Stirling meets Wankel

I have already talked about the Wankel engine. The beauty of one rotor spinning in the same direction all the time. The Wankel engine normally works by combustion though. This makes a quite inefficient use of fuel as the fuel doesn't burn optimally during combustion. The Wankel construction further worsens this by the shape of the combustion chamber, making Wankel engines consume even more fuel than their crank engine counterparts.

But there exist a different type of engine that makes much better use of the fuel. I am thinking about the Stirling engine or air engine as it was called by Stirling himself when he invented it 1816. This engine works by converting a temperature difference into rotational enegy. The basic principle is that a gas that is heated expands and a gas that is compressed increases in temperature. One part of the engine is hot and the other cold. Gas is expanded in the hot part and decompressed in the cold part. This construction usually make Stirling engines quite large as they need big cooling radiators.

The Wankel engine's drawback regarding fuel consumption and the bulkiness of the Stirling can maybe be overcome by combining them. We may not see Stirling engines in cars as the sole provider of energy but it could be used when acceleration is not needed. During constant speed on the highway for example. Stirlings have been used to great success in submarines where their quiet running and less need of oxygen is great benefits.

Some work has been done to fuse these two designs together. The QuasiTurbine and the Trochilic engine are good examples how the future may look like. I think there is much more to do in this field.