螺旋离心泵瞬态特性的数值分析

Numerical Analysis on Transient Regime of Screw-type Centrifugal Pump

基于雷诺时均Navier-Stokes方程(N-S方程)和RNG k-湍流模型对螺旋离心泵内部流动进行全三维数值计算。获得泵内不同流量、不同瞬时叶轮轴向力、径向力和流场内不同监测点压力脉动规律。结果显示非定常与定常数值模拟获得的扬程、效率误差均不超过2.5%。蜗壳内所有监测点压力脉动随时间变化有明显周期性,蜗壳中部P3点上压力有较剧烈的波动,同时出现二次压力脉动。在扩散管区域且靠近隔舌P2点的压力波动幅度随着流量增加变化最为剧烈,当流量增加1倍时压力脉动幅度增加了4倍多。叶片进出口工作面与背面监测点压力脉动随时间变化也有明显的周期性,工作面压力波动幅度大于背面,当流量增加时波动幅度有明显加大,流量变化对叶片进口压力脉动影响大于对叶片出口的影响。径向力方向呈周期性变化,当流量从大到小变化时,其方向逐渐向压水室隔舌靠近,并随着流量减小波动幅度加剧,而且在设计工况叶轮也有较大径向力。轴向力有波动但是波动幅值很小,其值随着扬程降低逐渐减小,两者呈非线性变化。

A three-dimensional unsteady numerical investigation is carded out in a screw centrifugal pump to study axial force, impeller radial force and pressure fluctuation rule of different instantaneous and conditions on monitoring points based on Reynolds Navier-Stokes in multiple reference frames and the RNG k - ε turbulence model. The results obtained show that the error is less than 2.5% to predict efficiency and head using unsteady and unsteady numerical model. The pressure fluctuations on the monitoring points have obvious periodic in the case, and the pressure of 3 has a severe fluctuations, and appear two times the pressure fluctuation. The pressure fluctuations of P2 near volute tongue is severe with the flow rate from low to high, and the pressure fluctuations range increase four times when flow rate increase a time. The monitoring point pressure fluctuation on the suction surface and pressure surface of blade inlet have obvious periodic, and pressure fluctuations on the suction surface are more than pressure surface. With the flow rate increasing, the pressure fluctuations increase obviously, and with flow rate changing, the pressure fluctuations are greater influence on the surfaces of blade inlet than blade outlet. The direction of the radial force is periodic changes, meanwhile as flow rate from high to low, the direction moves near to the volute tongue gradually. With the reduction of flow rate, the fluctuations range of radial force increase, but there is large radical force in design condition. Axial force has fluctuation but its range is very small, and with the value of head decreasing, the axial forces reduce in a nonlinear.