隐性汽蚀过渡过程主泵叶轮内瞬变流动特性研究

Transient Flow Characteristics of Nuclear Reactor Coolant Pump in Recessive Cavitation Transition Process

通过CFX程序对反应堆主泵叶轮流道内发生隐性汽蚀时瞬态流动特性进行数值模拟计算,研究分析从汽蚀初生工况起降低进口压力至临界汽蚀余量过渡过程中主泵内部瞬态流动特性。流场分析表明:在隐性汽蚀过渡过程中,汽泡相的增加会影响进口处速度变化,使得靠近主泵叶片进口处的速度随汽泡相区域的增大而变大,且汽泡的产生和溃灭会影响靠近进口处速度波动幅度;靠近叶片进口处涡量值受汽泡相影响而逐渐增大,汽泡的溃灭会降低溃灭处至叶轮出口处间的涡量值;由于泵体的非对称结构,导致叶轮各流道内的流量、流速及叶轮出口压力分布出现非对称性,引起瞬态径向力的不对称性。汽蚀发展到一定程度后,汽泡相开始对叶轮瞬态径向力值产生影响使其出现无规律波动。

The numerical simulation calculation of the transient flow characteristics of nuclear reactor coolant pump in the recessive cavitation transition process in the nuclear reactor coolant pump impeller passage is conducted by CFX, and the transient flow characteristics of nuclear reactor coolant pump in the transition process from reducing the inlet pressure at cavitation-born conditions to NPSHc condition is studied and analyzed. The flow field analysis shows that, in the recessive cavitation transition process, the speed diversification at the inlet is relative to the bubble increasing, and makes the speed near the blade entrance increase when the bubble phase region becomes larger. The bubble generation and collapse will affect the the speed fluctuation near the entrance. The vorticity close to the blade entrance gradually increasing is influenced by the bubble phase, and the collapse of bubble generated by cavitation will reduce the vorticity from the collapse to impeller outlet. Pump asymmetric structure causes the asymmetry of the flow, velocity and outlet pressure distribution within every impeller flow passage, which cause the asymmetry of the transient radial force. From the dimensionless t/T =0.6, the bubble phase starts to have impact on the impeller transient radial force, and results in the irregular fluctuations.