Abstract: A liquid ring machine comprises an outer drum having a cylindrical outer wall 1 surrounding a central axis 2, a vaned rotor 3 rotatable within the drum about an axis 4 which is parallel to, but offset from, the central axis 2 of the drum, and a liquid disposed within the drum such that, when the rotor 3 rotates at a sufficient speed, the liquid forms a rotating ring 5 adjacent the outer wall 1 of the drum. The ends of the vanes 6 on the rotor are maintained in contact with the liquid during such rotation so that a series of chambers 8 is formed between the vanes 6 of the rotor 3. The chambers 8 are bounded at the outer periphery by the liquid ring 5 and vary in volume in dependence on the angular orientation of the rotor 3 in view of the offset between the axis 4 of rotation of the rotor and the central axis 2 of the drum. An inlet 23 and an outlet 25 are provided by means of which a working fluid is introduced into, and discharged from, each of the chambers 8 at appropriate angular positions of the rotor 3.