基于混合润滑模型的往复密封动特性研究

Investigations on the Dynamic Reciprocating Sealing Performance with Partial Lubrication Model

为研究往复运动密封性能,采用MatLab数值方法建立一种混合润滑模型,该模型包含弹性力学、流体力学和接触力学分析。基于混合润滑模型,研究粗糙度和往复速度对动态往复密封摩擦力、泄漏量和油膜厚度等密封性能的影响规律,揭示液压往复密封机制。结果表明:往复运动密封圈处于混合润滑状态,接触区不仅有流体压力,还包含粗糙度接触压力;存在临界粗糙度σc和临界速度u c,当粗糙度σ<σc时,随粗糙度的增大内行程的泄漏表现为越来越小的内泄漏,当σ≥σc时,随粗糙度的增大内行程的泄漏表现为越来越大的外泄漏;当速度u<u c时,净泄漏量随速度的增大表现为越来越小的外泄漏,当u≥u c时,净泄漏量随速度的增大表现为越来越大的内泄漏;随着粗糙度的增加,膜厚与内行程的摩擦力增大,而外行程的摩擦力无明显变化;随着速度的增加,油膜厚度增加,内行程摩擦力减小,而外行程摩擦力变化很小。

A partial lubrication model was established by using MatLab software to investigate the sealing performance of reciprocating seals,which consists of the analysis of elastic mechanics,fluid mechanics and contact mechanics.The effects of surface roughness and reciprocating velocity on the dynamic sealing performance,including friction,leakage as well as film thickness,were studied based on the partial lubrication model.The sealing mechanism of reciprocating seals was discussed.The results show that the reciprocating seals experience partial lubrication conditions,which consists of fluid pressure and asperity contact pressure.The critical roughness andσc and critical velocity u c are observed.When the surface roughness is less thanσc,the internal leakage is decreased with the increase of surface roughness during the instroke.Otherwise,the external leakage is increased with increase of surface roughness during the instroke.Increasing of reciprocating velocity will result in a decrease of the external net leakage when the reciprocating velocity is less than the critical velocity u c.On the contrary,an increase of reciprocating velocity causes an increase of the internal net leakage under the conditions that the velocity is larger than the critical velocity u c.With the increase of surface roughness,the film thickness and instroke friction are increased,while the outstroke friction is independent of the surface roughness.The increasing of reciprocating velocity leads to a significant increase of film thickness and decrease of instroke friction,while the reciprocating velocity has little effect on the outstroke friction.