Presentation on theme: "A method of extracting more power from Internal Combustion Engines"— Presentation transcript:
1A method of extracting more power from Internal Combustion Engines JET ENGINE PROPULSIONChapter 9Thrust Augmentation SystemA method of extracting more power from Internal Combustion Engines
2Thrust Augmentation Piston engines:- Supercharging or turbo charging Forced air aspirationHigher Octane fuelsMore power per bangGas turbines engines:-Booster enginesHS121 Trident and early V/STOL a/cWater injection + more fuelMethanol – Argosy and BrittanniaWater injectionArgosy and BrittanniaAfterburningMainly military but also ConcordeOther methodsRocket boostersRATO – Rocket Assisted Take-OffSingle use onlyHercules
4Thrust Augmentation Water Methanol Injection Older style engines lacked power at high ambient temperature and thereforerequired some way of boosting power to be able to take-off.Modern engines do not require this as they are designed to cope with highambient temperatures.The limiting factor in achieving maximum thrust is the maximum burner temperature.Once this is reached no more power is available.But by injecting water into the airflow it cools the airflow and increases pressure and therefore density.This reduces the burner temperature so more fuel (can be methanol mixed withthe water) can be added to regain maximum burner temperature and so achievemore power.Using water injection continuously would damage the engine as it changes thecombustion characteristics of the engine.Also water weighs more than fuel and the extra weight needs more power toovercome it.A small amount of water is carried to be used just for take-off and initial climb.
5Thrust Augmentation Water Methanol Injection Dart Engine Series Water Methanol Tank and PumpDart Engine SeriesHow is it injected?Prop Shaft Torque (ENGINE POWER)Torque Pressure (ENGINE POWER)Water Methanol Control UnitIn the Dart engine, more power means coarser propeller pitch = more thrust.Use limited because of combustion characteristics
6Thrust Augmentation Water Injection Rolls-Royce Spey Series Increased Primary Fuel flowPrimary Fuel flowWater flowTake a closer look hereWater cools the burner which drops the burner temperature.This allows the maximum temperature control system to add more fuel to regain maximumburner temperatureThis will allow RPM to increase and therefore the airflow so producing more power.
7Reheat System (Afterburner) Thrust AugmentationEngine Rear EndReheat System (Afterburner)Heat ShieldsVariable NozzleVapour GuttersSpray Tubes
9Engine Gas Stream without Reheat Thrust AugmentationEngine Gas Stream without ReheatVariable Nozzle ‘Closed’
10Reheat Starts with Vapour Gutters Spraying Fuel Thrust AugmentationReheat Starts with Vapour Gutters Spraying Fuel
11Then Spray Tubes add more fuel to combustion process Thrust AugmentationThen Spray Tubes add more fuel to combustion processAnd Variable Nozzle ‘Opens’This is to prevent higher jet pipe pressureto ensure that reheat has no effect on jet engine
12Thrust Augmentation Typical Reheat System Rolls-Royce Phantom Spey and Jaguar Adour series
13MacDonald Douglas F4 Phantom – Reheat Lit Thrust AugmentationMacDonald Douglas F4 Phantom – Reheat LitVisible ‘Shock’ waves appear in exhaust plume!FA18 Hornet on Carrier Take-off – Reheat LitDoes the Afterburner get hot?Just a little bit!!Use of the afterburner is restricted to take-off and combat only (except Concorde of course) due to the extremely high fuel consumption rate