径向导叶对高速离心泵非定常流动影响的分析

Analysis of Unsteady Flow in High Speed Centrifugal Pump with a Vaned Diffuser

应用计算流体力学技术对带导叶与不带导叶高速离心泵的内部流场进行定常及非定常数值模拟,从而预测出带导叶与不带导叶两种方案下的外特性曲线走势情况。同时得到了流体流经关键位置时在不同工况下的压力脉动情况,并对相应的时域图及频域图进行了对比分析。结果表明,带有导叶的高速离心泵相比于无导叶离心泵扬程较高,扬程曲线更加平缓,同时在大流量工况下,高速离心泵效率更高也更稳定。从时域图分析,不同工况下两种方案中的高速离心泵压力脉动存在明显的周期性,其中带有导叶的高速离心泵在大流量工况下压力脉动幅值相对较小,不带导叶的高速离心泵在小流量下压力脉动幅值相对较小;从频域图分析看,两种方案中的高速泵都是在一倍叶频处存在较大峰值,即动静干涉作用是引起压力脉动的主要因素,同时通过对比,在不同工况下带有导叶的高速离心泵在二倍叶频处峰值较小,说明添加径向导叶对缓解动静干涉起到一定作用。通过比较不同方案下监测点压力脉动平均值及峰值曲线图,说明在高速泵中加装径向导叶可以有效地发挥扩压作用,降低液流速度,充分将速度能转化为压能。结合上述结论,可以得出带导叶高速离心泵适合在大流量高工况下运行,如消防灭火,石油化工,航空航天等领域。

Computational fluid dynamics(CFD) was used to conduct the steady and unsteady numerical simulation of internal flow field in the high speed centrifugal pump with and without vaned diffuser,and to predict the external characteristic curves. Meanwhile,the pressure fluctuation at key locations under different operating conditions were obtained,and compared and analyzed in the corresponding time-domain and frequency-domain plots. The result showed that the hydraulic head of high speed centrifugal pump with vaned diffuser is higher than that without vaned diffuser,and the head curve is smoother. Moreover,the efficiency of high speed pump with vaned diffuser is higher and more stable at large flow rate condition. The time-domain analysis showed that the pressure fluctuation of high speed centrifugal pump has clear periodicity. Under large flow rate condition,it is the case with vaned diffuser that has relatively small pressure fluctuation amplitude. Under small flow rate condition,however,it is the case without vaned diffuser that has relatively small pressure fluctuation amplitude. The frequency-domain plot indicated that both cases have relatively high peak value at one blade frequency,that is,the rotor-stator interaction is the major factor leading to pressure fluctuation. By contrasting,the peak value at the twice blade frequency is relatively smaller with vaned diffuser at different conditions,indicating that adding the vaned diffuser plays a certain role in alleviating rotor-stator interaction. Comparing the average and peak values of monitoring sites under different configurations indicated that centrifugal pumps with vaned diffuser decreases the flow velocity more sufficiently,and converts kinetic energy into pressure energy more effectively. Therefore,centrifugal pumps with vaned diffusers are suitable to operate under large flow rate conditions in various areas,such as fire-fighting service,petrochemical industry and aerospace industry.