旋流泵叶轮流道固液两相流动不稳定性分析

Instability analysis of solid-liquid two-phase flow in impeller channel of vortex pump

由于结构的特殊性以及固液两相存在的密度差,旋流泵在输送固液两相介质过程中,内部会出现多方面的不稳定性特征,基于Particle模型,运用ANSYS CFX软件对额定转速下旋流泵在不同流量下输送不同固相体积分数的多种工况进行了非定常数值模拟,分析了叶轮流道内的固相分布、压力脉动和叶轮径向力,从而深入了解叶轮内部不稳定性。结果表明:在C_(v)=5%体积分数下,0.8 Q_(d)、1.0 Q_(d)流量下叶轮流道内固相体积分布均匀,1.2 Q_(d)分布不均匀;在C_(v)=10%体积分数下,0.8 Q_(d)流量下分布均匀,1.0 Q_(d)和1.2 Q_(d)流量下分布不均匀;在C_(v)=20%体积分数下,0.8 Q_(d)、1.2 Q_(d)流量下分布均匀,1.0 Q_(d)分布不均匀;在C_(v)=20%、1.0 Q_(d)工况的一个旋转周期内,叶轮内部始终存在一个条形固相分布区域,且其旋转速度滞后于叶轮旋转速度。在1.0 Q_(d)流量下,随着固相体积分数的增加,各监测点压力系数幅值波动逐步变大;后缩腔监测点叶频处的幅值基本不变,叶轮流道内监测点轴频处的幅值逐步变大;在C_(v)=20%体积分数下,随着流量的增加,各监测点压力系数幅值波动先增后减,后缩腔监测点叶频处幅值逐步增大,流道内监测点轴频处的幅值先增后减。相同固相体积分数下,随着流量的增加,径向力逐步增大;不同固相体积分数下,随着体积分数的增加,0.8 Q_(d)流量下径向力波动不大,1.0 Q_(d)流量下波动逐步变大,1.2 Q_(d)流量下波动逐步变小。

Due to the particularity of the structure and the density difference between the solid and liquid phases,some instability characteristics are present in the vortex pump during the transportation of the solid-liquid two-phase medium.Based on the Particle model,this paper uses ANSYS CFX to carry out unsteady numerical simulation of various working conditions of vortex pump conveying different solid phase volume fractions at different flow rates under rated speed.The solid phase distribution,pressure pulsation and radial force in the impeller channel are analyzed,so as to deeply understand the internal instability of the impeller.The results show that,in terms of solid phase distribution,at C_(v)=5%volume fraction,the solid phase distribution in the impeller channel is uniform at 0.8 Q_(d)and 1.0 Q_(d)flow rates,and the 1.2 Q_(d)distribution is not uniform;at C_(v)=10%volume fraction,the distribution is uniform at 0.8 Q_(d)flow rate,and non-uniform at 1.0 Q_(d)and 1.2 Q_(d)flow rates.At C_(v)=20%volume fraction,the distribution is uniform at 0.8 Q_(d)and 1.2 Q_(d)flow rates,and the distribution of 1.0 Q_(d)is not uniform.In a rotation cycle of C_(v)=20%and 1.0 Q_(d),there is always a strip solid phase distribution area inside the impeller,and its rotation speed lags behind the impeller rotation speed.In terms of pressure pulsation,at 1.0 Q_(d)flow rate,with the increase of solid volume fraction,the amplitude fluctuation of pressure coefficient at each monitoring point gradually becomes larger;the amplitude at the blade frequency of the monitoring point in the post-shrinking cavity is basically unchanged,and the amplitude at the shaft frequency of the monitoring point in the impeller flow channel gradually increases.At the volume fraction of C_(v)=20%,with the increase of flow rate,the amplitude fluctuation of pressure coefficient at each monitoring point increases first and then decreases,and the amplitude at the blade frequency of the monitoring point in the post-shrinking cavity gradually increases.In terms of radial force,under the same solid volume fraction,the radial force gradually increases with the increase of flow rate;under different solid volume fractions,with the increase of volume fraction,the radial force fluctuation at 0.8 Q_(d)flow rate is small,the fluctuation at 1.0 Q_(d)flow rate gradually increases,and the fluctuation at 1.2 Q_(d)flow rate gradually decreases.