| 1. |
- Angantyr, Anders, et al.
(författare)
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Constrained optimization of gas turbine tilting pad bearing designs
- 2006
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 128:4, s. 873-878
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the constrained optimization of the tilting pad bearing design on a gas turbine rotor system. A real coded genetic algorithm with a robust constraint handling technique is used as the optimization method. The objective is to develop a formulation of the optimization problem for the late bearing design of a complex rotor-bearing system. Furthermore, the usefulness of the search method is evaluated on a difficult problem. The effects considered are power loss and limiting temperatures in the bearings as well as the dynamics at the system level, i.e., stability and unbalance responses. The design variables are the bearing widths and radial clearances. A nominal design is the basis for comparison of the optimal solution found. An initial numerical experiment shows that finding a solution that fulfills all the constraints for the system design is likely impossible. Still, the optimization shows the possibility of finding a solution resulting in a reduced power loss while not violating any of the constraints more than the nominal design. Furthermore, the result also shows that the used search method and constraint handling technique works on this difficult problem.
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| 2. |
- Bartlett, Michael A., et al.
(författare)
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A study of humidified gas turbines for short-term realization in midsized power generation - Part I : Nonintercooled cycle analysis
- 2005
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 127:1, s. 91-99
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Tidskriftsartikel (refereegranskat)abstract
- Humidified Gas Turbine (HGT) cycles are a group of advanced gas turbine cycles that use water-air mixtures as the working media. In this article, three known HGT configurations are examined in the context of short-term realization for small to midsized power generation: the Steam Injected Gas Turbine, the Full-flow Evaporative Gas Turbine, and the Part-flow Evaporative Gas Turbine. The heat recovery characteristics and performance potential of these three cycles are assessed, with and without intercooling, and a preliminary economic analysis is carried out for the most promising cycles.
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| 3. |
- Bartlett, Michael, et al.
(författare)
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A study of humidified gas turbines for short-term realization in midsized power generation - Part II : Intercooled cycle analysis and final economic evaluation
- 2005
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 127:1, s. 100-108
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Tidskriftsartikel (refereegranskat)abstract
- Humidified gas turbine (HGT) cycles are a group of advanced gas turbine cycles that use water-air mixtures as the working media. In this article, three known HGT configurations are examined in the context of short-term realization for small to mid-sized power generation: the steam injected gas turbine, the full-flow evaporative gas turbine, and the part-flow evaporative gas turbine. The heat recovery characteristics and performance potential of these three cycles are assessed, with and without intercooling, and a preliminary economic analysis is carried out for the most promising cycles.
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| 4. |
- Hannius, Olof, 1967, et al.
(författare)
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Derivation of Diagnostic Requirements for a Distributed UAV Turbofan Engine Control System
- 2008
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 130:2, s. 021602:1-021602:11
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a method for deriving requirements for the efficiency of diagnostic functions in distributed electronic turbofan engine control systems. Distributed engine control systems consist of sensor, actuator, and control unit nodes that exchange data over a communication network. The method is applicable to engine control systems that are partially redundant. Traditionally, turbofan engine control systems use dual channel solutions in which all units are duplicated. Our method is intended for analyzing the diagnostic requirements for systems in which a subset of the sensors and the actuators is nonredundant. Such systems rely on intelligent monitoring and analytical redundancy to detect and tolerate failures in the nonredundant units. These techniques cannot provide perfect diagnostic coverage and, hence, our method focuses on analyzing the impact of nonperfect diagnostic coverage on the reliability and safety of distributed engine control systems. The method is based on a probabilistic analysis that combines fault trees and Markov chains. The input parameters for these models include failure rates as well as several coverage factors that characterize the performance of the diagnostic functions. Since the use of intelligent monitoring can cause false alarms, i.e., an error is falsely indicated by a diagnostic function, the parameters also include a false alarm rate. The method was used to derive the diagnostic requirements for a hypothetical unmanned aerial vehicle engine control system. Given the requirement that an engine failure due to the control system is not allowed to occur more than ten times per million hours, the diagnostic functions in a node must achieve 99% error coverage for transient faults and 90–99% error coverage for permanent faults. The system-level diagnosis must achieve 90–95% detection coverage for node failures, which are not detected by the nodes themselves. These results are based on the assumption that transient faults are 100 times more frequent than permanent faults. It is important to have a method for deriving probabilistic requirements on diagnostic functions for engine control systems that rely on analytical redundancy as a means to reduce the hardware redundancy. The proposed method allows us to do this using an existing tool (FAULTTREE+) for safety and reliability analysis.
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| 5. |
- Knight, R, et al.
(författare)
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GTPOM: Thermo-economic optimization of whole gas turbine plant
- 2006
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 128:3, s. 535-542
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Tidskriftsartikel (refereegranskat)abstract
- Trends towards distributed power generation and the deregulation of energy markets are increasing the requirement for software tools that optimize power generation plant design and operation. In this context, this paper describes the GTPOM (thermo-economic optimization of whole gas turbine plant) European project, funded in part through the European Commissions 5th Framework Programme, focusing on the development and demonstration of an original software tool for the thermo-economic analysis and optimization of conventional and advanced energy systems based on gas turbine plant. PSEconomy, the software tool developed during the GTPOM project, provides a thermo-economic optimization capability for advanced and more-conventional energy systems, enabling the complex trade-offs between system performance and installed costs to be determined for different operational duties and market scenarios. Furthermore, the code is capable of determining the potential benefits of innovative cycles or layout modifications to existing plants compared with current plant configurations. The economic assessment is performed through a complete through-life cycle cost analysis, which includes the total capital cost of the plant, the cost of fuel, O&M costs and the expected revenues from the sale of power and heat. The optimization process, carried out with a GA-based algorithm, is able to pursue different objective functions as specified by the User. These include system efficiency, through-life cost of electricity and through-life internal rate of return. Three case studies demonstrating the capabilities of the new tool are presented in this paper covering a conventional combined cycle system, a biomass plant and a CO2 sequestration gas turbine cycle. The software code is now commercially available and is expected to provide significant advantages in the near and long-term development of energy cycles.
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| 6. |
- Korakianitis, T, et al.
(författare)
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Parametric performance of combined-cogeneration power plants with various power and efficiency enhancements
- 2005
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 127:1, s. 65-72
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Tidskriftsartikel (refereegranskat)abstract
- The design-point performance characteristics of a wide variety of combined-cogeneration power plants, with different amounts of supplementary firing (or no supplementary firing), different amounts of steam injection (or no steam injection), different amounts of exhaust gas condensation, etc., without limiting these parameters to present-day limits are investigated. A representative power plant with appropriate components for these plant enhancements is developed. A computer program,is used to evaluate the performance of various power plants using standard inputs for component efficiencies, and the design-point performance of these plants is computed. The results are presented as thermal efficiency, specific power, effectiveness, and specific rate of energy in district heating. The performance of the simple-cycle gas turbine dominates the overall plant performance; the plant efficiency and power are mainly determined by turbine inlet temperature and compressor pressure ratio; increasing amounts of steam injection in the gas turbine increases the efficiency and power; increasing amounts of supplementary firing decreases the efficiency but increases the power; with sufficient amounts of supplementary team injection the exhaust-gas condensate is sufficient to make up for water lost in steam injection; and the steam-turbine power is a fraction (0.1 to 0.5) of the gas-turbine power output. Regions of "optimum" parameters for the power plant based oil design-point power hot-water demand, and efficiency are shown. A method,for fuel-cost allocation between electricity and hot water is recommended.
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| 7. |
- Mörtberg, Magnus, et al.
(författare)
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Experimental Investigation of Flow Phenomena of a Single Fuel Jet in Cross-Flow during Highly Preheated Air Combustion Conditions
- 2007
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 129:2, s. 556-564
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Tidskriftsartikel (refereegranskat)abstract
- Particle image velocimetry and a spectroscopy technique has been used to obtain information on the flow dynamics and flame thermal signatures of a fuel jet injected into a cross-flow of normal temperature and very high-temperature combustion air Flame fluctuations were obtained using a high-speed camera and then performing fast Fourier transform on the signal. High-temperature air combustion has been demonstrated to provide significant energy savings, higher heat flux, and reduction of pollution and equipment size of industrial furnaces. The dynamics of flow associated with high temperature combustion air conditions (for mean velocity, axial strain rate and vorticity) has been obtained in two-dimensional using propane and methane as the fuels. The data have been compared with normal temperature combustion air case, including the nonburning case. A specially designed experimental test furnace facility was used to provide well-controlled conditions and allowed air preheats to 1100 degrees C using regenerative burners. Four different experimental cases have been examined. The momentum flux ratio between the burning and nonburning conditions was kept constant to provide comparison between cases. The results provide the role of high-temperature combustion air on the dynamics of the flow, turbulence, and mixing under nonburning and combustion conditions. The data provide the direct role of combustion on flow dynamics, turbulence, and flame fluctuations. High-temperature combustion air at low-oxygen concentration showed larger flame volume with less fluctuation than normal or high-temperature normal air cases. High-temperature combustion air technology prolongs mixing in the combustion zone to enhance the flame volume, reduce flame fluctuations, and to provide uniform flow and thermal characteristics. This information assists in model validation and model development for new applications and technology development using high-temperature air combustion principles.
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| 8. |
- Orbay, Raik, 1974, et al.
(författare)
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Off-Design Performance Investigation of a Low Calorific Value Gas Fired Generic-Type Single-Shaft Gas Turbine.
- 2008
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 130:3
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Tidskriftsartikel (refereegranskat)abstract
- When low calorific value gases are fired, the performance and stability of gas turbines may deteriorate due to a large amount of inertballast and changes in working fluid properties. Since it is rather rare to have custom-built gas turbines for low lower heating value (LHV) operation, the engine will be forced to operate outside its design envelope. This, in turn, poses limitations to usable fuel choices. Typical restraints are decrease in Wobbe index and surge and flutter margins for turbomachinery. In this study, an advanced performance deck has been used to quantify the impact of firing low-LHV gases in a generic-type recuperated as well as unrecuperated gas turbine. A single-shaft gas turbine characterized by a compressor and an expander map is considered. Emphasis has been put on predicting the off-design behavior. The combustor is discussed and related to previous experiments that include investigation of flammability limits, Wobbe index, flame position, etc. The computations show that at constant turbine inlet temperature, the shaft power and the pressure ratio will increase; however, the surge margin will decrease. Possible design changes in the component level are also discussed. Aerodynamic issues (and necessary modifications) that can pose severe limitations on the gas turbine compressor and turbine sections are discussed. Typical methods for axial turbine capacity adjustment are presented and discussed.
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| 9. |
- Rafidi, Nabil, et al.
(författare)
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High-temperature air combustion phenomena and its thermodynamics
- 2008
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 130:2, s. 023001-
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Tidskriftsartikel (refereegranskat)abstract
- The fundamentals and thermodynamic analysis of high-temperature air combustion (HiTAC) technology is presented. The HiTAC is characterized by high temperature of combustion air having low oxygen concentration. This study provides a theoretical analysis of HiTA C process from the thermodynamic point of view. The results demonstrate the possibilities of reducing thermodynamic irreversibility of combustion by considering an oxygen-deficient combustion process that utilizes both gas and heat recirculations. HiTA C conditions reduce irreversibility. Furthermore, combustion with the use of oxygen (in place of air) is also analyzed. The results showed that a system, which utilizes oxygen as an oxidizer results in higher first and second law efficiencies as compared to the case with air as the oxidizer. The entropy generation for an adiabatic combustion process is reduced by more than 60% due to the effect of either preheating or oxygen enrichment. This study is aimed at providing technical guidance to further improve efficiency of a combustion process, which shows very small temperature increases due to mild chemical reactions.
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| 10. |
- Salewski, Mirko, et al.
(författare)
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A comparison of single and multiphase jets in a crossflow using large eddy simulations
- 2007
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 129:1, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- Large eddy simulations (LES) are performed for single and multiphase jets in crossflow (JICF). The multiphase JICF are compared to the single-phase case for the same momentum and mass flow, ratios but with droplets of different sizes. Multiphase JICF have stronger counterrotating vortex pairs (CVPs) than a corresponding single-phase JICF. Moreover their trajectories are higher and their induced waves weaker. The smaller the Stokes number of the droplets, the more the solution approaches the solution for single-phase flow. The computed results show the formation of a CVP and horseshoe vortices, which are convected downstream. LES also reveals the intermittent formation of upright wake vortices from the horseshoe vortices oil the ground toward the CVP. The dispersion of polydisperse spray droplets is computed using the stochastic parcel method. Atomization and droplet breakup are modeled by a combination of the breakup model by Reitz and the Taylor analogy breakup model (see Caraeni, D., Bergstrom, C., and Fuchs, L., 2000, Flow, Turbid. Combust., 65(2), pp. 223-244). Evaporation and droplet collision are also modeled. The flow solver uses two-way coupling. Averages of the velocity and gaseous fuel mass fraction are computed. The single-phase JICF is validated against experimental data obtained by PIV. Additionally, the PDFs and frequency spectra are presented.
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