A rotating liquid ring rotating casing gas turbine (10) has at least one liquid ring rotating casing (13) having an eccentrically mounted impeller (11) adapted to rotate within a surrounding liquid ring (14) so as to form chambers (15) of successively increasing volume between adjacent vanes of the impeller. A working fluid formed by high pressure gas is injected into the impeller where the chambers are narrow via a fluid inlet (19) within a static axial bore (23) of the impeller so as to rotate the impeller and in so doing the gas expands isentropically. A fluid outlet (20) within the static axial bore of the impeller and fluidly separated from the fluid inlet allows the working fluid to escape at low pressure and low temperature.