弹流润滑下缸套-活塞环最小油膜厚度研究

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To make the minimum film thickness of piston ring and cylinder liner pair more realistic, an elastrohydrodynamie lubrication model, considering surface roughness, is developed combined with the average Reynolds＇ s equation, film thickness equation, elastic deformation equation as well as the force balance equation. The numerical calculation process of the model is given and an example is taken to compare the elastrohydrodynamie lubrication model with the mixed lubrication model. The results show that the calculated minimum film thickness is so thin （ less than 1 μm） that the surface roughness must be considered and the minimum film thickness is about as twice thicker when considering the elastrohydrodynamic lubrication as the mixed lubrication near the top dead-end of the cylinder liner. The existing difference is mainly due to the higher pressure （ about 40 MPa） there that makes elastic deformation of the mating surfaces and increase of the lubricant＇ s viscosity, both of which will increase the minimum film thickness. Therefore, it is necessary to consider the elastrohydrodynamie lubrication in calculation of the minimum film thickness.为获得更接近实际情况的缸套．活塞环间的最小油膜厚度，在考虑表面粗糙度的前提下，联立平均Reynolds方程、膜厚方程、弹性变形方程和载荷平衡方程，建立缸套一活塞环的弹流润滑模型。给出了数值求解模型的步骤，并通过计算实例对弹流润滑模型和混合润滑模型计算的最小油膜厚度进行比较。结果表明，在上止点附近，最小油膜厚度较小（〈1μm），必须考虑表面粗糙度对油膜厚度的影响；而且在上止点附近，考虑弹流润滑时的最小油膜厚度是混合润滑时的2倍左右，分析其原因主要是上止点附近较高的油膜压力（接近40MPa）使摩擦副产生弹性变形并增大了润滑油的黏度，这两者都会使油膜厚度增大。从而也说明在计算最小油膜厚度时考虑弹流润滑的必要性。