A novel fluid-structure interaction model for lubricating gaps of piston machines

Abstract

The lubricating gaps between movable parts in piston machines represent the main source of power loss. A deep understanding of the complex physical phenomena characterizing the complex fluid-structure interaction is crucial for improving existing design and designing new more efficient machines. 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. This paper discusses the different physical phenomena and presents a new fluid-structure interaction model for the piston/cylinder gap of axial piston machines. The model considers the squeeze film effect due to the micro-motion of the piston and simultaneously the change of fluid film thickness due to the deformation of parts caused by the fluid pressure field. In addition the fluid flow is considered as non-isothermal, which requires the coupling of a heat transfer model to predict the surface temperatures as boundary conditions for the non-isothermal fluid film model. The novelty of the developed fully coupled fluid-structure interaction model is the integration of a finite element solver in the dynamic non-isothermal fluid flow model. This allows for the first time to solve the elastohydrodynamic lubrication problem in complex changing load conditions, considering the impact of thermal effects. Simulation results of the piston/cylinder interface will be compared with pressure field and temperature measurements, obtained on a special test-rig. © 2009 WIT Press.