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Gas Turbine (gas + turbine)
Selected AbstractsCharacterization of First-Stage Silicon Nitride Components After Exposure to an Industrial Gas TurbineJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2006H.-T. Lin This paper provides a summary of recent efforts undertaken to examine the mechanical properties and microstructural stability of first-stage silicon nitride blades and nozzles after field testing in an industrial gas turbine. Two commercially available silicon nitrides, i.e., Kyocera SN282 vanes and SN281 blades, were successfully evaluated in the 100 h final phase engine test at Solar Turbines Incorporated. The turbine rotor inlet temperature was increased from 1010° to 1121°C at 100% speed during the engine test with efficiency increasing from 28.8% to 30.1%. Results of scanning electron microscopy showed that apparent materials recession still occurred during the 100 h engine test, especially in the leading and trailing edge regions where the gas pressure or velocity was the highest. The apparent material recession of the airfoils resulted from the volatilization of the normally protective silica layer, evidenced by the increased surface roughness and porous Lu2Si2O7 surface layer features. On the other hand, mechanical results generated using a ball-on-ring test technique showed that little strength degradation was measured after the 100 h engine test. [source] High Frequency AC Power SystemNAVAL ENGINEERS JOURNAL, Issue 4 2008RAYMOND M. CALFO The Navy's Next Generation Integrated Power System (NGIPS) master plan calls for the evolution of the IPS system from its current medium voltage, 60 Hz state to a high-frequency, medium-voltage AC (HFAC) system in the next 10 years. Beyond that, and pending development of key protection components, a medium-voltage DC system will be considered for implementation. The master plan calls for power generation modules at three power levels across these systems: ,A low power level (2,5 MW) driven by a fuel-efficient diesel prime mover, ,A medium power level (10,15 MW) driven by a gas turbine, and ,A main propulsion power level (20,40 MW) driven by a gas turbine. EMD is currently developing a high-speed, high-frequency, liquid-cooled generator under contract with NAVSEA that will effectively demonstrate the mid-level generator for the HFAC system. It will be coupled directly to the output of a GE LM1600 Gas Turbine to provide a TG set with power density four times more favorable than conventional ATG sets. The generator development is proceeding favorably, with testing at the Navy's land-based test site (LBTS) expected to begin in July 2008. The technology embodied in the high-speed generator can be easily extrapolated to main turbine generator power levels. Given the availability of prime movers at appropriate speeds, the power generation modules for the HFAC system, at all three power levels, could be provided in a much shorter time frame than noted in the NGIPS master plan. This paper will explore the combinations of prime movers and advanced generators that would suit the three power generation modules of the HFAC system. A description of the prime mover and the generator used for each module will be provided to demonstrate the modest level of development needed. The performance parameters for each generation module will be provided, along with key characteristics and dimensions for the set. In the end, the paper will make the case that demonstration of a HFAC power generation system can be made in the short term, allowing the shipbuilding community to take advantage of the benefits of state-of-the-art power dense electrical generation. [source] Cycle analysis of low and high H2 utilization SOFCs/gas turbine combined cycle for CO2 recoveryELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2008Takuya Taniuchi Abstract Global warming is mainly caused by CO2 emission from thermal power plants, which burn fossil fuel with air. One of the countermeasure technologies to prevent global warming is CO2 recovery from combustion flue gas and the sequestration of CO2 underground or in the ocean. SOFC and other fuel cells can produce high-concentration CO2, because the reformed fuel gas reacts with oxygen electrochemically without being mixed with air, or diluted by N2. Thus, we propose to operate the multistage SOFCs under high utilization of reformed fuel for obtaining high-concentration CO2. In this report, we have estimated the multistage SOFCs' performance considering H2 diffusion and the combined cycle efficiency of multistage SOFC/gas turbine/CO2 recovery power plant. The power generation efficiency of our CO2 recovery combined cycle is 68.5% and the efficiency of conventional SOFC/GT cycle is 57.8% including the CO2 recovery amine process. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 91(10): 38,45, 2008; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecj.10165 [source] Nonlinear reference tracking control of a gas turbine with load torque estimationINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 8 2008B. Pongrácz Abstract Input,output linearization-based adaptive reference tracking control of a low-power gas turbine model is presented in this paper. The gas turbine is described by a third-order nonlinear input-affine state-space model, where the manipulable input is the fuel mass flowrate and the controlled output is the rotational speed. The stability of the one-dimensional zero dynamics of the controlled plant is investigated via phase diagrams. The input,output linearizing feedback is extended with a load torque estimator algorithm resulting in an adaptive feedback scheme. The tuning of controller parameters is performed considering three main design goals: appropriate settling time, robustness against environmental disturbances and model parameter uncertainties, and avoiding the saturation of the actuator. Simulations show that the closed-loop system is robust with respect to the variations in uncertain model and environ-mental parameters and its performance satisfies the defined requirements. Copyright © 2007 John Wiley & Sons, Ltd. [source] Fault diagnosis of a simulated industrial gas turbine via identification approachINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 4 2007S. Simani Abstract In this paper, a model-based procedure exploiting the analytical redundancy principle for the detection and isolation of faults on a simulated process is presented. The main point of the work consists of using an identification scheme in connection with dynamic observer and Kalman filter designs for diagnostic purpose. The errors-in-variables identification technique and output estimation approach for residual generation are in particular advantageous in terms of solution complexity and performance achievement. The proposed tools are analysed and tested on a single-shaft industrial gas turbine MATLAB/SIMULINK® simulator in the presence of disturbances, i.e. measurement errors and modelling mismatch. Selected performance criteria are used together with Monte-Carlo simulations for robustness and performance evaluation. The suggested technique can constitute the design methodology realising a reliable approach for real application of industrial process FDI. Copyright © 2006 John Wiley & Sons, Ltd. [source] Cost numerical optimization of the triple-pressure steam-reheat gas-reheat gas-recuperated combined power cycle that uses steam for cooling the first GTINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2008A. M. Bassily Abstract Optimization is an important method for improving the efficiency and power of the combined cycle. In this paper, the triple-pressure steam-reheat gas-reheat gas-recuperated combined cycle that uses steam for cooling the first gas turbine (the regular steam-cooled cycle) was optimized relative to its operating parameters. The optimized cycle generates more power and consumes more fuel than the regular steam-cooled cycle. An objective function of the net additional revenue (the saving of the optimization process) was defined in terms of the revenue of the additional generated power and the costs of replacing the heat recovery steam generator (HRSG) and the costs of the additional operation and maintenance, installation, and fuel. Constraints were set on many operating parameters such as air compression ratio, the minimum temperature difference for pinch points (,Tppm), the dryness fraction at steam turbine outlet, and stack temperature. The net additional revenue and cycle efficiency were optimized at 11 different maximum values of turbine inlet temperature (TIT) using two different methods: the direct search and the variable metric. The optima were found at the boundaries of many constraints such as the maximum values of air compression ratio, turbine outlet temperature (TOT), and the minimum value of stack temperature. The performance of the optimized cycles was compared with that for the regular steam-cooled cycle. The results indicate that the optimized cycles are 1.7,1.8 percentage points higher in efficiency and 4.4,7.1% higher in total specific work than the regular steam-cooled cycle when all cycles are compared at the same values of TIT and ,Tppm. Optimizing the net additional revenue could result in an annual saving of 21 million U.S. dollars for a 439,MW power plant. Increasing the maximum TOT to 1000°C and replacing the stainless steel recuperator heat exchanger of the optimized cycle with a super-alloys-recuperated heat exchanger could result in an additional efficiency increase of 1.1 percentage point and a specific work increase of 4.8,7.1%. The optimized cycles were about 3.3 percentage points higher in efficiency than the most efficient commercially available H-system combined cycle when compared at the same value of TIT. Copyright © 2008 John Wiley & Sons, Ltd. [source] Analysis and cost optimization of the triple-pressure steam-reheat gas-reheat gas-recuperated combined power cycleINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2008A. M. Bassily Abstract Increasing the inlet temperature of gas turbine (TIT) and optimization are important methods for improving the efficiency and power of the combined cycle. In this paper, the triple-pressure steam-reheat gas-reheat recuperated combined cycle (the Regular Gas-Reheat cycle) was optimized relative to its operating parameters, including the temperature differences for pinch points (,TPP). The optimized triple-pressure steam-reheat gas-reheat recuperated combined cycle (the Optimized cycle) had much lower ,TPP than that for the Regular Gas-Reheat cycle so that the area of heat transfer of the heat recovery steam generator (HRSG) of the Optimized cycle had to be increased to keep the same rate of heat transfer. For the same mass flow rate of air, the Optimized cycle generates more power and consumes more fuel than the Regular Gas-Reheat cycle. An objective function of the net additional revenue (the saving of the optimization process) was defined in terms of the revenue of the additional generated power and the costs of replacing the HRSG and the additional fuel. Constraints were set on many operating parameters such as the minimum temperature difference for pinch points (,TPPm), the steam turbines inlet temperatures and pressures, and the dryness fraction at steam turbine outlet. The net additional revenue was optimized at 11 different maximum values of TIT using two different methods: the direct search and variable metric. The performance of the Optimized cycle was compared with that for the Regular Gas-Reheat cycle and the triple-pressure steam-reheat gas-reheat recuperated reduced-irreversibility combined cycle (the Reduced-Irreversibility cycle). The results indicate that the Optimized cycle is 0.17,0.35 percentage point higher in efficiency and 5.3,6.8% higher in specific work than the Reduced-Irreversibility cycle, which is 2.84,2.91 percentage points higher in efficiency and 4.7% higher in specific work than the Regular Gas-Reheat cycle when all cycles are compared at the same values of TIT and ,TPPm. Optimizing the net additional revenue could result in an annual saving of 33.7 million US dollars for a 481 MW power plant. The Optimized cycle was 3.62 percentage points higher in efficiency than the most efficient commercially available H-system combined cycle when compared at the same value of TIT. Copyright © 2007 John Wiley & Sons, Ltd. [source] Comparison of evaporative inlet air cooling systems to enhance the gas turbine generated powerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2007Mohammad Ameri Abstract The gas turbine performance is highly sensitive to the compressor inlet temperature. The output of gas turbine falls to a value that is less than the rated output under high temperature conditions. In fact increase in inlet air temperature by 1°C will decrease the output power by 0.7% approximately. The solution of this problem is very important because the peak demand season also happens in the summer. One of the convenient methods of inlet air cooling is evaporating cooling which is appropriate for warm and dry weather. As most of the gas turbines in Iran are installed in such ambient conditions regions, therefore this method can be used to enhance the performance of the gas turbines. In this paper, an overview of technical and economic comparison of media system and fog system is given. The performance test results show that the mean output power of Frame-9 gas turbines is increased by 11 MW (14.5%) by the application of media cooling system in Fars power plant and 8.1 MW (8.9%) and 9.5 MW (11%) by the application of fog cooling system in Ghom and Shahid Rajaie power plants, respectively. The total enhanced power generation in the summer of 2004 was 2970, 1701 and 1340 MWh for the Fars, Ghom and Shahid Rajaie power plants, respectively. The economical studies show that the payback periods are estimated to be around 2 and 3 years for fog and media systems, respectively. This study has shown that both methods are suitable for the dry and hot areas for gas turbine power augmentation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Performance characteristics and modelling of a micro gas turbine for their integration with thermally activated cooling technologiesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2007Adrián Vidal Abstract We have developed a simple model of a micro gas turbine system operating at high ambient temperatures and characterized its performance with a view to integrating this system with thermally activated cooling technologies. To develop and validate this model, we used experimental data from the micro gas turbine test facility of the CREVER research centre. The microturbine components were modelled and the thermodynamic properties of air and combustion gases were estimated using a commercial process simulator. Important information such as net output power, microturbine fuel consumption and exhaust gas mass flow rate can be obtained with the empirical correlations we have developed in this study. This information can be useful for design exhaust gas fired absorption chillers. Copyright © 2006 John Wiley & Sons, Ltd. [source] The concept of the gas turbine-based hybrid vehicle: system, design and configuration issuesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2006Roberto Capata Abstract The object of this study is a theoretical and experimental analysis of a new hybrid propulsion system for a passenger sedan in which the thermal engine is a small gas turbine set. Some preliminary results on the possibility of replacing the conventional ICE of a hybrid ,series' configuration by a turbogas were presented and discussed in previous papers by the same authors: several possible designs were examined under both a thermodynamic and an operative point of view. This paper presents a summary of the project and constitutes an attempt to put things in a proper engineering perspective: the technical feasibility of the project is assessed via a calculation of the required mission loads, a preliminary design of the most important elements of the propulsive system, the choice of the mission control strategy and the implementation of a numerical system simulator. The experiments that provided a verification for the assumed component efficiencies were carried out, in cooperation with the Research Centre of ENEA-Casaccia, on an ELLIOTT TA-45 group. Our results, though only preliminary, allow for a direct comparison between a GT-hybrid vehicle and a modern diesel car, and indicate that the GT-hybrid may be actually a competitor for the FC-powered vehicle concept. Our ,optimal' configuration is a combination of a 100 kg battery pack and two turbogas set of 5 and 16 kW, respectively. Copyright © 2005 John Wiley & Sons, Ltd. [source] A new type of EFHAT power generation system with effective utilization of latent heatINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2005Hongguang Jin Abstract On the basis of synergetic integration of an externally fired humid air turbine (EFHAT) cycle and effective recovery of latent heat from the exhaust gas of gas turbine, we have proposed a new type of EFHAT power generation system with effective utilization of latent heat, different from traditional EFHAT system. Due to use of clean humid air as working substance, latent heat can be recovered and utilized to generate hot water for the humidifier. This will enhance the humidification ability, giving rise to performance improvement of the system. As a result, at the turbine inlet temperature of 1123 K, the thermal efficiency of this new system may be expected to be as high as 47,48%. Additionally, we obtained the analytical expressions of system performance, and disclosed the relative relationship of system efficiency between the new EFHAT system and the pure externally fired power system. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ranking factors of an investment in cogeneration: Sensitivity analysis ranking the technical and economical factorsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2001Gunnel Sundberg Abstract A deregulation of the electricity market in Europe will result in increased competition among the power-producing companies. They will therefore carefully estimate the financial risk in an investment in new power-producing capability. One part of the risk assessment is to perform a sensitivity analysis. This paper presents a sensitivity analysis using factorial design, resulting in an assessment of the most important technical and economical factors affecting an investment in a gas turbine combined cycle and a steam cycle fired by woodchips. The study is performed using a simulation model that optimizes the operation of existing power plants and potential new investments to fulfil the desired heat demand. The local utility system analysed is a Swedish district heating system with 655 GWh y,1 heat demand. The conclusion is that to understand which of the technical and economical factors affect the investment, it is not sufficient to investigate the parameters of the studied plant, but also the parameters related to the competing plants. Both the individual effects of the factors and the effect of their interaction should be investigated. For the energy system studied the price of natural gas, price of woodchips and investment cost have the major influence on the profitability of the investment. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of mechanical driver and power generation configurations, Part 1: Optimization frameworkAICHE JOURNAL, Issue 9 2010Frank L. Del Nogal Abstract This article presents a novel, systematic, and robust procedure for driver and power plant selection based on mathematical programming. The discrete nature of gas turbines is considered as gas turbine drivers and gas turbine-based power plants are selected from a group of candidates. Plant availability with considering parallel compression has also been included, which allows a more comprehensive exploitation of the trade-offs between capital costs, operating costs, and availability. When neglecting process heating and any steam equipment, the formulation can be applied to heavily power dominated processes, such as LNG. However, a more comprehensive formulation, allowing waste heat recovery and the integration with a multilevel steam system, is also proposed to produce more thermally efficient systems. This approach proved to be flexible and robust and is the first in producing solutions ranging from no-steam to all-steam systems, including all-gas turbine, all-motor and hybrid gas turbine/motor/steam systems. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Characterization of First-Stage Silicon Nitride Components After Exposure to an Industrial Gas TurbineJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2006H.-T. Lin This paper provides a summary of recent efforts undertaken to examine the mechanical properties and microstructural stability of first-stage silicon nitride blades and nozzles after field testing in an industrial gas turbine. Two commercially available silicon nitrides, i.e., Kyocera SN282 vanes and SN281 blades, were successfully evaluated in the 100 h final phase engine test at Solar Turbines Incorporated. The turbine rotor inlet temperature was increased from 1010° to 1121°C at 100% speed during the engine test with efficiency increasing from 28.8% to 30.1%. Results of scanning electron microscopy showed that apparent materials recession still occurred during the 100 h engine test, especially in the leading and trailing edge regions where the gas pressure or velocity was the highest. The apparent material recession of the airfoils resulted from the volatilization of the normally protective silica layer, evidenced by the increased surface roughness and porous Lu2Si2O7 surface layer features. On the other hand, mechanical results generated using a ball-on-ring test technique showed that little strength degradation was measured after the 100 h engine test. [source] Influence of novel cycle concepts on the high-temperature corrosion of power plantsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2008Bettina BordenetArticle first published online: 29 MAY 200 Abstract The aim to reduce CO2 emissions has triggered the evaluation of new cycle concepts for power plants. CO2 -capture concepts are also evaluated to add on new and existing power plants. For combined cycle power plants (CCPP), different cycles are investigated such as integrated gasification (IGCC) or oxy-fuel firing. Besides the difference in combustion compared to a conventional CCPP, the environmental boundary conditions are changed and will affect the oxidation and corrosion life of the materials in the hot-gas path of the gas turbine and the heat-recovery steam generator. For the circulating fluidised bed power plants, the biomass co-firing and the oxy-fuel firing are also foreseen for CO2 -emission reduction. The fireside corrosion of the water walls will be influenced by these concepts and the changed fuel. The corrosion risk has been evaluated for two new power plant concepts: combined cycle with exhaust gas recirculation and pulverised coal-fired boiler with oxy-fuel firing. Based on this evaluation, the consequences for the testing conditions and the material selection have been discussed in detail. [source] High Frequency AC Power SystemNAVAL ENGINEERS JOURNAL, Issue 4 2008RAYMOND M. CALFO The Navy's Next Generation Integrated Power System (NGIPS) master plan calls for the evolution of the IPS system from its current medium voltage, 60 Hz state to a high-frequency, medium-voltage AC (HFAC) system in the next 10 years. Beyond that, and pending development of key protection components, a medium-voltage DC system will be considered for implementation. The master plan calls for power generation modules at three power levels across these systems: ,A low power level (2,5 MW) driven by a fuel-efficient diesel prime mover, ,A medium power level (10,15 MW) driven by a gas turbine, and ,A main propulsion power level (20,40 MW) driven by a gas turbine. EMD is currently developing a high-speed, high-frequency, liquid-cooled generator under contract with NAVSEA that will effectively demonstrate the mid-level generator for the HFAC system. It will be coupled directly to the output of a GE LM1600 Gas Turbine to provide a TG set with power density four times more favorable than conventional ATG sets. The generator development is proceeding favorably, with testing at the Navy's land-based test site (LBTS) expected to begin in July 2008. The technology embodied in the high-speed generator can be easily extrapolated to main turbine generator power levels. Given the availability of prime movers at appropriate speeds, the power generation modules for the HFAC system, at all three power levels, could be provided in a much shorter time frame than noted in the NGIPS master plan. This paper will explore the combinations of prime movers and advanced generators that would suit the three power generation modules of the HFAC system. A description of the prime mover and the generator used for each module will be provided to demonstrate the modest level of development needed. The performance parameters for each generation module will be provided, along with key characteristics and dimensions for the set. In the end, the paper will make the case that demonstration of a HFAC power generation system can be made in the short term, allowing the shipbuilding community to take advantage of the benefits of state-of-the-art power dense electrical generation. [source] Reformer and membrane modules plant to optimize natural gas conversion to hydrogenASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009M. De Falco Abstract Membrane technology may play a crucial role in the efficient production of hydrogen from natural gas and heavy hydrocarbons. The present work assesses the performance of a hydrogen production plant utilizing by reformer and membrane modules (RMM), by which the hydrogen produced in reaction units is separated by Pd-based membranes. A major advantage of RMM architecture is the shift of chemical equilibria favoring hydrogen production due to the removal of hydrogen through membranes at each reaction step, thus improving hydrogen yield while simultaneously allowing methane conversion at temperatures below 650 °C. Lower operating temperatures allow location of the modules downstream of a gas turbine, achieving an efficient hybrid system producing electric power and hydrogen with a significant reduction in energy consumption of approximately 10% relative to conventional systems. Fundamental concepts are analyzed and integrated into a process scheme. Effects of variables including reactor temperature outlet, steam-to-carbon ratio and recycle ratio throughout pinch and sensitivity analysis are described. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Performance and cost analysis of future, commercially mature gasification-based electric power generation from switchgrassBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 2 2009Haiming Jin Abstract Detailed process designs and mass/energy balances are developed using a consistent modeling framework and input parameter assumptions for biomass-based power generation at large scale (4536 dry metric tonnes per day switchgrass input), assuming future commercially mature component equipment performance levels. The simulated systems include two gasification-based gas turbine combined cycles (B-IGCC) designed around different gasifier technologies, one gasification-based solid oxide fuel cell cycle (B-IGSOFC), and a steam-Rankine cycle. The simulated design-point efficiency of the B-IGSOFC is the highest among all systems (51.8%, LHV basis), with modestly lower efficiencies for the B-IGCC design using a pressurized, oxygen-blown gasifier (49.5% LHV) and for the B-IGCC design using a low-pressure indirectly heated gasifier (48.6%, LHV). The steam-Rankine system has a simulated efficiency of 33.0% (LHV). Detailed capital costs are estimated assuming commercially mature (,Nth plant') technologies for the two B-IGCC and the steam-Rankine systems. B-IGCC systems are more capital-intensive than the steam-Rankine system, but discounted cash flow rate of return calculations highlight the total cost advantage of the B-IGCC systems when biomass prices are higher. Uncertainties regarding prospective mature-technology costs for solid oxide fuel cells and hot gas sulfur clean-up technologies assumed for the B-IGSOFC performance analysis make it difficult to evaluate the prospective electricity generating costs for B-IGSOFC relative to B-IGCC. The rough analysis here suggests that B-IGSOFC will not show improved economics relative to B-IGCC at the large scale considered here. © 2009 Society of Chemical Industry and John Wiley & Sons, Ltd [source] Coproduction of ethanol and power from switchgrassBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 2 2009Mark Laser Abstract Three process designs for producing ethanol and electricity from switchgrass are evaluated: a base-case technology scenario involving dilute acid pre-treatment and simultaneous saccharification and fermentation, and two mature technology scenarios incorporating ammonia fiber expansion pre-treatment and consolidated bioprocessing , one with conventional Rankine power coproduction, and one coproducing power via a gas turbine combined cycle. Material and energy balances , resulting from detailed Aspen Plus models , are reported and used to estimate processing costs and perform discounted cash flow analysis to assess plant profitability. The mature technology ,designs significantly improve both process efficiency and cost relative to base-case cellulosic ethanol technology, with the resulting fossil fuel displacement being decidedly positive and production costs competitive with gasoline, even at relatively low prices. © 2009 Society of Chemical Industry and John Wiley & Sons, Ltd [source] The Precipitation Behavior of Superalloy ATI Allvac 718PlusADVANCED ENGINEERING MATERIALS, Issue 3 2010Gerald A. Zickler Abstract ATI Allvac 718Plus is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace gas turbines. The precipitation kinetics of the intermetallic , (Ni3Nb) and ,, (Ni3(Al,Ti)) phases in this alloy are of scientific as well as technological interest because of their significant influence on the mechanical properties. Important parameters like grain size are controlled by coarse , precipitates located at grain boundaries, whereas small ,, precipitates are responsible for strengthening by precipitation hardening. In the present study, the microstructure is investigated by three-dimensional atom probe tomography and simulated by computer modeling using the thermo-kinetic software MatCalc. The results of numerical simulations and experimental data are compared and critically discussed. It is shown that the chemical compositions of the phases change during isothermal aging, and the precipitation kinetics of , and ,, phases interact with each other as shown in a time temperature precipitation (TTP) plot. The TTP plot shows C-shaped curves with characteristic discontinuities in the temperature range, where simultaneous and concurrent precipitation of the , and ,, phases occurs. This leads to a competition in the diffusion of Nb and Al, which are partly present in both phases. Thus, the present study gives important information on heat treatments for ATI Allvac 718Plus in order to achieve the desired microstructure and mechanical properties. [source] A fatigue and creep study in austenitic stainless steel 316L used in exhaust pipes of naval gas turbinesFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 9 2004R. F. MARTINS ABSTRACT Exhaust pipes of naval gas turbines are made of thin wall tubing of stainless steel grade AISI 316L. The tubes are fabricated by butt welding of different sections with longitudinal and circumferential joints. The plate thickness is about 4.0 mm, and the working temperature varies between 600 °C and 400 °C in the critical zones of the pipe, in the lower and central areas, respectively. The loadings in the tube induce high-temperature fatigue and creep-fatigue cracks have nucleated and propagated in the tube near some welded joints. The paper presents FCGR data obtained in CT specimens of used material taken from the pipes and tested at RT, 335, 500 and 600 °C. Preliminary creep data obtained in tension, in thin-sheet specimens (about 4 mm thickness), also taken from the conduct wall and tested at 500, 550 and 600 °C are also given. These results are crucial to perform a fatigue-creep interaction life assessment of the critical parts of the structure in the near future. Finally, the paper presents results of research work to investigate carbide precipitation and formation in virgin thin-sheet specimens subjected to several types of thermal exposures. In some cases, 3,4 d was the time interval between exposures. Grain size measurements were carried out together with microstructural observations in the SEM. The influence of time, temperature and time interval between thermal exposures was assessed comparing the microstructures. [source] Numerical simulation of gaseous fuel injection: A new methodology for multi-dimensional modellingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2010Luca Andreassi Abstract The use of natural gas (instead of liquid or solid fuels) is nowadays drawing an increasing interest in many applications (gas turbines, boilers, internal combustion engines), because of the greater attention to environmental issues. To facilitate the development of these applications, computer models are being developed to simulate gaseous injection, air entrainment and the ensuing combustion. This paper introduces a new method for modelling the injection process of gaseous fuels that aims to hold down grid requirements in order to allow the simulation also of other phenomena, like combustion or valve and piston motion, in reciprocating internal combustion engines. After a short overview of existing models, the transient jet model and the evaluation of inflow conditions are described in detail. Then a basic study of the grid effects on the jet evolution is presented. The model is updated and validated by comparing numerical results with available experimental data for two different operating conditions: a subsonic and a supersonic under-expanded case. The model demonstrates to be fast enough to be used in a multi-dimensional code and accurate enough to follow the real gas jet evolution. Copyright © 2009 John Wiley & Sons, Ltd. [source] Numerical assessment of thermo-acoustic instabilities in gas turbinesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8-9 2005L. Benoit Abstract A new methodology to assess the effect of the flame/acoustics coupling on the stability of the modes without combustion is presented. An asymptotic method is used to account for the acoustic flame transfer function. The efficiency and accuracy of the approach is demonstrated on an academic case similar to a Rijke tube configuration. Copyright © 2005 John Wiley & Sons, Ltd. [source] Dynamic energy and exergy analyses of an industrial cogeneration systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2010Yilmaz Yoru Abstract The study deals with the energetic and exergetic analyses of a cogeneration (combined heat and power, CHP) system installed in a ceramic factory, located in Izmir, Turkey. This system has three gas turbines with a total capacity of 13,MW, six spray dryers and two heat exchangers. In the analysis, actual operational data over one-month period are utilized. The so-called CogeNNexT code is written in C++ and developed to analyze energetic and exergetic data from a database. This code is also used to analyze turbines, spray dryers and heat exchangers in this factory. Specifications of some parts of system components have been collected from the factory. Based on the 720,h data pattern (including 43,200 data), the mean energetic and exergetic efficiency values of the cogeneration system are found to be 82.3 and 34.7%, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Comparison of evaporative inlet air cooling systems to enhance the gas turbine generated powerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2007Mohammad Ameri Abstract The gas turbine performance is highly sensitive to the compressor inlet temperature. The output of gas turbine falls to a value that is less than the rated output under high temperature conditions. In fact increase in inlet air temperature by 1°C will decrease the output power by 0.7% approximately. The solution of this problem is very important because the peak demand season also happens in the summer. One of the convenient methods of inlet air cooling is evaporating cooling which is appropriate for warm and dry weather. As most of the gas turbines in Iran are installed in such ambient conditions regions, therefore this method can be used to enhance the performance of the gas turbines. In this paper, an overview of technical and economic comparison of media system and fog system is given. The performance test results show that the mean output power of Frame-9 gas turbines is increased by 11 MW (14.5%) by the application of media cooling system in Fars power plant and 8.1 MW (8.9%) and 9.5 MW (11%) by the application of fog cooling system in Ghom and Shahid Rajaie power plants, respectively. The total enhanced power generation in the summer of 2004 was 2970, 1701 and 1340 MWh for the Fars, Ghom and Shahid Rajaie power plants, respectively. The economical studies show that the payback periods are estimated to be around 2 and 3 years for fog and media systems, respectively. This study has shown that both methods are suitable for the dry and hot areas for gas turbine power augmentation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Performance enhancement of gas turbines by inlet air-cooling in hot and humid climatesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2006Majed M. Alhazmy Abstract In this paper, a model to study the effect of inlet air-cooling on gas turbines power and efficiency is developed for two different cooling techniques, direct mechanical refrigeration and an evaporative water spray cooler. Energy analysis is used to present the performance improvement in terms of power gain ratio and thermal efficiency change factors. Relationships are derived for an open gas turbine cycle with irreversible compression and expansion processes coupled to air-cooling systems. The obtained results show that the power and efficiency improvements are functions of the ambient conditions and the gas turbine pressure ratio. The performance improvement is calculated for, ambient temperatures from 30 to 50°C, the whole range of humidity ratio (10,100%) and pressure ratio from 8 to 12. For direct mechanical refrigeration air-cooling, the power improvement is associated with appreciable drop in the thermal efficiency. The maximum power gain can be obtained if the air temperature is reduced to its lowest limit that is the refrigerant evaporation temperature plus the evaporator design temperature difference. Water spray cooling process is sensitive to the ambient relative humidity and is suitable for dry air conditions. The power gain and efficiency enhancement are limited by the wet bulb temperature. The performance of spray evaporative cooler is presented in a dimensionless working graph. The daily performance of the cooling methods is examined for an ABB-11D5 gas turbine operating under the hot humid conditions of Jeddah, Saudi Arabia. The results indicate that the direct mechanical refrigeration increased the daily power output by 6.77% versus 2.57% for the spray air-cooling. Copyright © 2005 John Wiley & Sons, Ltd. [source] Energy,exergy analysis and modernization suggestions for a combined-cycle power plantINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2006Ahmet Cihan Abstract Energy and exergy analysis were carried out for a combined-cycle power plant by using the data taken from its units in operation to analyse a complex energy system more thoroughly and to identify the potential for improving efficiency of the system. In this context, energy and exergy fluxes at the inlet and the exit of the devices in one of the power plant main units as well as the energy and exergy losses were determined. The results show that combustion chambers, gas turbines and heat recovery steam generators (HRSG) are the main sources of irreversibilities representing more than 85% of the overall exergy losses. Some constructive and thermal suggestions for these devices have been made to improve the efficiency of the system. Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthesis of mechanical driver and power generation configurations, Part 1: Optimization frameworkAICHE JOURNAL, Issue 9 2010Frank L. Del Nogal Abstract This article presents a novel, systematic, and robust procedure for driver and power plant selection based on mathematical programming. The discrete nature of gas turbines is considered as gas turbine drivers and gas turbine-based power plants are selected from a group of candidates. Plant availability with considering parallel compression has also been included, which allows a more comprehensive exploitation of the trade-offs between capital costs, operating costs, and availability. When neglecting process heating and any steam equipment, the formulation can be applied to heavily power dominated processes, such as LNG. However, a more comprehensive formulation, allowing waste heat recovery and the integration with a multilevel steam system, is also proposed to produce more thermally efficient systems. This approach proved to be flexible and robust and is the first in producing solutions ranging from no-steam to all-steam systems, including all-gas turbine, all-motor and hybrid gas turbine/motor/steam systems. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Temperature-Gradient Effects in Thermal Barrier Coatings: An Investigation Through Modeling, High Heat Flux Test, and Embedded SensorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Yang Tan The harsh thermal environment in gas turbines, including elevated temperatures and high heat fluxes, induces significant thermal gradients in ceramic thermal barrier coatings (TBCs), which are used to protect metallic components. However, the thermal conductivity of plasma-sprayed TBC increases with exposure at high temperatures mainly due to sintering phenomena and possible phase transformation, resulting in coating performance degradation and potential thermal runaway issues. An analytical thermal model and experimentally obtained coating thermal conductivity data are used to determine the coating through-thickness temperature profile and effective thermal conductivity under gradient conditions at high temperatures. High heat flux tests are then performed on TBCs to evaluate coating thermal behavior under temperature gradients close to service conditions. Coating internal temperature during the tests was also measured by thermally sprayed embedded thermocouples within the top coat. This combined approach provides a sintering map with a new model and allows for the assessment of temperature-gradient effects on the thermal performance of plasma-sprayed TBCs. [source] Microstructure,Property Correlations in Industrial Thermal Barrier CoatingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004Anand A. Kulkarni This paper describes the results from multidisciplinary characterization/scattering techniques used for the quantitative characterization of industrial thermal barrier coating (TBC) systems used in advanced gas turbines. While past requirements for TBCs primarily addressed the function of insulation/life extension of the metallic components, new demands necessitate a requirement for spallation resistance/strain tolerance, i.e., prime reliance, on the part of the TBC. In an extensive effort to incorporate these TBCs, a design-of-experiment approach was undertaken to develop tailored coating properties by processing under varied conditions. Efforts focusing on achieving durable/high-performance coatings led to dense vertically cracked (DVC) TBCs, exhibiting quasi-columnar microstructures approximating electron-beam physical-vapor-deposited (EB-PVD) coatings. Quantitative representation of the microstructural features in these vastly different coatings is obtained, in terms of porosity, opening dimensions, orientation, morphologies, and pore size distribution, by means of small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS) studies. Such comprehensive characterization, coupled with elastic modulus and thermal conductivity measurements of the coatings, help establish relationships between microstructure and properties in a systematic manner. [source] | ||||||||||||||||