Pistonless rotary engine

A pistonless rotary engine is a kind of engine that works differently from a normal engine. Instead of having pistons move up and down in cylinders, it has a circular shape with grooves cut into it. A big gear called a rotor is connected to this shape and an electric motor or something similar is used to make it spin. As the rotor spins it creates a vacuum inside the engine which sucks in air, compresses it and makes it explode creating energy which is then used to turn the wheels of a car or power something like a generator. This type of engine is usually simpler, lighter and takes up less space than a piston engine, so it is often used in things like airplanes where size and weight are really important.