Design Optimization of an Automotive Turbocharger Thrust Bearing Using a CFD-Based THD Computational Approach

Abstract

In a quest to reduce fuel consumption and emissions of automotive combustion engines, friction losses from many different sources need to be minimized. For modern designs of turbochargers commonly used in the automotive industry, reduction of friction losses results in better efficiency and also contributes to a faster transient response. The thrust bearing is one of the main contributors to the mechanical losses of a turbocharger. Therefore, it is crucial to optimize the design of the thrust bearing so that it has minimum friction losses while keeping sufficient thrust carrying capacity. One of the main challenges of turbocharger thrust bearing design, is that rotation speed is not fixed: the turbocharger may have a rotation speed which varies between 0 to as much as 250 kRPM. Moreover, the thrust bearing generates considerable heat, which changes the temperature of the oil film and its surroundings. In the present work, the design of the thrust bearing of an automotive turbocharger has been optimized. A CFD-based Thermohydrodynamic (THD) computational approach has been developed, taking into consideration heat dissipation, conjugate heat transfer throughout the bearing domain including the surrounding parts, as well as shear thinning and cavitation in the lubricant domain. An optimizer has been coupled to the CFD solver, with the aim of identifying bearing designs with reduced friction losses. Two bearing concepts have been evaluated: a taper-land design-which is a commonly applied thrust bearing concept-as well as a pocket bearing design. The resulting optimum pocket designs exhibit improved performance, in comparison to the optimum taper-land design. The present results indicate that (a) the pocket design concept can substantially contribute to further reducing the friction losses of a turbocharger, and (b) optimal design parameters of pocket bearings depend on the specific application (size, operating conditions), therefore detailed calculations should be performed to verify optimum performance.

Numerical and Experimental Studies on Performance Enhancement of Thrust Pad Bearing Employing Surface Texture: A Review

“… numerical studies incorporating thermal effects without considering cavitation [70][71][72][73][74][75] and…”

“…The heat created in the lubricant film has a severe effect on the performance behaviour of bearings, therefore, the thermal effects need to be considered. The performance behaviour of bearing can be obtained using CFD simulations [70][71][72][73][74][75] based on the solution of Navier Stokes equation along with the energy equation for steady-state incompressible Newtonian fluid in laminar flow. Bearing performance parameters are affected by types of texture such as dimples [70][71], grooves [73], and pockets [72][73][74] and texture parameters such as depth [71][72][73], extent [71,73,75], the shape of texture such as grooves [62] and elliptical It can be seen in Fig.…”

Computational evaluation of dynamic coefficients of thrust bearings; effect of artificial texturing on thermohydrodynamic performance

“…The steady-state THD model has been based on that developed by Charitopoulos et al in [12][13] and solves the Navier-Stokes equations coupled with the Energy equation to account for thermal effects by simulating a conjugate heat transfer problem between lubricant, pad and rotor. Cavitation, viscous dissipation and the temperature dependency of the lubricant's viscosity have also been considered.…”

A Generalised Method for Friction Optimisation of Surface Textured Seals by Machine Learning

“…In order to reduce the friction of a tribological system, the performance of the lubricant can be improved [26], the lubricant feeding conditions can be adjusted and optimised [27], special materials and coatings can be used [28], operational conditions can be modified [29], geometries can be optimised [30], and the contact surfaces can be modified [24]. In addition, it is possible to combine different processes, such as surface texturing and surface coating [31,32].…”