Question

A solid disc flywheel 0·4 m diameter and 100 mm thick is

made from cast iron of density 7 10

3

´ kg/m3

. Determine

(i) MI of flywheel and (ii) KE at 1000 rev/min​

Answer 1

Explanation:

flywheel can be used to smooth energy fluctuations and make the energy flow intermittent operating machine more uniform. Flywheels are used in most combustion piston engines.

Energy is stored mechanically in a flywheel as kinetic energy.

Kinetic Energy

Kinetic energy in a flywheel can be expressed as

Ef = 1/2 I ω2 (1)

where

Ef = flywheel kinetic energy (Nm, Joule, ft lb)

I = moment of inertia (kg m2, lb ft2)

ω = angular velocity (rad/s)

Angular Velocity - Convert Units

1 rad = 360o / 2 π =~ 57.29578o

1 rad/s = 9.55 rev/min (rpm) = 0.159 rev/s (rps)

Moment of Inertia

Moment of inertia quantifies the rotational inertia of a rigid body and can be expressed as

I = k m r2 (2)

where

k = inertial constant - depends on the shape of the flywheel

m = mass of flywheel (kg, lbm)

r = radius (m, ft)