jet engine mechanical arrangement

JET ENGINE MECHANICAL JET ENGINE MECHANICAL ARRANGEMENTARRANGEMENT

THE WORKING PARTS OF A JET ENGINE

More generally known as ‘GAS TURBINE’‘GAS TURBINE’ Engine

Rolls-Royce AVON – Canberra – 1950’s technologyRolls-Royce AVON – Canberra – 1950’s technology

JET ENGINE MECHANICAL ARRANGEMENTJET ENGINE MECHANICAL ARRANGEMENT

Rolls-Royce AVON - Rolls-Royce AVON - (Graphic Representation)(Graphic Representation)


Combustion Combustion Chambers Chambers

(Cans)(Cans)Jet Pipe Jet Pipe

(Exhaust)(Exhaust)

Front Front Engine Engine MountMount

Compressor Compressor Handling Handling

Bleed ValveBleed ValveIntake Anti-Intake Anti-Icing TubeIcing Tube

Rear Rear Compressor Compressor

CaseCase

Front Front Compressor Compressor

CasingCasing

Turbine Turbine SectionSection

Rear Engine Rear Engine MountMount

Oil Oil TankTank

Accessory Accessory GearboxGearbox

Fuel, Oil, and Fuel, Oil, and Hydraulic Pumps, Hydraulic Pumps,

Electrical Generators, Electrical Generators, RPM Governor. RPM Governor.

Turbo-jet = no Bypass DuctTurbo-jet = no Bypass Duct


Engine Casings – Static AssemblyEngine Casings – Static Assembly

STATOR VANES

NOZZLE GUIDE VANES (NGV’S)

SUPPORT BEARINGS

COMPRESSOR OUTER

CASINGS

COMBUSTION INNER CASING

COMBUSTION OUTER

CASINGS

COMBUSTION FLAME TUBE

REAR CONE AND SUPPORT

VANES

FRONT BULLET AND

SUPPORT VANES



Rotating AssemblyRotating Assembly

Compressor BladesCompressor Blades Turbine BladesTurbine Blades

Shaft AssemblyShaft Assembly

The shaded area is called the ‘GAS PATH’. The shaded area is called the ‘GAS PATH’.


(We’ll look at what happens to the air passing through the (We’ll look at what happens to the air passing through the GAS PATHGAS PATH in in

Gas Turbine Operation.)Gas Turbine Operation.)

Problem! TProblem! Teemmppeerraatuturree changes cause the shaft and casings to expand and contract changes cause the shaft and casings to expand and contract

But by different amounts!But by different amounts!

This could put tremendous unwanted forces on the casings and shaft leading to failuresThis could put tremendous unwanted forces on the casings and shaft leading to failures

Solution? Its all in the bearings!Solution? Its all in the bearings!

Ambient tempAmbient temp 450 Deg C450 Deg C 2,500 Deg C2,500 Deg C 1,000 Deg C1,000 Deg C Above Above ambientambient

These sections These sections expand firstexpand first

Front Front Bearing Bearing

ChamberChamber

Centre Centre Bearing Bearing

ChamberChamber

Rear Rear Bearing Bearing

ChamberChamber

Bearing ChambersBearing Chambers

Roller Roller BearingBearing

Ball Bearing Ball Bearing (Location Bearing)(Location Bearing)

Roller Roller BearingBearing


ShaftShaft

CasingCasing

CasingCasing

Front Front Bearing Bearing

ChamberChamber

Centre Centre Bearing Bearing

ChamberChamber

Rear Rear Bearing Bearing

ChamberChamber

Ball Bearings Ball Bearings Provide Positive Provide Positive Axial LocationAxial Location

Hot Hot sectionsection


Representation of jet engine bearing layoutRepresentation of jet engine bearing layout

CasingCasing

CasingCasing

ShaftShaft


Shaft and Casing have Shaft and Casing have no differential no differential

movement at this pointmovement at this point

The casing expands first - The casing expands first - pushing the rear outer pushing the rear outer

bearing with itbearing with it

Then, with ‘heat soak’ the Then, with ‘heat soak’ the shaft expandsshaft expands

The same happens at the front with The same happens at the front with pressured air and heat sink from the pressured air and heat sink from the

combustor heating the hardwarecombustor heating the hardware

Representation of jet engine layoutRepresentation of jet engine layout

The engine is actually designed to dimensions based on The engine is actually designed to dimensions based on normal operating temperaturesnormal operating temperatures

JET ENGINE COMBUSTOR JET ENGINE COMBUSTOR OPERATIONOPERATION

WHERE THE POWER IS PRODUCED

FUEL IS MIXED WITH AIR BEFORE ENTERING THE CYLINDERS

THE FUEL/AIR MIXTURE IS THEN COMPRESSED

THEN IT IS IGNITED BY A SPARK

IN A PISTON ENGINE: -

ONCE FOR TWO REVS OF THE ENGINE (IN THE 4 STROKE CYCLE)

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)

IN A JET ENGINE: -

COMBUSTION IS THEN CONTINUOUS WHILST THE ENGINE IS RUNNING

JET ENGINE – Combustion ProcessJET ENGINE – Combustion Process

THE COMBUSTION PROCESS

THE SAME AS A PLUMBERS BLOW TORCH!

We’re going to look in detail at

what happens here

But first we’ll look at the layoutof the combustion system

JET ENGINE – Combustor LayoutJET ENGINE – Combustor Layout

EACH CAN HAS A FUEL SPRAY NOZZLE (FSN)

COMBUSTOR LAYOUT – (ALSO HISTORICAL DEVELOPMENT)

INDIVIDUAL COMBUSTORS – ‘CANS’1st JET ENGINES

WHITTLE ETC

OUTERCASING INNER

CASING

ENGINE STRUCTURE

AND SHAFTS

FLAME CONTAINED WITHIN THIS TUBE

‘FLAME-TUBE’


COMBUSTOR LAYOUT – (ALSO HISTORICAL DEVELOPMENT)

CANS CONNECTED TOGETHER TO EQUALISE PRESSURES

AND

TO SPREAD THE FLAME ON START UP

TYPICAL OF DART SERIES

TURBO PROPS

IGNITERS


JET ENGINE COMBUSTER OPERATIONJET ENGINE COMBUSTER OPERATION

COMBUSTOR LAYOUT ‘CAN-ANNULAR’ LAYOUT

ANNULAR OUTER

CASING

ALSO FORMS THE ENGINE STRUCTURE

IGNITERS

INDIVIDUAL CANS WITH INTER-

CONNECTORS

TYPICAL OF SPEY &TAY

BYPASS ENGINES


COMBUSTOR LAYOUT ANNULAR LAYOUT

ANNULAR OUTER

CASING

ANNULAR INNER CASING

ALLOWS MORE FSN’S TO BE FITTED

GIVES EVEN TEMPERATURE FACE TO TURBINE BLADES

THE LAYOUT OF CHOICE FOR

MODERN BYPASS ENGINES


THE CROSS SECTION OF ALL THESE LAYOUTS IS VIRTUALLY IDENTICAL

AND THEREFORE SO IS THE AIRFLOW!


JET ENGINE – Combustion ProcessJET ENGINE – Combustion Process

Fuel Feed

Outer Combustion Casing

1st Stage NGV’s

18% Vortex Flow

Recirculating Vortex

Inner Flame Tube

82% Cooling Flow

Any Questions?Any Questions?

jet engine mechanical arrangement

Documents

piston engine

combustor firstthen

jet enginemore

pressured air

rear outer bearing

historical developmentcans

temperature face

temperature changes