INFLUENCE OF RECESS SHAPE AND BEARING FLEXIBILITY ON THE PERFORMANCE OF MEMBRANE COMPENSATED MULTIRECESS HYBRID JOURNAL BEARING SYSTEM

Abstract

The multirecess hydrostatic/hybrid journal bearings are currently finding numerous applications in machine tool industries, test equipments, rolling mills, reactor coolant pumps, liquid rocket engines and in nuclear applications. Their wide acceptability in the engineering applications is mainly owing to their excellent characteristics in respect of high fluid film thickness, high load carrying capacity at zero and low speed, high accuracy of precision and location, long life and smooth operation, low friction and minimum temperature rise, large fluid film thickness and excellent dynamic characteristics. A review of the available reported studies concerning multirecess hydrostatic/hybrid journal bearing systems has been presented in the literature. [: has been observed that in most of the studies, the geometric shape of recesses used in hydrostatic/hybrid journal bearing system is mainly rectangular. This could be due to ease in manufacturing and relative simplicity of this particular geometric shape of the recess. However, with the advent of newer and sophisticated manufacturing techniques such as CAM, EDM, etc., the other geometric shapes can also be easily manufactured. Further, when a bearing operates at heavy loads the performance of bearing is appreciably affected due to the bearing flexibility. Therefore, the present work is planed to study the combined influence of recess shape and bearing flexibility on the performance of a membrane compensated multirecess hybrid journal bearing system. The performance of membrane flow .valve compensated multirecess hydrostatic/hybrid journal bearing has been studied for the four different geometric shapes of recess, i.e., square, circular, elliptical and triangular, for the wide range of values of bearing flexibility parameter and external load. For computing the bearing performance characteristics, the Reynolds equation governing the flow of lubricant in the clearance space along with the equation of flow through the membrane flow valve restrictor as constraint is solved together with a three dimensional elasticity equations satisfying the appropriate boundary conditions. The deformable bearing shell has been discretized using 8 node three dimensional isoparametric elements. The study indicates that the performance of a membrane flow valve compensated journal bearing system gets affected significantly due to geometric shape of recess and bearing flexibility operating in hydrostatic/hybrid mode. The triangular recessed membrane flow valve compensated hydrostatic/hybrid journal bearing system provides largest values of stability threshold speed margin among all the bearing configurations studied. iv