离心泵内部空化特性的CFD模拟

CFD simulation on cavitation characteristics in centrifugal pump

基于ANSYS CFX软件应用标准k-ε湍流模型、均质多相模型和Rayleigh-Plesset方程,对一比转数为94的离心泵在不同工况下其内部的空化特性进行数值模拟.根据模拟结果预测了模型泵无空化时的能量特性和发生空化时的空化性能,分析了不同空化状态下叶轮中间流面内的空泡分布和叶片中间流线上的载荷特性,并与试验结果进行对比.结果表明:预测结果具有一定的精度,模型泵在3个工况下空化余量的绝对误差分别为0.25,0.29和0.06 m.流场分析表明:随着进口总压的降低,空泡首先在叶片背面进口边附近产生,然后沿流线向叶轮出口扩散,并随着流道过流面积的增加向叶片工作面扩展;与其他叶片相比,正对蜗壳隔舌叶片中间流线上的载荷最小.随着泵空化程度的加剧,除正对蜗壳隔舌的叶片外,其余叶片上相对位置为0.35～0.80处的载荷明显增加,说明空化对叶片载荷有较大的影响.

The standard k-ε turbulence model,homogeneous multiphase model and Rayleigh-Plesset equation were applied to simulate cavitation characteristics in a centrifugal pump with specific speed of 94 under different conditions based on ANSYS CFX software.According to the simulation results,the energy characteristics under the no-cavitation conditions and cavitation characteristics of the model pump were predicted,and the vapor volume distribution on the middle stream surface of impeller and the blade loading characteristics on the middle stream line under different cavitation conditions were analyzed.The comparison between prediction values and experimental values indicates that the prediction results are accurate to some extent,and the absolute errors of net positive suction head under different conditions are 0.25,0.29 and 0.06 m,respectively.The flow field analysis indicates that the vapors generated at suction side of blade near the leading edge at first and then extended to the outlet of impeller with the reduction of inlet total pressure.Compared with other blades,the loading on the blade that against the volute tongue is the least and the loading on the other blades at the relative position of 0.35-0.80 increased obviously with the deterioration of cavitation condition,which shows that the blade loading is significantly affected by cavitation.