叶片出口角对化工离心泵性能的影响

Effects of blade outlet angle on performance of chemical centrifugal pump

为了研究叶片出口角对化工离心泵性能的影响,以一台比转数为180的化工离心泵为研究对象,将叶片出口角从22°依次增大到27°,37°和47°.应用ANSYS 14.5软件进行数值计算,结果表明:叶片出口角对外特性影响显著,适当增大叶片出口角可以提高扬程及效率,但也不宜过度增大到47°;随着叶片出口角的增大,叶轮进口的低压区域逐渐向叶轮出口方向扩大,压力分布趋于紊乱,且在工作面附近有逆压梯度存在,会聚集不稳定的低压流体;在额定工况下,叶片出口角小于37°时,压力脉动幅值较小,且高频脉动很小;次主频有随叶片出口角的增大向低频处转移的趋势; 4个方案叶轮所受径向力都是在额定工况下达到最小,并在小流量下差异性最大;不同工况下叶片出口角为27°的叶轮所受径向力最小,这说明对非定常特性的影响,叶片出口角存在一个最优值.此外,针对叶片出口角为22°的模型进行了性能试验,对比发现数值计算的结果是可信的.

In order to investigate the influence of blade outlet angle on the performance of a chemical centrifugal pump,a chemical centrifugal pump with the specific speed of 180 was taken as a model,three different blade outlet angles,such as 27°,37° and 47°,were designed except the original impeller with 22° blade outlet angle. Then,the software ANSYS 14.5 was applied to carry out numerical calculations. The results show that blade outlet angle can affect the performance significantly,an appropria- tely increased blade outlet angle can improve the head and efficiency of the pump,but it shouldn′t exceed 47°. With increasing blade outlet angle,the low energy fluid area gradually expands from the blade leading edge to the trailing edge,the pressure distribution tends to be disordered,and an adverse pressure gradient exists near the blade pressure side,where the unsteady fluid with low energy gathers. Under design condition,when the blade outlet angle is less than 37°,the amplitude of pressure fluctuation is lower,and the amplitude of high frequency fluctuation is very small. The secondary frequency tends to shift to a lower frequency with increasing blade outlet angle. The impeller radial force in each design is the smallest under the design condition,and the difference is the largest under part-load condition. The impeller radial force is the minimum at 27° blade outlet angle compared with the other impellers under the same flow rate. It is suggested that there is an optimal blade outlet angle for unsteady flows. Meanwhile,a performance experiment conducted on the pump with 22° blade outlet angle confirms that the results of numerical simulation are reliable. Generally,this study has certain re-ferential significance to development of chemical centrifugal pumps.