Skip to main content

Components of reciprocating air compressor

Short answer

Primary components: cylinder with cooling, piston and rings, connecting rod-crankshaft, suction and delivery valves, cylinder head, crankcase, flywheel, filter, receiver, and safety valve. Working cycle: suction draws in air, compression raises pressure, delivery discharges to receiver; residual clearance air re‑expands before the next suction.

Describe the primary components of a single-stage reciprocating air compressor with a neat sketch, and explain its working.

A reciprocating compressor draws air into a cylinder, compresses it by the movement of a piston, and delivers it at a higher pressure.

            delivery valve   suction valve
               |                 |
         +-----v-----+-----------v----+
         |      cylinder head         |
         |  ______________________    |
  cooling|  |<-clearance->|       |   |cooling
  fins / |  |   piston |==|  rings|   |fins /
  jacket |  |__________|__|_______|   |jacket
         +---------------+------------+
                         |
                  connecting rod
                         |
                 crank --o-- crankshaft

Primary components

ComponentFunction
CylinderHolds the air during compression; made of cast iron with cooling fins or a water jacket
Piston and piston ringsCompress the air; the rings seal the gap against leakage and carry heat to the wall
Connecting rod and crankshaftConvert the rotary motion of the motor into the reciprocating motion of the piston
Suction valveSpring-loaded; opens automatically when the cylinder pressure falls below the suction pressure
Delivery valveOpens when the cylinder pressure exceeds the receiver pressure
Cylinder headHouses the valves and closes the cylinder
Crankcase and flywheelThe crankcase supports the shaft and holds the lubricating oil; the flywheel smooths the speed
Cooling systemFins or a water jacket remove heat and keep the lubricant stable
Air filter and receiverThe filter cleans the inlet air; the receiver stores air and damps pulsations
Safety valve and unloaderPrevent over-pressure and relieve the load at starting

Working

  1. Suction stroke: the piston moves away from the head, the pressure falls, the suction valve opens and air enters.
  2. Compression stroke: both valves are closed and the air is compressed as the piston returns.
  3. Delivery: when the pressure exceeds the receiver pressure, the delivery valve opens and air is delivered until the piston reaches the end of its stroke. The air in the clearance volume remains.
  4. Re-expansion: at the start of the next suction stroke, the trapped clearance air expands until its pressure falls below the suction pressure and the suction valve opens again.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Applied Thermodynamics chapter 2 questions →