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| Depressurized flow characteristics and critical cavitation prediction in passage of straight flow labyrinth valve channel |
| JIN Haozhe, DUAN Aoqiang, LIU Xiaofei, WANG Chao* |
| School of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, China |
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Abstract Aiming at the cavitation damage and failure phenomenon of the internal flow channel of the straight flow labyrinth regulating valve core with the characteristics of high pressure drop and high speed flow. Computational fluid dynamics(CFD)approach was adopted based on the critical cavitation pressure prediction method, combined with Schnerr-Sauer cavitation model in the Mixture multiphase flow and Realizable k-ε turbulence model. The critical cavitation inlet pressure of even stages 2N(N=1, 2, 3, 4)channel under different outlet pressures(0.1-0.8 MPa)was numerically simulated, and the variation laws of parameters, such as pressure, velocity and phase fraction of eight-stage channel are analyzed. The results show that vortices are generated only when fluid passes through a series of stages of perpendicular to the flow direction except the inlet stage, and the generation of vortex will lead to energy dissipation and pressure drop; the low pressure region formed by the vortex is lower than the saturated vapor pressure of the fluid at the outlet near the wall, and the local cavitation occurs in this region; The critical cavitation pressure difference presents a linear function increasing trend in the same channel stage situation by increasing outlet pressure. The critical cavitation pressure difference presents an exponential function increasing trend in the same outlet pressure situation by increasing channel stages. Therefore, according to the principle of eddy energy dissipation, pressure drop and the equation of critical cavitation linear and exponential trend line, the structure design of labyrinth channel can be improved and optimized to promote the generation of eddy current, and at the same time select the appropriate operating pressure and channel stages can be selected to avoid cavitation.
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Received: 19 June 2020
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