A Novel Thermal Model for the Piston/Cylinder Interface of Piston Machines

The lubricating gaps of piston machines represent the main source of energy dissipation. The lubricating gap in these machines has to fulfill a sealing and bearing function. Therefore the prediction of the gap flow, the load carrying ability and the energy dissipation is necessary. The paper discusses a novel fully coupled model for the determination of piston/cylinder gap behavior considering the contribution of solid parts temperature induced strain. In particular, the non-isothermal gap flow model considers the squeeze film effect due to the micro-motion of the moveable parts and simultaneously the change of fluid film thickness due to the elastic deformation of the solid bodies caused by the fluid pressure field and the parts temperature field. The determination of the temperature field inside the parts, by means of detailed finite volume models, allows for the first time to accurately predict solid parts thermal expansion, which is directly affecting the gap film thickness. Therefore, the novelty of the developed fully coupled fluid-structure-thermal interaction model is the integration of a finite element solver for the determination of surface thermo-elastic deformation in a dynamic non-isothermal fluid flow model. This will allow for the first time to solve the thermo-elastohydrodynamic lubrication problem under changing load conditions, considering the impact of several different physical phenomena.