离心泵环形平面密封动力特性的数值计算

Numerical Calculation of the Dynamic Characteristics of Centrifugal Pump Annular Seals

离心泵转子密封结构直接影响泵的密封性能及其转子动力学特性,为了研究离心泵转子环形平面密封的密封结构与密封性能、密封动力特性之间的关系,通过建立密封动力学模型,采用CFD方法计算分析了不同密封长度、密封间隙、密封压差、转子涡动速度比、涡动振幅、进口预旋速度等参数对密封泄漏量、流体作用力及密封动力特性系数的影响。结果表明:泄漏量随密封压差和密封间隙的增大而增大,随密封长度增加而减小。预旋速度、密封长度、密封间隙及涡动速度直接影响转子的稳定性,设计时合理选择负预旋速度、较大间隙、较短的密封结构,能有效减小交叉刚度系数,增大直接阻尼系数,减小转子的不稳定区域,提高转子的稳定性。预旋速度对质量系数、阻尼系数影响不明显,但对交叉刚度系数影响较大,直接影响转子的稳定性.密封质量系数、直接阻尼系数、交叉阻尼系数及交叉刚度系数随密封长度增加而增大,直接刚度系数随密封长度增大而减小。此方法和分析结果对离心泵转子的密封设计和动力学分析具有一定的参考价值和指导意义。

The seals property and rotor runs stably of centrifugal pumps are directly affected by seals structure. The parameters of annular structure, seals property, and seals dynamic characteristics contains sealing length, sealing clearance, pressure difference between inlet and outlet of the seal, the whirling speed, the whirling amplitude, and the preswirl velocity. In order to find out the relationships among the parameters, the dynamic model for annular seals is built up. Under different seal structures and running conditions, the CFD method is applied to compute the sealing leakage, the fluid force acting on seals,the stiffness coefficients,the damping coefficients and the mass coefficients. The results show that the annular seal owns better seals properties with a longer length and smaller clearance. There is a positive correlation between the leakage volume and pressure difference. The effect of preswirl velocity, sealing length, sealing clearance and whirling speed for rotor runs stably is significant. Therefore, the direction of preswirl velocity against the spinning direction, short seal and wide clearance are recommended to design annular seal structure for rotor runs more stably, as the good performance of minor cross coupling stiffness coefficient and superior direct stiffness coefficient, which is helpful for shrinking the unstable region. Besides, with sealing length increasing, mass coefficient, damping coefficient and cross coupling stiffness coefficient raise, except direct stiffness coefficient in an opposite tendency. The method and the results in this work may have a reference value and guidance significance for seals design and dynamics analysis of centrifugal pump rotor.