The Experts below are selected from a list of 24423 Experts worldwide ranked by ideXlab platform
Zheng-gui Li - One of the best experts on this subject based on the ideXlab platform.
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Analysis on Internal Flow Characteristics of Tubular Turbine Draft Tube
2019 IEEE Innovative Smart Grid Technologies - Asia (ISGT Asia), 2019Co-Authors: Zheng-gui Li, Xin-rui Li, Yong Zhi Zhao, Feng-chen LiAbstract:The internal flow characteristics of the tubular turbine draft tube have a great influence on the operation of the turbine. By the numerical simulation, the unsteady internal flow field in a Tubular Turbine of a plant was carried out The internal flow characteristics of the tubular turbine draft tube under different working conditions were also analyzed. The simulation results show that under the rated operating condition,the pressure fluctuation amplitude that from the runner inlet to the draft tube increases at first then decreases, and the overall pressure pulsation amplitude is small. Under the off design operations, along the flow Direction of the water flow, the amplitude of the low-frequency pressure pulsation increases,and the dominant effect of the low-frequency on the pressure pulsation becomes more and more obvious.Under the low flow conditions, the Rotating Direction of the vortex rope in the draft tube is consistent with the Rotating Direction of the runner. Under the large flow conditions, the rotational Direction of the vortex rope in the draft tube is opposite to the rotational Direction of the turbine runner. These changes are consistent with the trend of the calculated pressure pulsation at the outlet of the turbine runner chamber. These rules provide evidence for the design of the draft tube.
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transient characteristics during the closure of guide vanes in a pump turbine in pump mode
Renewable Energy, 2018Co-Authors: Deyou Li, Zheng-gui Li, Hongjie Wang, Torbjorn K Nielsen, Rahul GoyalAbstract:To achieve the flow mechanism during the closure of the guide vanes in a pump-turbine in pump mode, a three-dimensional (3-D) incompressible simulation using the shear stress transition (SST) k-ω turbulence model was performed. The dynamic mesh method was adopted to simulate the closing process of the guide vanes. Based on the validation of the steady experiments, the variation in performance characteristics (head, discharge, and torque), pressure, and velocity was presented, which shows dynamic instability at the end of the guide vanes closing process. Numerical results confirm that the dynamic instabilities at the end of the closing process originated from severe fluctuations that occurred in the guide and stay vanes. Detailed analyses of flow characteristics reveal that severe fluctuations occur due to vortices in the stay vanes, and a high-pressure circular ring in the vaneless space and a low-pressure circular ring between the guide vanes outlet and stay vanes inlet were identified. During the closing process of the guide vanes opening, the vortices appear in several passages initially, and then increasingly spread to all the passages. The position and Rotating Direction of the vortices vary with time. Using the Q-criterion method, the composition and evolution of vortex structures in stay vanes were identified. These structures comprise streamwise vortices, horseshoe-shaped vortices, and spanwise vortices, which lead to severe pressure fluctuations.
Quanjun Song - One of the best experts on this subject based on the ideXlab platform.
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Force Analysis of Arm Wrestling Entertainment System and its Application to Control Design
2006 International Conference on Mechatronics and Automation, 2006Co-Authors: Feng Chen, Quanjun SongAbstract:This paper analyzes the changes in interaction force between the arm wrestling entertainment system and human hand, and presents a control strategy of force/velocity for arm wrestling robot (AWR) system. Based on the mass-spring-viscidity system model, the AWR control system adjusts the motor Rotating Direction and speed by using the information of force and angular speed feedback. This robotic machine performs arm wrestling games with people on a table. And, we can make the competition interesting by choosing the different competition rank. The system has good adaptability and the feasibility of the control method is demonstrated by the experiment results.
Yongshui Lin - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the motion characteristics for a spring-mounted Rotating cylinder in flow
Journal of Marine Science and Technology, 2020Co-Authors: Wei Chen, Chang-kyu Rheem, Li Xiaobin, Yongshui LinAbstract:A spring mounted Rotating cylinder placed in flow is investigated using a two-dimensional newly improved discrete vortex method at Reynolds number of 105. In this study, the non-dimensional rotation rate, $$\alpha$$ (rate of the cylinder surface velocity and flow velocity), varies from 0 to 16, and the reduced velocity $${\text{Ur}}$$, increases from 1 to 14. The relationship between the wake formation, hydrodynamics, and motion of the cylinder has been illustrated. Three different motions (VIV, reverse Direction whirl, and same Direction whirl) have been identified and illustrated. The VIV mainly occurs in the cross-flow Direction, and it is generated at $$\alpha 3$$. The path of the same Direction whirl looks like a slight round circle, and the moving Direction is the same as the Rotating Direction. The frequency of the whirl is higher than that of the VIV at the same rotation rate. The same Direction whirl starts from $$\alpha = 8$$ with $${\text{Ur}} = 13$$, and the frequency of this whirl increases with increasing rotation rate. Unlike that of the same Direction whirl, the moving Direction of the reverse Direction whirl is opposite to the Rotating Direction, and the path of the whirl similarly seems to be a round circle. The reverse Direction whirl is generated at $$2 \le \alpha \le 7.5$$. The frequency of the reverse Direction whirl decreases with increasing the rotation rate due to the increased effective added mass. The relationship between the effective added mass coefficient and the rotation rate has been interpreted; the effective added mass coefficient remains steady at $$0 \le \alpha \le 1$$ then gradually increases at $$1 < \alpha < 2$$, and finally dramatically increases with increasing rotation rate at $$\alpha \ge 2$$.
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Experimental investigation of the whirl and generated forces of Rotating cylinders in still water and in flow
International Journal of Naval Architecture and Ocean Engineering, 2020Co-Authors: Wei Chen, Chang-kyu Rheem, Yongshui LinAbstract:Abstract The whirl and generated forces of Rotating cylinders with different diameters placed in still water and in flow are studied experimentally. For the Rotating cylinders in still water, the Same Frequency Whirl (SFW) and Different Frequency Whirl (DFW) have been identified and illustrated. The corresponding SFW and DFW areas are divided. The Root Mean Square (RMS) values of the generated force coefficient dramatically increase in the defined ranges of Resonance I and Resonance II. For the Rotating cylinders in flow, the hydrodynamics, SFW and DFW are illustrated. The hydrodynamic, SFW and DFW areas are divided. The RMS values of the generated forces in the range of Resonance II are much smaller than those in still water due to the generated lift forces. The discussion suggests that the frequency of the DFW may equal multiple times or one-multiple times that of the Rotating frequency: the whirl Direction of the DFW with multiple times the frequency of the Rotating frequency is the same as the Rotating Direction. The whirl Direction of the DFW with one-multiple times frequency of the Rotating frequency is opposite to the Rotating Direction.
Feng Chen - One of the best experts on this subject based on the ideXlab platform.
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Force Analysis of Arm Wrestling Entertainment System and its Application to Control Design
2006 International Conference on Mechatronics and Automation, 2006Co-Authors: Feng Chen, Quanjun SongAbstract:This paper analyzes the changes in interaction force between the arm wrestling entertainment system and human hand, and presents a control strategy of force/velocity for arm wrestling robot (AWR) system. Based on the mass-spring-viscidity system model, the AWR control system adjusts the motor Rotating Direction and speed by using the information of force and angular speed feedback. This robotic machine performs arm wrestling games with people on a table. And, we can make the competition interesting by choosing the different competition rank. The system has good adaptability and the feasibility of the control method is demonstrated by the experiment results.
Wei Chen - One of the best experts on this subject based on the ideXlab platform.
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Investigation of the motion characteristics for a spring-mounted Rotating cylinder in flow
Journal of Marine Science and Technology, 2020Co-Authors: Wei Chen, Chang-kyu Rheem, Li Xiaobin, Yongshui LinAbstract:A spring mounted Rotating cylinder placed in flow is investigated using a two-dimensional newly improved discrete vortex method at Reynolds number of 105. In this study, the non-dimensional rotation rate, $$\alpha$$ (rate of the cylinder surface velocity and flow velocity), varies from 0 to 16, and the reduced velocity $${\text{Ur}}$$, increases from 1 to 14. The relationship between the wake formation, hydrodynamics, and motion of the cylinder has been illustrated. Three different motions (VIV, reverse Direction whirl, and same Direction whirl) have been identified and illustrated. The VIV mainly occurs in the cross-flow Direction, and it is generated at $$\alpha 3$$. The path of the same Direction whirl looks like a slight round circle, and the moving Direction is the same as the Rotating Direction. The frequency of the whirl is higher than that of the VIV at the same rotation rate. The same Direction whirl starts from $$\alpha = 8$$ with $${\text{Ur}} = 13$$, and the frequency of this whirl increases with increasing rotation rate. Unlike that of the same Direction whirl, the moving Direction of the reverse Direction whirl is opposite to the Rotating Direction, and the path of the whirl similarly seems to be a round circle. The reverse Direction whirl is generated at $$2 \le \alpha \le 7.5$$. The frequency of the reverse Direction whirl decreases with increasing the rotation rate due to the increased effective added mass. The relationship between the effective added mass coefficient and the rotation rate has been interpreted; the effective added mass coefficient remains steady at $$0 \le \alpha \le 1$$ then gradually increases at $$1 < \alpha < 2$$, and finally dramatically increases with increasing rotation rate at $$\alpha \ge 2$$.
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Experimental investigation of the whirl and generated forces of Rotating cylinders in still water and in flow
International Journal of Naval Architecture and Ocean Engineering, 2020Co-Authors: Wei Chen, Chang-kyu Rheem, Yongshui LinAbstract:Abstract The whirl and generated forces of Rotating cylinders with different diameters placed in still water and in flow are studied experimentally. For the Rotating cylinders in still water, the Same Frequency Whirl (SFW) and Different Frequency Whirl (DFW) have been identified and illustrated. The corresponding SFW and DFW areas are divided. The Root Mean Square (RMS) values of the generated force coefficient dramatically increase in the defined ranges of Resonance I and Resonance II. For the Rotating cylinders in flow, the hydrodynamics, SFW and DFW are illustrated. The hydrodynamic, SFW and DFW areas are divided. The RMS values of the generated forces in the range of Resonance II are much smaller than those in still water due to the generated lift forces. The discussion suggests that the frequency of the DFW may equal multiple times or one-multiple times that of the Rotating frequency: the whirl Direction of the DFW with multiple times the frequency of the Rotating frequency is the same as the Rotating Direction. The whirl Direction of the DFW with one-multiple times frequency of the Rotating frequency is opposite to the Rotating Direction.
