On The Sealing Mechanism Of Lip Seals Containing Microundulations

Abstract

A mathematical model of the sealing process in rotary lip seals containing microundulations has been constructed. In this model, based on a mechanism proposed by previous investigators, shear deformation of the lip surface produces a vane-like undulation geometry, which results in reverse pumping of liquid and a reduction in leakage rate. At a critical shaft speed, the leakage rate is zero, and a free surface is formed at the low pressure edge of the sealing zone. When the shaft speed exceeds the critical speed, the free surface moves axially toward the high pressure side, and assumes an equilibrium position within the narrow gap between the lip and shaft surfaces. The model allows computation of the critical speed as a function of the design and operating parameters. Model predictions agree qualitatively with the experimental observations of previous investigators. Although the model deals specifically with microundulations on the lip surface, it has implications for other lip surface microgeometries.