Axially protruding, centrally cooled pistons rotate around a stationary primary rotation axis within a cylindrical piston chamber. The pistons are held on both of their axial ends by concentrically rotating crank disks as intertwined rotary assemblies. On the outside of each crank disk is hinged a driving piston that slides in a radial guide of two flywheels oppositely axially adjacent the piston chamber and crank disks. The flywheels rotate around an offset secondary rotation axis. As a result. The pistons are individually and oppositely alternately accelerated and decelerated. Volumes between them angularly expand and contract. Inlets and outlets are positioned along the piston chamber circumference in correspondence with expansion and contraction phases of the rotating volumes. A low number of moving parts, area sealed volumes, no valves, no dead volume, balanced mass forces, vibration free rotation and short force transmission paths provide for lightweight construction and high rotational speeds.