Conventional air compressors can be classified into reciprocating piston compressors, screw type air compressors and centrifugal machines according to the working principle. Reciprocating piston compressor is driven by the motor to drive the connecting rod and piston rod to make the piston do reciprocating motion in the cylinder to realize the process of suction, compression and exhaust. At present, reciprocating piston compressor due to vibration and noise defects are gradually replaced by screw compressor in many applications.
Centrifugal compressor is through the centrifugal impeller high-speed rotation of the air into the back end of the diffuser, and then by the diffuser to expand the pressure to achieve the air compression process. Centrifugal compressors are usually used for larger volumes of air due to their design principle.
The screw compressor is the more common compressor at present. Screw compressor is the working volume for the rotary movement of the volumetric gas compressor, in the compressor parallel configuration of a pair of mutually meshing rotor, through the rotation of the rotor and the change in clearance to achieve the process of air intake, compression, exhaust. Since the compression process generates a large amount of heat, lubricating oil is constantly injected in the cavity where the rotor is located to lubricate the rotor and cool the compressed air. With the development of technology, a considerable number of brands of oil-free machines have emerged one after another. Therefore, from the process can be divided into oiled and oil-free compressors. Reciprocating piston machines, centrifugal machines and oil-free screw machines are all oil-free compressors. As mentioned earlier, compressors in the food industry are often used in the process of direct or indirect contact with food such as material liquid conveying, ingredient mixing or filling blowing, so it is often recommended to use oil-free compressed air in the food and beverage industry to reduce the risk of contamination of food and beverages exposed to compressed air.
