多级液力透平效率理论分析及数值计算

为预测多级离心泵作透平的水力效率，以DG85-80多级离心泵为模型，对多级离心泵作透平的性能进行理论分析，提出多级离心泵透平工况下最优效率与泵工况下最优水力效率的关系，得到多级离心泵作透平时的最优效率，并应用CFD软件，对多级离心泵作透平时内部流场的水力性能进行数值分析，所得到的结果与理论分析的结果进行比较，发现在最优效率点的效率能够较好地吻合，误差为2.74%。为了获得多级离心泵的内部流场特性，对不同流量与同一流量下不同位置的相对速度和静压力进行分析，得出叶轮内低速区域随着流量增大而减小，在第1级到第4级压降基本相等，第5级的压降最小。  

The Oretical and Numerical Investigation of Efficiency for a Multistage Centrifugal Pump Turbine

When a pump works as a turbine, its hydraulic behavior will be changed. In order to predict the best efficiency of a pump which is used as a turbine, in this study, using multistage centrifugal pump DG85 ~ 80 for the model, through theoretical analysis on the performance of the multistage centrifugal pump in reverse, the relationship between the best efficiencies in direct and reverse modes was summarized, and then the best efficiency in reverse mode was obtained. In next step, the multistage centrifugal pump was simulated in the reverse modes by computational fluid dynamics. Using numerical results, the characteristic curves of the multistage centrifugal pump in reverse modes were obtained. Compared theoretical results with numerical results, the best efficiency was in an acceptable coincidence with the numerical datas for turbine mode, and the theoretical efficiency at the best efficiency point was 2. 74% bigger than the results of numerical simulation. In order to get the internal flow field characteristics of the multistage centrifugal pump, the relative velocity and static pressure were analyzed in different positions with the same flow or under different flow, there was a large low velocity zone on the working face of the blade at low flow, with the increase in discharge, the size of low velocity zones decreased. And the pressure drop from the first stage to the forth stage was same at the same working condition, and the pressure drop in them was bigger than it in the fifth stage.