2 Reheat or Afterburning Thrust AugmentationIs a method of extracting more powerfrom Internal Combustion Engines.It’s a form of ‘Power Boosting’We shall examine two main typesof augmentation systems,Water InjectionandReheat or Afterburning
3 Water Injection Water Injection Systems cools the turbine, Operation of eitherWater or Water Methanol systemscools the turbine,and allows water to be injectedinto the fuel spray nozzleswhich cools the air flow in the combustorallowing more fuel to be added.
4 Water Injection Water Injection allows water to be injected Rolls-Royce Spey Turbo Fan SeriesWater flowIncreasedPrimaryFuel flowPrimary Fuel flowCombustion ChamberWater Injection allows water to be injectedvia additional nozzles built into the fuel spray nozzles.Operation of the water injection systemautomatically resets the fuel control unitto allow more fuel to flow.
5 Water Injection Water Injection allows water to be injected Rolls-Royce Spey Turbo Fan SeriesWater flowIncreasedPrimaryFuel flowPrimary Fuel flowCombustion ChamberWater Injection allows water to be injectedvia additional nozzles built into the fuel spray nozzles.The water injection system automatically resetsthe fuel control unit to allow more fuel to flow.Water cools the turbine, increases pressure and velocity.More Power.Cooler turbine means more fuel can be added.
6 Water Injection Water cools the turbine, More Power. More Power. Rolls-Royce Spey Turbo Fan SeriesWater flowIncreasedPrimaryFuel flowPrimary Fuel flowCombustion ChamberWater cools the turbine,increases pressure and velocityMore Power.Cooler turbine means more fuel can be addedMore Power.
7 Water Methanol Injection Dart Engine Turbo Prop SeriesWater Methanol Tank and PumpWater Methanol Control UnitThe Control Unit has two functions:Switching water-methanol flow through the unitwhen the throttle moves to the take-off position.Regulating rate flow based upon engine power,and atmospheric pressure.
8 Water Methanol Injection Dart Engine Turbo Prop SeriesWater Methanol Tank and PumpTorque Pressure (ENGINE POWER)Water Methanol Control UnitWater cools the turbine, increases pressure & velocityMore Power.Cooler turbine means more methanol can be addedEven More Power.More power means coarser propeller pitchMore Thrust.
10 The Re-Heat/Afterburn System Provides extra thrustwithout increasingthe engine's frontal area
11 The Re-Heat/Afterburn System Engine Rear EndReheat System (Afterburner)Heat ShieldsVariable NozzleClosedJet PipeSpray TubesVapour GuttersThe system consists of a larger diameter jet pipe,with internal heat shields.Inside are vapour gutters and fuel spray tubes.The variable nozzle is closed (reheat off)or opened (reheat on)Reheat/Afterburn consists of burning additional fuelin the jet pipe.
12 The Re-Heat/Afterburn System Variable NozzleOpensVariable NozzleClosedJet PipeGas stream without reheatThe vapour gutters spray fuel into the gas stream.The Spray Tubes add more fuel to the process,which is fired by catalytic igniters,using oxygen from the combustion chambers.The variable nozzles open to maintain pressureand to ensure reheat has no effect on the engine.
13 The Re-Heat/Afterburn System Visible ‘shock waves’ appear in the exhaust plumeConcord was the only passenger aircraftto have Reheat/Afterburners.In military aircraft afterburner use is used forTake-off,In-flight accelerationand Combat onlydue to the extremely high fuel consumption rate.
15 Thrust Reversal altering Jet reaction to a forward direction, is simply a method ofaltering Jet reactionfrom a rearward direction(which provides normal forward thrust)to a forward direction,providing reverse thrust(using the power as a decelerating force)and is operated by the pilot on landing.
16 Reverser Effects Thrust reversers reduce the landing roll out. Shorter Landing Roll-outThrust reversersreduce the landing roll out.In civilian aircraft this is primarilyto save wear and tear on the brakes,to clear busy runways and to achievequick turn-rounds, i.e. keeping passengerdelays to a minimum.In military aircraft the above can apply,and also to give shorter landings for tactical reasons,i.e. the aircraft can land and unload supplies quickly,thus minimizing any risk in hostile environments.
17 Reverser Effects Diverting some or all of a rearward directed jet in an almost forward direction,will provide a reverse thrust.The gas stream should be directedin a completely forward direction;but this is not possible for aerodynamic reasons.Yet an angle of 90o to 45o forward is common,giving reverse thrust up to 50% of forward thrust.
19 Thrust Reversers Translating Cowl Type BLOCKER DOORSBLOCKER DOORSReverse ThrustCASCADESNormal Forward ThrustUsed on –The Tri-Star and C17 (illustrated)The C17 deployment is extremely unusualin that it can deploy the thrust reversers in flightfor a tactical descent from high altitude,thereby minimising the threat ofanti-aircraft fire etc in a hostile area.
20 Thrust Reversers Pivoting Door Type The RAF Sentinel R17 (illustrated) Reverse ThrustNormal Forward ThrustUsed on –The RAF Sentinel R17 (illustrated)It comprises of two doors on this system,but multi door systems are replacingthe translating cowl designson high by-pass fan engines.SENTINEL LANDING –THRUST REVERSERS DEPLOYED
21 VC10 LANDING – THRUST REVERSERS DEPLOYED Clam Shell Door TypeCLAM SHELL DOORCLAM SHELLDOORReverse ThrustNormal Forward ThrustVC10 LANDING – THRUST REVERSERS DEPLOYEDUsed on –The VC 10 (illustrated)All four engines have the reverser fitted,but on RAF aircraft, the two inboardreversers have been inhibitedbecause the jet blast from all fourcreated too much buffetingon the fin and elevator.
22 Thrust Reversers Target Door Type The Tornado (illustrated) Reverse ThrustNormal Forward ThrustUsed on –The Tornado (illustrated)This system does redirectthe jet thrust slightly forward,witness the exhaust stainingon the aircraft fuselage and tail.
23 Thrust Reversers Other Methods REVERSE PITCH PROPELLER Reversing the pitch ofthe propeller blades,sends the thrustin a totally forward direction.Used on HerculesDROGUE PARACHUTEParachutes can be deployed whichincrease the drag and increase thedeceleration of the aircraft.Used on Vulcan
24 Thrust Reversers Translating Cowl Type Pivoting Door Type The Tri-Star and C17Pivoting Door TypeThe Sentinel R17Clam Shell Door TypeThe VC 10Target Door TypeThe Tornado
26 Check of Understanding How does water injectionincrease power in a jet engine?It makes the combustion burn slowerIt heats the air flow into the engineallowing more fuel to be addedIt allows less fuel to be usedIt cools the air flow in the combustorallowing more fuel to be added
27 Check of Understanding Which of the following is a type ofjet engine augmentation system?Rocket BoostingWater InjectionSuperchargingTurbocharging
28 Check of Understanding In a typical reheat system,oxygen is required in the jet pipe for combustion.Where does the reheat oxygen come from?Oxygen is pumped inwith the extra fuelSlipstream air isscooped into the jet pipeUnburnt oxygen fromthe combustion chambersFrom on board oxygen bottles
29 Check of Understanding Which sentence is true? Afterburning….is restricted for take-off and combat.adds more fuel to the reheat section.c. results in an extremely high fuel consumption.d. produces visible shock waves in the exhaust.A and C onlyA, C and D onlyA, B and D onlyA, B, C and D
30 Check of Understanding After-burning in a jet engine involvesburning additional fuel in the:Combustion ChamberCompressorJet pipeTurbine
31 Check of Understanding What is the function of the Spray tubesin the afterburner?To inject waterto control the temperatureTo add more airto the combustion processTo controlthe afterburner internal pressureTo add more fuelto the combustion process
32 Check of Understanding When is reheat used in a combat aircraft?At take-offFor in-flight accelerationDuring combat manoeuvringsAll of the above
33 Check of Understanding In a modern reheat system,how is the flame ignited?By the heat from the combustorBy catalytic ignitersBy igniter plugs in the jet pipeBy heat and compression
34 Check of Understanding Thrust reversers generally fall into four types,what are these types?Transmission cowl, pilot doors, crab shell doors and bucket doorsTranslating cowl, balanced doors, clamshell doors and target doorsTranslating cowl, pivot doors, clamshell doors and target doorsTransmission cowl, pilot doors, clamshell doors and target doors
35 Check of Understanding What is thrust reversing?Turning the engine to point in the opposite directionRedirecting the engine exhaustin a forward directionMaking the engine shaftrotate in the opposite directionDriving the aircraft wheels backwards
36 Check of Understanding Which type of thrust reverseris shown in the illustration?Translating cowlClamshell doorPivot doorTarget door
37 Check of Understanding Reverse thrustis simply a method of altering what?Primary air-flowThe engine coolingJet reactionThe engine RPM
38 Check of Understanding Which type of thrust reverseris shown in the illustration?Translating cowlClamshell doorPivot doorTarget door
39 Check of Understanding Which of the following aircraftuse the clamshell door system?TornadoSentinel R17VC 10Tristar
40 Check of Understanding Which type of thrust reverseris shown in the illustration?Translating cowlClamshell doorPivot doorTarget door
41 Check of Understanding Which of the following aircraftuse the target door system?TornadoVulcanHerculesTristar
42 Check of Understanding Which type of thrust reverseris shown in the illustration?Translating cowlClamshell doorPivot doorTarget door
43 Check of Understanding Which of the following aircraftuse the translating cowl system?C17 GlobemasterVulcanR17 SentinelHercules
44 Check of Understanding Which type of thrust reverseris shown in the illustration?Translating cowlClamshell doorPivot doorTarget door
45 Check of Understanding Which of the following aircraftuse the pivot door system?TornadoSentinel R17VC 10Tristar
46 Check of Understanding Which of the following statementsapplies to the process of afterburning,as used in some jet engines?It provides extra thrust without:Increasing the exhaust velocityRemoving any more oxygenfrom the exhaust gasesIncreasing the engine's frontal areaThe use of additional fuel