Wankel Rotary Combustion Engines

The Wankel engine is a type of internal combustion engine using an 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, though this name applies also to other completely different designs. Its four-stroke cycle occurs in a moving combustion chamber between the inside of an oval-like epitrochoid-shaped housing and a rotor that is similar in shape to a Reuleaux triangle with sides that are somewhat flatter. Wankel rotary engines have been installed in a variety of vehicles and devices including: automobiles, motorcycles, racing cars, aircraft, go-karts, jet skis, snowmobiles, chain saws, and auxiliary power units.

Working of the Wankel engine is based upon four phase principle.( here phase word is for stroke of reciprocating engine). The three lobed rotor engine is driven in a casing( eccentrically) in a casing in such a way so between the rotor and the casing three separate volumes are trapped.Various processes in sequences are performed by these three volumes such as (1)Induction (2)Compression (3) Combustion (4)Expansion(5)Exhaust. For each revolution of rotor there are three power impulses. And at three times the speed of rotor the eccentric and output shaft rotates , for each revolution (of output shaft of single bank rotary engine) there is only one power impulse. This engine consist of various parts:Rotor: There are mainly three lobed. Eccentric(or output shaft) : there is a output shaft with integeral eccentric. There is no connecting rod is needed because the rotor rotates directly on the eccentric shaft. Torque is transmitted to shaft through eccentric. External and Internal timing gear: Phase relationship between the rotation of rotor and the eccentric shaft is maintained by the external and internal timing gear. Orbital motion of the motor is also controlled by this timing gea

Yanmar Diesel, a Japanese engine maker, was pioneer in introducing reed valves for flow control at intake ports of its small Wankel engines, showing an improvement in torque and performances at low rpm and under partial load of engine. Toyota, that discovered the benefits of injecting fresh air into the Wankel RCE exhaust port, also used a reed valve in the prototypes where they tested the SCRE concept (Stratified Charge Rotary Engine), however, this kind of intake port arrangement never reached the production line for automobile size RCEs. According to David W. Garside, who developed the Norton line of Wankel-powered motorcycles, data from other RCE producers pointed that reed valves do improve performances at low rpm and under partial load, but reduce the high speed power output of the engine, a feature considered non-convenient for motorcycle engines.


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