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Turbine Engine

© Devinder K Yadav

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Gas Turbine Fuels

Liquid hydrocarbons similar to kerosene

Some are blended with gasoline

Narrow cut/wide cut

Jet fuels are not color coded but may have

a natural pale straw colour

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Jet Fuel Qualities

Ease of flow

able to start readily but not be volatile

complete and rapid combustion

high calorific value

non-corrosive

lubricating

minimal fire hazard 4

Jet Fuel Types (AVTUR)

Jet A – no gasoline blend

Jet A1 – similar to Jet A but with a lower

freezing point (also called JP-8* or F34)

Jet B – contains a gasoline blend, higher

flammability, generally for cold climates

*JP-8 has additional additives

JP-5, JP-8 - Military fuels

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Some Fuel Comparisons

Flash point Avtur +38oC

Avgas –400C

Volatility Avtur lower than Avgas

Avtur harbours more dissolved water

which can freeze, produce waxes and allow

microbiological growth 6

Some Fuel Comparisons

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Jet Fuel Additives

The most common fuel additives are the

anti-icing and anti-microbiocidal agents

Anti-icing additives keep entrained water

from freezing

Microbiocidal agents kill microbes fungi

and bacteria which form a slime and in

some cases a matted waste in fuel systems 8

Fungus and bacteria grown in diesel/water

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Jet Fuel Additives

Reduces the freezing point of any water

present.

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Water Detection in Turbine Fuel

All aviation fuels can contain some

dissolved water

Turbine fuel more so than gasoline

CAO 20.2 Subsection 5

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Fuel Heat Content

Specific gravity Avgas 0.7 approx

Avtur 0.8 approx

Avtur yields more heat than Avgas per

unit volume

Avgas yields more heat than Avtur per unit

weight 13

Fuel Control

The purpose of the fuel control unit is to

maintain a correct combustion zone air-to-

fuel mixture ratio of 15:1 by weight

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Fuel Control

To maintain the correct air-to-fuel

relationship altitude, air temperature and

aircraft speed must be considered

These variables change the density of the

air at the engine intake and consequently

the mass of air induced through the engine

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Fuel Control

Many signals are sent to the fuel control unit

to maintain the correct fuel-to-air ratio

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Fuel Control

Engine speed (N2)

Used for both steady state fuel

scheduling and acceleration/deceleration

fuel scheduling

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Fuel Control

Inlet Pressure (Pt2)

A total pressure signal from a probe

in the engine inlet

The pressure will be the result of

aircraft speed, altitude and ram

conditions 18

Fuel Control

Compressor Discharge Pressure (PS3)

Static pressure signal of the mass

airflow at that point in the engine

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Fuel Control

Burner Can Pressure (PS4)

A static pressure signal from within

the combustion liner

The quick response this signal gives

makes it valuable in preventing stalls,

flameouts and over-temperature

conditions 20

Fuel Control

Inlet Temperature (Tt2)

A total temperature (actual plus

ram) signal from the inlet

This signal provides the control with

an airflow density value against which

a fuel schedule can be established

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Fuel Control

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Turbine Engine

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Turbine Engine Lubrication System

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Turbine Engine Lubrication System

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Dry Sump Lubrication System

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Dry Sump Lubrication System

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Wet Sump Lubrication System

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Oil Pump

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Oil Seals

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Fuel cooled oil cooler (FCOC)

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Fuel cooled oil cooler (FCOC)

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Turbine Engine

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Engine air bleed and internal cooling System

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Engine air bleed and internal cooling System

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Engine air bleed and internal cooling System

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Engine air bleed and internal cooling System

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Engine air bleed and internal cooling System

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Bleed Air Systems

Bleed air is tapped from various

compressor stages for use in the engine and

aircraft

Bleed air is typically 4 – 5% of total engine

airflow

A reduction in engine airflow results in a

reduction in engine performance

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Bleed Air Systems

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Bleed Air Systems

internal sealing

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Oil Seals

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Bleed Air Systems

Internal cooling

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Bleed Air Systems

Internal cooling

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Bleed Air Systems

Internal cooling

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Bleed Air Systems Internal cooling

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Bleed Air Systems

external cooling & sealing

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Engine Anti-ice System

• The engine anti-ice system uses engine bleed air to provide engine cowl inlet ice protection. •The system can be operated in-flight or on ground. •The left and right engines have identical, independent anti-ice systems. This allows the remaining system to operate, if one engine fails.

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Bleed

Air

Systems

engine

anti ice

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Bleed

Air

Systems

engine

anti ice

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Engine Anti-ice System

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