Rotary engines (also known as Wankel engines and Wankel rotary engines) are quite different from piston or "reciprocating" engines. One of the distinguishing features is that they don't need ...

In a rotary engine the typical Otto cycle takes place in an oval-shaped chamber in which a triangular rotor rotates, effectively taking the place of the pistons in a traditional engine.

the Avadi engine is connected to a central planetary gear, rotating a shaft (like a rotary) that then sends power outward.