Maximum Fluctuation of Energy

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Turning moment diagram for a multi-cylinder engine.
Fig. 1 Turning moment diagram for a multi-cylinder engine.

Maximum Fluctuation of Energy : A turning moment diagram for a multi-cylinder engine is shown by a wavy curve in Fig. 1. The horizontal line AG represents the mean torque line. Let a1, a3, a5 be the areas above the mean torque line and a2, a4 and a6 be the areas below the mean torque line. These areas represent some quantity of energy which is either added or subtracted from the energy of the moving parts of the engine.

Turning moment diagram for a multi-cylinder engine.
Fig. 1 Turning moment diagram for a multi-cylinder engine.

Let the energy in the flywheel at A = E, then from Fig. 22.4, we have
Energy at B = E + a1
Energy at C = E + a1 – a2
Energy at D = E + a1 – a2 + a3
Energy at E = E + a1 – a2 + a3 – a4
Energy at F = E + a1 – a2 + a3 – a4 + a5
Energy at G = E + a1 – a2 + a3 – a4 + a5 – a6 = Energy at A
Let us now suppose that the maximum of these energies is at B and minimum at E.
∴ Maximum energy in the flywheel
= E + a1
and minimum energy in the flywheel
= E + a1 – a2 + a3 – a4

∴ Maximum fluctuation of energy,
ΔE = Maximum energy – Minimum energy
= (E + a1) – (E + a1 – a2 + a3 – a4) = a2 – a3 + a4

Reference A Text book of Machine Design by R.S. Khurmi and J.K. Gupta

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