Turbocharger Bearing Friction Measurement and Simulation

Turbocharger (TC) bearing friction mostly affects the “low speed” operation of the turbocharger and is therefore relevant for the transient response and part load emissions of modern combustion engines. Further optimization of TC friction has to be supported by sophisticated simulation tools to shorten developmental time and reducing the costs for prototyping and testing.In this paper, a detailed analysis on the mechanical losses occurring in the bearing system of automotive turbochargers is presented. The measurement data is obtained using FEV’s unique test bench customized for TC bearing friction analysis. Friction losses have been measured experimentally up to rotational speeds of 120 000 1/min. Special focus was placed on the thrust bearing characteristics and its contribution to total friction losses. This information is used to validate a modern simulation tool. Furthermore, the current potential and limits of the existing simulation methods are described. The state-of-the-art simulation method shown in this paper is based on elastic-multi-body simulation and elasto-hydrodynamic bearing approaches. The aim is to investigate rotor dynamics, load bearing capacity and friction losses in an integrated simulation environment.