PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Propulsion Devices (Engines)Air-BreathingUse atmospheric air (+ some fuel) as main propellantRocketsCarry entire propellant (liquid/solid fuel + oxygen)Piston, Gas Turbine and Ramjet EnginesJet-engine.ppt, 10-7-01Gas Turbine Engines (most aircraft jet engines):• Use high-temperature gases to power a propeller or produce direct thrust by expanding and accelerating the exhaust gases through a nozzle.• Three main types: Turbojet, Turbofan and TurbopropJet Engines – Basic Operation• Air enters the trough the intake duct (cowl).• Air compressed by passage through the compressor.• Mixed with fuel in the combustion chamber. • Fuel is ignited, Pressure and Temperature raised• Some of the pressure used to turn a turbine; • Turbine shaft drives the compressor.• Hot, high pressure air forced through a nozzle.• The reaction force is the engine thrust.Jet Engine – Common Types• Turbojets: • Turbine used to drive the compressor. • All intake air passes through the combustion chamber and exits through the nozzle. • All thrust produced by hot, high-speed exhaust gases.•Turbofans (Fan-Jet):• A large propeller in the intake cowl, in front of compressor. • Dramatically increases the amount of air pulled in the intake. • Only a small percentage passed through the engine, the rest of cold air is Bypassed. • Part of the thrust through the hot exhaust gases and part by the cold bypassed air. Produces cooler exhausts and quieter engines.• High by-pass ratio are most commonly used in larger commercial aircraft.•Turboprops:• Jet engine used to turn a large propeller, which produces most (90% or more) of the thrust. Used in smaller aircraft.Jet Engine – Common TypesPratt-WhitneyEngine GalleryGE90 EngineJet Engine CombusterFilm cooling via convectionOne annular sectionTurbulent flame (fuel self-ignited)• Use spark plug to start the engineand re-light after flameoutFlame
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