kiertopyörä

Kiertopyörä, often translated as "rotary engine" or "Wankel engine," is a type of internal combustion engine that uses a rotor instead of pistons. Instead of reciprocating motion, the engine converts the pressure of combustion into rotational motion directly. The basic design features a triangular rotor that rotates eccentrically within an epitrochoid-shaped housing.

The cycle of operation in a kiertopyörä engine is similar to that of a conventional four-stroke piston engine, consisting of intake, compression, power, and exhaust phases. However, these phases occur simultaneously in different parts of the housing as the rotor turns. The rotor's three apexes maintain seals against the housing's walls, creating three distinct working chambers.

Kiertopyörä engines are known for their compact size, light weight, and smooth operation due to the absence of reciprocating parts. They also tend to have fewer moving parts compared to piston engines. However, they can present challenges related to fuel efficiency, emissions control, and apex seal wear. Despite these drawbacks, the unique characteristics of the kiertopyörä engine have led to its use in various applications, most notably in some sports cars and motorcycles. The design was invented by Felix Wankel and first put into production by NSU in the 1960s.