Sunday, May 13, 2012

¥ How a jet engine works ¥

This simplified diagram shows you the process through which a jet engine converts the energy in fuel into kinetic energy that makes a plane soar through the air:
1. For a jet going slower than the speed of sound, the engine is moving through the air at about 1000 km/h (600 mph). We can think of the engine as being stationary and the cold air moving toward it at this spe...ed.
2. A fan at the front sucks the cold air into the engine.
3. A second fan called a compressor squeezes the air (increases its pressure) by about eight times. This slows the air down by about 60 percent and it's speed is now about 400 km/h (240 mph).
4. Kerosene (liquid fuel) is squirted into the engine from a fuel tank in the plane's wing.
5. In the combustion chamber , just behind the compressor, the kerosene mixes withthe compressed air and burns fiercely, giving off hot exhaust gases. The burning mixture reaches a temperature of around 900°C (1650°F).
6. The exhaust gases rush past a set of turbine blades , spinning them like a windmill.
7. The turbine blades are connected to a long axle (represented by the middle gray line) that runs the length of the engine. The compressor and the fan are also connected to this axle. So, as the turbine blades spin, they also turn the compressor and the fan.
8. The hot exhaust gases exit the engine through a tapering exhaust nozzle . The tapering design helps to accelerate the gases to a speed of over 2100 km/h (1300 mph). So the hot air leaving the engine at the back is traveling over twicethe speed of the cold air entering it at the front—and that's what powers the plane. Military jets often have an after burner that squirts fuel into the exhaust jet to produce extra thrust. The backward-moving exhaust gases power the jet forward. Because the plane is much bigger and heavier than the exhaust gases it produces, the exhaust gases have to zoom backward much faster than the plane's own speed.

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