FLYWHEELS

A flywheel is an energy storage device. This device absorbs mechanical energy by increasing angular velocity and delivers energy by decreasing the angular velocity of the shaft that it is connected. Mostly it is used for smoothing the flow of energy between a power source and its load. If the load is a punch press, the actual punching operation requires energy for only a fracture of its motion cycle. If the power source is a two-cylinder four-cycle engine, the engine delivers energy during only half of its motion cycle.

Dynamic Theory

Ti : Input torque, increasing flywheel speed To: Output torque (load), absorbing energy and decreasing flywheel speed

Eqn. of motion of flywheel

Assuming rigid shafting,

Work input to the flywheel:

Work output of the flywheel:

If Ui > Uo than 4 > 1

If Ui = Uo than 4 = 1

If Ui < Uo than 4 < 1

System Permissible value

Pumps, Shearing machines 1/5 – 1/30

Machine Tools, Textile Machines 1/40 – 1/50

Generators 1/100 – 1/300

Automobiles 1/200 – 1/300

Aircraft Engines 1/1000 – 1/2000

Coefficient of fluctuation of speed

Crankshaft-Torque Characteristics and Flywheel 1-cylinder 4-stroke internal combustion engine

Mean torque

Tm

The largest positive loop is 0-180, yielding the largest speed change.

• Cs=0.1 =250r/s

• I=? 2=? 1=?

Crankshaft-Torque Summation for Multi-Cylinder Engines

4-cylinder 4-stroke internal combustion engine

• After the torque-displacement relation has been for a 1-cylinder, it is simple to assume these for multi-cylinder engine.

• For a 4-cylinder 4-stroke internal combustion engine, the torque events are spaced 720/4=180 apart. The total torque,

180 360 540totalT T T T T

Crank angle of the first cylinder

1-cylinder 4-stroke engine 4-cylinder 4-stroke engine

The Cam-Follower System FBD of cam

In the torque characteristic, the (+) area is equal to (-) area. i.e. Energy required to drive the follower in the forward direction is recovered when thefollower returns. A flywheel may be used on the cam shaft to handle this fluctuating enegy requirement.