Single-acting steam engine — identify admission and number of working strokes Which statement correctly describes a single-acting steam engine with respect to steam admission and working strokes per revolution of the crankshaft?

Introduction / Context:
Steam engines can be single-acting or double-acting. The distinction affects torque pulsation, valve gear, and sizing. This question checks the basic definition and operating consequence for the number of power strokes per revolution.

Given Data / Assumptions:

• Simple single-cylinder engine.
• Idealized uniform rotation for conceptual counting.
• Standard crank-and-connecting-rod mechanism.

Concept / Approach:
In a single-acting engine, steam does work on only one face of the piston. The return stroke is typically not powered by steam but by inertia and flywheel energy. Therefore, there is one working (power) stroke per crankshaft revolution. In contrast, a double-acting engine admits steam alternately to both sides, giving two working strokes per revolution in a single-cylinder arrangement.

Step-by-Step Solution:

Verification / Alternative check:
Indicator diagrams of single-acting engines show one expansion diagram per revolution; double-acting show two per revolution for the same cylinder.

Why Other Options Are Wrong:

• Both-sides admission with one or two working strokes describes double-acting operation.
• Two working strokes with one-side admission is contradictory.
• “Zero working strokes” is non-physical for an operating engine.

Common Pitfalls:
Confusing steam-engine stroke counts with internal combustion engine cycles; assuming the return stroke is always powered in single-acting machines.

Final Answer: