How does a Jet Engine work?

Jet Engines are all around us. They can be big or small. Powerful or not so powerful. But they power almost every plane that you will probably ride on in your lifetime. There are many different jet engines out there, powering a range of aircraft, from the 70 seater Bombardier CRJ-700 and the massive Airbus A380 that can seat more than 550 people in 3 classes. Some engine are very big in diameter such as the GE90 that power the Boeing 777-300ER and the much smaller Pratt & Whitney PW6000 that powers some Airbus A318s. So how do these massive jetliners fly? Because of jet engines of course. And here's how they fly:

First off, a jet engine is a gas turbine. But why use a gas turbine instead of a diesel engine? The first reason is because gas turbines are much smaller than diesel engines. A ginormous engine on an airplane would just cause a lot of drag. Also, gas turbines are much lighter, and they have a very good power-to-weight ratio than other engines. For example, if you get 500 N of power for a 50 Kilogram engine, you have a 500 N to 50 Kilograms or 10 N for every kilogram. Gas turbines can achieve a ratio of 56 N for every Kilogram, which is very good. That's the gas turbine advantage.

The most common jet engine is the turbofan. The turbofan has three main parts. First, there's the compressor at the front of the engine. Then, the combustion chambers. And finally, the turbines at the back of the engine. These parts make the airplane capable of flying with massive loads, long distances and it also achieves excellent fuel efficiency.

When you first look at the jet engine, you see these massive titanium fan blades that sucks the air into the engine. This fan can bring more than 2500 lbs of air into the engine per second.
Let's look at the first part of the jet engine: The compressors. The compressors are basically second set of smaller fan blades inside the front of the engine core that compresses the air a little bit.The compressors start by sucking in mass amounts of air and throws some of it into the main core of the engine, while the rest of the air becomes accelerated and bypasses the engine core. This can be called bypass thrust, bypass air or cold thrust.

Unlike the bypass thrust that bypasses the engine core, the air goes into the next stage, or the combustion chamber. The combustion chamber includes a set of fuel nozzles that burn and compress the air. The air can be compressed to that of 100 times more than atmospheric pressure. Inside the combustion chamber at the ends of the fuel nozzles are "flame holders" or "flame cans." These make sure that the compressed air traveling at more than 500 miles/hour does not make the flame blow out. Once the air goes through the combustion chamber, it then goes through its final stage.

The last major stage of a jet engine, or the turbines, are at the back of the jet engine. When the hot, compressed air leaves the combustion chamber, it goes through the turbines. The hot air from the core of the engine has so much energy that it turns the turbines while escaping the engine. The turbines don't do much, but they do play a critical role in the engines' operation.

The question comes, where comes the energy that turns the engine compressor and fan? The hot energy that comes from the combustion chamber turns the turbines while escaping the engine. The compressors and the turbines are connected by a shaft. This means that the moving turbines move the compressor and the fan blades at the front of the engine.

Sources: Civil Aerospace: Power Around the World, Rolls Royce
               How gas turbines engines work, howstuffworks.com