叶片进口边位置对离心泵性能的影响

为了研究叶片进口边位置对离心泵外特性能、内流场的影响规律,在原型泵的基础上,设计了叶片进口边位置不同的5种叶轮,基于SST k-ω湍流模型和Zwart空化模型,分别对5种叶轮的离心泵在清水和含沙水介质下进行三维全流道定常数值计算.结果表明:针对低比转数离心泵,叶片进口排挤严重,使叶片进口边向出口方向延伸可以使叶片进口处的流动更加均匀,液流的流动速度减小,叶片表面的压力变大,从而改善空化性能;在一定范围内变动叶片的进口边位置对离心泵的扬程、效率影响不大,但是当叶片的进口边位置向出口方向延伸过多会导致叶片对液流的做功能力下降,从而使离心泵的扬程明显下降;当离心泵在相同工况下运行时,离心泵进口沙粒含量的增大会使离心泵的扬程、效率降低,且会使流道内空化核的数量增大,从而导致空化性能变差.

Effects of blade leading edge position on hydraulic performances of centrifugal pump

In order to study effects of blade leading edge position on centrifugal pump performance and internal flow field characteristics, five impellers with different blade leading edge positions were designed based on the original impeller of a centrifugal pump, and three-dimensional steady flow fields in the entire flow passage of the pumps with these impellers were carried out based on the SST k-ω and Zwart cavitation models under water single-phase as well as water-sand two-phase flow conditions. The results demonstrate that the suction performance of the centrifugal pump can be improved when the blade leading edge position is moved towards the impeller eye. The reason for this is that for a low specific-speed centrifugal pump its blade leading edge position being moved towards the impeller eye can improve flow conditions, such as flow uniformization, fluid velocity decrease and pressure rise in the impeller inlet. When the edge position is altered in a certain range, the head and efficiency of the pump are affected little. However, if the edge position is extended too much to the impeller eye, the head will be declined considerably because the blades are subject to the impaired capacity of doing work. At the same flow rate, the increase of sand content can degrade the head and efficiency of the pump but also augment the number of cavitation nuclei, thus make the suction performance poor.