Question

$\text{A hydrodynamic journal bearing is subjected to 2000 N load at a rotational speed of 2000 rpm. Both bearing bore diameter and length are 40 mm. If radial clerance is}20\mu \text{m and bearing is lubricated with an oil having viscosity 0.03 Pa.s, the Sommerfeld number of the bearing is}$

• A. 0.8

Answer 1

The correct option is A 0.8
$r=20mm,N=2000rpm$
$c=20\times {10}^{-3},\mu =0.03Ns/m^2$
$p=\frac{2000}{1600}N/m{m}^2(p=\frac{W}{A})$
$=1.25MPa$
$S=\frac{ZN}{60p}{\left(\frac{r}{c}\right)}^2$ $=\frac{0.03\times 2000}{60\times 1.25\times {10}^6}{\left(\frac{20}{20\times {10}^{-3}}\right)}^2=0.8$