Project ForgeMachine Design
Design Against Static Load
GATE 2014
Hard
A hydrodynamic journal bearing is subject to 2000 N load at a rotational speed of 2000 rpm. Both bearing bore diameter and length are 40 mm. If radial clearance is 20 μm and the bearing is lubricated with an oil having viscosity 0.03 Pa·s, the Sommerfeld number of the bearing is __________.
0.8(± 0.05 accepted)
Explanation
r/c = (0.02 m)/(0.00002 m) = 1000. N=2000/60=33.33 rev/s. Bearing pressure P=W/(dl)=2000/(0.04×0.04)=1.25×10⁶ Pa. Sommerfeld number S=(r/c)²·μN/P=1000²×(0.03×33.33)/1.25×10⁶=10⁶×1.0/1.25×10⁶=0.8.
Source: GATE ME 2014 (Session 1 / Set-1) (2014)
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