Question

a 80 mm crankshaft main bearing journal rotates at 3000 rev/min while carring a normal load w= 20kN. If the coefficient of friction in the bearing =0.02, calculate the power lost in friction at this engine speed

Answer 1

To be given in question

length=80mm

n=3000rev/min

w=20kN

$\mu=0.02$

To be asked in question

Power poss in friction $P_{loss}=?$

We know that

Total friction torque

$l=Rcos\alpha$

$\tau =\frac{2}{3}\mu Wl$

$\tau=\frac{2}{3} \times0.02\times20\times10^3 \times80\times10^{-3} N\times m$

$P_{loss}=21.33 W$

$P_{loss}=\tau\omega$

$w=2\pi n$

$w=2\pi \times50$

$P_{loss}=21.33\times100\pi$

$P_{loss}=6.697\times10^3 W$