Elastohydrodynamic Lubrication and Asperity Contact Simulation of Engine Main Bearing with Flexible Rotating Crankshaft and Flexible Engine Block

Abstract

The main objective of this paper is to describe an approach to the elastohydrodynamic lubrication analysis of crankshaft-bearing systems in a locomotive diesel generator set. The analytical model used in this approach combines the elastic and inertial properties of the crankshaft, the flexibility of the crankshaft and block, and the elastohydrodynamic lubrication and asperity contact nature of the journal-bearing systems. The finite element structures of the crankshaft and block are discretized and condensed into a number of mass-beam structures, which eliminates the most degrees of freedom of the structures in the reduction procedures as well as kee** computational accuracy. The hydrodynamic characteristics of the journal-bearing systems are described using an approximate solution of the Extended Reynolds Equation. For highly sophisticated copulation between elastohydrodynamic lubrication and flexible structure motion (both large rigid-body motion and small elastic deformation), the iteration algorithm of a commercial software AVL EXCITE is used via numerical integration of pressure and numerical interpolation of the clearance gap. The asperity contact behavior of journal-bearing systems is simulated by the Greenwood-Tripp model under the mixed-lubrication condition.

This paper describes a simulation procedure of the bearing lubrication performance coupled with the crankshaft elastic response. Using this method, bearing lubrication and asperity contact status are predicted. Since the flexibilities of crankshaft and block can dramatically affect elastohydrodynamic performance of bearings, the elastics of journal-bearing system can not be ignored in rigorous bearing hydrodynamic lubrication analysis. The contact severity has been investigated by the asperity contact calculation, which is based on Grennwood-Tripp model. The lubrication simulation results of main bearings of a locomotive diesel generator set are presented as an example.