Experimental Comparison of the Performance of a Journal Bearing with a Single and a Twin Axial Groove Configuration

Abstract

It is often assumed that a twin groove arrangement will provide a more effective lubrication and a cooler operation than a single groove one, but little evidence has been found in support of this claim. Furthermore, there are no experimental works, to the authors’ knowledge, that compare the performance of single and twin axial groove bearings with the same geometry. An experimental assessment of a journal bearing with either two axial grooves located at +/-90º or just one single groove at +90º to the load line was performed. The comparison was made by using the same bearing for both groove configurations but the oil feeding to the -90º groove was shut with a valve in one of the cases in order to emulate a single groove bearing. Measurements of total and partial lubricant flow rate through each groove, shaft locus, inner bush surface temperature, oil outlet temperature and electrical motor consumption were performed. For the range of applied loads tested the twin groove journal bearing displayed a lower maximum temperature but a higher outlet temperature and eccentricity than the single groove journal bearing. Also the measured total flow rate in the bearing was approximately the same for the single and the twin groove arrangements. For the twin groove bearing, the partial flow rate through each groove varied dramatically with increasing load: At high eccentricities the flow being supplied to the active land of the bearing through the +90º groove was much lower than that supplied to the non-active land of the bearing through the -90º groove. Actually, the measured flow rate at the +90º groove was almost zero for the highest load tested, with nearly all the lubricant being fed to the non-active land of the bearing through the -90º groove. This means that under heavy load operation, the existence of an extra groove at -90º to the load line might actually deteriorate lubrication effectiveness when compared with a single groove arrangement.