Direct simulation of fluid lubricated contacts down to the surface roughness scale
Hugo Checo1; Alfredo Jaramillo1; Roberto Ausas1; Mohammed Jai2; Gustavo Buscaglia1
1 Instituto de Ciências Matemáticas e de Computação, USP-São Carlos; 2 INSA - Lyon
doi:10.20906/CPS/CON-2016-1311
Resumo
Mechanical losses in a car engine are due mostly to fluid bearings. Fluid bearings in car engines are present in the ring/liner contact, connecting rod, crankshaft bearings, valves, valve seats, camshaft contacts and seals in general, accounting for 10\% of the fuel consumption, more than half of it being due to the piston assembly. Microengineering techniques such as honing, ion beam texturing, etching and laser surface texturing among others (\cite{ets05}) have made viable to shape the surfaces of these devices down to the scale of the surface roughness. These patterned microstructures often come in the form of pockets, dimples and grooves, aiming to improve the load capacity, wear rate and reduce friction. Several experimental and theoretical studies have established the possibility of improving the performance of fluid bearings by controlling the topography of the surfaces, however, the fundamentals of why this takes place are not fully understood. Furthermore, determining the best surface in terms of friction and wear for each working condition by means of experimental procedures is a expensive process. What's more, accurate measurements of point-wise quantities like film thickness or pressure are extremely difficult. A practical approach is the mathematical modeling and numerical simulation of lubricated contacts. In this paper the lubrication problem taking into account cavitation effects and the bearing dynamics has been solved for realistic operational conditions. A mass-conserving model is used to treat cavitation. Textures have been set on the moving surface of the lubricated pair. Most researchers have tackled this problem considering non-moving surfaces and neglecting the bearing dynamics to reduce the computational burden. Our approach is more encompassing and complex than previous ones, as each simulation is intrinsically transient. Parametric studies of micro-textured surfaces and simulations with surfaces of known measured topography corresponding to various surface finishings such as honi
Palavras-chave: fluid bearing; numerical simulation; numerical methods; cavitation; honed surfaces