包角对中转速比离心泵流场及压力脉动的影响

Influence of blade wrap angle on flow field and pressure pulsationof medium specific speed centrifugal pump

为了研究叶片包角对中转速比离心泵性能的影响,以转速比为129的中转速比离心泵为研究对象,在确保叶轮其他设计参数恒定的同时,设计了90°、100°、110°、120°、130°5种包角的叶轮。运用Fluent仿真软件非定常数值模拟计算得到不同包角情况下泵外部特性曲线及叶轮内部压力和速度分布云图,通过测量水泵蜗壳及叶轮内7个监测点压力的数据得到离心泵压力脉动特性。研究结果表明:水泵扬程及效率随叶片包角的增大均有所降低且效率最高点向小流量方向偏移,包角增至130°时相比90°包角,扬程降低13%,效率降低5.2%;随着包角的增大,叶片进口低压区增多,出口高压区减少,叶轮内低速区减少,出口速度增大;额定流量下,蜗壳内压力脉动主频约为一倍叶频,流道内压力脉动主频约为一倍转频,各监测点压力脉动幅值随包角增大整体呈上升趋势。于是,综合考虑选取120°作为中转速比离心泵包角最优取值。探究叶片包角对中转速比离心泵内部流场及压力脉动影响规律,可为中转速比离心泵水力优化提供理论支持。

In order to study the influence of blade wrap angle on the performance of medium specific speed centrifugal pump,a medium specific speed centrifugal pump with a specific speed of 129 was taken as the research object.Five kinds of impellers were designed with different wrap angles of 90°,100°,110°,120°and 130°,other blade parameters being unchanged.Using Fluent unsteady numerical simulation,the study calculated the external characteristic curve of the pump with different wrap angles and the cloud chart of the internal pressure and velocity distribution of the impellers.The pressure pulsation characteristics of the centrifugal pump were obtained by measuring the pressure data of 7 monitoring points in the volute and impellers of the pump.The results show that:the head and efficiency of the pump decrease with the increase of the blade wrap angle,and the highest point of efficiency shifts to the small flow direction.When the wrap angle increases to 130°compared with 90°wrap angle,the head decreases by 13%and the efficiency decreases by 5.2%;with the increase of the wrap angle,the low-pressure area at the inlet of the blade increases,the high-pressure area at the outlet decreases,the low-speed area in the impeller decreases,and the outlet speed increases.The main frequency of pressure pulsation in the volute is about one time of the blade frequency,and the main frequency of the pressure pulsation the flow-path is about one time of the rotating frequency,the pressure fluctuation amplitude of each monitoring point increases with the increase of the wrap angle.Thus,120°is selected as the optimal wrap angle of medium specific speed centrifugal pump.The study has explored and summarized influence of blade wrap angle on internal flow field and pressure pulsation of medium specific speed centrifugal pump,which can provide theoretical support for further hydraulic optimization of medium specific speed centrifugal pump.