The first rotary engines were primarily used for aircraft during World War I, but the design was abandoned due to flaws and inefficiencies. In 1954, German engineer Felix Wankel invented a new ...

You are correct that significantly more well-known Wankel design rotary engines are of the “flying Dorito” type that utilizes a triangular rotor that compresses and exhausts fuel and air ...

Fuel and air are pulled in through the intake ... However, due to the design of the rotary engine, there is no way to keep the oil lubricating the seals out of the combustion chamber.

More energy efficiency means four, rather than six, open rotor engines Airbus’ latest hydrogen airliner concept features four, rather than six, open rotor engines.