1. JET PROPULSION
Part 4
Types of Jet Engines

2. Engine Types Turbo Jet Turbo Fan - Bypass Engines Turbo Prop
Avon, Olympus 593
Turbo Fan - Bypass Engines
SMALL BYPASS Spey, BR700
MEDIUM BYPASS Pegasus, BR715, V2500
LARGE BYPASS RB211, Trent Series
Turbo Prop
PROPELLER Dart, Tyne, BR715TP
Turbo Shaft
HELICOPTER Lycoming T55, Gem
RN SHIPS Marine Spey
POWER GENERATION Industrial Spey & Trent

3. Turbo Jet Rolls Royce Avon This is called: - COMPRESSOR SURGE
At low rpm the rear of the compressor
cannot get rid of all the air from the front of the compressor
This can result in the rear end of compressor ‘choking’
So air
blasts
forwards
17 Stage Compressor driven by a 3 stage turbine
Flame almost goes out - no power – no thrust.
This is called: - COMPRESSOR SURGE
With RPM (i.e. Thrust) changes,
the airflow velocity does not change
in proportion to engine RPM

4. Turbo Jet Rolls Royce Avon BUT air dumped sideways out of the engine
Rear end of compressor ‘unchoked’
Air dumped overboard
Rearward movement of air restored
Power restored
BUT
air dumped sideways out of the engine
produces no thrust.
So a more efficient system was required

5. ‘Excess’ air is dumped overboard through a valve
Turbo Jet
Rolls Royce Avon
‘Excess’ air is dumped overboard through a valve
‘Bleed’ valve

6. High Pressure Compressor Low Pressure Compressor
Turbo Jet
The Olympus 593
The Two Shaft Layout
Single Shaft Layout
driven by
High Pressure Compressor
High Pressure Turbine
driven by
Low Pressure Compressor
Low Pressure Turbine

7. Turbo Jet The Olympus 593 The Two Shaft Layout
Allows front end of compressor to slow down – move less air
and
Allows rear end of compressor to speed up – move more air
Compressor surges lessened
No wasted energy/thrust

8. Turbo Jet The turbojet is the simplest and earliest
form of gas turbine.
Used principally in high speed aircraft
where its relatively low frontal area
and high jet velocity are advantages.
Examples are the Concorde supersonic transport
and a variety of military aircraft
including the Dominie/HS125.

9. Turbo Fan Low Bypass Engine Rolls Royce Spey Adour BR710 Series
Part of the air is compressed fully
and passes into the combustion chamber,
while the remainder is compressed to a lesser extent
and ducted around the hot section.

10. Turbo Fan Medium Bypass Engine Pegasus
Two shaft layout with Contra-rotating shafts
It has low pressure and high pressure AXIAL Flow Compressors
Core flow to ‘Hot’
(rear) Nozzles
Bypass flow to ‘Cold’
(front) Nozzles

11. Turbo Fan High Bypass Engine RB211 Series (Trent)
Three shaft layout – all rotate same direction
LP(Fan) Intermediate and HP AXIAL Flow Compressors
In service with RAF – Wide-body Tristar Tanker/Transport
Boeing 747 and later series, Airbus A330 and larger a/c

12. Turbo Fan
High Bypass Engine
RB211 Series (Trent)

13. Turbo Fan Turbofan engines are loosely categorised by
the size of the bypass compared to the core flow.
(The amount of air entering the core engine
compared to the bypass duct)
which is called the Bypass Ratio.
The low bypass ratio is approximately 1:1.
Half the air goes through the core or hot section,
the other half goes through the bypass.
Medium bypass engines have a 5:1 ratio,
while high bypass have a ratio of 10:1 or more.

14. Turbo Fan The turbofan (bypass) reduces overall jet velocity,
giving better propulsive efficiency at lower speeds,
lower noise levels and
improved specific fuel consumption,
features which make the turbofan ideal
for both civil and military aircraft.
Examples are the Boeing 747 and 757,
the Jaguar and Hawk, and the Tornado.
The Harrier has a variation of the turbofan.

15. Turbo Prop Rolls Royce Dart
Dart RDa6 = 2 stage turbine Dart RDa7 = 3 stage turbine
Turbine drives 2 stage CENTRIFUGAL Compressor and Propeller
Reduction Gearbox
Prop Shaft
Over 70 Marks of Engine – different power levels – 15 different aircraft
Fokker F27, Fairchild F27, Briguet Alize,
(and P51 Mustang and Dakota!)

16. Turbo Prop
Tyne
C160 Transall, Shorts Belfast, Brequet Atlantic, Avro Lincoln,
Canadair CL44, Vickers Vanguard, Aeritalia 222.
Reduction Gearbox
9 Stage HP Compressor
1 Stage HP Turbine
6 Stage LP Compressor
3 Stage LP Turbine
Prop Shaft
(via Reduction Gearbox)

17. Turbo Prop RR Allison T56-A-15 Tyne
C160 Transall, Shorts Belfast, Brequet Atlantic, Avro Lincoln,
Canadair CL44, Vickers Vanguard, Aeritalia 222.
Reduction Gearbox
9 Stage HP Compressor
1 Stage HP Turbine
6 Stage LP Compressor
3 Stage LP Turbine
Prop Shaft
(via Reduction Gearbox)

18. Turbo Prop RR Allison T56-A-15 C130 Hercules Reduction Gearbox
Thrust Strut
Turbine drives compressor and propeller
Output Shaft
4 Stage Turbine
Air Intake
14 Stage HP Compressor

19. Turbo Prop The turboprop is basically a turbojet
with an extra turbine designed to absorb the energy
remaining in the gas stream after sufficient has
been removed to drive the compressor.
The turboprop is a very efficient power unit
for relative low speed, low altitude aircraft.
Examples are the 748 and F27,
and the Transall C-160 and Atlantic.

20. Turbo Shaft Lycoming T55-GA-714 Boeing CH47 Chinook
Front Rotor Transmission
Rear Rotor Transmission
Combining Transmission
Turboshaft with Free Power Turbine

21. Turbo Shaft The turboshaft is virtually a turboprop
without a propeller.
The power turbine absorbs as much of
the remaining gas energy as possible
and the residual thrust is very low.
The main use of the turboshaft is the helicopter
and industrial and marine application,
including power and pumping stations,
hovercraft and ships.
Examples are the Lynx, Chinook and the Sea King.

22. Which of these is a turbo jet engine?
Check Understanding
Which of these is a turbo jet engine?
Tyne
Spey
Pegasus
Olympus

23. Check Understanding Which of the following features makes
the turbofan ideal
for both civil and military aircraft?
The turbine absorbs as much of
the gas energy as possible
Lower noise levels and
improved specific fuel consumption
Very efficient power unit
for relative low speed, low altitude
It is ideal for high-speed,
high-altitude aircraft

24. Which of these is a turbo fan engine?
Check Understanding
Which of these is a turbo fan engine?
Tyne
Pegasus
Dart
Gem

25. Check Understanding Which application or type of operation
best suits the turbojet engine?
In low speed aircraft
operating at high altitudes
In high speed aircraft where
low frontal area is an advantage
In low speed aircraft
operating at low altitudes
In helicopters

26. Which of these is a turbo prop engine?
Check Understanding
Which of these is a turbo prop engine?
RB 211
Dart
Spey
Avon

27. Check Understanding Which of these statements
applies to a turboprop engine?
It has one less turbine
compared to a turbojet
It has an extra turbine
compared to a turbojet
It is ideal for high-speed,
high-altitude aircraft
It has a very high
residual thrust

28. Which of these is a turbo shaft engine?
Check Understanding
Which of these is a turbo shaft engine?
Tyne
Lycoming
RB 211
Trent

29. JET PROPULSION
End of Presentation