多级离心泵轴向力平衡装置的设计与分析

Design and analysis of an axial thrust balancing device for multistage centrifugal pumps

可靠的轴向力平衡装置是高压多级离心泵实现平稳可靠运行的重要机构。针对反渗透海水淡化高压泵对结构和运行可靠性的特殊要求,设计了一种用于节段式多级离心泵的新型轴向力平衡装置。基于计算流体力学(CFD)方法研究了平衡装置内部的流场结构及其轴向力平衡机理,分析了不同轴向间隙、径向间隙以及滑动轴承长径比条件下的轴向力平衡特性。结果表明,不同进出口压差条件下,滑动轴承间隙内流动结构存在明显区别,轴承支撑机理发生变化;平衡力和相对泄漏量随轴向、径向间隙的增大呈非线性增大,平衡力随长径比增大近似呈线性增大,相对泄漏量随长径比增大近似呈线性减小。对径向、轴向间隙和长径比进行各种组合分析计算,得到轴向间隙0.2mm、径向间隙0.3mm、长径比为1的结构优化的新型机构,该机构既可以很好地平衡轴向力,又提高了多级泵的可靠性。

Axial thrust balancing device is an important component for high-pressure multistage pump stable operations. In order to satisfy special reliability of structure and operation for high-pressure pumps used in reverse osmosis seawater desalination systems,a new kind of axial thrust balancing device was designed for multistage centrifugal pumps. Balancing device’s inner flow field and its mechanism were researched based on computational fluid dynamics method. Different axial and radial clearances’performances as well as different length-diameter ratios were analyzed.The results indicate that inner flow field of sliding bearing clearance and support mechanism of bearing change greatly as inlet and outlet pressure conditions change;there is nonlinear relationship between balance force and axial and radial clearances, while there is linear relationship for length-diameter ratios and negative linear relation for relative leakages.A new device which axial clearance is 0.2 mm,radial clearance is 0.3 mm and length-diameter ratio is 1 is designed by above analyses.This optimized device can well balance the axial force and improve the reliability of multistage high-pressure centrifugal pumps obviously.