Numerical Investigation of the Flow in a Hydrodynamic Thrust Bearing With Floating Disk

Abstract

In this paper we present a novel method for the numerical simulation of flow in a hydrodynamic thrust bearing with floating disk. Floating disks are commonly employed in turbochargers and are situated between the thrust collar, which is rotating at turbocharger speed, and the static casing. A floating disk reduces wear, improves the skew compensating capacity of the bearing, and is freely movable in the axial direction. The simulation model presented combines a commercial flow solver (ANSYS CFX) with a control unit. Based on physical principles and a predefined axial thrust, the control unit automatically sets the rotational speed of the floating disk, the mass flow of the oil supply, and the oil film thickness between the rotating disk and the casing wall and collar, respectively. The only additional inputs required are the temperature and the pressure of the oil at the oil feed and the turbocharger speed. The width of the computational grid of the thin lubricating oil film in the gaps is adjusted using a meshmorphing approach. The temperaturedependent variation in viscosity is included in the model. The calculated solution of the flow field in the domain, the oil film thickness, and the resulting rotational velocity of the floating disk are validated against experimental data and demonstrate favorable agreement. The influence of uncertainties in the measurements and the behavior of the systems are thoroughly investigated in parametric studies that reveal the key influencing factors. These are the temperaturedependent viscosity of the oil, the axial thrust, and turbulence effects in the supply grooves and ducts of the floating disk. Using the model presented here, it is now possible to predict design variants for this type of bearing.