6. Purpose
•Turning moment diagram is a graphical representation of turning moment or
torque (along Y-axis) versus crank angle (X-axis) for various positions of crank.
•The area under the TMD gives the work don per cycle.
•The work done per cycle when divided by the crank angle per cycle gives the
mean torque Tm.
•The mean torque Tm multiplied by the angular velocity of the crank gives the
power consumed by the machine or developed by an engine.
7. Fly wheels
The Fly wheel stores the excessive
mechanical energy from the engine.
It stores the energy during power stroke
and releases it during the other strokes.
Two types
Disk type
Rim type
9. Important Terms
1. Maximum fluctuation of speed
◦ It is the difference between the maximum & minimum speeds in a cycle.
N1 – N2
2. Coefficient of fluctuation of speed
◦ It is the ratio of maximum fluctuation of speed to the mean speed
◦ It is expressed as percentage of mean speed
10. Energy stored in flywheel
E = mk2w2Cs
Or Iw2Cs
Where,
m = mass (kg)
k = radius of gyration (m) [ k2 = D/4 for rim type k2 = D/8 for disc type]
w = angular velocity of flywheel (rad/s)
Cs = coefficient of fluctuation of speed (no unit)
E = excessive energy (J)
I = mass Moment of inertia (kg-m2)
12. Energy in fly wheels problems
Formulae
•Excess energy, stored in flywheel, E = mk2w2Cs or Iw2Cs
•Work done /cycle = area under the curve
•Work done /cycle = Tmean x (angle for one cycle)
• i.e. Net Area = Tmean x 4p (for 4 stroke engine)
17. A single cylinder 4 stroke gas engine develops 20 KW at 300 rpm
with work done by the gases during the expansion being 3 times
the work done on the gases during compression.The work done
during the suction & exhaust strokes is negligible. The total
fluctuation of speed is 2% of the mean. The TMD may be
assumed to be triangular in shape. Find the mass moment of
inertia of the flywheel.
18. Given:
Power = 20 kw
N = 300rpm
WE= 3xWC
Cs = 0.04
4 stroke engine
i.e q = 4p (2revs)
I = ?
19.
20.
21. Since the area above the mean turning moment line represents the maximum
fluctuation of energy, therefore maximum fluctuation of energy,
