Analyses of gasliquid twophase flow and pressure fluctuation during startup of municipal waterlogging selfpriming pump" />
市政排涝自吸泵启动过程气液两相流动及压力脉动分析
摘要 为了探明自吸泵的自吸机理.以外混式自吸泵为研究对象，利用CFX仿真软件中的VOF（volume of fluid）两相流模型和kε湍流模型，并结合网格滑移技术进行自吸过程非稳态数值模拟，分析了不同时刻下泵内气液两相体积、液相速度、出口气体体积分数和压力的分布情况.同时改变非稳态模拟的时间步长及总时长，监测自吸过程叶轮及蜗壳内监测点的压力变化.结果表明：自吸泵的吸气与排气主要集中在启动过程的初期和中期，叶轮入口和泵出口的气体体积分数分别超过60%和75%；叶轮出口的气液混合带导致了叶轮出口到蜗壳内侧大片区域内的流动紊乱现象，降低了叶轮的做功能力，进而影响了泵的正常排气；叶轮监测点压力脉动幅值与距叶片工作面的大小有关，蜗壳内监测点压力脉动幅值与距叶轮外缘的大小有关.
Abstract：To explore the selfpriming mechanism of selfpriming pump, the external mixing selfpriming pump was taken as the research object. Combining with grid slip technology, the unsteady numerical simulation of the selfpriming process was carried out by the VOF twophase flow model and kε turbulence model in CFX simulation software. The distributions of gasliquid twophase volume, liquid phase velocity, outlet void fraction and pressure in the pump at different times were analyzed. The time step and the total time of unsteady state simulation were changed to monitor the pressure change in the impeller and volute during the selfpriming process. The results show that the suction and exhaust of the selfpriming pump are mainly concentrated in the early and middle stages of the startup process, and the air contents in the impeller inlet and pump outlet are more than 60% and 75%, respectively. The gasliquid mixing zone at the impeller outlet leads to the flow disorder phenomenon in the large area from the impeller outlet to the inner side of the volute, which reduces the work capacity of the impeller and affects the normal exhaust of the pump. The pressure fluctuation amplitude of the monitoring point of the impeller is related to the distance from the blade working face, while the pressure fluctuation amplitude of the monitoring point in the volute is related to the distance from the outer edge of the impeller.
