PERFORMANCE OF A MULTIRECESS HYDROSTATIC/HYBRID JOURNAL BEARING OF DIFFERENT RECESS SHAPES WITH MEMBRANE RESTRICTOR

Abstract

Externally pressurized multirecess journal bearings have found increasing applications to meet the demands of large fluid-film stiffness , increased clamping capacity , high accuracy , long life, smooth operation , low lriclion, minimum temperature rise, etc. Frequently, turbo machinery and other machine tools , are required to operate at very high speed, high power, high load and with more precision. Thus, to cater to any specific or general requirement of machine tools, the performance characteristics of the bearings should be accurately known. The performance of hydrostatic/hybrid journal bearing systems gets affected by large number of design parameters such as number of pockets, type of restrictors, hearing flexibility, fluid inertia, bearing geometry and operating parameters, type of operation (hydrostatic/hybrid), type of compensating element etc. It has been observed that the shape of the recess, which is one of the significant parameter for the evaluation of performance of the bearing, in most of the studies undertaken were rectangular and the studies related to other geometric shapes of the recesses have not been done for membrane type of restrictor. Thus the present work is aimed to study the performance of multirecess hydrostatic/hybrid journal bearing with different shapes of the recesses viz. square pocket, circular pocket, elliptical pocket and triangular pocket configurations with membrane restrictor. To evaluate the performance of hydrostatic/hybrid journal bearing, different configuration has been compared for same bearing operating and geometric parameters and pocket area. The bearing performance characteristics has been computed using the Reynold's equation, governing the flow of lubricant in the clearance space between the journal and the bearing. The equation of flow of lubricant for the membrane restrictor together with appropriate boundary conditions and a suitable iterative scheme is used to get the results. To accomplish this task a computer program based on finite element analysis has been developed. The static and dynamic performance characteristics of compensated multirecess hydrostatic/hybrid journal bearing for various shapes of the recess has been presented in graphical form and logical conclusions about the effect of shape of the recesses on the performance characteristics of journal bearing are drawn. The study is expected to be useful to the bearing des