串列式双级轴流泵性能的数值模拟

为了揭示串列泵的内部流动机理及其能量特性，采用两个具有试验结果的轴流式叶轮和一新设计的导叶串联组成了一串列式轴流泵模型。应用Pro-E对该串列泵进行三维实体造型，用数值模拟的方法计算泵内的流场。数值计算采用NUMECA商业软件。在不同的工况条件下获得前后叶轮内部的速度矢量分布。基于流场计算结果，预测包括扬程、效率和轴功率在内的串列泵性能。将数值计算的结果与原叶轮的试验结果进行对比并与首级叶轮比较，串列轴流泵次级叶轮压力面和吸力面的速度具有较大的差值。与一般的轴流泵比较，串列式轴流泵具有比较宽的高效区，最优工况点向大流量区域偏移，其轴功率不再像普通轴流泵那样随流量的增加而减小。为了分析前后叶轮的相互作用，预测不同的后叶轮叶片偏转角条件下的串列泵性能，结果表明后叶轮的叶片偏转角对串列泵性能有重大的影响。

NUMERICAL SIMULATION OF THE PERFORMANCE OF TANDEM AXIAL FLOW PUMP

To shed light on the flow mechanisms associated with performance characteristics of a tandem pump, two axial flow impellers, which have been tested experimentally, are used to form a tandem axial flow pump model. Pro-Engineer software is used to create the 3D solid model of the pump. The internal flows and the performances of the pump are simulated numerically. The computations are performed by using NUMECA commercial software. For various working conditions, the velocity distributions in both the front and rear impellers are obtained. Based on the computational fluid dynamics (CFD) results, the performances, including the head, efficiency and shaft power of the tandem pump are predicted under different flow rates. The numerical results are compared with the experimental performances. Compared with that in the front impeller of the pump, difference between the velocities on the pressure and suction surfaces of the rear impeller is large. The tandem axial flow pump has unique performances which are different from a conventional axial flow pump obviously. The operating range with higher efficiency becomes wider and the optimum operating condition is attained at higher flow rate. The shaft power does not decrease with the increasing of the pump flow rate. To address the interactions between the front and rear impellers, the performance of the pump also predicted in different blade angles of the rear impeller. The results show the changes of the blade angle can sufficiently affect the pump performances.