An Improved Short Bearing Analysis for the Submerged Operation of Plain Journal Bearings and Squeeze-Film Dampers

Abstract

By allowing the film pressure to assume some subambient value and by allowing natural boundaries of the film to form in the unloaded region, the short-bearing theory of Ocvirk and Dubois is extended to include a detailed description of the cavitation zone. Two alternative cavitation configurations are shown to be possible, rendering different eccentricity (orbit size), attitude angle (phase), for the same load and minimum film pressure. The first configuration features an enclosed cavity maintained at a subambient level and is called “0” cavitation, which is crudely emulated by the conventional “half-film” approximation. The second configuration features ambient level side cavities, the boundaries of which are drawn inside the bearing ends by a sub-cavity film pressure, and is called “I” cavitation. The “I” cavitation, which is initiated by the aggregation of entrained bubbles in the ambient fluid, can present itself in the form of multiple striations causing substantial loss of load capacity.