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Northern Arizona University |
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Upon researching the current design configurations of thrust reversers used in aviation, several design solutions were looked into. Research was conducted by utilizing the internet, books, and journals. After extensive research, the three most commonly and successfully used thrust reversers emerged: cascade, clamshell, and cascade/clamshell hybrid. Although there are slight variations to each with respect to the way they are configured and deployed, almost every design looked at falls under those three categories. Ultimately, all three designs accomplish the same purpose, redirecting flow to produce reverse thrust in order to slow down an aircraft.
Cascade Thrust Reverser The cascade thrust reverser is mainly used in turbo-fan engines. Turbo-fan engines are typically found on very large aircraft and have a very large outer diameter. Turbo-fan engines utilize a large fan section that creates low pressure compression. This large fan pushes air through the outer part of the engine, with very little air through the combustion chamber and mixes the air with hot gasses at the exhaust. This cool compressed fan air in the nacelle is diverted by a blockage created through the deployment of the thrust reverser and is redirected through angled guide vanes out of the side of the engine.
Cascade Thrust Reverser Source: http://www.aerospaceweb.org/question/propulsion/q0008a.shtml
Clamshell Thrust Reverser The clamshell type design was specifically developed for turbojet engines. It is essentially two outer exhaust nozzles that can be unhinged in a manner that the two nozzles combine together to block and redirect exhaust flow after it leaves the turbine section. The clamshell is a proven design and has an extensive amount of research already done for this particular type of application. In addition to having a large amount of data on clamshell designs, there are also not as many major moving parts. Extensive modifications to the engines design can be avoided with the clamshell thrust reverser as it can attach to the outside of the original engine. Only an external addition and actuation system need to be designed and manufactured.
Clamshell Thrust Reverser Source: http://www.pilotoutlook.com/airplane_flying/thrust_reversers
Cascade/Clamshell Hybrid Thrust Reverser The thrust reverser that will be analyzed and designed for this project will use a turbojet engine, which does not have bypass fan airflow, only hot exhaust airflow. A turbojet engine is just like the turbofan, but without the large low pressure compressor. Instead it only has a series of high pressure compressors. So the only available air to be used for thrust reversing is hot exhaust air. The cascade thrust reverser can be designed so that it works on turbojet engines by incorporating a clamshell design. This cascade/clamshell hybrid thrust reverser for a turbojet engine works under the same principle as the turbofan cascade style. A blockage occurs on the exhaust tube with two shutters blocking the hot airflow redirecting the exhaust out of the cascades veins. This design would prompt additional modification to the jet engine.
Cascade/Clamshell Hybrid Thrust Reverser Source: http://cobweb.ecn.purdue.edu/~propulsi/propulsion/images/jets/basics/Frevers1.jpg
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Design Selection |