基于CFD的空间导叶内部流场分析及优化设计

Analysis of flow in vane diffuser and its optimization based on CFD method

针对空间导叶传统设计方法的不足,以离心泵的空间导叶为研究对象,采用设计工况下泵的扬程和效率提升为优化目标,在保证叶片进口安放角、出口安放角、导叶轴面等设计参数不变的前提下,通过CFD数值模拟计算不同包角的空间导叶叶型与泵的水力效率之间的关系,从而寻找效率最优的导叶叶型.计算结果表明:空间导叶的叶片包角对泵的内流场结构和泵的外特性有重要影响,在其他流道参数不变的情况下,存在使泵效率最高的最优包角;随着导叶叶片包角的增大,叶片工作面上的高压区域逐步由进口向出口移动,叶片由"前载型"逐步变为"后载型";小包角时,由于叶片前部分的叶片安放角变化较大,在叶片背面的中部到后部的部分区域存在低速脱流区,且随着叶片包角的增大该脱流区面积逐渐减小并逐渐向出口方向移动;随着叶片包角的增大,叶片进口堵塞现象加重,导叶进口速度逐渐增大.揭示了空间导叶流动结构与导叶包角、型线间的内在关系,为空间导叶的优化及设计提供一定的理论依据.

Concerning limitations in the traditional design approach for vane diffuser of centrifugal pump,a relationship between hydraulic performance and vane wrap angle is obtained by means of CFD analysis to achieve the best design of the diffuser. In the optimization,the pump efficiency and head are taken as the optimization objective functions,while the meridian shape,leading and trailing edges vane angles remain unchanged. The results show that the wrap angle has an important influence on the internal flow structure and hydraulic performance of the pump and there is an optimum wrap angle for the best efficiency when the rest geometrical parameters of the diffuser keep unchanged. The high pres-sure zone on the blade pressure side moves from the inlet to the outlet gradually with increasing of wrap angle,and the blade becomes ' post-loaded' from ' front-loaded'. As the vane angle changes greatly in the vane forepart,there is a flow separation zone starting from the middle of the vane chord; fortunately,the separation zone shrinks and is located at near the vane outlet with increasing wrap angle.The blocking aggravates at the vane inlet and subsequently the inlet velocity increases gradually with increasing wrap angle. The relations between flow structure and wrap angle have been revealed and some theoretical basis has been established for the optimization of vane diffuser.