A new approach for modeling and analysis of the lubricated piston skirt-cylinder system with multi-physics coupling

The lubrication of the piston skirt-cylinder interface involves multiple physical fields, and these physical fields are coupled. A new method is proposed in this study for modeling and analysis of the lubricated piston skirt-liner interface with multi-physics coupling. This method is implemented in COMSOL Multiphysics software by coupling the heat transfer of the cylinder and piston, multibody dynamics of the crank-connecting rod-piston-cylinder system, the hydrodynamics lubrication of the skirt-cylinder interface, the thermal and elastic deformation of the piston-cylinder system, as well as the rheological properties of lubricating oil. The proposed method is first validated with a previous method and then adopted to a four-stroke gasoline engine to predict its dynamics and tribological characteristics. Then, a case study of different skirt thicknesses is conducted to reveal the influence the stiffness of the piston skirt exerts on the tribo-dynamics performance of the piston-cylinder system. The results indicate that although a thinner skirt will affect the stability of piston motion and increase the slapping noise and wear, it will benefit hydrodynamic lubrication between skirt and cylinder and reduce friction power loss.