Misalignment-induced macro-elastohydrodynamic lubrication in rotary lip seals

Typically, film formation in a rotary lip seal is explained by microscopic effects, but here it will be explained from a macroscopic point of view. When the nominal parallelism between the shaft and the seal is lost, the contact area is distorted leading to a skewed sealing profile. The resultant slanted gap between the shaft and the seal presents a macroscopic wedge profile in the direction of rotation, hence constituting a source of hydrodynamics. An elastohydrodynamic model is developed predicting the implications of operating a rotary lip seal under misalignment. It is concluded that the non-concentric operation of rotary lip seals leads to a bidirectional fluid migration from the back to the spring side of the seal and vice versa.