Correct Answer - Option 1 : Sommerfeld number
Explanation:
For a journal bearing, the Petroff equation is used to determine the coefficient of friction.
\(f = 2{{\rm{\pi }}^2}\left( {\frac{r}{c}} \right)\left( {\frac{{{\rm{\mu }}{{\rm{N}}_{\rm{s}}}}}{P}} \right)\)
McKee’s equation:
A bearing characteristic number is given by McKee which helps is visualizing the transition from thin film lubrication to thick film hydrodynamic lubrication.
Bearing characteristic number = \(\left( {\frac{{\mu N}}{P}} \right)\)
The Sommerfield number (S) also known as bearing characteristic number is a dimensionless quantity used in the design of hydrodynamic journal bearings. It is very important in lubrication analysis because it contains all design variables.
The Sommerfield number (S) is given by,
\( S = {\left( {\frac{r}{c}} \right)^2}\frac{{μ {N}}}{P}\)
where μ = viscosity of the lubricant in N-s/mm2 or MPa-s, N = journal speed in rev/s, P = unit bearing pressure i.e. load per unit of the projected area in N/mm2, r = radius of the journal in mm, and c = radial clearance in mm.
