离心式上充泵小流量工况转换瞬态流动特性

Transient Flow Characteristics During Variable Operation to Small Flow Rate of Centrifugal Charging Pump

为研究核电站离心式上充泵由上充工况向小流量工况转换运行过程中的瞬态流动特性,基于RANS方程和RNGk-ε湍流模型,采用商业软件CFX对其进行定常数值模拟,并通过试验验证了数值计算方法的正确性。在此基础上,继续对该瞬态过程进行数值计算,得到上充泵内部流动瞬态压力及速度的变化规律。结果表明:在由上充工况向小流量工况转变过渡过程中,叶轮、导叶、出口涡壳的流道内压力有不同程度的上升趋势;在瞬态转变过程中,随着流量的减小,上充泵内部漩涡范围增大,流动形式也愈来愈差,导致压力和速度波动幅值增大;由于动静干涉影响,叶轮与导叶交界面附近监测点的压力和速度波动程度高于其他监测点的波动程度,双蜗壳流道内圈的波动高于外圈的波动。

In order to study transient flow characteristics during the process from charging operation to small flow rate operation of a centrifugal charging pump in the nuclear power plant,CFX software was used for the simulation of transient process on the basis of RANS equation and RNGk-εturbulence model.After test verification of the numerical method,the transient pressure and velocity characteristics of the charging pump were obtained from the simulation.The results show that the pressure in impellers,guide vanes and volute increase during the transient process.The vortexes generate and become serious with the flow rate decrease,so the flow pattern is getting worse and worse.As a result,the fluctuation amplitudes of pressure and velocity increase in this period.Because of the interference,fluctuations of pressure and velocity near the interface between impellers and guide vanes are stronger than that in other areas,and thefluctuations in inner channel is more serious than that of the outside channel in the volute.