The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Hidetoshi Fujii - One of the best experts on this subject based on the ideXlab platform.
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Improvement of Steam Turbine Stage Efficiency by Controlling Rotor Shroud Leakage Flows: Part II — Effect of Axial Distance Between a Swirl Breaker and Rotor Shroud on Efficiency Improvement
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2018Co-Authors: Chongfei Duan, Hisataka Fukushima, Kiyoshi Segawa, Takanori Shibata, Hidetoshi FujiiAbstract:The basic principle of a distinct idea to reduce an aerodynamic mixing loss induced by the difference in tangential velocity between mainstream flow and rotor shroud leakage flow is presented in “Part I: Design Concept and Typical Performance of a Swirl Breaker.” When the swirl breaker is installed in the circulating region of leakage flow at the rotor shroud exit cavity, the Axial Distance between the swirl breaker and the rotor shroud is a crucial factor to trap the leakage flow into the swirl breaker cavity. In Part II, five cases of geometry with different Axial Distances between the swirl breaker and the rotor shroud, which covered a range for the stage Axial Distance of actual high and intermediate pressure (HIP) steam turbines, were investigated using a single-rotor computational fluid dynamics (CFD) analysis and verification tests in a 1.5-stage air model turbine. By decreasing the Axial Distance between the swirl breaker and the rotor shroud, the tangential velocity and the mixing region in the tip side which is influenced by the rotor shroud leakage flow were decreased and the stage efficiency was increased. The case of the shortest Axial Distance between the swirl breaker and the rotor shroud increased turbine stage efficiency by 0.7% compared to the conventional cavity geometry. In addition, the measured maximum pressure fluctuation in the swirl breaker cavity was only 0.7% of the entire flow pressure. Consequently, both performance characteristics and structural reliability of swirl breaker were verified for application to real steam turbines.
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Improvement of Steam Turbine Stage Efficiency by Controlling Rotor Shroud Leakage Flows: Part II — Effect of Axial Distance Between a Swirl Breaker and Rotor Shroud on Efficiency Improvement
Volume 8: Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2018Co-Authors: Chongfei Duan, Hisataka Fukushima, Kiyoshi Segawa, Takanori Shibata, Hidetoshi FujiiAbstract:The basic principle of a distinct idea to reduce an aerodynamic mixing loss induced by the difference in tangential velocity between mainstream flow and rotor shroud leakage flow is presented in “Part I – Design Concept and Typical Performance of a Swirl Breaker” The design concept offers an effective geometry for improving steam turbine stage efficiency. When the swirl breaker is installed in the circulating region of leakage flow at the rotor shroud exit cavity, the Axial Distance between the swirl breaker and rotor shroud is a crucial factor to trap the leakage flow into the swirl breaker cavity. In this Part II of the study, five cases of swirl breaker geometry with different Axial Distances between the swirl breaker and rotor shroud, which covered a range for the stage Axial Distance of actual high and intermediate (HIP) pressure steam turbines, were investigated using computational fluid dynamics (CFD) analysis and tests. Compared to a conventional single-stage CFD analysis, by conducting an additional single-rotor analysis with the modified shear stress transport (SST) model coefficient, the prediction accuracy for typical improvements in stage efficiency was increased in comparison to the single-stage analysis with the default SST model. Based on CFD results, the verification tests were conducted in a 1.5-stage air model turbine. By decreasing the Axial Distance between the swirl breaker and rotor shroud, the tangential velocity and the mixing region in the tip side which is influenced by the rotor shroud leakage flow were decreased and the stage efficiency was increased. The case of the shortest Axial Distance between the swirl breaker and rotor shroud increased turbine stage efficiency by 0.7% compared to the conventional cavity geometry. In addition, the unsteady pressure was measured in the swirl breaker cavity to evaluate the structural reliability of the swirl breaker. These results showed the maximum pressure fluctuation was only 0.7% of the entire flow pressure. Consequently, both performance characteristics and structural reliability of swirl breaker were verified for application to real steam turbines.
K Hemalatha - One of the best experts on this subject based on the ideXlab platform.
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pulsatile flow of herschel bulkley fluid through stenosed arteries a mathematical model
International Journal of Non-linear Mechanics, 2006Co-Authors: D S Sankar, K HemalathaAbstract:Abstract In this paper, the pulsatile flow of blood through stenosed artery is studied. The effects of pulsatility, stenosis and non-Newtonian behavior of blood, assuming the blood to be represented by Herschel–Bulkley fluid, are simultaneously considered. A perturbation method is used to analyze the flow assuming the thickness of plug core region to be non-uniform changing with Axial Distance. An expression for the variation of plug core radius with time and Axial Distance is obtained. The variation of pressure gradient with steady flow rate is given. Also the variation of wall shear stress distribution as well as resistance to flow with Axial Distance for different values of time and for different values of yield stress is given and the results analyzed.
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Pulsatile flow of Herschel–Bulkley fluid through stenosed arteries—A mathematical model
International Journal of Non-linear Mechanics, 2006Co-Authors: D S Sankar, K HemalathaAbstract:Abstract In this paper, the pulsatile flow of blood through stenosed artery is studied. The effects of pulsatility, stenosis and non-Newtonian behavior of blood, assuming the blood to be represented by Herschel–Bulkley fluid, are simultaneously considered. A perturbation method is used to analyze the flow assuming the thickness of plug core region to be non-uniform changing with Axial Distance. An expression for the variation of plug core radius with time and Axial Distance is obtained. The variation of pressure gradient with steady flow rate is given. Also the variation of wall shear stress distribution as well as resistance to flow with Axial Distance for different values of time and for different values of yield stress is given and the results analyzed.
Chongfei Duan - One of the best experts on this subject based on the ideXlab platform.
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Improvement of Steam Turbine Stage Efficiency by Controlling Rotor Shroud Leakage Flows: Part II — Effect of Axial Distance Between a Swirl Breaker and Rotor Shroud on Efficiency Improvement
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2018Co-Authors: Chongfei Duan, Hisataka Fukushima, Kiyoshi Segawa, Takanori Shibata, Hidetoshi FujiiAbstract:The basic principle of a distinct idea to reduce an aerodynamic mixing loss induced by the difference in tangential velocity between mainstream flow and rotor shroud leakage flow is presented in “Part I: Design Concept and Typical Performance of a Swirl Breaker.” When the swirl breaker is installed in the circulating region of leakage flow at the rotor shroud exit cavity, the Axial Distance between the swirl breaker and the rotor shroud is a crucial factor to trap the leakage flow into the swirl breaker cavity. In Part II, five cases of geometry with different Axial Distances between the swirl breaker and the rotor shroud, which covered a range for the stage Axial Distance of actual high and intermediate pressure (HIP) steam turbines, were investigated using a single-rotor computational fluid dynamics (CFD) analysis and verification tests in a 1.5-stage air model turbine. By decreasing the Axial Distance between the swirl breaker and the rotor shroud, the tangential velocity and the mixing region in the tip side which is influenced by the rotor shroud leakage flow were decreased and the stage efficiency was increased. The case of the shortest Axial Distance between the swirl breaker and the rotor shroud increased turbine stage efficiency by 0.7% compared to the conventional cavity geometry. In addition, the measured maximum pressure fluctuation in the swirl breaker cavity was only 0.7% of the entire flow pressure. Consequently, both performance characteristics and structural reliability of swirl breaker were verified for application to real steam turbines.
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Improvement of Steam Turbine Stage Efficiency by Controlling Rotor Shroud Leakage Flows: Part II — Effect of Axial Distance Between a Swirl Breaker and Rotor Shroud on Efficiency Improvement
Volume 8: Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2018Co-Authors: Chongfei Duan, Hisataka Fukushima, Kiyoshi Segawa, Takanori Shibata, Hidetoshi FujiiAbstract:The basic principle of a distinct idea to reduce an aerodynamic mixing loss induced by the difference in tangential velocity between mainstream flow and rotor shroud leakage flow is presented in “Part I – Design Concept and Typical Performance of a Swirl Breaker” The design concept offers an effective geometry for improving steam turbine stage efficiency. When the swirl breaker is installed in the circulating region of leakage flow at the rotor shroud exit cavity, the Axial Distance between the swirl breaker and rotor shroud is a crucial factor to trap the leakage flow into the swirl breaker cavity. In this Part II of the study, five cases of swirl breaker geometry with different Axial Distances between the swirl breaker and rotor shroud, which covered a range for the stage Axial Distance of actual high and intermediate (HIP) pressure steam turbines, were investigated using computational fluid dynamics (CFD) analysis and tests. Compared to a conventional single-stage CFD analysis, by conducting an additional single-rotor analysis with the modified shear stress transport (SST) model coefficient, the prediction accuracy for typical improvements in stage efficiency was increased in comparison to the single-stage analysis with the default SST model. Based on CFD results, the verification tests were conducted in a 1.5-stage air model turbine. By decreasing the Axial Distance between the swirl breaker and rotor shroud, the tangential velocity and the mixing region in the tip side which is influenced by the rotor shroud leakage flow were decreased and the stage efficiency was increased. The case of the shortest Axial Distance between the swirl breaker and rotor shroud increased turbine stage efficiency by 0.7% compared to the conventional cavity geometry. In addition, the unsteady pressure was measured in the swirl breaker cavity to evaluate the structural reliability of the swirl breaker. These results showed the maximum pressure fluctuation was only 0.7% of the entire flow pressure. Consequently, both performance characteristics and structural reliability of swirl breaker were verified for application to real steam turbines.
N. Mahdizadeh - One of the best experts on this subject based on the ideXlab platform.
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Saturation mechanism in a two-stream free-electron laser
Journal of Plasma Physics, 2015Co-Authors: N. MahdizadehAbstract:The effect of a guide field on the saturation mechanism in a two-stream free-electron laser (FEL) is verified. Two monoenergetic electron beams with a vanishing pitch-angle spread are considered. Nonlinear wave–particle interaction is described by a set of coupled differential equations in a 1-D approximation. Output power is presented as a function of the Axial Distance. It was found that through using a focusing mechanism, the two-stream FEL reached the saturation regime in a shorter Axial Distance in comparison with the case of no focusing mechanism.
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Effect of two-stream instability on the saturation mechanism of a two-stream free-electron laser with a helical wiggler pump
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2012Co-Authors: N. Mahdizadeh, F. M. AghamirAbstract:Abstract In this paper we will investigate the effect of two-stream instability on saturation mechanism in Two-Stream Free Electron Laser (TSFEL) with a helical wiggler pump. A two-velocity relativistic electron beam propagates through the helical wiggler field. The relativistic electron stream is assumed to be cold. The slippage of the electromagnetic wave with respect to the electron beam is ignored. Self-consistent evolution of an electromagnetic wave in the presence of two-velocity electron beam is described by a set of coupled nonlinear differential equations in 1D approximation. Slowly varying envelope approximation is used and by the Runge–Kutta method algorithm is solved numerically. The power versus the Axial Distance has been plotted. It has been found that the TSFEL reaches the saturation regime in a shorter Axial Distance in comparison with the conventional FEL.
Shanyuan Wang - One of the best experts on this subject based on the ideXlab platform.
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effect of licl on electrospinning of pan polymer solution theoretical analysis and experimental verification
Polymer, 2004Co-Authors: Jihuan He, Juan Zhang, Jianyong Yu, Shanyuan WangAbstract:Abstract Polyacrylonitrile(PAN) is used to study the effect of surface charge on electrospinning by adding LiCl. The theoretical analysis shows that the relationship between radius r of jet and the Axial Distance z from nozzle follows an allometric law in the form r ∼ z −0.5 in case of full surface charge, and the scaling exponent becomes larger for partly charged fibers in electrospinning.
