JET ENGINES
Turbofan Engine
Most of today's airliners are powered by turbofans. A turbofan engine was developed for aiplanes at higher speeds and higher altitudes. Most of the air flow is on the outside of the engine which allows increased thrust at low speeds. Then there are two streams of air that flow through a large internal propellor or duct fan. One of the air streams travels through all the components of the engine. The other stream is mixed with the main exhaust stream after it accelerates through the nozzle. These different inlets for air are like a bypass system that increases thrust without increasing fuel consumption. The figure below illustrates the design of a low-bypass and high-bypass turbofan engine.
