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JET PROPULSION Part 6 Thrust Augmentation and Reversers.

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Presentation on theme: "JET PROPULSION Part 6 Thrust Augmentation and Reversers."— Presentation transcript:

1 JET PROPULSION Part 6 Thrust Augmentation and Reversers

2 Thrust Augmentation Is a method of extracting more power from Internal Combustion Engines. Its a form of Power Boosting We shall examine two main types of augmentation systems, Water Injection and Reheat or Afterburning

3 Water Injection Systems Operation of either Water or Water Methanol systems cools the turbine, and allows water to be injected into the fuel spray nozzles which cools the air flow in the combustor allowing more fuel to be added. Water Injection

4 Rolls-Royce Spey Turbo Fan Series Primary Fuel flow Water flow Water Injection allows water to be injected via additional nozzles built into the fuel spray nozzles. Operation of the water injection system automatically resets the fuel control unit to allow more fuel to flow. IncreasedPrimary Fuel flow Combustion Chamber

5 Water Injection Rolls-Royce Spey Turbo Fan Series Primary Fuel flow Water flow Water Injection allows water to be injected via additional nozzles built into the fuel spray nozzles. The water injection system automatically resets the 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. More Power. IncreasedPrimary Fuel flow Combustion Chamber

6 Water Injection Rolls-Royce Spey Turbo Fan Series Primary Fuel flow Water flow Combustion ChamberIncreasedPrimary Fuel flow Water cools the turbine, increases pressure and velocity More Power. Cooler turbine means more fuel can be added More Power.

7 Water Methanol Control Unit Water Methanol Injection Dart Engine Turbo Prop Series Water Methanol Tank and Pump The Control Unit has two functions: 1. Switching water-methanol flow through the unit when the throttle moves to the take-off position. 2. Regulating rate flow based upon engine power, and atmospheric pressure.

8 Water Methanol Control Unit Water Methanol Injection Dart Engine Turbo Prop Series Water Methanol Tank and Pump Torque Pressure (ENGINE POWER) More power means coarser propeller pitch More Thrust. Cooler turbine means more methanol can be added Even More Power. Water cools the turbine, increases pressure & velocity More Power.

9 Questions ?

10 The Re-Heat/Afterburn System Provides extra thrust without increasing the engine's frontal area

11 Engine Rear End Reheat System (Afterburner) The Re-Heat/Afterburn System The 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 fuel in the jet pipe. Spray Tubes Vapour Gutters Heat Shields Jet Pipe Variable Nozzle Closed

12 The Re-Heat/Afterburn System Jet Pipe The 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 pressure and to ensure reheat has no effect on the engine. Gas stream without reheat Variable Nozzle Opens Closed

13 The Re-Heat/Afterburn System Visible shock waves appear in the exhaust plume Concord was the only passenger aircraft to have Reheat/Afterburners. In military aircraft afterburner use is used for Take-off, In-flight acceleration and Combat only due to the extremely high fuel consumption rate.

14 Questions ?

15 Thrust Reversal is simply a method of altering Jet reaction from 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 Thrust reversers reduce the landing roll out. In civilian aircraft this is primarily to save wear and tear on the brakes, to clear busy runways and to achieve quick turn-rounds, i.e. keeping passenger delays 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. Reverser Effects Shorter Landing Roll-out

17 Diverting some or all of a rearward directed jet in an almost forward direction, will provide a reverse thrust. The gas stream should be directed in a completely forward direction; but this is not possible for aerodynamic reasons. Yet an angle of 90 o to 45 o forward is common, giving reverse thrust up to 50% of forward thrust. Reverser Effects

18 Questions ?

19 Thrust Reversers Translating Cowl Type BLOCKER DOORS TRANSLATING COWL Reverse Thrust CASCADES Used on – The Tri-Star and C17 (illustrated) The C17 deployment is extremely unusual in that it can deploy the thrust reversers in flight for a tactical descent from high altitude, thereby minimising the threat of anti-aircraft fire etc in a hostile area. Normal Forward Thrust

20 Thrust Reversers Pivoting Door Type Normal Forward Thrust Reverse Thrust PIVOTING DOOR SENTINEL LANDING – THRUST REVERSERS DEPLOYED Used on – The RAF Sentinel R17 (illustrated) It comprises of two doors on this system, but multi door systems are replacing the translating cowl designs on high by-pass fan engines.

21 Thrust Reversers Clam Shell Door Type Normal Forward Thrust CLAM SHELL DOOR CLAM SHELL DOOR Reverse Thrust VC10 LANDING – THRUST REVERSERS DEPLOYED Used on – The VC 10 (illustrated) All four engines have the reverser fitted, but on RAF aircraft, the two inboard reversers have been inhibited because the jet blast from all four created too much buffeting on the fin and elevator.

22 TARGET DOOR Thrust Reversers Target Door Type Normal Forward Thrust Reverse Thrust Used on – The Tornado (illustrated) This system does redirect the jet thrust slightly forward, witness the exhaust staining on the aircraft fuselage and tail.

23 Thrust Reversers Other Methods Reversing the pitch of the propeller blades, sends the thrust in a totally forward direction. Used on Hercules REVERSE PITCH PROPELLER Parachutes can be deployed which increase the drag and increase the deceleration of the aircraft. Used on Vulcan DROGUE PARACHUTE

24 Thrust Reversers Translating Cowl Type The Tri-Star and C17 Pivoting Door Type The Sentinel R17 Clam Shell Door Type The VC 10 Target Door Type The Tornado

25 Questions ?

26 How does water injection increase power in a jet engine? It cools the air flow in the combustor allowing more fuel to be added It makes the combustion burn slower It allows less fuel to be used It heats the air flow into the engine allowing more fuel to be added Check of Understanding

27 Which of the following is a type of jet engine augmentation system? Turbocharging Rocket Boosting Supercharging Water Injection

28 In a typical reheat system, oxygen is required in the jet pipe for combustion. Where does the reheat oxygen come from? From on board oxygen bottles Oxygen is pumped in with the extra fuel Unburnt oxygen from the combustion chambers Slipstream air is scooped into the jet pipe Check of Understanding

29 Which sentence is true? Afterburning…. a.is restricted for take-off and combat. b.adds more fuel to the reheat section. c. results in an extremely high fuel consumption. d. produces visible shock waves in the exhaust. A, B, C and D A and C only A, B and D only A, C and D only Check of Understanding

30 After-burning in a jet engine involves burning additional fuel in the: Turbine Combustion Chamber Jet pipe Compressor Check of Understanding

31 What is the function of the Spray tubes in the afterburner? To add more fuel to the combustion process To inject water to control the temperature To control the afterburner internal pressure To add more air to the combustion process Check of Understanding

32 When is reheat used in a combat aircraft? All of the above At take-off During combat manoeuvrings For in-flight acceleration Check of Understanding

33 In a modern reheat system, how is the flame ignited? By heat and compression By the heat from the combustor By igniter plugs in the jet pipe By catalytic igniters Check of Understanding

34 Thrust reversers generally fall into four types, what are these types? Transmission cowl, pilot doors, clamshell doors and target doors Transmission cowl, pilot doors, crab shell doors and bucket doors Translating cowl, pivot doors, clamshell doors and target doors Translating cowl, balanced doors, clamshell doors and target doors Check of Understanding

35 What is thrust reversing? Driving the aircraft wheels backwards Turning the engine to point in the opposite direction Making the engine shaft rotate in the opposite direction Redirecting the engine exhaust in a forward direction

36 Check of Understanding Which type of thrust reverser is shown in the illustration? Target door Pivot door Clamshell door Translating cowl

37 Reverse thrust is simply a method of altering what? The engine RPM Primary air-flow Jet reaction The engine cooling Check of Understanding

38 Which type of thrust reverser is shown in the illustration? Target door Translating cowl Pivot door Clamshell door

39 Which of the following aircraft use the clamshell door system? Tristar Tornado VC 10 Sentinel R17 Check of Understanding

40 Which type of thrust reverser is shown in the illustration? Target door Translating cowl Pivot door Clamshell door

41 Which of the following aircraft use the target door system? Tristar Tornado Hercules Vulcan Check of Understanding

42 Which type of thrust reverser is shown in the illustration? Target door Pivot door Clamshell door Translating cowl

43 Which of the following aircraft use the translating cowl system? Hercules C17 Globemaster R17 Sentinel Vulcan Check of Understanding

44 Which type of thrust reverser is shown in the illustration? Target door Pivot door Clamshell door Translating cowl

45 Which of the following aircraft use the pivot door system? Tristar Tornado VC 10 Sentinel R17 Check of Understanding

46 Which of the following statements applies to the process of afterburning, as used in some jet engines? It provides extra thrust without: The use of additional fuel Increasing the exhaust velocity Increasing the engine's frontal area Removing any more oxygen from the exhaust gases Check of Understanding

47 Questions ?

48 JET PROPULSION End of Presentation


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