Liquid ring compressors generally fall into the “blower” category. They are a type of positive displacement pump .
These pumps have an impeller, which is placed off center in a housing. The impeller has a series of cupped blades arranged radially around a hub. The housing has a charge of low viscosity liquid inside, usually water.As the impeller is rotated, the water is forced out to the housing inside diameter (ID) through centrifugal action and forms an air cavity at the center. The interaction of the impeller and the liquid ring forms a series of expanding and contracting cavities. As the cavity volume increases, it draws in air through the suction port. The impeller rotates the cavity to the other side and its volume starts to decrease. As the cavity volume decreases, the air is forced through the discharge port. Some liquid escapes through the discharge port, so a constant source of makeup water must be added to the ring at all times during operation.