1. JET PROPULSION
Part 6
Thrust Augmentation
and Reversers

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

3. Water Injection Water Injection Systems cools the turbine,
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.

4. Water Injection Water Injection allows water to be injected
Rolls-Royce Spey Turbo Fan Series
Water flow
Increased
Primary
Fuel flow
Primary Fuel flow
Combustion Chamber
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.

5. Water Injection Water Injection allows water to be injected
Rolls-Royce Spey Turbo Fan Series
Water flow
Increased
Primary
Fuel flow
Primary Fuel flow
Combustion Chamber
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.

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

7. Water Methanol Injection
Dart Engine Turbo Prop Series
Water Methanol Tank and Pump
Water Methanol Control Unit
The Control Unit has two functions:
Switching water-methanol flow through the unit
when 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 Series
Water Methanol Tank and Pump
Torque Pressure (ENGINE POWER)
Water Methanol Control Unit
Water cools the turbine, increases pressure & velocity
More Power.
Cooler turbine means more methanol can be added
Even More Power.
More power means coarser propeller pitch
More Thrust.

9. Questions ?

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

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

12. The Re-Heat/Afterburn System
Variable Nozzle
Opens
Variable Nozzle
Closed
Jet Pipe
Gas stream without reheat
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.

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 altering Jet reaction to a forward direction,
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. Reverser Effects Thrust reversers reduce the landing roll out.
Shorter Landing Roll-out
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.

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 directed
in 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.

18. Questions ?

19. Thrust Reversers Translating Cowl Type
BLOCKER DOORS
BLOCKER DOORS
Reverse Thrust
CASCADES
Normal Forward Thrust
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.

20. Thrust Reversers Pivoting Door Type The RAF Sentinel R17 (illustrated)
Reverse Thrust
Normal Forward Thrust
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.
SENTINEL LANDING –
THRUST REVERSERS DEPLOYED

21. VC10 LANDING – THRUST REVERSERS DEPLOYED
Clam Shell Door Type
CLAM SHELL DOOR
CLAM SHELL
DOOR
Reverse Thrust
Normal Forward 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. Thrust Reversers Target Door Type The Tornado (illustrated)
Reverse Thrust
Normal Forward 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 REVERSE PITCH PROPELLER
Reversing the pitch of
the propeller blades,
sends the thrust
in a totally forward direction.
Used on Hercules
DROGUE PARACHUTE
Parachutes can be deployed which
increase the drag and increase the
deceleration of the aircraft.
Used on Vulcan

24. Thrust Reversers Translating Cowl Type Pivoting Door 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. Check of Understanding
How does water injection
increase power in a jet engine?
It makes the combustion burn slower
It heats the air flow into the engine
allowing more fuel to be added
It allows less fuel to be used
It cools the air flow in the combustor
allowing more fuel to be added

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

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 in
with the extra fuel
Slipstream air is
scooped into the jet pipe
Unburnt oxygen from
the combustion chambers
From 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 only
A, C and D only
A, B and D only
A, B, C and D

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

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

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

33. Check of Understanding
In a modern reheat system,
how is the flame ignited?
By the heat from the combustor
By catalytic igniters
By igniter plugs in the jet pipe
By 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 doors
Translating cowl, balanced doors, clamshell doors and target doors
Translating cowl, pivot doors, clamshell doors and target doors
Transmission cowl, pilot doors, clamshell doors and target doors

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

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

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

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

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

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

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

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

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

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

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

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

47. Questions ?

48. JET PROPULSION
End of Presentation