What is Wankel Engine?

What is Wankel Engine?

Introduction -  This Engine works on ordinary Otto cycle, but differs from the reciprocating I.C. Engine in that the piston in this case undergoes rotary instead of reciprocating motion. This design of Felix Wankel has provided a new challenge to the existing reciprocating engine. This has been developed by N.S.U. of Germany and Curtis Wright Co. of U.S.A. for commercial purposes. However, research is still going on to make it more efficient and to solve the sealing problem more efficiently. Mazda of Japan introduced its Wankel Engine sports car, RX-7 in 1979, which was most successful rotary engine powered car and was sold till 1995. Mazda R-8, a new car from Mazda has rotary engine called Renesis, which is a two rotor engine and has been named the international engine of the year 2003.

Construction -  Fig 1 shows in simplified form the construction of Wankel Engine. Three lobed rotor rotates in the housing, which is epitrochoidal in shape. This combination of housing and rotor shapes ensures that they remain in contact with each other throughout the rotation. Epitrochoid is the locus of a point on the radius of a circle, which rolls along the circumference of circle.

Fig. 1 Wankel Engine

 Instead of valves, there are inlet and exhaust ports. The housing is surrounded by water jackets for cooling. The rotor is having internal teeth cut into the center of one side(Fig. 2) and rotates about the pinion in an epicyclic manner. The pinion is fixed to the housing. However, the rotor is mounted on an output shaft having eccentric lobes, one for each rotor(Fig. 3). Each rotor is mounted over one of these lobes. The lobes provide the eccentricity and act like crankshafts in a reciprocating engine, causing the shaft to spin, thus providing torque.

Fig. 2 Rotor of Wankel Engine

Fig. 3 Output Shaft of Wankel Engine