GAS TURBINESGAS TURBINESGAS TURBINESGAS TURBINES Power Augmentation SystemsPower Augmentation SystemsPower Augmentation SystemsPower Augmentation Systems

1. 1. 1. 1. Outline the basic requirements, arrangements and principles of operation of the following gas turbine Outline the basic requirements, arrangements and principles of operation of the following gas turbine Outline the basic requirements, arrangements and principles of operation of the following gas turbine Outline the basic requirements, arrangements and principles of operation of the following gas turbine

power augmentation systems and components: power augmentation systems and components: power augmentation systems and components: power augmentation systems and components:

a. a. a. a. Water (demineralised) injectionWater (demineralised) injectionWater (demineralised) injectionWater (demineralised) injection

~ to restore, or even boost, the thrust from a gas turbine operating from hot and high altitude airfields

~ when the mixture is sprayed into the compressor inlet, the temperature of the compressor inlet air is

reduced and consequently the air density and thrust are increased.

~ uses latent heat of evaporation principle to remove heat energy from the air

~ the heat from the air is transferred to the water droplets, cooling the air and making the gas flow

more dense

~ demineralised must have less than 10ppm of solids

b. b. b. b. Water/methanol Water/methanol Water/methanol Water/methanol injectioninjectioninjectioninjection

~ generally a blend of 35 to 50 percent methanol to water

~ methanol is often added because it has anti-freezing properties and it is also a fuel; therefore

water/methanol increases the density of the airflow and provides the extra fuel necessary to

match the increased weight of air

~ when methanol is added, the turbine inlet temperature is partially restored by burning the methanol

in the combustion chamber; this restores the engine power without adjusting the fuel flow

2. 2. 2. 2. Specify the effect that fluid injection has on performance and efficiency across the various stages of Specify the effect that fluid injection has on performance and efficiency across the various stages of Specify the effect that fluid injection has on performance and efficiency across the various stages of Specify the effect that fluid injection has on performance and efficiency across the various stages of

the engine:the engine:the engine:the engine:

~ causes denser air to enter the compressor stages, increasing compression and mass flow

~ when introduced into the combustion gases, the water allows additional fuel to be added without

exceeding maximum temperature limits

3. 3. 3. 3. Identify where on an engine water may be injected into the gas flow:Identify where on an engine water may be injected into the gas flow:Identify where on an engine water may be injected into the gas flow:Identify where on an engine water may be injected into the gas flow:

~ The water/methanol mixture can be:

Injected as a spray into the compressor air intake, or

Injected direct into the combustion chamber

~ Spraying the mixture into the air intake is more effective for engines with centrifugal compressors where an

even distribution of the mixture is obtained, whereas with an axial flow compressor an even

distribution is uncertain.

~ Water/methanol injection into the combustion chamber used to be carried out on older

engines where the combustion chambers were relatively long and the methanol had time to

separate and burn before entering the turbine.

GAS TURBINESGAS TURBINESGAS TURBINESGAS TURBINES Power Augmentation SystemsPower Augmentation SystemsPower Augmentation SystemsPower Augmentation Systems

4. 4. 4. 4. Specify how injected fluid actually increases power output of an engine. Identify the power increase Specify how injected fluid actually increases power output of an engine. Identify the power increase Specify how injected fluid actually increases power output of an engine. Identify the power increase Specify how injected fluid actually increases power output of an engine. Identify the power increase

a modern water injection system may achieve:a modern water injection system may achieve:a modern water injection system may achieve:a modern water injection system may achieve:

~ any condition that reduces the air density will reduce also the engine power output

~ the engine power can be restored and in some instances increased, by cooling the airflow to increase

its density

~ The addition of water has two effects upon the performance of the engine: the cooling effect of water

increases the density of the airflow to increase the thrust and, when the water is converted into steam, it

provides a high volumetric expansion that increases the thrust even further.

~ When methanol is added, the turbine inlet temperature is partially restored by burning the methanol

in the combustion chamber; this restores the engine power without adjusting the fuel flow.

~ Results in a thrust increase in the range of 10 15 percent

5. 5. 5. 5. DesDesDesDescribe the relationship, location and function of the engine power augmentation system cribe the relationship, location and function of the engine power augmentation system cribe the relationship, location and function of the engine power augmentation system cribe the relationship, location and function of the engine power augmentation system

components and the interrelationship between the augmentation system and the fuel control system:components and the interrelationship between the augmentation system and the fuel control system:components and the interrelationship between the augmentation system and the fuel control system:components and the interrelationship between the augmentation system and the fuel control system:

~ When the injection system is switched on, water/methanol mixture is pumped from an aircraft

mounted tank to a control unit.

~ The control unit meters the flow of mixture to the compressor inlet through a metering valve

that is operated by a servo piston.

~ The control unit high pressure control lever is interconnected to the throttle control system in

such a manner that, until the throttle is moved towards the take-off position, the fluid supply

remains closed, and thus the metering valve remains closed, preventing any mixture flowing to the

compressor inlet.

~ Movement of the throttle control to the take-off position opens the fluid supply to the compressor

inlet.

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