基于流固耦合的离心泵口环间隙泄漏对叶轮强度的影响

Analyzing the Impact of Clearance Leakage on Impeller Strength in Centrifugal Pump Using Fluid-solid Coupling

基于流固耦合方法,以DG-350型多级离心泵次级叶轮为研究对象,研究了口环间隙泄漏对水泵次级叶轮变形和强度的影响。通过单向流固耦合分析和双向流固耦合分析得到了叶轮的等效应力和变形分布图,并对结果进行了对比分析。结果表明,在考虑间隙泄漏时,叶轮的最大总变形幅度为0.021 4 mm,最大等效应力为21.51 MPa。在不考虑间隙泄漏时,叶轮的最大总变形幅度为0.053 6 mm,最大等效应力为87 MPa。口环间隙的存在使得叶轮与导叶间的间隙流体产生较大的压力并作用于叶轮的前后盖板,从而抵消了一部分叶轮内腔的流体压力,减小了叶轮的变形幅度和应力集中。在叶轮最大变形和等效应力的最大集中区域附近随机选择A、B节点,通过瞬态分析,在最后1个旋转周期内,节点A、B处的等效应力随时间呈周期性变化。节点B处的等效应力始终大于节点A处,并且接近于最大等效应力,说明节点B附近的区域为应力集中的高发区。而节点A处的等效应力虽低于节点B处,但应力的变化幅度高于节点B处,说明节点A处更容易发生疲劳破坏。

Taking the secondary impeller of DG-350 multistage centrifugal pump as a test model, this paper studied the influence of clearance leakage on secondary impeller deformation and strength based on fluid-struc- ture interaction. The deformation distribution and equivalent stress were obtained from sequential fluid-solid coupling and strong fluid-solid coupling respectively. The results showed that the maximum deformation and the maximum equivalent stress were 0.021 4 mm and 21.51 MPa respectively when the clearance leakage was taken into account, and were 0.053 6 mm and 87 MPa respectively without considering the clearance leakage. The clearance between the wear-rings resulted in a great pressure between the impeller and the fluid guide vanes applied to the impeller front and rear covers. This pressure could offset some fluid pressure on the impel- ler cavity and hence reduced the deformation and maximum equivalent stress zone on the impeller. Randomly selecting a point A and a point B near the maximum deformation zone and the maximum equivalent stress on the impeller respectively, transition analysis showed that the equivalent stress at points A and B varied periodi- cally with time in the last rotation period. The equivalent stress at node B was always higher than that at node A and was close to the maximum equivalent stress, revealing that the region in the proximity of B has the highest stress. The equivalent stress at node A was less than that at node B, but it fluctuated more profoundly, indicating a likely occurrence of fatigue.