The Wankel engine is an internal combustion engine in which one or more triangular-shaped circular pistons convert the pressure generated during combustion of the fuel-air mixture into kinetic energy. The gas volumes transported in the spaces between the rotor flanks and the housing pass alternately through four different phases: a) intake phase; b) compression phase; c) expansion phase; and d) exhaust phase. These stages are referred to as strokes and make the Wankel engine a four-stroke engine, similar to the Otto reciprocating engine.
During this phase, a pressure drop caused by the movement of the rotor draws the fuel-air mixture into the cold chamber. The rotation of the rotor forces the mixture into the second stroke of the cycle.
As the piston continues to rotate, the volume enclosed between the rotor and housing decreases, compressing the fuel-air mixture.
When the mixture volume is minimal, one or more spark plugs initiate combustion, resulting in a rapid increase in pressure and temperature. The sudden expansion of the now gaseous fuel mixture further rotates the rotor and the eccentric.
The expanding exhaust gases leave the chamber through the exhaust port opened in the fourth cycle. As the piston continues to rotate, the exhaust port closes while the inlet port opens again to begin a new cycle.