Abstract: An engine (1) comprises a compressed gas source (3) and a fluid circuit connected to an output of the compressed gas source such that compressed gas can be driven through the circuit by the compressed gas source. The output of the compressed gas source is connected, through the fluid circuit, to a turbine component (5) connected to a rotating shaft (9) that acts as the output of the engine in use. A heat exchanger (13) receives fluid in the circuit that has passed through the turbine component (5) and is arranged to reduce the temperature and pressure of the fluid. The turbine component (5) comprises a boundary layer turbine comprising a plurality of axially aligned discs (51), wherein each disc comprises an outlet vent (53) arranged towards the centre of the disc.

Abstract: An engine comprises a compressor and a closed fluid circuit connected to the input and output of the compressor such that compressed gas can be driven through the circuit by the compressor. The output of the compressor is connected, through the fluid circuit, to a turbine component comprising at least one set of turbine blades connected to a rotating shaft that acts as the output of the engine in use. A condenser receives fluid in the circuit that has passed through the turbine component and is arranged to reduce the temperature and pressure of the compressed gas, the outlet of the condenser being connected to the inlet of the compressor.