Viper jet engine AFRC

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Unlike piston engines, jet engines burn air and fuel at an almost constant pressure. One of the main issues with piston engines is that too much heat, caused particularly by excessively lean mixtures can build up heat. This, together with the high pressure burn in the cylinders can cause something called detonation which can destroy or damage the cylinders. The combustion chambers of a jet engine can burn the fuel and air at the perfect stoichiometric ratio (15:1) without causing any damage. But the turbines in the back are not very fond of higher temperatures. So, the air that comes in for combustion is mechanically controlled to lean the mixture. The combustion chamber of jet engines are designed in such a way that only a very small part of the air that is engulfed by the engine is actually subjected to full combustion. This accounts for about 20% of air. The other 80% of air is mainly used to cool the chamber with some of them introduced into the chamber through holes drilled in the skin of the combustor. The reintroduced air leans the mixture and reduces the temperature of the burn before the air is passed on to the turbines.The air flow control through jet engines is purely mechanical. If you are interested to know, jet engines usually have a air to fuel ratio of about 130:1.