A rotary steam engine includes: a stator mechanism including two stators forming a track therebetween; a rotor rotatably arranged between the stators and including cylinders and perorations open on an outer surface of the rotor and communicating with the cylinders; a mandrel disposed through the stator mechanism and the rotor; pistons respectively received in the cylinders and respectively including piston shafts movable along the track, an engine lubricating system being formed between the cylinders, pistons and stators; and gas covers radially movable, resiliently disposed on the stator mechanism and covered on the rotor; wherein when a gas injection space between the gas cover and the rotor communicating with the perorations, steam can flow to enter the cylinders to drive the pistons; wherein when the gas injection space is not in communication with the perorations, the pistons move to discharge steam in the cylinders via the perorations.

A structural arrangement for an internal combustion engine and/or star shaped air compressor, without a crankshaft and connecting rods and with one or more surrounded pistons, being able to use any fuels in the case of the engine, liquid or gaseous including hydrogen and obtain high thermodynamic efficiency. The engine and/or air compressor has an arrangement that makes it possible to transmit linear movement into circular movement by means of a ring together with an eccentric and with a coupling structure, The structure joins the pistons to the ring, which can be polygonal in the case of the use of at least three pistons or welded in the case of one or two pistons.