Steam remaining in cylinder clearance After each stroke, some steam remains trapped in the clearance space. This retained steam is called ________.

Introduction / Context:
Cylinder clearance is the small volume left when the piston is at the end of its stroke. The steam that occupies this volume at the completion of the exhaust process affects the thermodynamics and mechanics of the next cycle. Understanding its role is important for indicator diagram interpretation and efficiency analysis.

Given Data / Assumptions:

• Piston-cylinder steam engine with finite clearance volume.
• Normal valve timing: exhaust closes before admission opens.
• Steam properties near saturation at cylinder conditions.

Concept / Approach:
The steam trapped in the clearance volume is commonly termed “cushion steam.” During the return stroke, this steam is compressed (recompression) before fresh steam admission, cushioning the piston as it approaches dead center and reducing mechanical shock. It also preheats the cylinder, moderating condensation during subsequent admission.

Step-by-Step Solution:
At end of exhaust, some steam remains in the clearance volume.As the piston reverses, this trapped steam is compressed (its pressure and temperature rise).Compression cushions the piston near dead center and reduces clearance losses by preheating surfaces.Fresh steam then admits, mixing with the compressed steam to begin the power stroke.

Verification / Alternative check:
Indicator cards show a compression curve in the upper left corner due to cushion steam. The area reduces shock and can improve volumetric efficiency if optimized.

Why Other Options Are Wrong:
Wet, saturated, and superheated describe thermodynamic states, not the functional role of trapped clearance steam. “Reheat steam” relates to turbines, not reciprocating engine clearance.

Common Pitfalls:
Assuming clearance steam is purely a loss; in moderation it serves useful cushioning and heating roles.

Final Answer:
cushion steam