An ignition transformer includes a primary winding and a secondary winding and are electromagnetically coupled to each other. A battery is connected to a first end of the primary winding. A switch connected to a second end of the primary winding is turned on or off in response to an ignition signal. A saturable reactor includes a saturable core and includes a first winding, and a second winding the first and second windings electromagnetically coupled to each other. A first end of the first winding is connected to a first end of the second winding. A second end of the first winding is connected to the ignition plug. A reset circuit applies a reset voltage to the first and second ends of the second winding. The reset voltage is a voltage to switch a magnetization status of the saturable core between a saturated state and an unsaturated state.

An ignition device includes a spark plug and an ignition coil. The spark plug is attached to a cylinder head such that a center electrode and a ground electrode project into a combustion chamber. In an internal combustion engine, airflow is generated in a predetermined direction to the spark plug during a compression step. The ignition coil has a primary coil and a secondary coil. An output voltage of the secondary coil after interruption of energization of the primary coil is restricted to a predetermined voltage or less. The ground electrode has a leg portion extending from a housing of the spark plug and an opposing portion that extends in a direction intersecting with the leg portion and forms a gap by opposing the center electrode. The leg portion is attached to a position further upstream than the gap in a flow direction of the airflow during the compression step.

A rotating piston internal combustion engine including a housing which includes a housing wall that forms an operating chamber, and in which housing a rotatable rotating piston is arranged which extends through the operating chamber and moves edges of the rotating piston along the housing wall that forms a running surface, wherein a portion of the operating chamber functions as a combustion chamber together with an associated combustion chamber wall for igniting a fuel that is arranged in the operating chamber, characterized in that at least one microwave window is arranged in the combustion chamber wall, wherein a device for injecting microwave energy in a form of microwaves into the combustion chamber of the operating chamber is arranged at a side of the microwave window that is oriented away from the combustion chamber.