JET ENGINE PROPULSION

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JET ENGINE PROPULSION
Chapter 4
Types
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JET ENGINE TYPES
There are two ways of using the power from a jet
engine.
By taking as little power from the engine to turn
the engine and using most of the power as thrust
out of the exhaust.
Or by taking most of the power from the engine to
turn the engine and a drive shaft, which can be
used to drive a piece of machinery. i.e.
propeller, rotor or pump.
The engine designer will look at the requirements
and then decide on the best design for the job.
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JET ENGINE TYPES
Different types -
Turbo Jet
Avon, Olympus 593
Bypass Engine
Small Bypass
Conway, Spey, BR700
Medium Bypass
Pegasus, BR715, V2500
Large Bypass
RB211, Trent Series
Propeller
Dart, Tyne, BR715TP
Turbo Prop
Helicopter
Gem
Turbo Shaft
RN Ships
Marine Spey
Power Generation
Industrial Spey and Trent
To understand what is meant by Turbo Jet,
Bypass, Turbo Prop and Turbo Shaft
We need to look at the development of Gas Turbine
Engines
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JET ENGINE TYPES
Rolls-Royce AVON Basic Shape and Layout
Turbo Jet
17 Stage Compressor
driven by -
a 3 Stage turbine
With RPM (I.e. Thrust) changes, the airflow
velocity does not change in proportion to engine
RPM
This can cause problems at low RPM.
The rear of the compressor cannot cope with all
of the air from the front of the compressor.
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Turbo Jet
JET ENGINE TYPES
i.e. NO or insufficient rearward movement of air
Flame almost goes out - no power no thrust
This is called - Compressor SURGE
To alleviate this problem we need to get rid of
some of the air at the rear of the compressor.
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Turbo Jet
JET ENGINE TYPES
Rear end of compressor unchoked
Power restored
BUT - air dumped sideways out of the engine
(aircraft) produces no thrust
This is done through a Bleed Valve.
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Turbo Jet
JET ENGINE TYPES
Excess air is dumped overboard through a valve
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Turbo Jet
JET ENGINE TYPES
Air dumped overboard reduces thrust and wastes
fuel
So a more efficient system was required
Enter - Multiple shaft engines and the
Bypass system
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Turbo Jet
JET ENGINE TYPES
Allows front end of compressor to slow down
move less air
AND
Allows rear end of compressor to speed up move
more air
Two shaft layout (Twin Spool System)
Compressor surges lessened
No wasted energy/thrust
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JET ENGINE TYPES
Low Bypass
Bypass Layout
Adour
Rolls-Royce Spey
BR 710 series
Bypass allows air not required in the HPC to flow
around the outside of it
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JET ENGINE TYPES
Bypass Layout
Medium Bypass
Pegasus
Two shaft layout Contra-rotation
LP and HP AXIAL Flow Compressors
In USAF Service Harrier series
Core flow to Hot (rear) Nozzles
Bypass flow to Cold (front) Nozzles
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JET ENGINE TYPES
High Bypass Engine
Bypass Layout
Three shaft layout all rotate same direction
RB211 Series (Trent)
LP(Fan) IP and HP AXIAL Flow Compressors
Boeing 747 and later series, Airbus A330 and
larger a/c
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JET ENGINE TYPES
The fan produces a large amount of thrust from
the volume of air it moves backwards.
The core engine has a two stage compressor which
receives pressure air from the fan and so
improves efficiency.
The ratio of the air bypassing the core engine to
the air in the core engine gives a dimension to
the power split between the fan and the core.
A normal bypass ratio is 5 or 4 to 1. i.e. 5
times more thrust from the fan.
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JET ENGINE TYPES
Rolls Royce Trent
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JET ENGINE TYPES
Turbo Prop
RR Dart
Dart RDa6 2 stage turbine
Dart RDa7 3 stage turbine
Turbine drives 2 stage CENTRIFUGAL Compressor and
Propeller
Over 70 different Marks of Engine basically
different power levels 15 different aircraft
Was in service with RAF Andover and Argosy
Transport Aircraft.
Fokker F27, Fairchild F27, Briguet Alize, (and
P51 Mustang and Dakota!)
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JET ENGINE TYPES
Turbo Prop
Tyne
Prop Shaft (via Reduction Gearbox)
C160 Transall, Shorts Belfast, Bristol Britannia,
Brequet Atlantic, Avro Lincoln, Canadair CL44,
Vickers Vanguard, Aeritalia 222.
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JET ENGINE TYPES
RR Allison T56-A-15
Turbo Prop
Turbine drives compressor and propeller
C130 Hercules, P3 Orion, Lockheed Electra, E2C
Hawkeye.
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JET ENGINE TYPES
Lycoming T55-GA-714 - with Free Power Turbine
Turboshaft
Boeing CH47 Chinook
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JET ENGINE TYPES
Any Questions?