Simulation of multi-body dynamics and elastohydrodynamic excitation in engines especially considering piston-liner contact

Abstract

The computational simulation of the vibrational behaviour of running engines at the design stage is one of the most challenging targets in the present design analysis work of automotive engineers. In order to describe oil-lubricated body contacts (piston-liner, shaft-bearing) a detailed model of the geometrical and physical properties of the contact area is necessary. This paper presents a comprehensive simulation tool for modelling multi-body dynamics. The concept is based on dividing the non-linear mechanical system into subsystems with linear elastic behaviour and with non-linearities occurring only at the connections between these subsystems. Therefore, in the simulation model, linear elastic bodies, e.g. piston and liner, and highly non-linear connections, e.g. oil film at the inner liner wall, are distinguished. The paper describes the mathematical modelling of body structures and the calculation of the non-linear connecting forces resulting from elastohydrodynamic contacts between these bodies and outlines the methodology of the simulation procedure. Results of parametric studies, e.g. the influence of piston surface profile on the contact mechanism between piston and liner, are shown. Future aspects of the application of this method to support noise optimization of internal combustion engines as well as minimization of frictional losses and wear are discussed.