This type of compressor is called a centrifugal compressor because it continuously draws in refrigerant vapor during operation and continuously throws it out radially.
Based on the number of impellers installed in the compressor, it is divided into single-stage and multi-stage types. If there is only one impeller, it is called a single-stage centrifugal compressor; if it consists of several impellers in series, it is called a multi-stage centrifugal compressor. In air conditioning systems, since the pressure increase is relatively small, single-stage compressors are generally used. Centrifugal refrigeration compressors used in other applications are mostly multi-stage. The structure of a single-stage centrifugal refrigeration compressor mainly consists of an impeller, a diffuser, and a volute casing.
During operation, the refrigerant vapor enters the suction chamber axially through the suction port. The guide vanes in the suction chamber guide the refrigerant vapor from the evaporator (or intercooler) to uniformly enter the high-speed rotating impeller (the impeller is also called a rotor, and it is an important component of the centrifugal refrigeration compressor because only through the impeller can energy be transferred to the gas). Under the action of the blades, the gas rotates at high speed with the impeller, and at the same time, due to the centrifugal force, it undergoes diffusive flow in the blade channels, thus increasing both the pressure and velocity of the gas.
The gas exiting the impeller then enters the diffuser, which has a gradually increasing cross-sectional area (because the gas has a high velocity when it flows out of the impeller, the diffuser partially converts kinetic energy into pressure energy, thereby increasing the pressure of the gas). As the gas flows through the diffuser, its velocity decreases, while its pressure further increases. After passing through the diffuser, the gas collects in the volute casing and is then guided through the exhaust port to the intercooler or condenser.