Air compressors (also known as air pumps) are the core of air source devices. They convert the mechanical energy of the prime mover into gas pressure energy and are the pressure-generating devices for compressed air. The following are the working principles of several common types of air compressors:
Screw air compressor is a type of positive displacement compressor that compresses air through a pair of intermeshing helical rotors. The male rotor (or male screw) is connected to the prime mover and drives the female rotor (or female screw) to rotate. The ball bearings at the exhaust end of the rotors provide axial positioning for the rotors and bear the axial forces in the compressor.
The compressor body has suction and exhaust ports at both ends. As the rotor rotates, each pair of meshing teeth successively completes the same working cycle. The gas sealed in the volume between the teeth is compressed as the volume occupied by the teeth decreases and the pressure rises. When the volume between the teeth communicates with the exhaust port, the exhaust process begins.
The single screw air compressor compresses gas through the interactive rotation of two star wheels, which are symmetrically arranged and divide the space into two parts, each compressing the gas within its own part.
Piston air compressors
Piston air compressors use a crankshaft connecting rod mechanism to convert the rotational motion of the prime mover into the linear reciprocating motion of the piston, and through the automatic opening and closing of the intake and exhaust valves, they perform the intake, compression and discharge of gas. Due to the use of a relatively outdated method, the gas contains a large amount of engine oil and is not suitable for industries with high requirements for air purity.
The sliding vane air compressor
The sliding vane compressor adopts traditional technology and is directly driven at a relatively low speed. There are several slots cut along the length of the rotor, in which sliding vanes that can slide on an oil film are inserted. The rotor rotates in the stator of the cylinder. Centrifugal force throws the vanes out of the slots, forming individual compression chambers. As the rotor rotates, the volume of the compression chambers continuously decreases, and the air pressure continuously increases.
Due to the use of a relatively backward method, the gas will contain a large amount of engine oil and needs to be filtered by an oil and gas separator before it can be used. It is not suitable for industries with high requirements for gas purity.
The working principle of a centrifugal compressor is that when air enters the machine, the impeller rotates rapidly, and the gas then enters the diffuser, gradually completing the compression. Its advantages include energy conservation, large exhaust volume, low failure rate, low operating cost, and oil-free compressed air.
Through the introduction of these working principles, we can better understand the operation mode of air compressors and choose the air compressor that suits our own needs.
