View the video above to learn about the Wankel rotary engine and how it works.

History

The Wankel rotary engine was born out of a desire to make a lighter combustion engine that could directly produce rotational motion as opposed to indirectly as with the reciprocal motion in a cylinder engine. It was invented by a German engineer named Felix Wankel in 1951, with the first prototype built in 1957. Throughout his life, Felix Wankel continued to refine the engine that bears his name, heading his own research company at Lindau in Germany. He died in 1988.

Advantages

• Less moving parts and Vibration -  only the triangular rotors and the eccentric shaft rotate on a Wankel engine whereas a there  are at least 40 moving parts on the simplest of piston engines.
• Compact & light-weight -  with less parts and more open space the Wankel engine is easier to maintain than a piston engine of the same horse power.
• Flexible fuel usage & Direct Injection – Because combustion energy is more directly turned into rotary motion the engine can run on almost any combustible gas or fluid such as propane, hydrogen, peanut oils.  Because combustion happens in a moving space, air and fuel are more evenly mixed.
• Power through failure -  Wankel engines are not prone to seizing when failing like piston engines usually do.  Instead, they provide decreasing amounts of power in their failure stages, even with loss of compression, oil, leakage or cooling failure. This makes them ideal for airplanes where a crippled engine is better than a seized one.

Disadvantages

• Sealing & Lowered Efficiency -  The main disadvantage of the Wankel engine is problematic sealing. Each of the 3 chambers formed throughout the cycle of the rotor have to be entirely separated. Piston rings are used to achieve that in reciprocating engines. Unfortunately, due to the expansion of the materials, the sealing is far from perfect. This leads to decrease in overall engine efficiency.
• Slow Combustion & Pollution -  Another problem is slow combustion. Although the air & fuel are better mixed, the combustion chamber is big and, more importantly “moving”. This prevents the flame from reaching chamber trailing side – especially at high rotor speeds. The exhaust is therefore, enriched with unburned mixture and carbon monoxide. It’s level of pollution are so high that it is very hard to meet, for instance, US emissions regulations. Also, in general, Wankel engines consume more fuel than regular piston engines though delivering more power. However, with the Mazda 26B/renesis engine a 3-spark plug ignition system is used.

Future

The advantages of the Wankel engine makes it popular for home-built aircraft and ultralights with several companies using them for small aircraft such as the Rotapower Engine used by Moller Internationals Skycar. While Mazda continues to be the only manufacturer to use the Wankel in production automobiles in large numbers, their continued development of the Wankel has yielded appreciable improvements in efficiency, emission, and fuel consumption, reducing the few disadvantages of the engine.