余热排出泵叶轮内空化流动特性的数值分析

Numerical analysis of cavitating flow characteristics in impeller of residual heat removal pump

为研究余热排出泵叶轮内空化流动特性,基于Rayleigh-Plesset方程的混合物均相流空化模型和剪切应力运输SST k-ω湍流模型,对余热排出泵水力样机叶轮内空化流动进行数值计算.根据计算结果获得了余热排出泵水力样机空化性能、设计流量工况不同装置空化余量条件下叶轮内空泡分布规律及其叶片表面载荷分布.研究结果表明:设计流量工况下,叶轮内空泡随着装置空化余量的降低逐渐呈不对称性分布,当装置空化余量低至2.63 m时,个别流道发生了堵塞.叶轮不同切面上的空泡分布不一样,切面越靠近后盖板,叶片吸力面上空化区面积越大,扬程发生突降之前,泵叶轮内空化表现为准静态空穴的特征.由于主流方向在叶轮进口处发生了急剧变化,使得叶片压力面靠近叶片进口边上叶片载荷出现了先突然增大然后又迅速降低的变化规律.

In order to investigate internal cavitating flow characteristics of the impeller in residual heat removal pumps, the three-dimensional cavitating flow in a residual heat removal model pump is numeri- cally calculated by using the homogeneous mixture cavitation model based on the Rayleigh - Plesset equalion and the shear stress transport SST κ-ω turbulence model. The hydraulic performance curves, distrihutions of vapor volume fraction at NPSHA and the blade load profiles at the design flow rate are obtained. The numerical results show that the distribution of vapor volume fraction becomes non-axi- symmetric with the decreasing of NPSHA, even some blade passages are blocked when NPSHA drops to 2.63 m. Vapor w）lume fi＇action distribution varies across blade span; the shorter the distance to the hub ler s side Key is, the higher the vapor fraction on the blade suction side is. Additionall hows a quasi-steady characteristic before the head starts to be deteriorat change in the primary flow direction near the eye of impeller, the blade shows a sudden increasing and drop effect.