Abstract: An internal combustion engine designed to convert thermal energy into mechanical energy according to the same general principle employed in conventional reciprocating piston-and-cylinder combustion engines, wherein the equivalent of the cylinder of the conventional engine is replaced by two series of chambers, a first series and a second series, each series of chambers being separately disposed in a circumferential arrangement about a common axis and separated in space one from another and wherein the conventional piston is replaced by one or more vanes, said vanes being adapted to form sealing contact with the chambers and the two series of chambers being connected by one or more transfer ports wherein air is compressed in one series of chambers and combustion gasses are exhausted by means of the other series of chambers.