A Comparative Elastohydrostatic Analysis of CFV- and Capillary-Compensated Multirecess Hydrostatic/Hybrid Journal Bearing Operating with Micropolar Lubricant
A comparative study on the performance characteristics of the flexible multirecess hydrostatic journal bearing system with constant flow valve and capillary restrictors has been presented considering the effect of micropolar parameters. The modified Reynolds equation for the flow of micropolar lubricant through the bearing has been solved using finite element method, and the resulting elastic deformation in the bearing shell has been determined iteratively. The results indicate that the micropolar parameters of the lubricant affect the performance of the flexible multirecess hydrostatic journal bearing system quite significantly. 1. Introduction In hydrostatic lubrication, the lubricant is pushed between the surfaces by means of an external pressurization system. The main advantages of hydrostatic lubrication are a very low friction and negligible wear, and the only drawback is a certain complexity of lubricant supply system. At present, hydrostatic lubrication is used in the entire field of mechanical engineering, from large machines, where speed is in general low, to small high-velocity machinery. Due to the absence of stick-slips and to the high degree of stiffness and damping of the pressurized fluid film, hydrostatic lubrication is particularly suitable for machines like machine tools, where medium or high precision is required to move great weights for large boring, milling, and grinding machines and numerical control machine tools, which require very accurate positioning and freedom from vibration, and telescopes and big radar antennas, which must move slowly and accurately. In multirecess hydrostatic lubrication, the supply system must allow the different pressures to occur in the recesses. In practice, this may be accomplished either by using a separate pump to feed each recess directly, this is commonly referred to as the constant flow supply system, or by using a common source of pressurized lubricant, which is carried to each recess through compensating devices called restrictors; since the pressure is generally held constant, upstream from the restrictors (compensating devices), this is commonly referred to as the constant pressure supply systems [1]. The commonly used restrictor includes constant flow valve, capillary, orifice, and diaphragm or membrane. It has been realized that the hydrostatic journal bearing system undergoes elastic deformation when operating under heavy loads. The bearing deformations are generally of the order of the magnitude of fluid-film thickness, and thus, the fluid-film profile is modified, and the performance
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