Air Compressor :
• A mechanically operated machine that rises the fluid pressure by reducing its volume is called a Compressor.
• If the compressor uses gas as a working fluid, it is called a gas compressor.
• If the compressor uses air as a working fluid, it is called an air compressor.
• So, an air compressor is a device which sucks in air from atmosphere, increases its pressure by compressing it and deliver to a storage level.
Classification of Air Compressors:
Reciprocating Air Compressor :
• Reciprocating of a machine means moving backward and forward (or upward & downward) in a straight line.
• It is a famous type of air compressor which comes under the category of positive displacement compressor.
• It is called a positive displacement air compressor because air is first sucked in a chamber and then compression is achieved by decreasing the area of the chamber by using piston which does reciprocating motion.
• It compresses air due to the upward and downward motion of the piston therefore it is also called a piston compressor.
Main Parts of Reciprocating Air Compressor :
Piston: It does reciprocating motion in the cylinder and responsible for the compression of the air.
Cylinder: It is a chamber in which air is compressed.
Connection Rod: It connects the piston and crankshaft.
Crankshaft: It is connected to the shaft of electric motor. And transfers its rotary motion to the piston.
Suction valve: The air is sucked through suction valve when piston moves to BDC.
Discharge valve: The compressed air is discharged through the discharge valve to the storage tank.
• RAC is either powered by electric motor, diesel or gas engines.
• As power is ON, the electric motor starts rotating and also rotates the crankshaft attached to it.
The piston starts doing to and fro motion inside the cylinder.
During downward stroke, ⬇️
• Both the valves are closed.
• The piston moves towards BDC and the pressure inside the cylinder reduces.
• Due to this, the inlet valve opens and the low pressure air is sucked inside the cylinder.
During upward stroke, ⬆️
• The piston moves towards TDC and the pressure of air inside the cylinder increases.
• When the pressure increases above the pressure of discharge valve, the discharge valve opens.
•The compressed air is delivered to an air storage tank, from where it is utilised for further work.
•When the compressed air is delivered, the piston starts its downward stroke and the cycle terrorists during reach revolution of crankshaft.
Single Stage Reciprocating Air Compressor :
In the first stroke, it sucks the air from the atmosphere and in the second stroke it compresses it and deliver it to the storage tank.
Multi Stage Reciprocating Air Compressor :
• Finally the compressed air is stored in a tank.
• There is an intercooler present in between the two cylinders, which is used to cool the air at constant pressure before it is compressed in the second cylinder.
Single Acting Reciprocating Air Compressor :
Double Acting Reciprocating Air Compressor :
• In double acting reciprocating air compressor, both the sides of the piston is used for the compression of the air.
• When suction takes place at one side than compression is taking place at other side.
• Both suction and compression takes place on each stroke of the piston.
