高比转数混流泵非定常流场压力脉动特性

为了研究高比转数混流泵内部流场的压力脉动情况,采用大涡模拟方法对泵内三维非定常湍流场进行数值模拟,通过对监测点数据的分析得到了叶轮进口、叶轮出口、导叶中间和导叶出口4个截面的压力脉动的时域和频域情况,探讨了产生压力脉动的主要决定因素,同时也对不同流量下的压力脉动情况进行了对比．研究表明:这4个截面的压力脉动幅值从轮毂到轮缘均逐渐增大;叶轮进口截面压力脉动时域图规律性不明显,叶轮出口截面时域图在整个周期内呈现4个小周期,叶轮转动频率控制着叶轮进出口的压力脉动，且其影响随着流体远离叶轮而逐渐减弱；在导叶中间截面和导叶出口截面,叶轮对流体压力脉动的影响逐渐减小,压力脉动以低频振动为主,脉动幅值也大为减小;在不同流量下的压力脉动表现为小流量下幅值较大以及流量对主要频率影响较小,大流量工况下压力脉动情况要优于小流量工况．

Pressure fluctuation of unsteady flow in high specific speed mixed-flow pump

In order to study the pressure fluctuation of a high specific speed mixed flow pump, large eddy simulation was conducted to simulate the three dimensional unsteady turbulent flow field in the mixed flow pump. By monitoring and analyzing pressures, the pressure fluctuations of both time domain and frequency domain at impeller inlet, impeller outlet, guide vane channels and guide vane outlet were obtained. Main causes of pulse pressure were discussed and pressure pulsations under different flow rates were compared. Studies have shown that: the pressure pulse amplitudes at impeller inlet, impeller outlet, guide vane channels and guide vane outlet, have all gradually increased from hub to tip; pressure pulsation of time domain at impeller inlet shows no regularity while those at the impeller outlet presented four small cycles. Pressure pulses at impeller inlet and outlet are mainly determined by impeller rotation frequency. Pressure pulsation effects of the impeller on the fluid gradually decline, pressure pulsation is mainly low frequency vibration and pulse amplitude has greatly diminished at the vane channels and vane outlet. However, under low flow rates, the manifestation of pressure pulsation is greater amplitude and slight influence of flow on dominant frequency; under large flow rates, pressure pulsations are better than that under small flow rates.