直流式迷宫调节阀流道降压流动特性及临界空化预测

Depressurized flow characteristics and critical cavitation prediction in passage of straight flow labyrinth valve channel

针对高降压、高速流的直流式迷宫压力调节阀阀芯内部流道空化损伤失效现象,基于临界空化压力预测方法进行流体力学计算,结合Mixture多相流中的Schnerr-Sauer空化模型和Reali-zable k-ε湍流模型,数值模拟了偶数级数2 N(N=1,2,3,4)流道在不同出口压力(0.1~0.8 MPa)下的临界空化进口压力,并分析了八级流道的压力、速度、相分率等参数的变化规律.研究结果表明:除进口级数外,流体经过垂直于进口流动方向的级数后才会产生旋涡,旋涡的产生会导致能量耗散和降压;在出口近壁面处,旋涡形成的低压区低于流体的饱和蒸气压,发生了局部空化;相同流道级数递增出口压力下的临界空化压差呈现线性函数增长趋势;相同出口压力递增流道级数下的临界空化压差呈现指数函数增长趋势.因此,可根据涡流能量耗散降压原理及临界空化线性、指数趋势线方程在改进优化迷宫流道结构设计促进涡流产生的同时选择合适的工况压力和流道级数来避免空化.

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-εturbulence model.The critical cavitation inlet pressure of even stages 2 N(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 were 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,the appropriate operating pressure and channel stages can be selected to avoid cavitation.