Improved Estimation of Bearing Pads' Inlet Temperature: A Model for Lubricant Mixing at Oil Feed Ports and Validation against Test Data

Abstract

Energy efficient operation of fluid film bearings demands savings in delivery flow while also managing to reduce the temperature in the fluid film and bearing pads. To achieve this goal, tilting pad journal bearings (TPJBs) implement a variety of oil feed arrangements, use pads with highly conductive material and engineered back surface, and also end seals to keep (churning) lubricant within the bearing housing. This paper introduces a novel model for the mixing of flow and thermal energy transport at a lubricant feed port and which sets the temperature of the lubricant entering a pad leading edge. Precise estimation of this temperature (and inlet oil viscosity) largely determine the temperature, and the current model aids to deliver improved temperature predictions in conditions that limit a conventional model, including the ability to impose an actual lubricant supplied flow, specifically when the bearing is operating in either an over-flooded or a reduced flow conditions. An empirical groove efficiency parameter regulates the temperature of the above-mentioned flows to represent conventional and direct lubricant feeding arrangements as well as end-sealed (flooded) or evacuated bearing configurations. Predicted temperatures are compared against published test data for two bearings while revealing the advantages of the novel model, in particular for operation under lubricant starvation. This paper delivers recommendations for the feed port efficiency parameter for various types of oil supply configurations. This parameter, not being a function of bearing operating conditions, allows for proper sizing of pumps, oil reservoirs, and heat exchangers in lube oil delivery systems for a packaged-unit machine.