基于非线性空化的离心泵内部流动特性分析

Analysis of Internal Flow Characteristics of Centrifugal Pump Based on Nonlinear Cavitation

为研究离心泵发生空化时叶轮内部瞬态不稳定流动变化规律,本文应用ANSYS-CFX软件对离心泵内部发生空化时进行定常和非定常计算,采用泵内部不同流道的速度场、压力场、气体体积分数以及压力脉动情况的计算结果分析流道内部瞬态非线性的流动变化规律。研究结果表明:受动静干涉及蜗壳喉部面积等因素的影响,离心泵内部各流道空化的发展是非线性的,随着空化的发展,叶轮内部压力场、速度场和各流道气体体积分数的分布是不对称的。导致这种非线性空化现象的主要原因是蜗壳结构的不对称以及流道内中间流面到叶片背面所在流道区域的空化进程不同步;在空化不严重的情况下,不同流道的脉动呈现相同的规律,但严重空化情况下,压力脉动主频混乱,规律性减弱。

For studying transient unstable flow variation in centrifugal pump impeller with cavitation,steady and transient calculations with cavitation taking place in centrifugal pump impeller were carried out by using ANSYS-CFX software.The transient nonlinear flow in flow channel was analyzed by applying the calculation results of the velocity field,the pressure field,the gas volume fraction and the pressure fluctuation of the different flow channels in the pump.The research results show that influenced by rotor-stator interference,volute throat area and other factors,the cavitation developing in each channel of centrifugal pump impeller is nonlinear.With the development of cavitation,the distributions of pressure field,velocity field and gas volumetric fraction of the impeller interior are asymmetrical.The main reason leading to this kind of nonlinear cavitation phenomenon is the asymmetry of the spiral case structure and the non-synchronous of the cavitation process in the flow channel region from the middle surface in the flow channel to the back of the blade.In case of no significant cavitation,pulsating flow of different flow channels depicts the same regularity,but the main frequency of the pressure fluctuation is chaotic and the regularity is weakened under the condition of severe cavitation.