多级离心泵叶轮与导叶的匹配特性

基于CFX软件,采用k-ε模型对某一立式三级离心泵全流场进行数值模拟,并进行试验验证,表明在设计工况下数值计算结果与试验结果吻合较好,但泵内流场分析发现,叶轮-导叶间隙及导叶内的流动损失较大.为了减少流动损失,提高多级离心泵叶轮与导叶之间的匹配特性,分别重新设计4种采用不同进口结构形式的导叶.在设计工况下对4种不同进口的导叶模型进行定常数值计算,并对水力性能、内部流动规律及叶片表面压力分布规律进行分析.结果表明:导叶进口采用扩散结构,与叶轮出口边相平行的模型水力性能最好;导叶进口采取扭曲结构时,能够提高叶轮扬程,但也会增大导叶与叶轮间隙的流动损失,并导致导叶进口压力不稳定;当导叶进口与叶轮出口平行时,可以减小导叶内的流动损失,提高导叶的水力性能;当导叶进口与轴线平行时,可以弱化叶轮与导叶之间的干涉作用,提高叶轮的水力性能,但会增大叶轮与导叶间隙处产生的流动损失.

Matching characteristic between impeller and bowl diffuser in multi-stage centrifugal pump

The flow field in a three-stage centrifugal pump was simulated by using CFX software based on the standard k-ε turbulence model, the predicted performance curves were compared with the measurements, and good agreement was showed. After a further analysis on the flow details, however, a larger hydraulic loss has occurred in the gap between the impeller and the bowl diffuser as well as in the diffuser itself. In order to reduce the hydraulic loss and improve the matching characteristic of the diffuser to the impeller, four diffusers with different inlet structures are designed. The steady flow in the three-stage pumps with these diffusers is simulated at the design point, and the pump performance, flow pattern and the pressure distribution over the diffuser vane pressure side are analysed. The results show that the diffuser with untwisted inlet and in parallel with the impeller outlet has the best hydraulic performance. The diffuser with twisted inlet results in an increased impeller head, but the hydraulic loss in the gap between the impeller and the diffuser rises, and the pressure at the inlet of diffuser becomes instable. The diffuser with inlet edge in parallel with the impeller outlet can reduce the inside loss to improve the hydraulic performance. Even though the diffuser with inlet edge in parallel with the pump shaft can compromise the interference with the impeller to increase the impeller hydraulic performance, the hydraulic loss in the gap is increased.