In a compressor, work is done by the rotor on the fluid element.
Classification of Fluid Machine
The machines where the mechanical energy from moving parts is transferred to a fluid to increase its stored energy by increasing either its pressure or velocity are known as pumps, compressors, and or blowers.
The machines whose functioning depends essentially on the change of volume of a certain amount of fluid within the machine are known as positive displacement machines.
The rotating element of the machine usually consisting of a number of vanes or blades, is known as a rotor, while the fixed part is known as the stator or impeller.
For turbines, the work is done by the fluid on the rotor, while, in the case of the pump, compressor, fan, or blower, the work is done by the rotor on the fluid element.
Depending upon the main direction of the fluid path in the rotor, the machine is termed a radial flow or axial flow machine.
In a radial flow machine, the main direction of flow in the rotor is radial while in flow of an axial flow machine, it is axial.
For a radial flow turbine, the flow is towards the center of the rotor, while, for pumps and compressors, the flow is away from the center.