The Minimum Film Thickness of Piston Ring and Cylinder Liner Pair in Partial Elastohydrodynamic Lubrication

Taking surface roughness into account, the partial elastohydrodynamic lubrication (PEHL) model was developed by combination of the average Reynolds equation with film thickness equation, elastic deformation equation as well as the force balance equation to make the minimum film thickness between piston ring and cylinder liner pair more realistic. The numerical process of the model was given and an example was taken to compare the PEHL model with the mixed lubrication (ML) model and the elastohydrodynamic lubrication (EHL) model. The results show that, in close vicinity to the dead top center of the cylinder liner, the minimum film thicknesses in the given parameters under these three models are 0.59 mum, 0.31 mum and 0.92 mum, respectively. The difference is mainly due to the consideration of the oil pressure and surface roughness in the PEHL model. Consequently, it is necessary to take the PEHL into account when calculating the minimum film thickness.