Effect of Aspect Ratio and Semi Cone Angle on the Stability Behaviour of a Conical Hydrodynamic Journal Bearing

Abstract

The combined radial and axial load carrying features of conical hydrodynamic journal bearing emerge as a better option in many turbo-machines for two separate bearings i.e. journal and thrust pad bearings. Requirements of accurate rotation of the spindle for high precision machining operations are depend on load carrying capacity and dynamic stability of bearings. The present study proposed the analysis of conical hydrodynamic journal bearing for aspect ratio (λ = 0.5, 1.0, 1.5) and semi-cone angles (γ = 5°, 10°, 20°), when load variations in terms of eccentricity (e = 0.35, 0.55) for wide range of operating speeds (Ω = 0.25-1.5). FEA based analytical method was used and results were presented for radial and axial load carrying capabilities, stiffness coefficients, damping coefficients and threshold speed. It was found that load carrying capabilities of conical hydrodynamic journal bearing is increases with increase of aspect ratio and semi cone angle. Threshold speed (ω _th) of bearing is marginally decreases with increase of semi cone angle. Whereas results also indicate the improvement of stability in terms of threshold speed (ω _th) for short length conical journal bearing (λ = 0.5).