高压高剪切率下密封环缝隙流体动态润滑特性

Hydrodynamic lubrication characteristics of piston ring gap under high pressure and high shear rate

为减少高压高剪切率下热效应对密封环缝隙流体润滑性能的影响,以密封环缝隙流体剪切速度梯度、壁面剪切应力和油膜温升表征摩擦副润滑性能,采用RNG k-ε湍流模型,通过Workbench建立流-固-热多场模型,计算得到不同主轴转角下缝隙流动形态变化规律和温升前后油膜厚度变化量、不同L型槽内外径比及长径比下流速流型分布规律、壁面剪切应力、温度分布和热变形量。研究结果表明:密封环L型槽黏性底层随剪切速度增大而增厚,油膜厚度随运动周期增加而变薄;当L型槽内外径比小于1.07时,随比值减小密封环壁面剪切应力不断增大,最大变化率为7%;密封环L型槽长径比在0.19时平均壁面剪切应力达到最大,当长径比继续增大时,油膜区剪切速度梯度逐渐减小,油膜温升和热变形亦随之减小。研究结果可为马达优化以减少能量损失和改善密封环润滑条件提供理论指导和依据。

In order to reduce the thermal effect on the lubrication performance of piston ring under high pressure and high shear rate, the friction pair lubrication performance is characterized by the shear velocity gradient, the wall shear stress and the oil film temperature rise. RNG k-ε turbulence model is used and the fluid-solid-thermal multi-physics model is established through Workbench to calculate the change rule of gap flow pattern, the film thickness change before and after temperature rise, the flow velocity and pattern distribution rule, wall shear stress, temperature distribution and thermal deformation under different L-shaped groove internal and external diameter ratio and length-to-diameter ratio. The results show that the L-groove viscous bottom layer thickens with the increase of shear speed, and the oil film thickness becomes thinner with the increase of motion period.When the ratio of the internal diameter to the external diameter of the L-groove is less than 1.07, the shear stress increases as the ratio decreases, and the maximum change rate is 7%.The average shear stress of the piston ring reaches the maximum when the length-to-diameter ratio is 0.19. If the ratio continues to increase, the oil film temperature rise and thermal deformation decrease as the velocity gradient decreases. The research results can provide theoretical guidance and basis for the optimization of motor to reduce energy loss and improve the lubrication condition of piston ring.