An internal combustion engine comprises an engine block defining a cylinder having a longitudinal axis A. A piston is arranged slidably within the cylinder and an impeller is arranged at one end of the cylinder. The impeller is rotatably mounted on a shaft, which extends out of the cylinder and which is driven in rotation by rotation of the impeller. The engine further comprises an anti-rotation formation to prevent the piston rotating about a longitudinal axis of the cylinder and a swirl-inducing vane arranged on the face of the piston which faces the end of the cylinder at which the impeller is arranged. Combustion gas generated by combustion of a fuel in the cylinder between the piston and the impeller is caused to swirl by reaction with the swirl-inducing vane and the swirling combustion gases, in turn, cause the impeller to rotate.

An internal combustion engine has a chamber that has a longitudinal centerline, inlet valving operable to admit constituents of a combustible mixture into the chamber for combustion in the chamber to provide a pressure increase in the chamber and outlet valving operable to release an outflow of liquid from the chamber under an influence of the pressure increase. An annular flow passage is defined in the chamber to conduct liquid towards the outlet valving and cause spiraling of the liquid in the flow passage by which a rotatable part exposed to the spiraling flow is caused to rotate. An electrical generator disposed externally of the chamber is driven by rotation of the rotatable part.

An internal combustion engine has a chamber that has a longitudinal centerline, inlet valving operable to admit constituents of a combustible mixture into the chamber for combustion in the chamber to provide a pressure increase in the chamber and outlet valving operable to release an outflow of liquid from the chamber under an influence of the pressure increase. An annular flow passage is defined in the chamber to conduct liquid towards the outlet valving and cause spiraling of the liquid in the flow passage by which a rotatable part exposed to the spiraling flow is caused to rotate. An electrical generator disposed externally of the chamber is driven by rotation of the rotatable part.