Stability Analysis of Various Lengths Conical Hydrodynamic Bearing for Variable Load Conditions

Abstract

Conical hydrodynamic journal bearing is used to sustain radial load and observed to adjust the effect of axial load on rotating elements. Small compact size conical hydrodynamic fluid film bearings are used in many applications, such as compact hard disc drive. Hence need arises to explore the performance of these bearing for variable load condition and various sizes in terms of aspect ratio. These conical bearings also emerge with better feature to replace two separate bearings (journal and thrust bearings) in various applications. The present study proposed the stability analysis of conical hydrodynamic journal bearing in terms of stiffness and damping coefficients for bearing of semi cone angle (γ = 30o) and bearing size in terms of aspect ratio (λ = 0.5, 0.8, 1.0) for a wide range of radial load ((W_r ) =0.1-0.9) on rotating journal at a speed of 500 rpm. Finite element method has been used to solve the modified Reynolds equation in spherical coordinate system to investigate the flow of lubricant in the clearance space. Stability parameters for various configuration of conical hydrodynamic bearing have been presented and discussed in terms of direct and cross coupled stiffness coefficients, damping coefficients and threshold speed margin. Results show that threshold speed (ω _th) of conical journal bearing is improved for short bearings when aspect ratio changes from 1.0 to 0.5.