Effect of shaft microcavity patterns for flow and friction control on radial lip seal performance–a feasibility study

It has been shown that deterministic microfeatures on the shaft of a radial lip seal impact seal behavior. This work seeks to determine whether it is feasible to control lubricant pumping direction and enhance pump rate with microcavities. The effect of nickel film triangular cavity orientation on seal performance, in particular the flow direction, the pumping rate, and the friction torque, is investigated experimentally. Cavity shape, area fraction, and depth are held constant while cavity orientation is varied. The oil drop test results are compared to those for conventional seals; i.e., plain stainless steel shafts and shafts with an electroplated nickel surface but no micro-cavities. It was found that shafts with surface texture designs can control the pumping direction and increase the sealing capability via enhanced pump rates by up to eight times that of stainless steel shafts. Preferential orientations pumped oil toward the wider end, or base, of the triangular cavities while patterns in neutral, or nonpreferential, orientations were found to reverse pump. The presence of microcavities reduced the friction torque by as much as 51% when pumping and in all cases reduced the operating temperatures. In some cases, the microcavities also reduced the friction torque 8–13% when the seal was operating in a starved condition.