Abstract:

The performance of liquid film seals is significantly affected by non-Newtonian behavior of lubricating fluids at seal interface. A mathematical model of spiral groove non-Newtonian liquid film seal was established by combination of mass conservation at JFO cavitation boundary condition and power law model of non-Newtonian fluids. The governing equation was discretized by finite difference method and solved by SOR iterative algorithm to obtain liquid film pressure distribution. The effects of non-Newtonian fluids on sealing performance were analyzed, including load-carrying capacity, leakage, friction torque, and cavitation occurrence in liquid film. The results indicate that with the increase of power law index, the load-carrying capacity first increases then decreases but the leakage and cavitation rate always increase and the friction torque consistently decreases. At power law index n=0.96, non-Newtonian fluids had increase by 4.6% in the load-carrying capacity and 0.3% in the friction torque but decrease by 98.6% in the cavitation rate of sealing face and 5.8% in leakage than Newtonian fluids. When operating parameters were changed, non-Newtonian fluids with various power law indices showed similar trending behavior of liquid film hydrodynamic performance. Suitable lubricant selection is important to improve sealing performance of liquid films.

Key words: spiral groove liquid film seals, power law model, non-Newtonian fluids, JFO boundary condition, hydrodynamic performance

摘要：

密封端面间润滑流体的非牛顿特性对密封的性能有重要影响。基于满足质量守恒的JFO空化边界条件及描述流体非牛顿特性的幂律模型，建立了考虑流体非牛顿特性的螺旋槽液膜密封数学模型。采用有限差分法对控制方程进行离散，通过SOR迭代方法对离散方程进行求解，得到了密封端面液膜压力分布。探讨了润滑流体的非牛顿特性对螺旋槽液膜密封的液膜承载能力、泄漏量、摩擦扭矩等性能参数及液膜中空化发生情况的影响规律。结果表明：随着幂律指数的增大，液膜承载能力先增大后减小，泄漏量和空化率增大，摩擦扭矩减小；幂律指数为0.96时，相对于牛顿流体，液膜承载能力提升约4.6%，密封端面空化率下降约98.6%，泄漏量下降约5.8%，摩擦扭矩增加约0.3%；随着操作参数的改变，不同幂律指数下的流体动压性能参数变化规律具有相似性；润滑流体的合理选择对液膜密封性能改善有重要意义。

关键词: 螺旋槽液膜密封, 幂律模型, 非牛顿流体, JFO边界条件, 流体动压特性