Principle

Gas entering via the suction port is conveyed into the impeller casing AB and trapped in the space between two impeller blades. As the impeller rotates-eccentrically to the liquid ring and casing - the volume between the blades increases creating vacuum. As the cycle progresses towards the discharge port the volume decreases as the liquid ring creates compression.
 This compression continues until the gas in discharged through the discharge port CD. A small make-up continuously. The make-up liquid also maintains the liquid ring and absorbs the heat energy of compression.
 I = Suction phase
 II = Compression phase