Compound Steam Engines — Flywheel Size Requirement Among receiver, tandem, and Woolf compound steam engine arrangements, which generally requires the smallest flywheel for smooth running?

Introduction / Context:
Flywheels compensate for cyclic torque fluctuation. Different compound engine layouts distribute expansion and phasing differently, altering the uniformity of torque and thus the necessary flywheel inertia for steady speed.

Given Data / Assumptions:

• Receiver compound: HP and LP cylinders on separate cranks, typically about 90° apart, connected via a receiver.
• Tandem compound: HP and LP in line on a common rod, single crank.
• Woolf compound: cylinders share a common rod without an intermediate receiver.

Concept / Approach:
Torque ripple diminishes when power strokes are phase-shifted. The receiver type uses cranks set roughly at right angles; when one cylinder approaches dead center (low torque), the other is near mid-stroke (high torque). The receiver also buffers pressure pulsations between cylinders. This phasing improves turning-moment uniformity, allowing a smaller flywheel than single-crank tandem or Woolf types, where torque peaks coincide more and smoothing is poorer.

Step-by-Step Solution:
Compare crank phasing: receiver → two cranks ~90° apart; tandem/Woolf → single crank.Relate phasing to torque uniformity: orthogonal cranks even out net torque.Infer flywheel requirement: better uniformity → smaller required inertia.

Verification / Alternative check:
Indicator and turning-moment diagrams for receiver compounds show reduced amplitude of fluctuation compared to single-crank designs.

Why Other Options Are Wrong:
Tandem type: single crank → larger torque swings → larger flywheel.Woolf type: also single crank and no receiver → limited smoothing capacity.all of these: cannot all be smallest simultaneously; receiver type is best.

Common Pitfalls:
Confusing “more cylinders” with smoother torque irrespective of phasing; phasing is crucial.

Final Answer:
Receiver type