A wankel engine is a combination of both conventional IC engine and gas turbine. It is basically a rotary engine in which the cyclic performance of IC engine is taken. This engine operates on Otto cycle.

Working of Wankel engine:

The engine consists of 3-sided rotor which rotates inside a stator of some specific shape. The rotor has three sides and these sides are given specific geometrical shape as shown in fig 6.1. the stator is a two lobe type having an epitrochoid curve derived from a family of curves based upon the path of a point on the radius of a circle which rolls on the outside a fixed circle.

The rotor is provided within internal gear or annulus rotates around a smaller fixed pinion gear. The rotor revolves about the geometric centre of the engine casing and also rotates about its ownscentre at 1/3 of the angular velocity of the main shaft. As three sided rotor is used, a gear ratio 1:3 between the main shaft and the rotor is necessary. For this purpose an epicyclic gearing is used.

Like conventional 4-stroke engine IC engines, the four phases of wankel engine are suction, compression, expansion, and exhaust. The four positions of the rotor with respect to casing are shown in fig 6.2 to illustrate working of Wankel engine.