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Theory of Machines
Governors & Flywheels
GATE 2021
Hard

The torque provided by an engine is given by T(θ) = 12000 + 2500 sin(2θ) N.m, where θ is the angle turned by the crank from inner dead center. The mean speed of the engine is 200 rpm and it drives a machine that provides a constant resisting torque. If variation of the speed from the mean speed is not to exceed ±0.5%, the minimum mass moment of inertia of the flywheel should be ___ kg.m² (round off to the nearest integer).

570 kg.m²(± 15 accepted)

Explanation

T−Tmean = 2500 sin(2θ) crosses zero at θ=0° and 90°. Max energy fluctuation ΔE = ∫₀^(π/2) 2500 sin(2θ) dθ = 2500 J. ωmean = 2π×200/60 ≈ 20.944 rad/s. Cs = 1% = 0.01 (±0.5% total swing). I = ΔE/(ωmean²·Cs) = 2500/(20.944²×0.01) ≈ 570 kg.m².

Source: GATE ME 2021 Session 2 (ME-2) (2021)

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