This week continues the ABCs series by introducing three characteristics of aircraft turbine engines–afterburner, bypass ratio, and compressor–with an Edwards AFB F-15C/D Eagle as the example.
Afterburner
This is the afterburner section of the F-15.
This Pratt and Whitney drawing shows a cutaway of the F100 engine, in use on the F-15. The aft section (which appears orange in this drawing) is the afterburner section where fuel is ignited.
Bypass Ratio
A certain amount of air goes around the jet engine core. The ratio of air that bypasses the core to that air that goes through the core is the bypass ratio. If you look closely at the drawing above, you can see this near the compressor where it is most evident. The F-15 has a low bypass ratio. It is also illustrated in this wikipedia graphic below–the bypass air is the arrow on the top left, a light purple color in the engine.
Compressor
Again, reference the Pratt & Whitney drawing above as well as the labeled wikipedia graphic. In the first, the compressor section (just in front of the orange section near the middle of the core part of the engine) is where turbine blades accelerate the air and increase the pressure, preparing it for combustion in the chamber just aft of the compressor.
This photo shows an excellent view the engine compartment along the full length of the bottom side of the F-15.
The inlet is also a critical part of the aircraft design because it ducts air to the engine. This photo of the lower part of the inlet also shows the engine compartment running the length of the underside of the Eagle.
The orange paint scheme, often referred to as a “clown jet,” is a distinctive characteristic of flight test operations.
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