PURPOSE: To improve energy efficiency, by correspondingly providing pistons to the periphery of a housing case, in which an impeller is housed, and applying exhaust pressure to rotate the impeller.

CONSTITUTION: Cylinders 3 are correspondingly provided to the periphery of a housing case 1 in which an impeller 2 is housed. A mixture is sucked by the cylinders 3 and fed to the upper cylinder while being compressed, if the mixture is explosively ignited by a spark plug 18, exhaust holes 8 and 9 are opened to apply exhaust pressure from an exhaust window 10 to rotate the impeller. During operation, exhaust is always sealed to the inside of the housing case so as to obtain fixed pressure. In short, explosive force is applied to once sealed high pressure exhaust gas and to the impeller, and efficiency of a piston and turbine can be increased.