多级旋涡泵内部流动特性与压力脉动的数值分析

Numerical analysis of internal flow characteristic and pressure fluctuation of multistage vortex pump

为了揭示旋涡泵内部流场结构和非定常压力脉动特性,研制具有开式叶轮和闭式流道结构的多级旋涡泵,基于RNG k-ω湍流模型、SIMPLEC算法与块结构化网格,对旋涡泵内部流场进行数值模拟和试验验证.通过外特性数值预测验证了该旋涡泵能够满足设计参数的要求.基于CFD数值模拟技术,对旋涡泵内部流场进行数值模拟.结果表明:随着流量逐渐增大,旋涡泵扬程呈现陡降的趋势,同时叶轮叶片的做功能力变差,叶片对液体的增压能力逐渐降低.在叶轮吸入口和压出口两侧的叶片流道内部,其速度分布和湍动能分布变化梯度较大,其他叶片流道内部速度分布和湍动能分布较为相似.叶轮流道内部叶顶区域中间流道内存在1个低速区,随着流量的逐渐增大,低速区越来越小.叶轮流道内部叶根区域中间流道内存在1个速度梯度密集区,该区域湍动能较大,即叶片流道的叶根区域存在较大的损失耗散区,随着流量的逐渐增大,该损失耗散区越来越小.分析旋涡泵各特征位置的压力脉动特性发现,在叶轮叶片不同监测位置和闭式流道不同监测位置,压力脉动频率特性较为明显,即此处会诱发较为明显的水力振动和噪声.结果揭示了旋涡泵内部流场和性能的影响机理,为旋涡泵的设计提供了理论依据.

In order to reveal pressure fluctuation characteristics of internal fluid field＇ s structures in vortex pump,a multistage side pump with unshrouded impellers and closed runners was developed.Based on RNG k-ω turbulence model,SIMPLEC algorithm and structural grid,numerical simulations and experimental tests of the vortex pump were conducted. The external characteristic predictions indicated that the pump performance meet design requirements. Based on numerical simulation techniques,the internal flow field in the vortex pump was simulated. The results show that the vortexpump＇s head has the tendency of plunge and at the same time blade power capacity becomes worse,blade pressurizing ability to liquid decreases gradually. Inside the blade runner of impeller inlet and outlet,degrees of velocity and turbulence energy distribution change sharply,velocity and turbulence energy distributions in other blade runners are very much alike. Inside the middle of impeller blade tip flow channel exists a low velocity region and the region becomes smaller and smaller with the flow rate increasing gradually. Inside the middle of impeller blade root flow channel exists a concentration zone of velocity gradient,in which the turbulence kinetic energy is larger,namely there exists a larger dissipation loss area in impeller blade root flow channel,and it is becoming smaller with the increasing of flow rate. Analysis of pressure fluctuation characteristics in vortex pump＇s characteristic locations found that at different monitoring locations of impeller blades and closed runners,pressure fluctuation frequency characteristics are more obvious,where obvious hydraulic vibration and noise can be induced.The results reveal the impact mechanism of internal fields and performance of vortex pump,which provides a theoretical basis for vortex pump＇s design.