Air conditioning system, compression system with gas secondary injection and judgment and control method thereof

A compression system with gas secondary injection, comprising a compressor, a gas secondary injection pipeline and a gas secondary injection valve disposed on the gas secondary injection pipeline, wherein, a first pressure detecting device and a first temperature detecting device are disposed at an inlet port of the gas secondary injection valve, and a second temperature detecting device is disposed at an outlet port of the gas secondary injection valve, the inlet port and the outlet port of the gas secondary injection valve are determined based on flowing direction of refrigerant in the gas secondary injection pipeline,

• the compression system further comprising a second pressure detecting device and a third temperature detecting device disposed on an air discharge pipeline of the compressor, wherein whether or not liquid is carried in the secondary injected gas is determined based on a superheat degree of the secondary injected gas, a temperature difference of the secondary injected gas before and after the gas secondary injection valve and a superheat degree of the discharged air;
• and wherein the superheat degree of the secondary injected gas is detected and calculated by the first pressure detecting device and the first temperature detecting device, the temperature difference is detected and calculated by the first temperature detecting device and the second temperature detecting device, and the superheat degree of the discharged air is detected and calculated by the second pressure detecting device and the third temperature detecting device.