piston-compressor is a widely used compressor. It is based on the principle as
described in chapter 2.
the volume in the cylinder increases by moving the piston outwards, pressure in
the cylinder will drop. The pressure in the cylinder will get less than
atmospheric pressure. On the inlet valve we will get atmospheric pressure on one
side and an underpressure on the other side. This makes the valve to go open and
air from the atmosphere can enter the cylinder.
the piston has fully moved outwards it will start to move back in. This causes
pressure to rise in the cylinder. The inlet valve will close as soon as pressure
in the cylinder reaches atmospheric pressure. The piston will continue to move
inwards causing pressure to further rise. When pressure in the cylinder reaches
the (high) pressure in the buffer the outlet valve will open and the pressurized
air in the cylinder can escape into the buffer.
the piston moves outwars again, volume will increase, pressure will drop, outlet
valve will close, inlet valve will open, atmospheric air can enter, ….
as single stage compressor the piston-compressor can create a pressure of about
10 bar. If higher pressures are needed then multi-stage is used where more
pistons will be placed in series.