多级离心泵内部非定常压力脉动的数值模拟

为了研究多级离心泵内部稳态和瞬态的流动特征,以不锈钢冲压多级离心泵为研究对象,基于计算流体动力学(computational fluid dynamics, CFD)软件ANSYS CFX,选取标准k-ε湍流模型,在设计工况下对整机进行两级全流场非定常数值模拟.计算结果与试验结果吻合较好,验证了数值模型和计算方法的准确性.在叶轮某一流道的压力面和吸力面分别设置了4个监测点,在导叶的某一流道设置了6个监测点,分别分析了叶轮和流道式导叶内不同位置的压力脉动特性,并对其进行了频域分析.结果表明:叶轮与导叶间的动静干涉是产生静压波动的原因,静压波动均值从叶轮进口到叶轮出口逐渐增大;整体式冲压叶轮的形状影响正导叶内的压力脉动,一个周期内的压力波动间隔相似;叶轮和导叶间的动静干涉影响显著,首级泵体反导叶中部及出口位置脉动频率为3倍叶频,而在其他位置处均为1倍叶频;额定工况下导叶内部脉动主频均出现在低频处,表现为叶频压力脉动.

Numerical simulation of unsteady pressure pulsation in multistage centrifugal pump

In order to study steady and transient characteristics of fluid flow in centrifugal multistage pumps, the unsteady flow field in two stages of a multistage centrifugal pump made of stainless steel was simulated under design flow condition by making use of ANSYS CFX and the standard k-ε turbulence model. The performance curves predicted are in good agreement with the experimental data, validating the accuracy of the flow models and numerical methods. Additionally, four monitoring points are specified on the pressure and suction sides in a flow passage of the impeller, respectively; meanwhile other six monitoring points are positioned in various locations in a flow passage of the diffuser and guide vane. The pressure pulsation characteristics are analysed in time and frequency domains at these points. The results show that the rotor-stator interaction between impeller and guide vane is the cause for the static pressure fluctuation, and the average fluctuation of static pressure increases gradually from the inlet to the outlet of impeller. The shape of integrally formed stamping impeller can affect the pressure pulsation in the diffuser, and the pressure pulsation in one period is similar in another. The influence of rotor-stator interaction is dominated in the first guide vane; as a result, the pressure fluctuation is in 3 times blade passing frequency in the middle and at the outlet of guide vane, but is in 1 time blade passing frequency only at the other locations. The pressure pulsation in the diffuser is in a frequency as low as blade passing frequency.