The wancle engine

The Wankel engine is a form of heat engine which has a rotary piston. In other words, instead of going up and down the Wankle piston rotates in the cylinder. Both cylinder and piston are quite different in shape from those of conventional engines. The Wankle piston is triangular with curved sides and the cylinder is roughly oval in shape. The piston has an inner bore which is linked through an eccentric gear to the output shaft. The other end of the bore is toothed and engaged with a stationary gear fixed to the cylinder end. This arrangement ensures that the piston follows an elliptical path round the cylinder so that the apexes of the piston, which carry gastight seals, are always in contact with the inside surface of the cylinder.

The piston thus forms three crescent-shaped spaces between itself and the cylinder wall, which vary in size as the piston rotates. Fuel enters the cylinder through the inlet port when one of these spaces is increasing in size. The fuel trapped in this section is then compressed by the turning piston and ignited by the sparkling plug. The expanding gases subject the piston to a twisting moment which makes the piston revolve further until the exhaust gases escape through the exhaust port. A fresh charge is then induced into the cylinder. Meanwhile the same process is being repeated in the other two spaces between the piston and the cylinder.

The Wankel engine has many advantages over the reciprocating piston engine. Fewer moving parts are necessary because it produces a rotary movement without using a connecting rod and a crankshaft. Because of this rotary movement it has no vibration. In addition it has no valves, it is smaller and lighter than conventional engines of the same power, and it runs economically on diesel and several other fuels.

1. Translate the following international words.

Oval, eccentric, stationary, elliptical, vibration, economically, diesel

1. Speak about: a) a form of cylinder and piston; b) the motion of the piston in the cylinder.
2. Set the following sentences according to the working process of that engine.

- The expanding gases make the piston revolve further.

- The fuel is ignited by the spark plug.

- Fuel enters the cylinder through the inlet port.

- The exhaust gases are expelled through the exhaust port.

- The fuel is compressed by the rotating piston.

1. Compare the characteristics of the conventional engine and the rotary engine. Fill in the table.

6. Speak about the Wankle Engine using the following plan:

a) The design features.

b) The principle of Operation.

b) Advantages (and disadvantages).