1. JET ENGINE MECHANICAL ARRANGEMENT
More generally known as ‘GAS TURBINE’ Engine
THE WORKING PARTS OF A JET ENGINE

2. JET ENGINE MECHANICAL ARRANGEMENT
Rolls-Royce AVON – Canberra – ’s technology
JET ENGINE MECHANICAL ARRANGEMENT

3. JET ENGINE MECHANICAL ARRANGEMENT
Rolls-Royce AVON Cut away view
JET ENGINE MECHANICAL ARRANGEMENT

4. JET ENGINE MECHANICAL ARRANGEMENT
Rolls-Royce AVON - (Graphic Representation)
Compressor Handling Bleed Valve
Front Engine Mount
Rear Compressor Case
Combustion Chambers (Cans)
Intake Anti-Icing Tube
Jet Pipe (Exhaust)
Front Compressor Casing
Accessory Gearbox
Oil Tank
Turbine Section
Rear Engine Mount
Fuel, Oil, and Hydraulic Pumps, Electrical Generators, RPM Governor.
JET ENGINE MECHANICAL ARRANGEMENT

5. JET ENGINE MECHANICAL ARRANGEMENT
Turbo-jet = no Bypass Duct
JET ENGINE MECHANICAL ARRANGEMENT

6. JET ENGINE MECHANICAL ARRANGEMENT
Engine Casings – Static Assembly
FRONT BULLET AND SUPPORT VANES
SUPPORT BEARINGS
NOZZLE GUIDE VANES (NGV’S)
REAR CONE AND SUPPORT VANES
STATOR VANES
COMBUSTION OUTER CASINGS
COMPRESSOR OUTER CASINGS
COMBUSTION INNER CASING
COMBUSTION FLAME TUBE
JET ENGINE MECHANICAL ARRANGEMENT

7. JET ENGINE MECHANICAL ARRANGEMENT
Rotating Assembly
Compressor Blades
Turbine Blades
Shaft Assembly
JET ENGINE MECHANICAL ARRANGEMENT

8. These sections expand first
Problem! Temperature changes cause the shaft and casings to expand and contract
But by different amounts!
Ambient temp
450 Deg C
2,500 Deg C
1,000 Deg C
Above ambient
The shaded area is called the ‘GAS PATH’.
These sections expand first
This could put tremendous unwanted forces on the casings and shaft leading to failures
(We’ll look at what happens to the air passing through the GAS PATH in
Gas Turbine Operation.)
Solution? Its all in the bearings!
JET ENGINE MECHANICAL ARRANGEMENT

9. Centre Bearing Chamber Ball Bearing (Location Bearing)
Bearing Chambers
Front Bearing Chamber
Centre Bearing Chamber
Rear Bearing Chamber
Roller Bearing
Ball Bearing (Location Bearing)
Roller Bearing
JET ENGINE MECHANICAL ARRANGEMENT

10. Representation of jet engine bearing layout
Ball Bearings Provide Positive Axial Location
Hot section
Casing
Front Bearing Chamber
Centre Bearing Chamber
Rear Bearing Chamber
Shaft
JET ENGINE MECHANICAL ARRANGEMENT

11. JET ENGINE MECHANICAL ARRANGEMENT
Representation of jet engine layout
The casing expands first - pushing the rear outer bearing with it
The same happens at the front with pressured air and heat sink from the combustor heating the hardware
Casing
Then, with ‘heat soak’ the shaft expands
The engine is actually designed to dimensions based on normal operating temperatures
Shaft
Shaft and Casing have no differential movement at this point
JET ENGINE MECHANICAL ARRANGEMENT

12. JET ENGINE COMBUSTOR OPERATION WHERE THE POWER IS PRODUCED

13. JET ENGINE – Combustion Process
THE COMBUSTION PROCESS
IN A PISTON ENGINE: -
FUEL IS MIXED WITH AIR BEFORE ENTERING THE CYLINDERS
THE FUEL/AIR MIXTURE IS THEN COMPRESSED
THEN IT IS IGNITED BY A SPARK
ONCE FOR TWO REVS OF THE ENGINE (IN THE 4 STROKE CYCLE)
IN A JET ENGINE: -
AIR IS COMPRESSED AND FORCED INTO THE COMBUSTOR FIRST
THEN THE FUEL IS SPRAYED IN UNDER PRESSURE
IT IS THEN IGNITED BY A SPARK (BUT ONLY ONCE FOR STARTING)
COMBUSTION IS THEN CONTINUOUS WHILST THE ENGINE IS RUNNING
THE SAME AS A PLUMBERS BLOW TORCH!
JET ENGINE – Combustion Process

14. We’re going to look in detail at what happens here
But first we’ll look at the layout
of the combustion system
JET ENGINE – Combustor Layout

15. JET ENGINE – Combustor Layout
COMBUSTOR LAYOUT – (ALSO HISTORICAL DEVELOPMENT)
INDIVIDUAL COMBUSTORS – ‘CANS’
EACH CAN HAS A FUEL SPRAY NOZZLE (FSN)
1st JET ENGINES
WHITTLE ETC
ENGINE STRUCTURE AND SHAFTS
INNER
CASING
OUTER
CASING
FLAME CONTAINED WITHIN THIS TUBE ‘FLAME-TUBE’
JET ENGINE – Combustor Layout

16. TYPICAL OF DART SERIES TURBO PROPS JET ENGINE – Combustor Layout
COMBUSTOR LAYOUT – (ALSO HISTORICAL DEVELOPMENT)
CANS CONNECTED TOGETHER
TO EQUALISE PRESSURES
AND
TO SPREAD THE FLAME ON START UP
IGNITERS
TYPICAL OF DART SERIES TURBO PROPS
JET ENGINE – Combustor Layout

17. JET ENGINE COMBUSTER OPERATION

18. INDIVIDUAL CANS WITH INTER-CONNECTORS
COMBUSTOR LAYOUT
‘CAN-ANNULAR’ LAYOUT
INDIVIDUAL CANS WITH INTER-CONNECTORS
ANNULAR OUTER CASING
ALSO FORMS THE ENGINE STRUCTURE
IGNITERS
TYPICAL OF SPEY &TAY BYPASS ENGINES
JET ENGINE – Combustor Layout

19. JET ENGINE COMBUSTER OPERATION

20. JET ENGINE – Combustor Layout
ANNULAR LAYOUT
GIVES EVEN TEMPERATURE FACE TO TURBINE BLADES
ANNULAR OUTER CASING
ANNULAR INNER CASING
THE LAYOUT OF CHOICE FOR MODERN BYPASS ENGINES
ALLOWS MORE FSN’S TO BE FITTED
JET ENGINE – Combustor Layout

21. JET ENGINE COMBUSTER OPERATION

22. JET ENGINE – Combustor Layout
THE CROSS SECTION OF ALL THESE LAYOUTS IS VIRTUALLY IDENTICAL
AND THEREFORE SO IS THE AIRFLOW!
JET ENGINE – Combustor Layout

23. JET ENGINE – Combustion Process
82% Cooling Flow
Inner Flame Tube
Outer Combustion Casing
1st Stage NGV’s
Fuel Feed
Recirculating Vortex
18% Vortex Flow
JET ENGINE – Combustion Process

24. Any Questions?