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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 *** 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 *** 3-D transient simulation method can well predict the rotation speed and mass flow curves in the state of load *** simulation outcomes of the system performance are basically consistent with the measurement data of the *** 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 ***,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 *** breaks downstream,aggravating the instability of the draft ***,the transient characteristics span for the first five seconds,demonstrating the importance of establishing an efficient governing *** 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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Numerical and experimental investigation into the evolution of the shock wave when a muzzle jet impacts a constrained moving body

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Defence Technology（防务技术） 2024年第3期33卷 317-326页

作者： Zijie Li Hao Wang Changshun Chen Kun Jiang School of Energy and Power Engineering Nanjing University of Science and TechnologyNanjing 210016China

The gun-track launch system is a new special launch device that connects the track outside the *** it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle ***,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of *** this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving *** designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving *** also considered models without a constrained track for the sake of *** results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the *** the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric *** in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been *** results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving *** work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch *** also sheds light on the

关键词： Shock wave/vortex interference Muzzle jet Constrained boundary dynamic grid

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Research on buffer structure and flow field simulation of swash plate plunger type hydraulic transformer

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High Technology Letters 2022年第4期28卷 425-433页

作者：王晓晶 HUO Shuhang LI Wenjie Beijing Key Laboratory of Performance Guarantee on Urban Rail Transit Vehicle Beijing University of Civil Engineering and ArchitectureBeijing 102616P.R.China Beijing Engineering Research Center of Monitoring for Construction Safety Beijing University of Civil Engineering and ArchitectureBeijing 102616P.R.China School of Mechanical and Power Engineering Harbin University of Science and TechnologyHarbin 150080P.R.China

In order to solve the problem of excessive noise and vibration during the operation of the hydraulic transformer,an optimization method of valve plate damping hole structure is proposed to alleviate the phenomenon of pressure ***,the mathematical model of oil pressure gradient in the plunger cavity is established,and the incremental equation of pressure change is ***,a kind of buffering structure is proposed,the corresponding relationship between the pressure change and the envelopment angle of the buffering hole and the aperture size is determined by analyzing the oil pressure change curve in the plunger ***,the flow field models with buffering holes are established,and the transient simulation of the pressure change process under the optimal solution is carried out with ANSYS software and the flow field pressure distribution contours are *** the analysis of simulation results,it is concluded that the optimal envelope angle of the three buffer holes ofA-T-B-Ais 5°,and the optimal aperture is 1.8 mm,1.6 mm,and 1.7 mm,*** buffer hole can achieve a better-buffering effect in the range of variable pressure angle[0°,101°].The buffer hole structure can effectively alleviate the pressure shock and reduce the noise level,which lays a foundation for the design and theoretical research of hydraulic transformers.

关键词： hydraulic transformer pressure shock buffer structure flow field simulation dynamic grid

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Self-ignition characteristics of the high-speed ramjet kinetic energy projectile in the launch process

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Chinese Journal of Aeronautics 2019年第4期32卷 851-860页

作者： Changfei ZHUO Haotian CHEN Wenjin YAO Xiaoming WANG School of Mechanical Engineering Nanjing University of Science and Technology

To research the self-ignition characteristics of high-speed ramjet kinetic energy projectile in the launch process, the self-ignition process based on the solid fuel of polyethylene was numerically simulated by using the dynamic grid technology. The effect of different muzzle velocity on the self-ignition performance, and the effect of opening the blockage at different times on the flow field stability of the combustion chamber and the flow field characteristics after the solid fuel ramjet stabilized were analyzed. The results show that the occurrence of self-ignition is not only related to the pressure, temperature in the combustion chamber, and the muzzle velocity, but also to the content of C_2H_4 and its degree of mixing with air in the combustion chamber. After the kinetic energy projectile gets out of the muzzle and before the blockage opens, there is oscillation occurring in the combustion chamber. The higher the muzzle velocity of the kinetic energy projectile, the more prone to the occurrence of the self-ignition and the negative effects can be avoided due to the pressure oscillation in the combustion chamber. The effect of opening the blockage at different times on the flow field stability after the self-ignition occurs in a period of time is weak. After the blockage opens, the solid fuel ramjet can reach a stable working condition quickly.

关键词： dynamic grid Kinetic energy projectile Muzzle velocity Self-ignition Solid fuel ramjet

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