A Study of Rayleigh-Step Hybrid Bearing with a Circumferential Feeding Groove

• Main Authors: Lin-Kan Yang, 楊琳鏗
• Other Authors: Yuan Kang
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/x5b2q2

博士 === 中原大學 === 機械工程研究所 === 91 === Abstract This thesis studies the characteristics of Rayleigh-step hybrid journal bearing with a circumferential feeding groove without outer throttling, supply pressure same as recess inlet pressure, it has been simulated the lubricant film. The bearing surfaces between shaft and bearing are separated by a film of liquid under pressure as a hydrostatics bearing, also stepped condition and shallow recess intense hydrodynamic force as a hydrodynamics bearing. This thesis studies the influence of recess depth, land-width ratios and speed parameter on the load capacity, flow rate, friction force, attitude angle, stability and critical whirl ratio of a Jeffcott rotor supported by recessed hybrid bearing. The calculation of fluid static and dynamics of lubricant film using the perturbation method, the Reynolds equation was linearity and subsequently solved under finite difference techniques, to determine the influences of number of recesses, aspect ratio, recess depth, recess circumferential width and journal speed on the static performances of load capacity, flow rate, friction force and attitude angle. The determination of stability threshold uses the Routh-Hurwitz method, stability threshold, and the critical whirl ratio, versus the changing parameters. When the value of speed parameter is very small, static effects of bearing become significant, thus, for hybrid bearings the load capacity becomes larger as the recess depth is larger. When speed parameter is large over a critical value, the dynamic effects increase then when the speed parameter is large enough the dynamic effect has been saturated, the load capacity is larger as the recess depth is smaller. The designs of recess depth and land size are optimized for bearings use small or large eccentricity ratio. For a constant land ratio and the same eccentricity ratio, the stability thresholds are identified under greater speed. Overall, for a rotor-bearing system to operate stably, the subjects of this study are the designs of recess depth, location and recess number, and land size as well as the investigations of their influences on the stability characteristics.