On the effects of sliding velocity and operating pressure differential in rotary O-ring seals

Abstract

An experimental study is conducted to investigate the effect of sliding velocity and pressure differential across an O-ring seal. Of specific interest are the power loss, friction torque and temperatures at the interface between the O-ring and rotating shaft. Nitrile butadiene rubber of circular cross-section with 70 Shore A hardness is used as a test specimen. The O-ring power loss and temperatures at a distance of 0.61 mm away from the O-ring tip are measured during the tests. In order to analyze the temperature at the interface, a two-dimensional axisymmetric computational fluid dynamics (CFD) model is preprocessed in GAMBIT and thermal heat transfer analysis is carried out using a commercial CFD package, FLUENT. Variations of frictional torque, O-ring friction power loss and interfacial temperatures with changes in sliding velocity and operating pressure differential are presented. Results reveal that the O-ring power loss increases in an approximately linear fashion with sliding velocity. Further, it is found that the friction power significantly increases with relatively higher pressure differentials across an O-ring. Friction torque is found to drop with an increase in shaft speed and it rises at relatively higher pressure differentials. Moreover, the interfacial temperatures are found to increase with increase in sliding speed and operating pressure differentials. The physical and practical usefulness of these results are discussed.