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Bhola Thapa - One of the best experts on this subject based on the ideXlab platform.
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selection of Guide Vane profile for erosion handling in francis turbines
Renewable Energy, 2017Co-Authors: Hari Prasad Neopane, Ravi Koirala, Oblique Shrestha, Baoshan Zhu, Bhola ThapaAbstract:In Guide Vane cascade of Francis turbine, highest acceleration occurs, which generates equivalent amount of force for work done and erosion due to instantaneous change in flow dynamics. Hence in addition to runner Vane, suitable selection of Guide Vane profile has equal importance. Usually, NACA defined hydrofoils are used for Guide Vanes. Numerous options are available, but selection of best one for optimum energy harness is important. Primarily, Guide Vane torque and turbine efficiency is prioritized. For the turbines operating in sediment laden water, pressure difference between two sides of Guide Vane and erosion resistivity are additional factors to be considered. This work was performed in the vicinity of Guide Vane profile selection for Francis turbines operating in sediment laden water. Computational analysis on turbine flow passage and experimental study with Rotating Disc Apparatus were performed in order to identify suitable profile. Unsymmetrical profiles were found to be better handling erosion maintaining consistency in turbine performance.
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Sediment erosion induced leakage flow from Guide Vane clearance gap in a low specific speed Francis turbine
Renewable Energy, 2017Co-Authors: Ole Gunnar Dahlhaug, Bhola ThapaAbstract:Opportunities of future hydropower developments in Asia comes with challenges of handling sediments in rivers. Hard minerals in flow causes turbine parts to erode with several undesirable effects. In Francis turbines, sediment erosion causes an increase of clearance gap between Guide Vane walls and cover plates. Due to inherit pressure difference between Guide Vane surfaces, a leakage flow arises from the clearance gap. A Guide Vane cascade is developed to study the characteristics of the leakage flow in a low specific speed Francis turbine. Velocity and pressure measurements are done at 80% of BEP flow as that in a reference prototype turbine. Cases with five different sizes of clearance gaps are investigated. Strong cross-wise jet-like leakage flow is observed from the clearance gap. A vortex filament developed due to mixing of leakage flow with the main flow is found to hit the hub at runner inlet. The existence of a critical clearance gap size for which the leakage velocity and its effects are maximum is revealed. Interpretations of the experimental results show a close match with the observations of eroded turbine parts from a power plant.
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velocity and pressure measurements in Guide Vane clearance gap of a low specific speed francis turbine
IOP Conference Series: Earth and Environmental Science, 2016Co-Authors: Biraj Singh Thapa, Ole Gunnar Dahlhaug, Bhola ThapaAbstract:In Francis turbine, a small clearance gap between the Guide Vanes and the cover plates is usually required to pivot Guide Vanes as a part of governing system. Deflection of cover plates and erosion of mating surfaces causes this gap to increase from its design value. The clearance gap induces the secondary flow in the distributor system. This effects the main flow at the runner inlet, which causes losses in efficiency and instability. A Guide Vane cascade of a low specific speed Francis turbine has been developed for experimental investigations. The test setup is able to produce similar velocity distributions at the runner inlet as that of a reference prototype turbine. The setup is designed for particle image velocimetry (PIV) measurements from the position of stay Vane outlet to the position of runner inlet. In this study, velocity and pressure measurements are conducted with 2 mm clearance gap on one side of Guide Vane. Leakage flow is observed and measured together with pressure measurements. It is concluded that the leakage flow behaves as a jet and mixes with the main flow in cross-wise direction and forms a vortex filament. This causes non-uniform inlet flow conditions at runner blades.
Ravi Koirala - One of the best experts on this subject based on the ideXlab platform.
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selection of Guide Vane profile for erosion handling in francis turbines
Renewable Energy, 2017Co-Authors: Hari Prasad Neopane, Ravi Koirala, Oblique Shrestha, Baoshan Zhu, Bhola ThapaAbstract:In Guide Vane cascade of Francis turbine, highest acceleration occurs, which generates equivalent amount of force for work done and erosion due to instantaneous change in flow dynamics. Hence in addition to runner Vane, suitable selection of Guide Vane profile has equal importance. Usually, NACA defined hydrofoils are used for Guide Vanes. Numerous options are available, but selection of best one for optimum energy harness is important. Primarily, Guide Vane torque and turbine efficiency is prioritized. For the turbines operating in sediment laden water, pressure difference between two sides of Guide Vane and erosion resistivity are additional factors to be considered. This work was performed in the vicinity of Guide Vane profile selection for Francis turbines operating in sediment laden water. Computational analysis on turbine flow passage and experimental study with Rotating Disc Apparatus were performed in order to identify suitable profile. Unsymmetrical profiles were found to be better handling erosion maintaining consistency in turbine performance.
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effect of Guide Vane clearance gap on francis turbine performance
Energies, 2016Co-Authors: Ravi Koirala, Baoshan Zhu, Hari Prasad NeopaneAbstract:Francis turbine Guide Vanes have pivoted support with external control mechanism, for conversion of pressure to kinetic energy and to direct them to runner Vanes. This movement along the support is dependent on variation of load and flow (operating conditions). Small clearance gaps between facing plates and the upper and lower Guide Vane tips are available to aid this movement, through which leakage flow occurs. This secondary flow disturbs the main flow stream, resulting performance loss. Additionally, these increased horseshoe vortex, in presence of sand, when crosses through the gaps, both the surfaces are eroded. This causes further serious effect on performance and structural property by increasing gaps. This paper discusses the observation of the severity in hydropower plants and effect of clearance gaps on general performance of the Francis turbine through computational methods. It also relates the primary result with the empirical relation for leakage flow prediction. Additionally, a possible method to computationally estimate thickness depletion has also been presented. With increasing clearance gap, leakage increases, which lowers energy conversion and turbine efficiency along with larger secondary vortex.
Hari Prasad Neopane - One of the best experts on this subject based on the ideXlab platform.
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selection of Guide Vane profile for erosion handling in francis turbines
Renewable Energy, 2017Co-Authors: Hari Prasad Neopane, Ravi Koirala, Oblique Shrestha, Baoshan Zhu, Bhola ThapaAbstract:In Guide Vane cascade of Francis turbine, highest acceleration occurs, which generates equivalent amount of force for work done and erosion due to instantaneous change in flow dynamics. Hence in addition to runner Vane, suitable selection of Guide Vane profile has equal importance. Usually, NACA defined hydrofoils are used for Guide Vanes. Numerous options are available, but selection of best one for optimum energy harness is important. Primarily, Guide Vane torque and turbine efficiency is prioritized. For the turbines operating in sediment laden water, pressure difference between two sides of Guide Vane and erosion resistivity are additional factors to be considered. This work was performed in the vicinity of Guide Vane profile selection for Francis turbines operating in sediment laden water. Computational analysis on turbine flow passage and experimental study with Rotating Disc Apparatus were performed in order to identify suitable profile. Unsymmetrical profiles were found to be better handling erosion maintaining consistency in turbine performance.
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effect of Guide Vane clearance gap on francis turbine performance
Energies, 2016Co-Authors: Ravi Koirala, Baoshan Zhu, Hari Prasad NeopaneAbstract:Francis turbine Guide Vanes have pivoted support with external control mechanism, for conversion of pressure to kinetic energy and to direct them to runner Vanes. This movement along the support is dependent on variation of load and flow (operating conditions). Small clearance gaps between facing plates and the upper and lower Guide Vane tips are available to aid this movement, through which leakage flow occurs. This secondary flow disturbs the main flow stream, resulting performance loss. Additionally, these increased horseshoe vortex, in presence of sand, when crosses through the gaps, both the surfaces are eroded. This causes further serious effect on performance and structural property by increasing gaps. This paper discusses the observation of the severity in hydropower plants and effect of clearance gaps on general performance of the Francis turbine through computational methods. It also relates the primary result with the empirical relation for leakage flow prediction. Additionally, a possible method to computationally estimate thickness depletion has also been presented. With increasing clearance gap, leakage increases, which lowers energy conversion and turbine efficiency along with larger secondary vortex.
Manabu Takao - One of the best experts on this subject based on the ideXlab platform.
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a straight bladed vertical axis wind turbine with a directed Guide Vane row effect of Guide Vane geometry on the performance
Journal of Thermal Science, 2009Co-Authors: Manabu Takao, Hideki Kuma, Takao Maeda, Yasunari Kamada, Michiaki Oki, Atsushi MinodaAbstract:The objective of this study is to show the effect of Guide Vane geometry on the performance. In order to overcome the disadvantages of vertical axis wind turbine, a straight-bladed vertical axis wind turbine (S-VAWT) with a directed Guide Vane row has been proposed and tested by the authors. According to previous studies, it was clarified that the performance of the turbine can be improved by means of the directed Guide Vane row. However, the Guide Vane geometry of S-VAWT has not been optimized so far. In order to clarify the effect of Guide Vane geometry, the effects of setting angle and gap between rotor blade and Guide Vane on power coefficient and starting characteristic were investigated in the experiments. The experimental study of the proposed wind turbine was carried out by a wind tunnel. The wind tunnel with a diameter of 1.8m is open jet type. The wind velocity is 8 m/s in the experiments. The rotor has three straight blades with a profile of NACA0018 and a chord length of 100 mm, a diameter of 0.6 m and a blade height of 0.7 m. The Guide Vane row consists of 3 arc plates.
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A straight-bladed vertical axis wind turbine with a directed Guide Vane row — Effect of Guide Vane geometry on the performance —
Journal of Thermal Science, 2009Co-Authors: Manabu Takao, Hideki Kuma, Takao Maeda, Yasunari Kamada, Michiaki Oki, Atsushi MinodaAbstract:The objective of this study is to show the effect of Guide Vane geometry on the performance. In order to overcome the disadvantages of vertical axis wind turbine, a straight-bladed vertical axis wind turbine (S-VAWT) with a directed Guide Vane row has been proposed and tested by the authors. According to previous studies, it was clarified that the performance of the turbine can be improved by means of the directed Guide Vane row. However, the Guide Vane geometry of S-VAWT has not been optimized so far. In order to clarify the effect of Guide Vane geometry, the effects of setting angle and gap between rotor blade and Guide Vane on power coefficient and starting characteristic were investigated in the experiments. The experimental study of the proposed wind turbine was carried out by a wind tunnel. The wind tunnel with a diameter of 1.8m is open jet type. The wind velocity is 8 m/s in the experiments. The rotor has three straight blades with a profile of NACA0018 and a chord length of 100 mm, a diameter of 0.6 m and a blade height of 0.7 m. The Guide Vane row consists of 3 arc plates.
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Experimental Study of a Straight-Bladed Vertical Axis Wind Turbine With a Directed Guide Vane Row
Volume 4: Ocean Engineering; Ocean Renewable Energy; Ocean Space Utilization Parts A and B, 2009Co-Authors: Manabu Takao, Takao Maeda, Yasunari Kamada, Hiroyuki Takita, Yohei Saito, Kazuhiko ToshimitsuAbstract:The objective of this study is to show the effect of Guide Vane geometry on the performance of wind turbine. In order to overcome the disadvantages of vertical axis wind turbine, a straight-bladed vertical axis wind turbine (S-VAWT) with a directed Guide Vane row has been proposed and tested by the authors. According to previous studies, it was clarified that the performance of the turbine can be improved by means of the directed Guide Vane row. However, the Guide Vane geometry of S-VAWT has not been optimized so far. In order to clarify the effect of Guide Vane geometry, the effects of distance between the Guide Vanes and the number of Guide Vanes on power and torque coefficients were investigated in the experiments. The experimental study was carried out by a wind tunnel. The wind tunnel with a diameter of 1.8m is open jet type. The wind velocity is from 5 to 9 m/s in the experiments. The rotor has three straight blades with a profile of NACA4518 and a chord length of 100 mm, a diameter of 0.6 m and a blade height of 0.7 m. The Guide Vane row consists of some arc plates.Copyright © 2009 by ASME
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a straight bladed vertical axis wind turbine with a directed Guide Vane row
ASME JSME 2007 5th Joint Fluids Engineering Conference, 2007Co-Authors: Manabu Takao, Takao Maeda, Yasunari Kamada, Michiaki Oki, Hideki KumaAbstract:A straight-bladed vertical axis wind turbine with a directed Guide Vane row has been proposed in order to enhance its torque. The experimental study of the proposed wind turbine was carried out by a wind tunnel with an outlet diameter of 1.8m. The tested rotor has some straight rotor blades with a profile of NACA0015, a radius diameter of 0.3 m and a height of 0.7 m. The Guide Vane row having 3 arc plates rotates around the rotor and is directed to the wind by aerodynamic force generated by tail Vanes, so as to put the Guide Vane row in upstream of the rotor. As a result, the performance of the straight-bladed vertical axis turbine was improved by means of the directed Guide Vane row. Further, by the use of the Guide Vane row adopted in the study, the power coefficient of the proposed wind turbine was approximately 1.5 times higher than that of the original wind turbine which has no Guide Vane.Copyright © 2007 by ASME
Congtruong Dinh - One of the best experts on this subject based on the ideXlab platform.
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numerical aero thermal study of high pressure turbine nozzle Guide Vane effects of inflow conditions
Physics of Fluids, 2020Co-Authors: H M Phan, P H Duan, Congtruong DinhAbstract:Accurate predictability of high-pressure turbine nozzle Guide Vane aero-thermal performance is highly desired in the development campaign due to the exposure of the component to a frequent and high...