Etude sur les paliers de Turbocompresseur cavitants à haute vitesse avec prise en compte de l’effet élastohydrodynamique en régime instationnaire

Abstract

This study focuses on the analysis of the dynamic behavior of crankshaft and turbocharger bearings, critical components in engines and rotating machines, whose performance directly impacts the efficiency, reliability and overall system performance. The study explores in detail the effects of cavitation and surface deformations on these bearings, particularly those of the connecting rod (big end and small end) and the turbocharger. For turbocharger bearings, a dynamic computational model has been developed to determine key parameters such as the pressure field, minimum lubricant film thickness, leakage flow and friction torques. The minimum lubricant film thickness is a key indicator to assess the risk of friction and wear. The study also highlights the challenges of high-speed elastohydrodynamic lubrication, taking into account the interaction between the Reynolds equation and bearing surface deformations. These calculations are performed using the Booker mobility method and the Winkler deformation model, in an iterative numerical approach.

Concerning connecting rod bearings, the analysis focuses on the rupture and reformulation of the fluid film in the contact zone, particularly in the inactive cavitation zone. The operating parameters are studied for finite length bearings and compared to those obtained with the simplified assumption of short bearings. This comparison shows that the assumption of short bearings significantly reduces the calculation time while providing results similar to those of more complex models. In summary, this thesis proposes an advanced numerical approach to simulate the hydrodynamic and elastohydrodynamic lubrication conditions in connecting rod and turbocharger bearings, using a calculation program implemented in FORTRAN. The results obtained contribute to a better understanding of the physical phenomena involved and to the optimization of the performances of these critical components.