Double-acting compressor: location of compression For a double-acting reciprocating air compressor, where does compression take place with respect to the piston and cylinders?

Difficulty: Easy

Correct Answer: in a single cylinder on both sides of the piston

Explanation:


Introduction / Context:
Reciprocating compressors may be single-acting or double-acting. The distinction is whether one or both sides of the piston contribute to compression and delivery, which changes capacity and mechanical design details.



Given Data / Assumptions:

  • Classic crosshead-type construction allowing rod-side sealing.
  • Valving on both head and crank ends.
  • Single cylinder considered for the definition.


Concept / Approach:
In a double-acting machine, both the head end and the crank end of the same cylinder undertake compression alternately as the piston shuttles. This effectively doubles the number of compression events per revolution compared to a single-acting cylinder of the same size and speed.



Step-by-Step Solution:
Identify acting surfaces: two sides of the piston.Each stroke: one side compresses while the other side intakes or delivers.Therefore, compression occurs in a single cylinder on both sides of the piston.



Verification / Alternative check:
Indicator diagrams show two loops per revolution (one for each side) for a double-acting cylinder.



Why Other Options Are Wrong:

  • “In one cylinder” describes single-acting behavior.
  • “Two cylinders” or “both sides in two cylinders” confuses multi-cylinder with double-acting architecture.
  • “Multistage only” is unrelated to single vs. double acting.


Common Pitfalls:
Assuming double-acting implies two cylinders; the term refers to two working faces of one piston.



Final Answer:
in a single cylinder on both sides of the piston

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