CFD Analysis of a Low Friction Pocketed Pad Bearing

A CFD method has been applied to model lubricant flow behavior within linear pad bearings having large, closed pockets or recesses. The study shows that the presence of closed pockets can result in a significant reduction in bearing friction coefficient and that there are two different origins for this, depending on the bearing convergence ratio. At high convergence ratios, as used in conventional thrust bearings, a pocket located in the high-pressure region of the bearing produces a reduction in local shear stress and thus friction. This friction reduction is larger than the reduction in load support resulting from the presence of the pocket so there is a net overall reduction in friction coefficient. In low convergence ratio bearings, each pocket also acts as an effectively-independent step bearing and thereby generates a higher local pressure than would otherwise be the case. This results in the overall bearing having enhanced load support and thus a reduced friction coefficient. This effect is particularly large at very low convergence ratios when cavitation occurs in the pocket inlet.