This document discusses the sections and components of gas turbine engines used in aircraft. It describes how gas turbine engines are divided into two main sections - the cold section and the hot section. The cold section contains the air inlet duct, compressor, and diffuser. The hot section contains the combustor, turbine, and exhaust. It also discusses the different types of air inlet ducts used for subsonic and supersonic flight, including single entrance, divided entrance, convergent-divergent, and movable spike/plug designs.

1. TURBINE ENGINE
 Aircraft Gas Turbine Power plants by Otis
 FAA 12A
 Aircraft Gas Turbine Engine Technology by Treager
 Aircraft Power plant by Kroes& Wild
 The Jet Engine by Rolls-Royce

2. TURBINE ENGINE
 Gas turbine engine are considered to be of two types:-
Gas turbine engine
Torque Producing
Engine
Thrust Producing
Engine
Turbojet
Engine
Turbofan
Engine
Turboprop
Engine
Turbo shaft
Engine

3. SECTIONS OF GAS TURBINE ENGINE

4. SECTIONS OF GAS TURBINE ENGINE
 An aircraft gas turbine engine is divided into two sections:

Cold section
Hot section
 The cold section contains:


Air Inlet Duct
Compressor
Diffuser
 The hot section contains:


Combustor
Turbine
Exhaust

5. ENGINE STATION DESIGNATION
To standardize the locations in gas turbine engines, a
numbering system has been devised that allows a person to
identify a location by numbers.

6. STUDY OF AIR INTAKE CONFIGURATION

7. NEED OF AIR INTAKE IN AN AIRCRAFT
• A widely used method to increase the thrust
generated by the aircraft engine is to increase
the air flow rate in the air intake by using
auxiliary air intake systems.
• The air flow enters the intake and is required
to reach the engine face with optimum levels
of total pressure and flow uniformity hence
need of an air intake system.
• Deceleration of airflow at high flight mach
numbers or aerodynamic compression with
help of air intake.

8. AIR INTAKE DESIGN REQUIREMENTS
• The air intake requires enormous effort properly to control
•
•
•
•
•
airflow to the engine.
The intake must be designed to provide the appropriate amount
of airflow required by the engine.
Furthermore this flow when leaving the intake section to enter the
compressor should be uniform stable and of high quality.
Good air intake design is therefore a prerequisite if installed
engine performance is to come close to performance figures
obtained at the static test bench.
The engine intake must be a low drag, light weight construction
,that is carefully and exactly manufactures.
These above conditions must be met not only during all phases of
flight but also on the ground with the aircraft at rest and the
engine demand maximum, thrust prior to take off

9. THE COLD SECTION
AIR INLET DUCTS
 The air inlet duct is technically a part of the airframe, but
it is so important in the development of thrust that it is
included with the engine as a part of the clod section.
 The air inlet duct must supply uniform flow of air to the
compressor so that it can operate stall free.
 It must produce as little drag as possible.
 If taken only a small obstruction to the air flow inside the
duct to cause a significant loss of efficiency.
 Inlet cover must be installed to prevent damage or
corrosion in this vital area.

10. THE COLD SECTION
AIR INLET DUCTS
Air Inlet Ducts
Single Entrance
Duct
Divided Entrance
Duct

11. AIR INLET DUCTS
SINGLE ENTRANCE DUCT
 Duct inlet is located directly
ahead of the engine and aircraft
in such a position that it scoops
undisturbed air.
 It is either straight configuration
or with relatively genital
curvatures.
 Due to long shape there is a
chance of pressure lost but that is
offset by smooth airflow
characteristic.
 In multi engine installation a
short straight duct results
minimum pressure drop.

12. SINGLE ENTRANCE DUCT

13. AIR INLET DUCTS
DIVIDED ENTRANCE DUCT
 It is used in high speed, single
engine aircraft where pilot sits
low in the fuselage and close to
the nose.
 This divided duct can be either a
wing root inlet or a scoop at each
side of fuselage.
 Create huge amount of drag

14. AIR INLET DUCTS
DIVIDED ENTRANCE DUCT

15. THE COLD SECTION
AIR INLET DUCTS
Air Inlet Ducts
Subsonic Inlet Duct
Supersonic Inlet Duct

16. THE COLD SECTION
SUBSONIC AIR INLET DUCTS
 The inlet duct is used in the multiengine subsonic aircraft is a fix
geometry duct whose diameter progressively increases from the front
to back. It is diverging duct and is also called an inlet diffuser
because of the effect, it has the effect on the pressure of the air
entering the engine.
 As air enters the inlet at ambient pressure it beguns to defuse, or
spread out, and by the time it arrives at the inlet to the compressor
its pressure is slightly higher than the ambient pressure.
 Usually the air diffuses in the front portion the duct and than it
progresses along at a fairly constant pressure passes the engine inlet
fairing and then into the compressor. This allows the engine to
receive the air with less turbulence and at a more uniform pressure.

17. THE COLD SECTION
SUBSONIC AIR INLET DUCTS
Turbojet Engine

18. THE COLD SECTION
AIR INLET DUCTS
Turbofan Engine

19. THE COLD SECTION
AIR INLET DUCTS
Turbofan Engine

20. AIR INLET DUCTS
TURBOPROP ENGINE
The propeller reduction gears are located at the front of the engine and
thus interfere with a smooth flow of air entering the compressor.
Generally 3 types of inlet duct is used:i) Ducted spinner inlet ii) Conical spinner inlet iii) Under scoop inlet

21. AIR INLET DUCTS
TURBOPROP ENGINE

22. AIR INLET DUCTS
TURBO SHAFT ENGINE

23. BELLMOUTH COMPRESSOR INLET
 Bellmouth inlet are converging in shape, found primarily
on helicopter.
 It provides an inlet with very thin boundary layers and
corresponding low pressure losses.
 Actually duct lost is so slight that it is considered zero.

24. SUPERSONIC INLET DUCT
 The air approaching the compressor inlet must always be at speed
below the speed of sound.
 when an aircraft is flying at supersonic speed, the inlet air must be
slowed down to subsonic speed before it reaches the compressor. This
is done by :
Using a convergent-divergent or CD inlet duct

Raising a Wedge or Spike or Plug inlet

25. SUPERSONIC INLET DUCT
Convergent-divergent or CD inlet duct

26. SUPERSONIC INLET DUCT
Using movable
wedge inlet

27. FLOW CONDITIONS OVER WEDGE AND CONE
In the design of supersonic air intakes flow conditions over
wedge and cone are of the greatest importance as these are
simple geometric bodies and relatively easy to manufacture.

28. COMPARISON OF SUPERSONIC FLOW
OVER CONE AND WEDGE
The major advantage of a (supersonic) conical flow is a smaller total pressure
loss (when compared to a wedge of the same half-angle), together with the
fact that a conical shock sustains lower mach numbers until it becomes
detached to form a high loss bow shock.
A major disadvantage of conical flows is that it is less tolerant to asymmetric
flow conditions which cause distortion to the intake flow. As combat aircraft
are frequently required to maneuver at higher angles of attack, the flow
inevitably gets asymmetric- hence a performance for the (horizontally
arranged) wedge in all modern combat aircraft, despite its reduced
efficiency.

30. SUPERSONIC INLET DUCT
Using movable Plug
inlet
Using movable spike inlet

31. EXAMPLES OF USE OFF OBLIQUE SHOCK
DIFFUSERS
Mirage ||| fighter with
side mounted obliqueshock diffuser
Two dimensional
oblique shock
diffuser (Northrop F5 with vertical ramp)

32. SUPERSONIC
STUDIES
F-16 intake
characteristics
AIR
INTAKE
CASE

33. SUPERSONIC INLET DUCT
 Inlet Buzz: The buzz is an airflow instability which occur when a shock wave is
alternately slowed and irregular flow occur at the inlet.
 In increasing condition it can cause violent fluctuations in pressure
through the inlet, which occur when a shock wave is alternately
swallowed and regulate by the inlet.
 This condition also cause damage to the inlet structure or possibly to
engine itself.
 A suitable variable geometry duct is used to eliminate the buzz by
increasing of airflow within the inlet duct.

34. INTAKE CONFIGURATION AND
OPERATION
Present-day turbine aero engines require subsonic flow at the entry to
the compressor, even if the aircraft is flying at supersonic speed. The
task of air intake is therefore to decelerate the supersonic external
flow to a subsonic speed acceptable to the compressor. As intake
discharge mach number are required to be in range of mach 0.4 to
0.7 great care must be exercised when decelerating the flow in order
to keep total pressure losses to a minimum .
Normal shock diffuser
For aircraft operating at a maximum speed equivalent to mach 1.5 a
normal shock diffuser is generally sufficient to decelerate
the supersonic airflow efficiently to the speed needed by
the compressor.

35. NACA SUBMERGED INLET IN A EURO
FIGHTER
The NACA submerged type intake is not very efficient for use with propulsion
installations. However, they are frequently used as intakes of auxiliary
systems (auxiliary power unit, heating and avionics bay cooling) as seen in
Fig above

36. Various types of
supersonic inlets

37. RAM RECOVERY
 When a turbine engine is operated there is a negative
pressure in the inlet because of the high velocity of the
airflow. As the aircraft moves forward in the flight, air
rams in to the inlet duct and ram recovery takes place.
This ram pressure rise cancel the pressure drops due to
friction inside the duct and the inlet pressure return to
ambient. Ram recovery occur above about 160 miles/hrs
or 0.1 mach to 0.2 mach in most of the aircraft.
 From this point the pressure continue to increases with
aircraft speed and additional thrust is created by the
engine with less expenditure of fuel.

38. PRESSURE RECOVERY AND NOSE
SUCTION FORMATION

39. BLOW-IN -DOOR
 It is used to prevent compressor stall.
 It is installed in the side of inlet duct and are spring loaded
to hold them closed.
 But when the inlet pressure becomes a specified amount
lower than that of the ambient air, the pressure differential
forces then open and furnishes additional air to the
compressor inlet.