转速对导叶式液力回收透平性能的影响

Influence of Rotating Speed on the Performance of Hydraulic Turbine with Guide Vane

为了研究转速对导叶式液力回收透平性能影响的特征和规律,采用CFD方法对960~2960 r/min(间隔500 r/min共5组)转速下运行的含导叶部件的离心泵反转作液力透平进行了数值计算。结果表明:不同转速下透平的外特性曲线变化趋势基本一致,最佳工况的效率及比转速较为接近,改变转速对提高透平在偏工况下的运行效率效果显著;降低转速在外部流量和压差均降低的条件下较为适宜,提高转速在外部流量和压差均升高的条件下较为适宜,当调节转速不能完全适应外部条件的变化时,需采取其他调节方式配合实施;提高转速后透平的工作流量范围变宽,该范围内扬程和功率曲线变陡;降低转速工作流量范围缩小,该范围内的扬程与功率曲线相对平坦;随着转速的提高,流量换算系数KQ、扬程换算系数KH及功率换算系数KP均呈先增大后减小的趋势,各换算系数均接近于1,表明比例定律能够较好地预测导叶式液力透平的最佳工况性能。

In order to study the influence of rotating speed on the performance of hydraulic turbine with guide vane,the computational fluid dynamics(CFD)method is used to calculate the pump as turbine(PAT)with guide vane operating at five rotating speeds from 960 to 2960 r/min with a step of 500 r/min.The results show that the variation trend of the external characteristic curve of PAT is basically the same at different rotating speeds,the efficiency and specific speed of the Best Efficiency Point(BEP)are close to each other,the effect of changing rotating speed on improving the efficiency of the PAT is remarkable at partial operating conditions.It is better to run at reduced speed when the external flow and differential pressure decrease,while increasing the rotational speed is more suitable when the external flow and differential pressure increase,when speed adjustment can not adapt to the changes of external process parameters,other adjustment methods should be adopted.The working flow range of PAT becomes wider,and the head and power curves of this area are relatively steep when increasing the rotating speed,while reducing the speed is opposite.With the increase of rotating speed,discharge conversion coefficient KQ,head conversion coefficient KH and power conversion coefficient KP increase at first and then decrease,the values of each conversion coefficient are close to 1,which shows that the law of proportion can make a good prediction of the performance parameters under the BEP conditions.