INFLUENCE OF SURFACE ROUGHNESS EFFECTS, ON THE PERFORMANCE OF HOLE-ENTRY HYBRID JOURNAL BEARING

Abstract

Hole-entry hybrid journal bearings are extensively used in number of applications owing to their favorable characteristics over recessed bearings. A scan of literature related to these classes of bearings reveals that no study is yet available in case of non-recessed hybrid journal bearing system which includes the surface roughness effects in the analysis. However the inclusion of surface roughness effects does affects the bearing performance characteristics of hydrodynamic journal bearings. Therefore it is expected that in non-recessed hybrid journal bearings too, the inclusion of surface roughness considerations in the analysis would affect the performance characteristics. Thus, the objective of present study is to theoretically study the influence of surface roughness effects on the static and dynamic performance of capillary compensated non-recessed hybrid journal bearing in the analysis. The analysis considers an average Reynold's equation for a rough surface for the solution of lubricant flow field in the clearance space of journal bearing. The finite element method and Galarkin's technique has been used to derive the system equation for lubricant flow field. The non-dimensional parameters A (surface roughness parameter) and y (surface pattern parameter) have been defined to present the magnitude of height distribution of surface irregularities and their orientation respectively. The influence of surface roughness on the bearing performance has been studied for the transverse, isotropic and longitudinal surface roughness patterns. The bearing performance characteristic has been computed for a symmetric and an asymmetric capillary compensated hole-entry journal bearing configurations for various values of external load (Wo), surface roughness pattern parameter (y), concentric design pressure ratio ((3+) and eccentricity ratio (E). The computed results indicated that the inclusion of surface roughness effects in the analysis affects the performance of a bearing quite significantly. The study indicates that for generation of accurate bearing characteristics data, the inclusion of surface roughness effects in the analysis is essential. IM