A STUDY OF PLAIN/CONICAL HYBRID POROUS JOURNAL BEARINGS SYSTEM

Abstract

Bearings, in particular, play a crucial role in the performance of many rotating machines, including turbines, pumps, generators, and electric motors. Without reliable and efficient bearings, the overall performance of these machines would be severely impacted. In addition to this, bearings are also used to support external loads and provide the desired relative motion. The proper functioning of the bearing is essential for an accurate and smooth operation of the machines. During the last few decades, technological advancements throughout the world have necessitated that machine elements be designed for precision, accuracy, enhanced performance, increased life span, etc. In recent years, numerous researchers around the world have engaged in a variety of research initiatives to improve the performance of bearings. Advances in fluid film bearing technology led to the development of newer bearing configurations to harness better performance. Porous hybrid journal bearings are categorized as circular and conical porous hybrid journal bearings. Circular porous hybrid journal bearings exhibit the problem of instability when the bearing operates at higher speeds. High-speed and heavily-loaded conditions often create a complicated problem of whirl or whip during the bearing operations. Therefore, in order to overcome this limitation, conical porous hybrid journal bearings are efficiently used to enhance bearing performance under heavy load and high speed operation. Conical porous hybrid journal bearings have been widely used in different engineering applications like high-speed rotating machineries and precision machine tool application like lathes and grinding machine for their excellent capability of carrying both axial and radial loads at the same time. Moreover, the adjustment of clearance of the conical bearing during assembly and the self-guiding nature of the conical surfaces are its additional advantages. Further, the porous hybrid journal bearings are also classified in two categories as single layer porous hybrid journal bearing and double layer porous hybrid journal bearing. In the porous journal bearings having a single layer of porous journal shows exhibits lower stability and have less load capacity due to lubricant seepage through the bearing. This problem may be overcome by restricting the seepage of lubricant through the bearing wall. Bearing designers tempted to overcome this limitation by using double layer porous journal bearings with a thin layer of surface backed by a highly permeable thick layer substrate.Lubricants are substances, either organic or inorganic, that are applied to the tribo-contacts so as to ensure smooth relative motion and to minimize friction and wear. The ability of lubricants to lubricate tribo-pairs greatly influences its performance. To achieve the desired lubricating performance, a wide range of lubricants are now used in the tribological systems. Nowadays, the tribologists/lubricating engineers quite often blends the different type of external organic or inorganic additives in base oil to improve the lubricating performance of lubricants. The additization of these types of additives cause the base oil lubricant to behave as a non-Newtonian lubricant. The classical theory of Newtonian fluids fails to describe the behaviour of non-Newtonian fluids, such as polymer-thickened oils, lubricants with various additives, synthetic and bio-fluids, because it disregards the size of fluid particles. Generally, the length of these long-chain organic compounds (additives) is a million times the diameter of a water molecule, which significantly impacts the bearing's performance. In the couple stress fluid model, the size of long-chain polymer molecules (additives) has been considered. For a new generation of machines, the magneto-hydrodynamic lubrication technology has emerged as an effective smart way to enhance the performance of tribocontacts (fluid film bearings) with adjustable dynamic characteristics. Thus, in the present work, five different types of non-Newtonian lubricants such as Power law lubricant, Cubic stress law lubricant, Pseudoplastic lubricant, Couple stress lubricant, and Magneto-hydrodynamic (MHD) lubricant have been used to investigate the performance analysis of circular/conical porous hybrid journal bearing systems.