Experimental identification of turbocharger mechanical friction losses

Abstract

Understanding the friction losses of automotive turbochargers is a key parameter in assessing properly the mechanical efficiency of these machines. Current turbochargers are mostly equipped with oil bearings: two journal bearings and one double-acting axial thrust bearing. In order to know on which element improvement efforts have to be focused, it is important to determine their contribution to the total friction losses. This will also make it possible to calibrate the computation models of friction losses of the bearings separately. Measuring the friction losses of a turbocharger is not easy and existing methods measure only the total losses due to the association of journal and thrust bearings. A novel turbocharger test bench equipped with a highly accurate torquemeter and a magnetic axial load device has been developed. Measuring methodologies have been fine-tuned to measure the total friction losses, the influence of axial load on the thrust bearing, and the mechanical friction losses of the journal bearings alone. The experimental device and measuring methods are detailed in this paper. Experimental results are presented and analysed. The influence of axial load, oil inlet pressure and the distribution of friction power and oil mass flow between thrust bearing and journal bearings are discussed.