叶顶间隙对斜流泵进口压力脉动影响的数值分析

Numerical analysis of effect of blade tip clearance on pressure fluctuation in mixed-flow pump inlet

由于叶顶间隙对斜流泵内外特性的影响甚大,因此在斜流泵设计时叶顶间隙的合理选取具有重要的工程意义.为了研究叶顶间隙大小对斜流泵进口压力脉动特性的影响,选取叶顶间隙分别为0,0.5,1.0,1.5 mm共4种设计方案的斜流泵为研究对象,基于SST k-ω湍流模型和LES大涡模拟方法,采用SIMPLEC算法与块结构化网格,在小流量工况下,对斜流泵内部流场进行三维非定常数值计算,并监测叶轮进口处压力脉动特性.计算结果表明:随着叶顶间隙的增大,斜流泵的扬程逐渐降低;叶顶间隙对斜流泵叶轮进口压力脉动的径向分布影响显著,叶轮进口主流区的压力脉动幅值较小,而近壁区压力脉动幅值较大;较大的叶顶间隙可以降低叶轮进口的压力脉动幅值,有利于改善模型斜流泵运行的稳定性.

Because of considerable influence of blade tip clearance on performance and flow in a mixed-flow pump,a proper selection of the clearance is important in the design of the pump. In order to identify the effects of the blade tip clearance on the pressure fluctuation characteristics in a mixedflow pump inlet,the unsteady,three-dimensional turbulent flows in the pump are simulated at 0,0. 5,1. 0,1. 5 mm clearances,based on the SST k-ω turbulence model and large eddy simulation( LES)approach. Also,the SIMPLEC algorithm and block structured grids are adopted. The simulations are conducted at low flow rates,and the pressure fluctuation characteristics in the impeller inlet are monitored. The results show that with the increasing tip clearance the pump head decreases gradually. The tip clearance has a significant effect on the pressure fluctuation distribution along radius in the impellerinlet,the pressure fluctuation amplitude is smaller in the primary flow region in the impeller inlet,while it gets larger near the wall. The dominated pressure fluctuation frequencies at various tip clearances are the blade passing frequency,but the pressure fluctuation is quite different from one clearance to another. Specially,a larger tip clearance can reduce the pressure fluctuation amplitude. This can be in favour of improving the operational stability of the pump.