bluuebunny/crossref_metadata_2025 huggingface dataset:
Rotordynamic Coefficients Measurements Versus Predictions for a High Speed Flexure-Pivot Tilting-Pad Bearing (Load-Between-Pad Configuration)
Authors: Al-Ghasem Adnan , Childs Dara
Published: November 2008

Experimental dynamic force coefficients are presented for a flexure-pivot-tilting-pad (FPTP), bearing in load-between-pad (LBP) configuration for a range of rotor speeds and bearing unit loadings. The bearing has the following design parameters: 4 pads with pad arc angle 72° and 50% pivot offset, pad axial length 0.0762 m (3 in), pad radial clearance 0.254 mm (0.010 in), bearing radial clearance 0.1905 mm (0.0075 in), preload 0.25 and shaft nominal diameter of 116.84 mm (4.600 in). Measured dynamic coefficients have been compared with theoretical predictions using an isothermal analysis for a bulk-flow Navier-Stokes model. Predictions from two models — the Reynolds equation and a bulk-flow Navier-Stokes (NS) equation model are compared with experimental, complex dynamic stiffness coefficients (direct and cross-coupled) and show the following results: (i) The real part of the direct dynamic-stiffness coefficients is strongly frequency dependent because of pad inertia, support flexibility, and the effect of fluid inertia. This frequency dependency can be accurately modeled for by adding a direct added mass term to the conventional stiffness/damping matrix model. (ii) Both models underpredict the identified added-mass coefficient (∼32 kg), but the bulk-flow NS equations predictions are modestly closer. (iii) The imaginary part of the direct dynamic-stiffness coefficient (leading to direct damping) is a largely linear function of excitation frequency, leading to a constant (frequency independent) direct damping model. (iv) The real part of the cross-coupled dynamic-stiffness coefficients shows larger destabilizing forces than predicted by either model. The direct stiffness and damping coefficients increase with load, while increasing and decreasing with rotor speed, respectively. As expected, a small whirl frequency ratio (WFR) was found of about 0.15, and it decreases with increasing load and increases with increasing speed. The two model predictions for WFR are comparable and both underpredict the measured WFR values. Rotors supported by either conventional tilting PAD bearings or FPTP bearings are customarily modeled by frequency-dependent stiffness and damping matrices, necessitating an iterative calculation for rotordynamic stability. The present results show that adding a constant mass matrix to the FPTP bearing model produces an accurate frequency-independent model that eliminates the need for iterative rotordynamic stability calculations.
Techno-Economic Evaluation of Commercially Available High Fogging Systems
Authors: Savic Sasha M. , Rostek Katharina E. , Klaesson Daniel K.
Published: November 2008

High fogging (wet compression, spray inter-cooling) is a technology used for gas turbine (GT) power augmentation. By evaporative spray inter-cooling of the air during compression, which is the main physical effect associated with the HF, a 5–7% power boost of the GT (for each percent of injected water per mass of air) is achieved. HF of a gas turbine can be accomplished using different spray technologies. In this study three different, commercially available spray technologies — pressure-swirl, hot water injection and air-assisted atomization — are compared regarding both technical and economical benefits and risks. The comparison is based on droplet sizing results, system complexity, the feasibility of system integration into the GT’s control and plant operation concept, GT performance and operational and additional O&M costs. It is also known that high fogging carries certain risks to the safe operation of a GT, such as compressor blades erosion, reduction in compressor surge margin and cooling airflows. To minimize the negative impact of high fogging, it is therefore important to select the most appropriate high fogging system as well as to provide for its full engine integration.
Uncertainty Analysis of a Polytropic Compression Process and Application to Centrifugal Compressor Performance Testing
Authors: Gilarranz Jose´ L.
Published: November 2008

In recent years, several papers have been written concerning the application of uncertainty analyses for isentropic compression processes under the assumption of ideal gas behavior. However, for high-pressure ratio machines, the ideal gas model fails to capture the physics of the process. Still, the estimation of test uncertainty for polytropic processes is hindered by the complexity of the equations used to calculate the performance parameters and by the incorporation of real gas equations into the models. This paper presents an uncertainty analysis developed to estimate the error levels in data gathered during factory aero-performance tests of single- or multi-stage centrifugal compressors. The analysis incorporates the effects of the variation and uncertainty levels of every parameter used to calculate centrifugal compressor aero-thermal performance. Included are the variables used to define the thermodynamic states of the fluid inside the compressor, as well as geometric and operational parameters associated with the machine and test loop. Two different methods have been utilized and the results compared to evaluate the advantages and drawbacks of each. The first method is based on the direct use of the Monte Carlo simulation technique combined with real gas equations of state. The second method employs uncertainty propagation equations and the methodology included in the ASME PTC-19.1 (1998) Test Code. Both approaches utilize the polytropic compression model and equations for performance evaluation that are included in the ASME PTC 10 (1997) Power Test Code for compressors and exhausters. The methods and results from this work may be easily extended to the isentropic compression model as well. The use of real gas equations of state make the methods applicable to virtually any gas composition. Although the analysis was intended to be applied to ASME PTC 10 Type 2 tests, the method can be extended to evaluate Type 1 and/or on-site field tests, as long as certain considerations are addressed. The uncertainty analysis presented is then used to evaluate data from several machines, ranging from a low-pressure ratio gas pipeline compressor to an eight-stage machine used for natural gas processing. Comments are offered concerning the effects of machine pressure ratio on the levels of uncertainty, as well as the importance of proper selection of instrumentation to minimize the error level of the test data. Special emphasis is placed on the benefits of using this analysis during the planning phase of the test program, to determine the optimal combination of instruments, to guarantee acceptable levels of uncertainty.
Catalytic Combustion Systems for Micro-Scale Gas Turbine Engines
Authors: Spadaccini C. M. , Peck J. , Waitz I. A.
Published: November 2008

As part of an ongoing effort to develop a micro-scale gas turbine engine for power generation and micropropulsion applications, this paper presents the design, modeling, and experimental assessment of a catalytic combustion system. Previous work has indicated that homogenous gas-phase microcombustors are severely limited by chemical reaction time-scales. Storable hydrocarbon fuels, such as propane, have been shown to blowout well below the desired mass flow rate per unit volume. Heterogeneous catalytic combustion has been identified as a possible improvement. Surface catalysis can increase hydrocarbon-air reaction rates, improve ignition characteristics, and broaden stability limits. Several radial inflow combustors were micromachined from silicon wafers using Deep Reactive Ion Etching (DRIE) and aligned fusion wafer bonding. The 191 mm3 combustion chambers were filled with platinum coated foam materials of various porosity and surface area. For near stoichiometric propane-air mixtures, exit gas temperatures of 1100 K were achieved at mass flow rates in excess of 0.35 g/s. This corresponds to a power density of approximately 1200 MW/m3; an 8.5-fold increase over the maximum power density achieved for gas-phase propane-air combustion in a similar geometry. Low order models including time-scale analyses and a one-dimensional steady-state plug-flow reactor model, were developed to elucidate the underlying physics and to identify important design parameters. High power density catalytic microcombustors were found to be limited by the diffusion of fuel species to the active surface, while substrate porosity and surface area-to-volume ratio were the dominant design variables.
Effect of Fuel System Impedance Mismatch on Combustion Dynamics
Authors: Richards Geo A. , Robey Edward H.
Published: November 2008

Combustion dynamics are a challenging problem in the design and operation of premixed gas turbine combustors. In premixed combustors, pressure oscillations created by the flame dynamic response can lead to damaging pressure oscillations. These dynamics are typically controlled by designing the combustor to achieve stable operation for planned conditions, but dynamics may still occur with minor changes in ambient operating conditions, or fuel composition. In these situations, pilot flames, or adjustment to fuel flow splits can be used to stabilize the combustor, but often with a compromise in emissions performance. As an alternative to purely passive design changes, prior studies have demonstrated that adjustment to the fuel system impedance can be used to stabilize combustion. Prior studies have considered just the response of individual fuel injector and combustor. However, in practical combustion systems, multiple fuel injectors are used. In this situation, individual injector impedance can be modified to produce a different dynamic response from individual flames. The resulting impedance mismatch prevents all injectors from strongly coupling to the same acoustic mode. In principle, this mismatch should reduce the amplitude of dynamics, and may expand the operating margin for stable combustion conditions. In this paper, a 30 kW laboratory combustor with two premixed fuel injectors is used to study the effect of impedance mismatch on combustion stability. The two fuel injectors are equipped with variable geometry resonators that allow a survey of dynamic stability while changing the impedance of the individual fuel systems. Results demonstrate that a wide variation in dynamic response can be achieved by combining different impedence fuel injectors. A baseline 7% RMS pressure oscillation was reduced to less than 3% by mismatching the fuel impedance.
Thermo-Economic Evaluation of Bio-Ethanol Humidification EvGT Cycle
Authors: Thern Marcus , Lindquist Torbjo¨rn , Torisson Tord
Published: November 2008

The evaporative gas turbine pilot plant (EvGT) has been in operation at Lund Institute of Technology in Sweden since 1997. This article presents the latest development in the evaporative technology, the evaporation of bio-ethanol in a gas turbine power plant as a means to reduce the emission of greenhouse gases. Bio-ethanol is produced from a feedstock consisting of corn-stover, and the bio-ethanol is here considered to be a renewable fuel with zero impact regarding CO2 in the exhaust gases. This concept is evaluated and compared to a direct-fired Rankine cycle in the size range of 3–5 MWel and 15–30 MWel concerning plant efficiency and investment cost. The proposed bio-ethanol evaporation technology provides fuel for a Humid Air Turbine by evaporating bio-ethanol into the compressor discharge air. This evaporation process creates a combustible gas that is led to the combustor as the primary fuel. The bio-ethanol used in the process has not been distilled. The bio-ethanol is supplied to the process as a mash, i.e. a mix of water and ethanol with low concentration of ethanol. To extract the ethanol from the mash, energy is required. In this process, low-level heat from the gas turbine cycle is used for the separation process. All power cycles studied have been modeled in IPSEpro™, a heat and mass balance software, using advanced component models developed by the authors. An equilibrium model is used to model the behavior of the evaporation of ethanol and water into an air stream. A correction parameter has been introduced into the equilibrium model to account for the deviation from equilibrium. This parameter has been validated through experimental work on the Evaporative Gas Turbine pilot plant. The evaporation technology can be used with different types of cycle configurations attaining electrical efficiencies of 29% for a simple version of a Humid Air Turbine. The Humid Air Turbine can sustain a combustor outlet temperature of 1100°C without supplementary firing. The proposed cycle configuration also shows to be an economically viable alternative to direct fired Rankine cycle.
Development of Near-Net Shape Casting Technology for MGC Components
Authors: Waku Yoshiharu , Nakagawa Narihito , Kobayashi Kenji , Yokoi Shinya
Published: November 2008

Much attention has been paid to unidirectionally solidified ceramic composites as a candidate for a high-temperature structural material. Eutectic composites, known as Melt Growth Composites (MGCs), have recently been developed. The MGCs (Al2O3/YAG, Al2O3/GAP binary and Al2O3/YAG/ZrO2 ternary systems) have a novel microstructure consisting of three-dimensionally continuous and complexly entangled single-crystal Al2O3 and single-crystal oxide compounds (YAG or GAP or YAG and ZrO2). Therefore, the MGCs have excellent high-temperature strength characteristics, creep resistance, superior oxidation resistance and thermal stability in an air atmosphere at very high temperatures. Manufacturing processes for the MGCs (Al2O3/YAG and Al2O3/GAP binary systems) are being examined under a Japanese national project, scheduled from 2001–2005. The molybdenum mold for near-net-shaped casting of the gas turbine component was fabricated by plasma spraying the molybdenum powders on the copper model. Near-net-shape casting of MGCs is being examined under the NEDO project using the plasma sprayed mold and a new Bridgman-type furnace.
A Study on Transient Performance Characteristics of the CRW Type UAV Propulsion System During Flight Mode Transition
Authors: Kong Changduk , Park Jongha , Kang Myoungcheol
Published: November 2008

A propulsion system of the CRW (Canard Rotor Wing) type UAV (Unmanned Aerial Vehicle) was composed of the turbojet engine, exhaust nozzles including some tip jet nozzles and a main nozzle and the duct system including straight ducts, curved ducts and master valve. The CRW type UAV has three different flight modes such as the rotary wing mode for take-off and landing, the high-speed forward flight mode with the fixed wing and the transition flight mode between the previously mentioned two flight modes. In order to evaluate transient performance characteristics of the CRW type UAV propulsion system during flight mode transition, the propulsion system was modeled using SIMULINK®, which is an user-friendly GUI type dynamic analysis tool provided by MATLAB, in this study. Considering area variation of the master valve and the main exhaust nozzle simulated the transition flight mode between the rotary wing mode and the fixed wing mode. In order to verify acceptability of the main turbojet engine model, performance simulation results using SIMULINK® were compared with results using the commercial program GSP. Moreover the performance characteristics of the propulsion system were investigated depending on position angle variation of the master valve at both the rotary wing mode and the fixed wing mode. In the transient performance behaviors at the rotary wing flight mode, the more turbine inlet temperature over shoot occurs and the net thrust at tip jet nozzles, decreases rapidly at initial condition then increase fast to the converged steady-state condition. Therefore, the fuel throttle should be slowly performed for safe operation of engine. During flight mode transition from the rotary wing mode to the fixed wing mode, rotary duct pressure was fell down to atmospheric pressure, but main duct pressure was mostly kept due to very small friction loss. Total net thrust was oscillatory increased. During flight mode transition from the fixed wing mode to rotary wing mode, rotary duct pressure was rapidly increased, but main duct pressure was mostly kept. Total net thrust also was oscillatory decreased. Through this investigation, it was found that severe thrust fluctuation should be considered for safe flight during flight mode transition even though operation of the master valve is slowly scheduled. Therefore a solution for improving the thrust oscillation will be suggested later.
Demonstration of a Turbojet Engine Using an Air Foil Bearing
Authors: Heshmat Hooshang , Walton James F. , Tomaszewski Michael J.
Published: November 2008

A test of the target drone main propulsion turbojet engine was recently conducted that demonstrated successful operation of a turbojet engine with a compliant foil air bearing. For this effort, the hot section rolling element bearing and the entire existing lubrication system was replaced with a compliant foil air bearing. This technology demonstration test showed the ability of the foil bearing to operate in the extremely challenging environment behind the turbine. Detailed engine integration studies, bearing component rig testing and hot engine simulator tests were completed prior to the successful engine test. The rig and simulator tests verified high temperature capabilities of the bearing and its surface coating, the bearing journal design, bearing dynamic performance, and rotor-bearing system dynamic stability, prior to engine integration and test. Based on these preliminary efforts, the engine and bearing were assembled and tests were conducted that included over 70 start stop cycles (including hot restarts), seven simulated mission cycles and more than 14 hours of run time. The foil bearing and engine operated flawlessly throughout the test. Vibrations were very low and all temperatures and pressures were as expected. A posttest tear down and hardware inspection revealed that the bearing, journal and all components remained in perfect condition. These data will be used to further the application of foil bearings to numerous other gas turbine engines for both military and commercial systems.
Experimental Study and Modeling of Autoignition of Natural Gas/Air-Mixtures Under Gas Turbine Relevant Conditions
Authors: Koch Andreas , Naumann Clemens , Meier Wolfgang , Aigner Manfred
Published: November 2008

The objective of this work was the improvement of methods for predicting autoignition in turbulent flows of different natural gas mixtures and air. Measurements were performed in a mixing duct where fuel was laterally injected into a turbulent flow of preheated and pressurized air. To study the influence of higher order hydrocarbons on autoignition, natural gas was mixed with propane up to 20% by volume at pressures up to 15 bar. During a measurement cycle, the air temperature was increased until autoignition occurred. The ignition process was observed by high-speed imaging of the flame chemiluminescence. In order to attribute a residence time (ignition delay time) to the locations where autoignition was detected the flow field and its turbulent fluctuations were simulated by numerical codes. These residence times were compared to calculated ignition delay times using detailed chemical simulations. The measurement system and data evaluation procedure are described and preliminary results are presented. An increase in pressure and in fraction of propane in the natural gas both reduced the ignition delay time. The measured ignition delay times were systematically longer than the predicted ones for temperatures above 950 K. The results are important for the design process of gas turbine combustors and the studies also demonstrate a procedure for the validation of design tools under relevant conditions.
A Promising New Energy-Based Fatigue Life Prediction Framework
Authors: Scott-Emuakpor Onome , Shen M.-H. Herman , Cross Charles , Calcaterra Jeffrey , George Tommy
Published: November 2008

An energy-based fatigue life prediction framework has been developed for prediction of axial and bending fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was developed in accordance with the approach in our previous study which states: the total strain energy dissipated during a monotonic fracture process is a material property that can be determined by measuring the area underneath the monotonic true stress-strain curve. The framework consists of the following two elements: (1) Development of a bending fatigue criterion by observing the total strain energy of the effective volume, which is achieved by computing the total plastic strain energy with consideration of the stress gradient influence through the thickness of a specimen, in the fatigue area, during cyclic loading. A comparison between the prediction and the experimental results from 6061-T6 aluminum specimens was conducted and shows that the new energy-based fatigue criterion is capable of predicting accurate fully reversed bending fatigue life. (2) Development of a new life prediction criterion for axial fatigue at various stress ratios. The criterion was constructed by accounting for both the residual energy dissipated, monotonically, due to the mean stress, and the incorporation of the mean stress effect into the total strain energy density dissipated per cycle. The performance of the criterion was demonstrated by experimental results from 6061-T6 aluminum dog-bone specimens subjected to axial stress at various stress ratios. The comparison shows very good agreement, thus validating the capability of producing accurate fatigue life predictions.
High-Productivity, Low-Cost, Gas Turbine System Modeling Software
Authors: Cunningham Tom , Medlock Allen , Sandefur Matt , Rowse Jack
Published: November 2008

Honeywell Engines Systems & Services has written Fast Accurate Simulation of Turbine engines (FAST), a gas turbine system modeling program. Software design and development concepts, capabilities, and improved problem solving using FAST are discussed. Software design emphasis was placed on improving an engineer’s productivity, being easy to learn and use, adding new capability, and having low development and maintenance costs. Capability to replace all legacy modeling software, and make conversion of old models to the new model format simple was also required. The result was a significant increase in the productivity of the performance engineering staff in their efforts to support the design, development, and production, of gas turbine engines. FAST has provided the performance engineering staff with a simple but powerful input language and a robust numerical solver. With FAST, the user can perform preliminary engine design, model steady-state and transient off-design conditions, perform test data analysis, perform system modeling (multiple engine, installations, and engine/vehicle), connect FAST to other software, and generate customer programs quickly with auto-code features. FAST has permitted significant orders of magnitude increase in the volume of cycle analysis coupled with a 70% reduction in engineering staff and an 80% reduction in software development staff.
Post Engine Test Characterization and Flight Test Experience of Self Sealing Ceramic Matrix Composites for Nozzle Seals in Gas Turbine Engines
Authors: Bouillon E. , Ojard G. , Ouyang Z. , Zawada L. , Habarou G. , Louchet C. , Feindel D. , Spriet P. , Logan C. , Arnold T. , Rogers K. , Stetson D.
Published: November 2008

The advancement of self-sealing ceramic matrix composites offers durability improvements in hot section components of gas turbine engines. These durability improvements come with no need for internal cooling and with reduced weight. Building on past material efforts, ceramic matrix composites based upon a silicon carbide or carbon fiber with a novel self-sealing matrix have been developed for gas turbine applications. The specific application being pursued on this effort is an F100-PW-229 nozzle seal. Ground engine testing has been completed that exceeds the full design life. The ground testing has demonstrated a significant durability improvement from the baseline metal design. Residual properties have been determined by extracting tensile and microstructural coupons from the ceramic matrix composite seal. This was done as a function of design life. Nondestructive interrogation was used as a guide in setting cutting diagrams. The results from this effort will be presented.
The Implementation of the Data Validation Process in a Gas Turbine Performance Monitoring System
Authors: Chen Pen-Chung , Andersen Helmer
Published: November 2008

It is an important issue for the power generation industry to minimize maintenance cost; increase plant reliability and availability and enhance equipment performance. Knowing the operating conditions of a gas turbine, engineers can analyze and optimize the process throughout the operation. The accuracy of the performance measurement data is very critical in the gas turbine operation, because it is the foundation of the analysis. To verify the accuracy of measurement data, this paper will present a mathematical approach based on the data validation process. The data validation process is a method for correcting and verifying the measurement data and associated uncertainties by satisfying the different conservation laws like mass balance, energy balance and other related balances. The data validation process will increase the overall accuracy of the measurement data. The procedure of data validation will be illustrated by determining the inlet mass flow of a compressor. For the practical purpose, the measurement data presented in this paper is acquired from a commercial gas turbine plant. The inlet mass flow of compressor can be calculated using multiple mass- and energy balance equations. The result of the comparison of the initial measured data and the validated data will be discussed. This paper will also show that the data validation process can identify serious measurement errors and eliminate the common contradictions among the balance equations. After applying the data validation method on the performance measurement data, plant users will have more confidence to optimize the daily operation. The data validation is an auxiliary method to evaluate the quality of measured data and uncertainties. However, it still cannot replace the accurate and calibrated measurement equipments during the performance test. The data validation approach is used as an auxiliary tool for Alstom’s Plant Monitoring and Diagnostic System (AMODIS) [1], which can optimize plant operation and enhance turbine monitoring in critical areas for early warning.
Measurements Inside a Bluff-Body Stabilized Gas Turbine Combustor for Application of Pressurized Biomass Derived Low Calorific Value Fuel Gas and Comparison of the Results
Authors: van der Wel Marco , de Jong Wiebren , Spliethoff Hartmut
Published: November 2008

A medium size gas turbine combustor of 1.5 MW of Delft University (TUD) has been tested to combust low calorific value (LCV) fuel gas. The LCV gas was obtained from pressurized gasification of wood pellets class A, miscanthus giganteus and brown coal and was cleaned from its particulates by high temperature ceramic filters of β-cordierite. Stable combustion of (biomass derived) low calorific value fuel gas with heating values (LHV) between 1.64 and 4.48 MJ/m3n (50 to 120 Btu/scf) was accomplished due to high fuel gas temperatures ranging from 845 to 1099 K. Main species (O2, CO2,) and minor species (Ar, CH4, H2, CO, NO) were measured in the exhaust and by a traversing probe after the primary zone of the combustor. The water and nitrogen contents in the exhaust were calculated from the element balances. The results are compared with a previously tested combustor of ALSTOM Power of the RQL type.
Development of Japanese Super Marine Gas Turbine
Authors: Sugimoto Takao , Miyaji Hiroshi , Sano Hikaru
Published: November 2008

In 1997, five Japanese gas turbine manufacturers — Kawasaki Heavy Industries, Ishikawajima-Harima Heavy Industries, Daihatsu Diesel, Niigata engineering, and Yanmar — joined forces to establish the Technological Research Association for Super Marine Gas Turbine (SMGT) and embarked on development of a next generation gas turbine for the maritime industry. The goal of this project was to develop a marine gas turbine with high thermal efficiency (38–40%) and low NOx emissions of less than 1g/kWh. In 2003, this project was completed with success. SMGT is a two shaft, re-generative cycle gas turbine with an axial-radial compressor, multi-can dry low emission combustor, air cooled gas generator, power turbine, and a recuperator. Additionally, the new technologies incorporated into the SMGT deliver high performance and low emissions. Development of the commercial version, the SMGT2, followed, and the program came to a successful end in 2005. The three purposes of development were to improve the design of the power turbine and recuperator, to prove durability using endurance bench tests, and to apply a waste heat recovery system. Using a waste heat recovery boiler and an inlet cooler with an absorption chiller, energy efficiency improved by 50% and shaft output increased to 2,300kW, even when at high ambient temperatures. High energy efficiency reduces fuel consumption, thus reducing the cost of operating a vessel.
A Further Step Towards a Graz Cycle Power Plant for CO2 Capture
Authors: Sanz W. , Jericha H. , Luckel F. , Go¨ttlich E. , Heitmeir F.
Published: November 2008

Introduction of closed cycle gas turbines with their capability of retaining combustion generated CO2 can offer a valuable contribution to the Kyoto goal and to future power generation. Therefore research and development work at Graz University of Technology since the nineties has led to the Graz Cycle, a zero emission power cycle of highest efficiency. It burns fossil fuels with pure oxygen which enables the cost-effective separation of the combustion CO2 by condensation. The efforts for the oxygen supply in an air separation plant are partly compensated by cycle efficiencies far higher than for modern combined cycle plants. At the ASME IGTI conference 2004 in Vienna a high steam content S-Graz Cycle power plant was presented showing efficiencies for syngas firing up to 70% and a net efficiency of 57% considering oxygen supply and CO2 compression. A first economic analysis gave CO2 mitigation costs of about 10 $/ton CO2 avoided. These favourable data induced the Norwegian oil and gas company Statoil ASA to order a techno-economic evaluation study of the Graz Cycle. In order to allow a benchmarking of the Graz Cycle and a comparison with other CO2 capture concepts, the assumptions of component efficiency and losses are modified to values agreed with Statoil. In this work the new assumptions made and the resulting power cycle for natural gas firing, which is the most likely fuel of a first demonstration plant, are presented. Further modifications of the cycle scheme are discussed and their potential is analyzed. Finally, an economic analysis of the Graz Cycle power plant is performed showing low CO2 mitigation costs in the range of 20 $/ton CO2 avoided, but also the strong dependence of the economics on the investment costs.
A Partially Integrated Approach to Component Zooming Using Computational Fluid Dynamics
Authors: Pachidis Vassilios , Pilidis Pericles , Guindeuil Geoffrey , Kalfas Anestis , Templalexis Ioannis
Published: November 2008

This study focuses on a simulation strategy that will allow the performance characteristics of an isolated gas turbine engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of resolution. This work will enable component-level, complex physical processes to be captured and analyzed in the context of the whole engine performance, at an affordable computing resource and time. The technique described in this paper utilizes an object-oriented, zero-dimensional (0-D) gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional (3-D) computational fluid dynamics (CFD) component model. The technique is called ‘partially integrated’ zooming, in that there is no automatic link between the 0-D engine cycle and the 3-D CFD model. It can be applied to all engine components and involves the generation of a component characteristic map via an iterative execution of the 0-D cycle and the 3-D CFD model. This work investigates relative changes in the simulated engine performance after integrating the CFD-generated component map into the 0-D engine analysis. This paper attempts to demonstrate the ‘partially integrated’ approach to component zooming by using a 3-D CFD intake model of a high by-pass ratio (HBR) turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The CFD-generated performance map can fully define the characteristic of the intake at several operating conditions and is subsequently used to provide a more accurate, physics-based estimate of intake performance (i.e. pressure recovery) and hence, engine performance, replacing the default, empirical values within the 0-D cycle model. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the CFD-generated map is presented in this paper. The analysis carried out by this study, demonstrates relative changes in the simulated engine performance larger than 1%.
A Study in the Process Modeling of the Startup of Fuel Cell/Gas Turbine Hybrid Systems
Authors: Shelton Michael , Celik Ismail , Liese Eric , Tucker David
Published: November 2008

As energy demands increase and the associated costs increase with that demand, newer energy alternatives are becoming more important to society. Although not new, fuel cell technology is taking a lead role in the quest for a cleaner and competitive power generation system. High efficiencies on the order of 50% are now possible with stand-alone fuel cells. When coupled with a gas turbine, efficiencies of around 70% may be expected. However, the fuel cell/gas turbine hybrid has inherent problems of stability and unpredictable response to adverse transients that first must be addressed to make this technology viable. The National Energy Technology Laboratories (NETL) in Morgantown is involved in the development of such hybrid technology. This study details a process modeling approach based on the commercial modeling package, Protrax™, and is associated specifically with the NETL HYBRID PERFORMANCE (HYPER) research effort. Simulation versus experimental test data is presented to validate the process model during the cold flow startup phase. The results provide insight into the transients of the system built at NETL.
A CMC Handbook With a Focus on Design, Testing and Data: MIL Handbook 17 Vol 5
Authors: Gonczy Stephen T.
Published: November 2008

The Department of Defense Handbook — Ceramic Matrix Composites (MIL-HDBK 17, Volume 5) is a comprehensive volume of technical information about the design, testing, and application of ceramic matrix composite (CMC) materials. The handbook provides design and analysis guidelines for CMC utilization and life prediction; best practices on CMC testing; instruction on the collection of statistically meaningful data; and authoritative performance data on current and emerging CMC systems. The target audience for the handbook are the OEM designers who are considering CMCs for cutting-edge high temperature applications in turbines, combustors, heat exchangers, and environmental control. The CMC Handbook provides a framework for rapid, comprehensive, and effective technical communication between the CMC designer and the CMC producer. The handbook has been written through the collaboration of a wide cross section of engineers and scientists from the CMC user and producer communities.
High Pressure Turbine Deposition in Land Based Gas Turbines From Various Synfuels
Authors: Bons Jeffrey P. , Crosby Jared , Wammack James E. , Bentley Brook I. , Fletcher Thomas H.
Published: November 2008

Ash deposits from four candidate power turbine synfuels were studied in an accelerated deposition test facility. The facility matches the gas temperature and velocity of modern first stage high pressure turbine vanes. A natural-gas combustor was seeded with finely-ground fuel ash particulate from four different fuels: straw, sawdust, coal, and petroleum coke. The entrained ash particles were accelerated to a combustor exit flow Mach number of 0.31 before impinging on a thermal barrier coating (TBC) target coupon at 1150°C. Post exposure analyses included surface topography, scanning electron microscopy, and x-ray spectroscopy. Due to significant differences in the chemical composition of the various fuel ash samples, deposit thickness and structure vary considerably for each fuel. Biomass products (e.g. sawdust and straw) are significantly less prone to deposition than coal and petcoke for the same particle loading conditions. In a test simulating one turbine operating year at a moderate particulate loading of 0.02 parts per million by weight, deposit thickness from coal and petcoke ash exceeded 1 mm and 2 mm respectively. These large deposits from coal and petcoke were found to detach readily from the turbine material with thermal cycling and handling. The smaller biomass deposit samples showed greater tenacity in adhering to the TBC surface. In all cases, corrosive elements (e.g. Na, K, V, Cl, S) were found to penetrate the TBC layer during the accelerated deposition test. Implications for the power generation goal of fuel flexibility are discussed.
Reacting Spray Structure of a Counter-Rotating Swirl Cup
Authors: Fu Yongqiang , Cai Jun , Jeng San-Mou , Mongia Hukam
Published: November 2008

An experimental study was conducted to characterize the two-phase nonreacting and reacting flow characteristics of a mixer comprised of concentric counter-swirlers installed in a 3-inch square test section. A two-component Phase Doppler Particle Analyzer (PDPA) system was used to measure mean and fluctuating velocity components in the three directions, as well as the droplet size distribution and volume flux. Detailed measurements have been used to improve mechanistic understanding of reacting counter-swirling complex flow-field with attendant changes expected in future modeling direction. As known empirically for the mixer studied, the present indepth experimental results show that the reacting flowfield characteristics are significantly different from that of the isothermal flow in regard to, for example, the recirculation zone, and decay of the counter-swirl velocity component.
Tailored Rheological Behavior of Mullite and BSAS Suspensions Using a Cationic Polyelectrolyte
Authors: Kirby Glen H. , Cooley Kevin M. , Armstrong Beth L.
Published: November 2008

The effects of a cationic polyelectrolyte, polyethylenimine, on the rheological behavior of aqueous mullite and celsian phase, barium strontium aluminosilicate (BSAS) suspensions have been studied to optimize a dip-coating process. The surface of the ceramic particles was characterized in aqueous media using zeta potential measurements. The ionization behavior and hydrodynamic radius of polyethylenimine in aqueous media was characterized by potentiometric titration and dynamic light scattering measurements, respectively. The rheological behavior of concentrated ceramic suspensions containing polyethylenimine was characterized by stress viscometry and elastic modulus measurements. Polyethylenimine imparts repulsive, electrosteric interactions between mullite and BSAS particles in aqueous suspension, resulting in shear thinning flow behavior, linear elastic moduli, and yield stress values that are minimized for suspensions with a critical PEI concentration of 0.2 mg PEI per m2 of mullite and 0.4 mg PEI per m2 of BSAS, respectively. The elastic moduli and yield stress of mullite and BSAS suspensions were nearly identical at equivalent fractions of their critical PEI concentration. Uniform coatings were obtained upon dipping SiC, Si3N4, and Si-metal substrates into shear-thinning suspensions containing PEI at 81–88% of the critical concentration. Dense mullite coatings were demonstrated on SiC substrates after sintering at 1400°C.
The Effect of Water Vapor on Cr Depletion in Advanced Recuperator Alloys
Authors: Pint Bruce A.
Published: November 2008

Durable alloy foils are needed for gas turbine recuperators operating at 650°–700°C. It has been established that water vapor in the exhaust gas causes more rapid consumption of Cr in austenitic stainless steels leading to a reduction in operating lifetime of these thin-walled components. Laboratory testing at 650°–800°C of commercial and model alloys is being used to develop a better understanding of the long-term rate of Cr consumption in these environments. Results are presented for commercial alloys 709, 120 and 625. After 10,000h exposures at 650° and 700°C in humid air, grain boundary Cr depletion was observed near the surface of all these materials. In the Fe-base alloys, 709 and 120, this depletion led to localized Fe-rich nodule formation. This information then can be used to develop low-cost alternatives to currently available candidate materials.
Development and Evaluation of Hybrid Oxide/Oxide Ceramic Matrix Composite Combustor Liners
Authors: Szweda Andy , Butner Steve , Ruffoni John , Bacalski Carlos , Lane Jay , Morrison Jay , Merrill Gary , van Roode Mark , Fahme Anthony , Miriyala Naren , Leroux Don
Published: November 2008

Oxide/Oxide Ceramic Matrix Composites (CMCs) are an attractive class of materials for gas turbine hot section applications. The oxide fiber reinforcement and inherent matrix porosity contributes to favorable fracture toughness and thereby enhanced resistance against impact by foreign objects. Also, the oxide composition ensures superior environmental resistance against accelerated attack by corrosive species in the gas turbine hot section and resulting surface recession typically observed in silicon-based ceramic monolithic and composite materials. Under a program sponsored by the US National Institute of Standards and Technology (NIST) a hybrid oxide/oxide CMC system has been developed with potential application for stationary gas turbine hot section components. COI Ceramics, Inc. has fabricated subscale and full scale combustor liners which have been evaluated in rig and engine testing at Solar, and in field testing in a Solar Centaur® 50S engine at a commercial end user site. Following the conclusion of the NIST program in June 2003 the engine field testing is being continued under a Solar-led program sponsored by the US Dept. of Energy (DOE). As of November 2004, a hybrid oxide/oxide CMC outer combustor liner has accumulated 12,582 field test hours with 63 starts and an extensive material experience base has been developed. The paper will summarize the progress to-date for this hybrid CMC combustor liner development and demonstration, including selected fabrication approach, NDE, and rig/engine test experience.
Diagnostics of a Small Jet Engine-Neural Networks Approach
Authors: Ghoreyshi M. , Pilidis P. , Ramsden K. W.
Published: November 2008

This paper presents the design procedure and application of a nested neural network for diagnostics of a small jet engine. Such a diagnostics technique is based on the performance analysis while the performance model was developed with TURBOMATCH, the Cranfield University’s gas turbine simulation code. To validate this model, an outdoor test was conducted to run the small engine. Areas examined in this paper are performance validation of the engine, neural network design, training data generation, and networks training procedures. The assumptions, measured parameters selection and the results obtained are presented and discussed. The results obtained show the good prospects for the use of NNs for detection of existing faults, isolation of faults and quantification of fault levels.
On LMI-Based Optimization of Vibration and Stability in Rotor System Design
Authors: Cole Matthew O. T. , Wongratanaphisan Theeraphong , Keogh Patrick S.
Published: November 2008

This paper considers optimization of rotor system design using stability and vibration response criteria. The initial premise of the study is that the effect of certain design changes can be parameterized in a system dynamic model through their influence on the system matrices obtained by finite element modeling. A suitable vibration response measure is derived by considering an unknown axial distribution of unbalance components having bounded magnitude. It is shown that the worst-case unbalance response is given by an absolute row-sum norm of the system frequency response matrix. The minimization of this norm is treated through the formulation of a set of linear matrix inequalities (LMIs) that can also incorporate design parameter constraints and stability criteria. The formulation can also be extended to cover uncertain or time-varying system dynamics arising, for example, due to speed-dependent bearing coefficients or gyroscopic effects. Numerical solution of the matrix inequalities is tackled using an iterative method that involves standard convex optimization routines. The method is applied in a case study that considers the optimal selection of bearing support stiffness and damping levels to minimize the worst-case vibration of a flexible rotor over a finite speed range. The main restriction in the application of the method is found to be the slow convergence of the numerical routines that occurs with high-order models and/or high problem complexity.
Knowledge-Based Operation and Maintenance of Combined-Cycle Power Plants
Authors: Decoussemaeker Pascal , Umbricht Walter
Published: November 2008

One of the main factors in creating a competitive advantage once a plant is installed, is through improved Operation and Maintenance. There are several routes that allow improvements in operation and maintenance. However, they all require an improved pool of knowledge on the technical and economical condition of the plant and its boundary conditions. This change of focus from hardware to knowledge is a general trend observed in all branches of industry and commerce. Dealing with these challenges that the knowledge society imposes on everyone requires a change in culture. The winners will be those that can effectively manage and use their knowledge. This paper will analyze the Operation and Maintenance process and define the general routes of improvement. It will then illustrate how these improvements can be realized by moving to more knowledge-based processes.
Emission, LBO and Combustion Dynamic Characterization of Several Alternative Fuels
Authors: Oumejjoud Khalid , Stuttaford Peter , Jennings Steve , Henriquez John , Rizkalla Hany , Chen Yan
Published: November 2008

Regulations are becoming increasingly stringent regarding gas turbine emissions. In addition fuel costs are at record highs. Power plant operators are exploring all alternatives for reducing operational cost. Refinery offgas represents an attractive cost reduction measure if one could burn it in the gas turbine. Hydrogen and methane are often the main components of such offgas. In an attempt to define the potential for an LEC-III® (Power Systems Mfg., LLC. Low Emission Combustor) performance with such an offgas, rig testing has been successfully carried out with several alternative fuels. Small quantities of hydrogen blended with natural gas and burned in specific zones of the combustor allowed emissions levels of sub 2ppm NOx and sub 9ppm CO to be demonstrated at full base load engine operating conditions on the test rig. Based upon rig to engine benchmarking these same emissions levels should be realized upon the full engine.