A novel rotational internal combustion engine has been investigated in this study. No eccentric rotational component is used in this engine, resulting in vibration-free operation. The engine consists of rotor casing and two types of rotor; cycloid rotor and trochoid rotor. The shape of the cycloid rotor is characterized by epicycloid surface, and the trochoid rotor also superior-epitrochoid surface. In this paper, first, the typical configuration was shown. Next, a procedure for designing the rotors were described in detail. Furthermore the design drawing and appearance of the prototype engine were given. Its cyclic behavior, the time variations of the chamber volume and the estimated pressure were also indicated. Additionally the flame behavior in the working volume of the prototype engine driven in motoring condition, was presented. Finally the compactness and S/V ratio of the engine was investigated.
