There are many kinds of air compressors, and different types have different working principles. 

1. The working principle of piston compressor

Piston compressor is one of the earliest compressor designs, but it is still the most versatile and highly efficient compressor. The piston compressor moves the piston forward in the cylinder through connecting rods and crankshafts. If only one side of the piston is compressed, it is called single acting. If the upper and lower sides of the piston are used, it is called double acting. Piston compressors are widely used. It can compress the air and compress the gas, so it hardly needs any modification. Piston compressors are the only type of compressor that compresses air and gas to high pressures for applications such as breathing air compressors. Piston compressor configurations can range from single cylinder configurations, which are suitable for low pressure and small capacity applications, to multistage configurations capable of compressing of high pressure. In the multistage compressor, the air is compressed in different stages, and the pressure is increased step by step. 

2. Working principle of rotary screw air compressor

The screw type air compressor is a positive displacement compressor, and its piston is in the form of screw. The main components of the screw compression element are the convex rotor and the concave rotor. The two rotors move close to each other, making the distance between them and the volume in cavity decreases gradually. The screw pressure ratio depends on the length and shape of the screw and the shape of the exhaust port. Screw elements are not equipped with any valves, and there is no mechanical force can cause imbalance. Therefore, it can work at high axial speed, and can accommodate both large flow and small external dimensions.