Batch Pre-expander Machine is a machine that uses the principle of outputting mechanical work to reduce the temperature of the gas when the compressed gas is expanded and depressurized to obtain cooling capacity. Batch Pre-expander Machine is often used in cryogenic equipment. The Batch Pre-expander Machine is divided into two categories: Piston Batch Pre-expander Machine and Turbine Batch Pre-expander Machine according to the movement form and structure. Piston Batch Pre-expander Machine is mainly suitable for small and medium high, medium pressure and deep low temperature equipment with high pressure ratio and small flow.

The main work of the Batch Pre-expander Machine is done in the nozzle and the impeller. When the high-speed, low-temperature gas passes through the impeller channel, the gas speed drops rapidly due to the high-speed rotation of the impeller. At the same time, when the gas flows in the increasingly larger channel, the internal energy of the gas is reduced due to the decrease of pressure and speed, and the gas temperature is further greatly reduced, so as to achieve the purpose of cooling and refrigeration. Due to the rapid rotation of the impeller of the Batch Pre-expander Machine, the compressor impeller on the other end of the same axis as the impeller of the Batch Pre-expander Machine is driven to rotate, and the rotation of the compressor impeller compresses the gas passing through the impeller of the supercharger. It not only compresses the gas, utilizes the power from the Batch Pre-expander Machine, but also controls the speed of the Batch Pre-expander Machine.