Question

If speed is increased by 50%, absolute viscosity decreased by 25% and pressure increased by 25% what will be the effect on bearing characteristic number?

Answer 1

Answer:

The bearing characteristic number will decrease by 10%

Explanation:

Bearing characteristic Number is given by

$\boxed{S=\frac{ZN}{P}}$

Where,

Z is the absolute viscosity

N is the speed of the rotating shaft

P is the bearing pressure

If speed is increased by 50%, the new speed will be = N + N/2 = 3N/2

If absolute viscosity is decreased by 25%, the new viscosity will be = Z - Z/4 = 3Z/4

If pressure is increased by 25%, the new pressure will be = P + P/4 = 5P/4

Thus the new bearing characterstic number

$S'=\frac{(3Z/4)(3N/2)}{(5P/4)}$

$\implies S'=\frac{9ZN}{10P}}$

Decrease in Bearing Characteristic Number

= S - S'

$=\frac{ZN}{P}}-\frac{9ZN}{10P}}=\frac{ZN}{10P}}$

% Decrease = $\frac{S'-S}{S}\times 100$

                    = 1/10 × 100 = 10%

Therefore, The bearing characteristic number will decrease by 10%