 kW turbine generator were uniformly positive. At full load conditions, levels of under 2.5 parts per million (ppmv) of NOx were achieved, over 90% lower than the baseline emissions, with CO emissions under 5 ppmv. These emission levels were in fact lower than those recorded at full load with a similar model microturbine, fueled with natural gas. These low levels were achieved without the increase in CO that is typically observed with water injection. It is suspected that these results are caused not only by thermal effects of the steam but by altering reactions in the flame.
An Undergraduate Gas Turbine Engine Program Enhanced by Design and Research Threads
Authors: Haven Brenda A. , Byerley Aaron R. , Barlow D. Neal
Published: February 2009

This paper describes an undergraduate program at the USAF Academy that uses the threads of engine design and research to teach and reinforce the fundamentals of gas turbine engines. Each year approximately twelve cadets who have chosen to specialize in the propulsion track of the Aeronautical Engineering major enter a five-course sequence that includes 1.) engineering thermodynamics, 2.) intro to propulsion (advanced cycle analysis), 3.) advanced propulsion (focus on engine component performance), 4.) intro to aircraft and propulsion system design, and 5.) aircraft engine design. During the fifth course, the cadets perform a preliminary engine design to meet various specified performance requirements unique to that semester. The cadets must select the engine cycle, size the engine considering installation effects, design the major components, select the materials, and consider safety, reliability, maintainability, and cost issues. The cadets then make an oral and written design presentation to a group from government and industry. In addition to the course work and the detailed design project, the cadets take a course in experimental methodology that is centered around an actual ongoing research project. The cadets are teamed up with experienced faculty researchers who lead them through each step in the research process. Examples of past research projects include: boundary layer separation on linear cascade blades, enhanced heat transfer in internal blade passages, and high-cycle fatigue forcing functions. Facilities that are available for cadet propulsion research include: a linear cascade wind tunnel, a Garrett F109 turbofan engine, a Continental J69 turbojet engine, and an Allison T63 turboshaft engine. Cadets are also encouraged to participate in a six-week research experience at one of several government, industry, or university laboratories. Finally, cadets can continue their participation with an independent study project. The design and research threads that are woven through the course work equip the cadets for success in graduate school or for making immediate contributions in the USAF propulsion community.
Operational Experience With Internal Coatings in Aero- and Industrial Gas Turbine Airfoils
Authors: Kool G. A. , Agema K. S. , van Buijtenen J. P.
Published: February 2009

The internal surfaces of air cooled gas turbine airfoils will oxidize severely during service depending upon operational conditions, chosen design, substrate alloy and the presence of an internal coating. Contradictory experiences by Dutch operators about the need and the performance of internal coatings lead to a research project within the Dutch Gas Turbine Association (VGT). The work focussed on internally coated and non-coated airfoils of civil and military aero engines and industrial gas turbines. Cross-sections from airfoils for metallographic evaluation were selected from the civil aero engines, GE CF6-50 and -80C2 and PW4000, from military engines, PW F100-200 and -220, and from industrial engines, GE Frames 6 and 9. Coating thickness distributions, oxidation resistance and blockage of drilled film cooling holes were reviewed. Particularly the field experiences on the gas turbine airfoils are highlighted in this paper.
Fuel System Suitability Considerations for Industrial Gas Turbines
Authors: Elliott F. G. , Kurz R. , Etheridge C. , O’Connell J. P.
Published: February 2009

Industrial Gas Turbines allow operation with a wide variety of gaseous and liquid fuels. To determine the suitability for operation with a gas fuel system, various physical parameters of the proposed fuel need to be determined: Heating value, dew point, Joule-Thompson coefficient, Wobbe Index and others. This paper describes an approach to provide a consistent treatment for determining the above physical properties. Special focus is given to the problem of determining the dew point of the potential fuel gas at various pressure levels. A dew point calculation using appropriate equations of state is described, and results are presented. In particular the treatment of heavier hydrocarbons, and water is addressed and recommendations about the necessary data input are made. Since any fuel gas system causes pressure drops in the fuel gas, the temperature reduction due to the Joule-Thompson effect has to be considered and quantified. Suggestions about how to approach fuel suitability questions during the project development and construction phase, as well as in operation are made.
Numerical Investigation of the Effect of Ash Particle Deposition on the Flow Field Through Turbine Cascades
Authors: El-Batsh Hesham , Haselbacher Hermann
Published: February 2009

Ash deposition on turbine blade surfaces is studied in this work using a particle deposition model. The model involves the three main processes: particle transport to the blade surface particle sticking at the surface and particle detachment from the surface. The model is used to investigate the effect of ash particle deposition on the flow field through turbine cascades. The surface velocity and the downstream total pressure coefficient are calculated for the clean and the fouled blade profiles and used in this investigation. The profile of the clean blade is chosen from the literature for which flow field measurements are available. The two dimensional compressible flow field is solved for the clean blade using the RNG k-ε turbulence model with the two layer zonal model for the near-wall region. The results are compared to the experimental data. The flow field is solved at the conditions expected in modern gas turbines. The deposition distribution on the blade surface is calculated during three periods of 12 operating hours each assuming inlet particle concentration as 100 ppmw. The fouled blade profile is predicted after each period. Then the flow field and deposition calculations are repeated to account for the time-dependent particle deposition. The flow field is calculated for the fouled blade after operating hours and investigated using the experimental data and the numerical calculations of the clean blade. The profile loss of the fouled blade is also predicted and compared to that of the clean blade.
Acoustically-Induced Structural Fatigue of Impeller Discs: A Brief Note
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: February 2009

Coincidence of both the out-of-plane structural wave numbers and frequencies of the impeller disc with the corresponding wave numbers and frequencies of the acoustic waves inside the machine casing may lead to structural-acoustic coupling, to extreme dynamic loading of the impeller disc and consequently to fatigue failures. Of primary concern is the interaction between the diametral structural modes and the higher order diametral acoustic modes. Avoiding the match between the wave numbers and assuring sufficient separation between structural and acoustic frequencies will prevent structural-acoustic coupling and eliminate the dangers of impeller disc failures from acoustic loadings. In this paper, the coupling phenomena and the relationship between the structural and acoustic fields will be discussed more broadly. A numerical example will also be included for illustration.
Improved Methodology for Turbine Engine Emission Measurements
Authors: Jalbert Paul A. , Zaccardi Vincent A.
Published: February 2009

Whether the intended application of a gas turbine engine is aero-propulsion or power production, the engine exhaust gas emissions must comply with all applicable air quality regulations. For an aircraft gas turbine engine, the current range of certifiable operating conditions includes the landing and takeoff cycle. For a stationary, power-producing engine the range of operating conditions is narrow, but there is increasing interest in measurements of speciated hydrocarbons and other species that pose health and environmental hazards. Existing emission measurement methodologies are time consuming and expensive. An engine emissions survey was performed on a JT-12 engine at Middle Tennessee State University using a new integrated rapid sampling, measurement, and analysis system. Improved methodologies should be considered for turbine engine emissions certification.
Liquid Fuel Modulation by Fluidic Valve for Active Combustion Control
Authors: Sun Fanping , Cohen Jeffrey M. , Anderson Torger J.
Published: February 2009

Fluidic modulation of liquid fuel flow has potential as an actuator for active control of gas turbine engine combustors, improving thrust and emissions performance. This paper describes an experimental investigation into the feasibility of liquid fuel modulation using a bi-stable fluidic diverter for active combustion control. The results demonstrate that a practical bi-stable fluidic valve can be designed for the gas turbine combustor application, satisfying requirements for flowrate, pressure drop and tolerance to downstream pressure variations. A limiting frequency of approximately 100 Hz was obtained in this investigation, demonstrating that the flow capacity requirement sets the upper limit of the fluidic valve response. A suggestion for improving the frequency response is discussed.
Computational Issues for Simulating Finite-Rate Kinetics in LES
Authors: Kapoor Rajat , Menon Suresh
Published: February 2009

At present, large-eddy simulations (LES) of turbulent flames with multi-species finite-rate kinetics is computationally infeasible due to the enormous cost associated with computation of reaction kinetics in 3D flows. In a recent study, In-Situ Adaptive Tabulation (ISAT) and Artificial Neural Network (ANN) methodologies were developed for computing finite-rate kinetics in a cost effective manner. Although ISAT reduces the cost of direct integration considerably, the ISAT tables require significant on-line storage in memory and can continue to grow over multiple flow-through times (an essential feature in LES). Hence, direct use of ISAT in LES may not be practical, especially in parallel solvers. In this study, a storage-efficient Artificial Neural Network (ANN) is investigated for LES application. Preliminary studies using ANN to predict freely propagating turbulent premixed flames over a range of operational parameters are described and issues regarding the implementation of such ANNs for engineering LES are discussed.
The LAJ Cycle: A New Combined-Cycle Fossil Fuel Power System
Authors: Judkins Roddie R. , Armstrong Timothy R. , Labinov Solomon D.
Published: February 2009

Oak Ridge National Laboratory (ORNL) has developed a novel system for combined-cycle power generation, called the LAJ cycle. This system could serve as a basis for the development of a new generation of high-efficiency combined cycles. In one of several possible configurations of the new combined-cycle fossil fuel power system, natural gas enters the system at 4.0 MPa and about 300 K, is heated and reformed, and is transferred to a turbine at 4.0 MPa and 1200 K. The gas expands in the turbine to 0.6 MPa and 800 K, and then flows successively to heat exchangers and a condenser-separator, after which it is separated into two gas streams, one containing principally CO with some CH4 and water vapor and the other containing pure H2. The CO and H2 flow to separate fuel cells and undergo electrochemical oxidation with the concomitant production of electricity. Separate streams of water and carbon dioxide (CO2) are produced, making this cycle compatible with carbon mitigation strategies based on sequestration. Model calculations indicate combined-cycle efficiencies greater than 70% based on the lower heating value of natural gas. The high efficiencies realized result from a combination of the high-pressure natural gas reformate expansion and the highly efficient CO and H2 fuel cells. Most of the power derives from the fuel cells in the system.
Two-Equation Versus Reynolds-Stress Modeling in Predicting Flow and Heat Transfer in a Smooth U-Duct With and Without Rotation
Authors: Gu X. , Wu H.-W. , Schock H. J. , Shih T. I.-P.
Published: February 2009

Computations were performed by using Version 5.5 of the Fluent-UNS code to compare two turbulence models in predicting the three-dimensional flow and heat transfer in a smooth duct of square cross section with a small radius of curvature 180-degree bend under rotating and non-rotating conditions (Re = 25,000; Ro = 0.0 and 0.24). The two turbulence models investigated are the standard k-ε model and a Reynolds stress model. For both models, the two-layer low-Reynolds model of Chen and Patel was used in the near-wall region. Results obtained show that though the k-ε model predicts turbulence quantities incorrectly, the predicted velocity and temperature fields and the surface heat transfer are similar to those from the Reynolds stress model when there is no rotation. When there is rotation, there is significant difference in the predicted surface heat transfer on the leading surface. But, the predicted flow field is still qualitatively similar.
A Novel Two Dimensional Viscous Inverse Design Method for Turbomachinery Blading
Authors: de Vito L. , Van den Braembussche R. A. , Deconinck H.
Published: February 2009

This paper presents a novel iterative viscous inverse method for turbomachinery blading design. It is made up of two steps: The first one consists of an analysis by means of a Navier-Stokes solver, the second one is an inverse design by means of an Euler solver. The inverse design resorts to the concept of permeable wall, and recycles the ingredients of Demeulenaere’s inviscid inverse design method that was proven fast and robust. The re-design of the LS89 turbine nozzle blade, starting from different arbitrary profiles at subsonic and transonic flow regimes, demonstrates the merits of this approach. The method may result in more than one blade profile that meets the objective, i.e. that produces the viscous target pressure distribution. To select one particular solution among all candidates, a target mass flow is enforced by adjusting the outlet static pressure. The resulting profiles are smooth (oscillation-free). The design of turbine blades with arbitrary pressure distribution at transonic and supersonic outflow illustrates the correct behavior of the method for a large range of applications. The approach is flexible because only the pitch chord ratio is fixed and no limitations are imposed on the stagger angle.
Development of an (Adaptive) Unstructured 2-D Inverse Design Method for Turbomachinery Blades
Authors: Choo Benjamin M. F. , Zangeneh Mehrdad
Published: February 2009

An aerodynamics inverse design method for turbomachinery blades using fully (adaptive) unstructured meshes is presented. In this design method, the pressure loading (i.e. pressure jump across the blades) and thickness distribution are prescribed. The design method then computes the blade shape that would accomplish this loading. This inverse design method is implemented using a cell-centred finite volume method which solves the Euler equations on Delaunay unstructured triangular meshes using upwind flux vector splitting scheme. The analysis/direct Euler solver first is validated against some test cases of cascades flow. Computational grid and solution adaptation is performed to capture any flow behaviors such as shock waves using some error indicators. In the inverse design method, blade geometry is updated at the end of each design iteration process. A flexible and fast remeshing process based on a classical ‘spring’ methodology is adopted. An improved spring smoothing methodology for large changes of blades geometry is also presented. This flexible remeshing method can be used in designing a real blade (i.e. round leading and trailing edge) and also ‘fat’ turbine blades with blunt leading and trailing edge. The inverse design method using unstructured triangular meshes is validated by regeneration of a generic compressor rotor blade geometry subjected to a specified pressure loading and blade thickness. Finally, the method is applied to the design of the tip section of Nasa Rotor 67. The result shows that the design method is very useful in controlling shock waves.
On Board Adaptive Models: A General Framework and Implementation Aspects
Authors: Stamatis A. , Kamboukos Ph. , Aretakis N. , Mathioudakis K.
Published: February 2009

The principles on which an adaptive engine performance model is based are first discussed. The mathematical ways of matching given performance data are presented and their implications for practical implementation are discussed. The consequences of using a number of measurements equal or fewer than the number of adapting parameters are analysed. The numerical behaviour of an adaptive model is also discussed. Solution methods based on non-linear system solvers are compared to methods using optimisation techniques. Execution time requirements are also discussed for the different approaches and implications for possible on-line or off-line applications are evaluated.
Environmental Barrier Coatings Having a YSZ Top Coat
Authors: Lee Kang N.
Published: February 2009

Environmental barrier coatings (EBCs) with a Si bond coat, a yttria-stabilized zirconia (YSZ) top coat, and various intermediate coats were investigated. EBCs were processed by atmospheric pressure plasma spraying. The EBC durability was determined by thermal cycling tests in water vapor at 1300°C and 1400°C, and in air at 1400°C and 1500°C. EBCs with a mullite (3Al2O3·2SiO2)+BSAS (1-xBaO·xSrO·Al2O3·2SiO2) intermediate coat were more durable than EBCs with a mullite intermediate coat, while EBCs with a mullite/BSAS duplex intermediate coat resulted in inferior durability. The improvement with a mullite+BSAS intermediate coat was attributed to enhanced compliance of the intermediate coat due to the addition of a low modulus BSAS second phase. Mullite+BSAS/YSZ and BSAS/YSZ interfaces produced a low melting (<1400 °C) reaction product, which is expected to degrade the EBC performance by increasing the thermal conductivity. EBCs with a mullite+BSAS/graded mullite+YSZ intermediate coat showed the best durability among the EBCs investigated in this study. This improvement was attributed to diffused CTE mismatch stress and improved chemical stability due to the compositionally graded mullite+YSZ layer.
Development and Evaluation of Environmental Barrier Coatings for Silicon Nitride
Authors: Sun Ellen Y. , Eaton Harry E. , Holowczak John E. , Linsey Gary D.
Published: February 2009

Environmental barrier coatings (EBCs) are required for applications of silicon nitride (Si3N4) and silicon carbide (SiC) based materials in gas turbine engines because of the accelerated oxidation of Si3N4 and SiC and subsequent volatilization of silica in the high temperature high-pressure steam environment. EBC systems for silicon carbide fiber reinforced silicon carbide ceramic matrix composites (SiC/SiC CMC’s) were first developed and have been demonstrated via long-term engine tests. Recently, studies have been carried out at United Technologies Research Center (UTRC) to understand the temperature capability of the current celsian-based EBC systems and its suitability for silicon nitride ceramics concerning thermal expansion mismatch between the EBC coating and silicon nitride substrates. This paper will present recent progress in improving the temperature capability of the celsian –based EBC systems and discuss their effectiveness for silicon nitride.
Evaluating Environmental Barrier Coatings on Ceramic Matrix Composites After Engine and Laboratory Exposures
Authors: More Karren L. , Tortorelli Peter L. , Walker Larry R. , Kimmel Josh B. , Miriyala Narendernath , Price Jeffrey R. , Eaton Harry E. , Sun Ellen Y. , Linsey Gary D.
Published: February 2009

SiC/SiC continuous fiber-reinforced ceramic matrix composite (CFCC) combustor liners having protective environmental barrier coatings (EBCs) applied to the liner working surfaces have been field-tested in a Solar Turbines’ Centaur 50S SoLoNOx engine at the Chevron, Bakersfield, CA engine test site. This latest engine test ran for a total of 13,937h. The EBCs significantly increased the lifetime of the in-service liners compared with uncoated CFCC liners used in previous field-tests. The engine test was concluded when a routine borescope inspection revealed the formation of a small hole in the inner liner. Extensive microstructural evaluation of both the inner and outer liners was conducted after removal from the engine. Post-test analysis indicated that numerous degradation mechanisms contributed to the EBC and CFCC damage observed on the liners, including EBC volatilization, sub-surface CFCC oxidation and recession, and processing defects which resulted in localized EBC spallation and accelerated CFCC oxidation. The characterization results obtained from these field-tested liners have been compared with the analyses of similarly-processed CFCC/EBCs that were laboratory-tested in a high-pressure, high temperature exposure facility (the ORNL “Keiser Rig”) for >6000h.
Thermal Gradient Cyclic Behavior of a Thermal/Environmental Barrier Coating System on SiC/SiC Ceramic Matrix Composites
Authors: Zhu Dongming , Lee Kang N. , Miller Robert A.
Published: February 2009

Thermal barrier and environmental barrier coatings (TBCs and EBCs) will play a crucial role in future advanced gas turbine engines because of their ability to significantly extend the temperature capability of the ceramic matrix composite (CMC) engine components in harsh combustion environments. In order to develop high performance, robust coating systems for effective thermal and environmental protections of the engine components, appropriate test approaches for evaluating the critical coating properties must be established. In this paper, a laser high-heat-flux, thermal gradient approach for testing the coatings will be described. Thermal cyclic behavior of plasma-sprayed coating systems, consisting of ZrO2-8wt%Y2O3 thermal barrier and NASA Enabling Propulsion Materials (EPM) Program developed mullite+BSAS/Si type environmental barrier coatings on SiC/SiC ceramic matrix composites, was investigated under thermal gradients using the laser heat-flux rig in conjunction with the furnace thermal cyclic tests in water-vapor environments. The coating sintering and interface damage were assessed by monitoring the real-time thermal conductivity changes during the laser heat-flux tests and by examining the microstructural changes after the tests. The coating failure mechanisms are discussed based on the cyclic test results and are correlated to the sintering, creep, and thermal stress behavior under simulated engine temperature and heat flux conditions.
Rotor Balancing Without Trial Weights
Authors: El-Shafei A. , El-Kabbany A. S. , Younan A. A.
Published: February 2009

The traditional balancing methods using trial or calibration weights are quite effective, yet too many trials may result in a lengthy balancing process. It had been suggested in the literature that it is possible to balance flexible rotors without the use of trial weights, if a rotor model is available. A procedure is developed in this paper to balance flexible rotors using complex modes and complex vibration measurements. It is shown that a complex rotor model is essential for the success of the technique. Moreover, careful calibration of the rotor model is the major cornerstone of the procedure. Experimental results illustrate the success of the procedure.