WORKING PRINCIPLE OF WANKEL ENGINE

WORKING  PRINCIPLE OF WANKEL ENGINE

The Wankel engine is a type of internal combustion engine. It uses rotors instead of pistons inside its combustion chamber. eccentric rotary design to convert pressure into rotating motion. Over the commonly used reciprocating piston designs, the Wankel engine delivers advantages of: simplicity, smoothness, compactness, high revolutions per minute, and a high power-to-weight ratio. The engine is commonly referred to as a rotary engine

Wankel developed the Wankel-type rotary engine in 1957

The rotary engine is composed of a cocoon-shaped housing and a triangular-shaped rotor inside of it. The space between the rotor and the housing wall provides the chamber for internal combustion and the pressure of expanding gases serves to turn the rotor. In order to make the rotary engine work as an internal combustion engine, the four processes of intake, compression, combustion and exhaust had to be performed in succession in the working chamber. Suppose that the triangularshaped rotor were concentrically placed inside a true circular housing. In this case, the working chamber would not vary in volume as the rotor turned inside the housing. Even if the fuel-air mixture were ignited there, the expansion pressure of combustion gas would merely work toward the center of the rotor and would not result in rotation. That was why the inner periphery of the housing was contoured as a trochoid-shape and assembled with the rotor installed on an eccentric shaft. The working chamber changes in volume twice per revolution, thus the four processes of the internal combustion engine could be achieved. With the Wankel-type rotary engine, the rotor’s apices follow the oval contour of the inner periphery of the engine casing while remaining in contact with the gear on the output shaft which is also in eccentric orbit around the center point of the engine casing. A phase gear mechanism dictates the orbit of the triangular rotor. The phase gear consists of an inner-toothed gear ring fixed on the inside of the rotor and an outer-toothed gear fixed on an eccentric shaft. If the rotor gear were to have 30 teeth inside it, the shaft gear would have 20 teeth on its perimeter so the gear ratio is 3:2. Due to this gear ratio, the rate of turning speed between the rotor and the shaft is defined as 1:3. The rotor has a longer rotation period than the eccentric shaft. The rotor rotates one turn while the eccentric shaft rotates three turns. With the engine running at 3000rpm, the rotor will run at a mere 1000rpm.

Advantages

·         A far higher power to weight ratio than a piston engine

·         It is approximately one third of the weight of a piston engine of equivalent power output

·         It is approximately one third of the size of a piston engine of equivalent power output.