Single-Acting Air Compressor Cylinder:

A section of a classical reciprocating single-stage, single-acting compressor cylinder is displays in another figure. Inlet and discharge valves are situated in the clearance space and linked by ports within the cylinder head to the inlet and discharge links.

Figure: Single-Acting Air Compressor Cylinder

During the suction stroke the compressor piston begins its downward stroke and the air under pressure within the clearance space rapidly expands until the pressure falls below which on the opposite side of the inlet valve. This difference in pressure causes the inlet valve to open inside the cylinder until the piston reaches the bottom of its stroke.

In During the compression stroke the piston begins upward; compression begins, and at point D has reached the similar pressure as the compressor intake. The spring-loaded inlet valve after that closes. As the piston continues upward, air is compressed until the pressure within the cylinder becomes great sufficient to open the discharge valve against the pressure of the valve springs and the pressure of the discharge line. By this point, to the end of the stroke, the air compressed inside the cylinder is discharged at practically constant pressure.