A COMPARATIVE STUDY OF A MULTIRECESS HYBRID WORN JOURNAL BEARING SYSTEM OPERATING IN TURBULENT REGIME COMPENSATED WITH DIFFERENT FLOW CONTROL DEVICES

摘要

The objective of the present work is to study analytically the performance of a four-pocket hybrid worn journal bearing system operating in turbulent regime compensated with different flow control devices i.e. orifice, capillary and constant flow valve (CFV) restrictors. The wear caused on the bearing surface is modeled using Dufrane's abrasive wear model. The Reynolds equation based on Constantincscu turbulent lubrication theory has been solved using FEM and Newton Raphson method along with the appropriate boundary conditions. The numerically simulated results have been presented for a wide range of restrictor design parameter, non-dimensional external load, wear depth parameter and Reynolds number. The numerically simulated results suggest that when the bearing operates in turbulent regime under unworn condition, the performance of the bearing from the viewpoint of minimum fluid film thickness, fluid film stiffness and damping coefficients and the lubricant flow requirement gets improved vis a vis the bearing operating in laminar regime under unworn condition for all the compensated bearings studied. However, this improvement in bearing performance comes at the cost of higher value of frictional torque. Further, it has been observed that when the bearing operates in turbulent regime, the influence of wear on bearing performance is appreciably less as compared to bearing operating in laminar regime for all the compensated bearings studied. Another notable observation made from the study is that among the various compensated bearings studied in the present work, the constant flow valve compensated bearing appears to be more suitable from the viewpoint of minimum fluid film thickness, fluid film stiffness and damping coefficients and stability threshold speed margin, when the bearing operates in turbulent regime under worn/unworn conditions. The present study suggests that, a proper selection of type of flow control device and the value of its restrictor design parameter is essential in order to obtain an improved performance of a bearing operating in turbulent regime under worn/unworn conditions.