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Numerical simulation of transient characteristics in a bulb turbine during the load rejection process

Journal of Hydrodynamics 2024年第1期36卷 170-183页

作者： Yue Lu Yu-quan Zhang Zhong-wei He Yuan Zheng College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210098China College of Energy and Electrical Engineering Hohai UniversityNanjing210098China Huadong Engineering Corporation Ltd. Hangzhou311122China

To evaluate the safety of the bulb tubular turbine,the dynamic hydraulic characteristics of a hydropower station system during the load rejection process are studied through numerical simulations and a prototype test.In the developed model,a dynamic grid technology(DGT)controls the closure of the guide vane and the blade,whilst the moment balance equation and the user-defined function(UDF)provide the runner’s rotation speed.The 3-D transient simulation method can well predict the rotation speed and mass flow curves in the state of load rejection.The simulation outcomes of the system performance are basically consistent with the measurement data of the prototype.As observed,the runner is subjected to the reversely increased torque and axial force,the system is in a braking phase,and the maximum speed peaks at 144.6%of the rated speed.Moreover,the internal flow of the runner is greatly affected by the closure of the guide vane,and the draft tube forms an eccentric spiral vortex rope.It breaks downstream,aggravating the instability of the draft tube.Overall,the transient characteristics span for the first five seconds,demonstrating the importance of establishing an efficient governing controller.The obtained results are useful for designing the turbine’s flow channel with a double regulating function and comprehending the turbine’s transient characteristics.

关键词： Bulb tubular turbine load rejection numerical simulation dynamic grid prototype test

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The Gait Planning Theory and Technology Research on the Wheel-foot Multi-joint Mobile Robot

The Gait Planning Theory and Technology Research on the Whee...

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第26届中国控制与决策会议

作者： Zhang Yeqing Luo Qingsheng Wang Meiling Wu Fan Wu Di Key Laboratory of Intelligent Control and Decision of Complex System Beijing Institute of Technology School of Mechanic and Electronic Engineering Beijing Institute of Technology

ISBN: (纸本)9781479937066

Based on the excellent mechanical structure of the wheel-foot multi-joint mobile robot, we have strictly deduced the direct and inverse kinematical formulas of the robot’s legs. So the theoretical method and technology of gaits control for the wheel-foot multi-joint mobile robot have been explored out. By precisely analyzing the obstacle performance and the workspace of the robot’s feet, the constraints and efficiency of the robot have been illustrated clearly. After studying the features of various gaits, we also have designed four kinds of specific gaits for the wheel-foot multi-joint mobile robot, including the swing forward gait, the crab-lateral gait, the bent-knee forward gait and the wheel-turn gait, to verify the mobile ability and control effects of the robot. Then we research most fully on the control features, the attitudes of legs, the simulation effects and the fluctuation of the robot’s body when walking with these four kinds of gaits, in order to fully understand the performance of the robot. The results of simulations and actual prototype tests have proved that the wheel-foot multi-joint mobile robot, with special mechanical structure and reasonable gaits planning, can move fast and steadily with versatile gaits in various complex terrains. The effectiveness of the theoretical exploration and the technical implementation has been fully proved in this paper.

关键词： mechanical structure kinematical formulas workspace of feet walking gaits prototype test

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