Rotary piston motor – wankelmotor

The rotary piston engine belongs to the group of rotary piston engines named after its inventor Felix Wankel. There is another principle and that is the rotary engine, but it has not become established in practice. In the case of rotary piston motors, only the principle of the Wankel motor has been put into practice, although there are considerably more patents for other types of motors.

The rotary piston engine has a significantly different design than a reciprocating piston engine. Inside is an arched-triangular rotary piston that rotates on its own axis. This takes over simultaneously both the function of the power output and the control of the gas change. There is no crankshaft, but an eccentric shaft, which has a very low imbalance and can be precisely balanced by weights. Therefore, rotary piston engines run much more quietly than "conventional" reciprocating piston engines.

How the rotary piston motor works


rotary piston motor - wankelmotor


The rotary piston engine also works on the four-stroke principle, but in a different form. The cylinder interior consists of a triangular piston with rounded sides, intake and exhaust valves are located directly next to each other. The piston runs in an oval cavity. The four cycles occur during one full revolution of the piston.
In the first cycle, a gas mixture flows through the inlet valve. This is transported further in the second cycle and compressed further and further by a decreasing volume of the free space.
In the third stroke, it is then ignited by one or two spark plugs and in the fourth stroke, the exhaust gas is discharged through the exhaust valve.
The energy released by the rotary engine is directly converted into a rotary motion of the eccentric shaft.

Inlets and outlets of the rotary engine

The inlets and outlets can be realized by two variants, either by circumferential or by side inlet and outlet.

Reception inlet

With the circumferential inlet, a large cross-section can be achieved, thus a higher output is obtained. This method is mainly used in motor sports. However, it can come to sliding jerks, with racing cars no problem, with most normal passenger cars for comfort reasons more or less unthinkable.

Side inlet and outlet

This problem does not occur with the side inlet and outlet, but the circumference of the openings is significantly smaller and thus only slightly poorer performance can be achieved.

Lubrication and cooling of the Wankel engine

The engine bearings are lubricated by pressure lubrication, just as in the four-stroke reciprocating engine, but it is also possible to use mixture lubrication.
The cooling of the casing is of great importance, as the work cycles always happen in the same place, hotspots occur, i.e. places on the casing that are significantly warmer. The cooling is to provide for an even distribution of the temperature, so that the mixture does not ignite itself, in addition the material load sinks so. Water, fresh air or gas mixture cooling is used to cool the individual elements accordingly.

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