2. Gtt - Engine Parts

8/12/2019 2. Gtt - Engine Parts

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ENGINE PARTS

UNIT 2


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Engine Parts

1. Inlet Duct2. Compressor

3. Diffuser4. Combustion Chamber5. Turbines

6. Exhaust System


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Compressor

Provides high pressure air to the combustionchamber.

Energy released in the combustion chamber isdirectly proportional to the mass of airsupplied.

Compression ratio 25:1 . Efficiency 90%. Air flow 160kg/s.


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Types of compressors

Centrifugal flow Axial flow

Axial Centrifugal flow


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Centrifugal flow compressors

Centrifugal compressor flow, pressure and velocity changes.a) Airflow through a typical centrifugal compressor.b) Pressure and velocity changes through a centrifugal

compressor


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Axial flow compressors

Compressor Assembly


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Axial flow compressors

Comparison of centrifugal and axial flow compressorefficiencies with increasing pressure ratios


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BurnersTypes of burners

1. Can type2. Annular type

1. Through flow annular type

2. Side entry annular type3. Reverse flow annular type

3. Can annular type


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Can type burner

External view of a can type burner


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Can type burner

Section view of a typical can type burner


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Annular type burner

External view of the annular type burner


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Annular type burner

Section view of a annular combustion chamber


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Annular type burner

Annular combustion chamber using vaporizing tubes


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Can annular type burner

Combination of can and annular type burner. Makes good use of available space

Employs a number of individually replaceablecylindrical inner liners that receive air througha common annular housing.

Good control of fuel and airflow patterns. Greater structural stability. Lower pressure loss than that of the can type.


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In order to assure ignition in the burner, themixture of fuel and air should be stoichiometric,

and not moving very fast.The burner starts by separating out a small portion

of the air and decelerates it for combustion in the``primary zone''.

The gases leaving this region are too hot to betolerated by turbines.

The remaining air (dilution air) is then mixed with

the hot gases from the primary zone to produce anearly uniform temperature stream entering theturbine.


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Influence of design factors on burner performance

1. Methods of air distribution.

2. Physical dimensions of burner.3. Fuel air operating range(blow out limit).4. Fuel nozzle design.


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Combustion chamber


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Operating variables1. Pressure

2. Inlet air temperature3. Fuel air ratio4. Flow velocity

Effect of operating variables on burner performance


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1.Combustion efficiency: The combustion efficiency increases with increase in

pressure of air. At 1 atm pressure, the efficiency becomes stable.

The combustion efficiency increases with increase intemperature of air. The combustion efficiency increases with increase in fuel

air ratio and then becomes stable . The combustion efficiency increases with increase in flow

velocity. Increasing the flow velocity beyond a certain point reduces

combustion efficiency, since it reduces the time availablefor mixing and burning.



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3. Temperature distribution: Uniform temperature can be obtained by

creating better mixing of the hot and cold

gases at the cost of an increase in pressureloss.

If fuel/air ratio and flow velocity are increased,

the exit temperatures tend to become less-uniform because more heat is released andthere is less time for mixing.



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4.Starting: Starting is easier with high temperature, high

pressure and low velocity. Optimum fuel/air ratio.



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5.Carbon deposits: Carbon deposit increases with increase in the

temperature and pressure. Carbon deposit burn off at very high

temperature. Carbon deposit increases with increase in the

fuel air ratio. Changes in fuel air ratio may change the location

of carbon deposits within the burner.



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6. Temperature and cooling requirements: Increasing the pressure and temperature of

the incoming charge causes more heattransfer from burning gases to the liner.

Increase in fuel air ratio increases thetemperature of combustion and liner.

Increase in flow velocity reduces the linertemperature.



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i) High combustion efficiency.ii) Stable operation.iii) Low pressure loss.iv) Uniform temperature distributionv) Easy starting.vi) Small size.vii) Low smoke burner.viii)Low carbon formation

Performance requirements of combustionchambers


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High combustion efficiency: Necessary for longrange.Stable Operation: freedom from blowout at

airflow ranging from idle to maximum powerand at pressures representing the aircraftsentire altitude range is essential.

Low pressure loss: pressure loss reduce thrust

and increase specific fuel consumption.Uniform temperature distribution: Temperature

of gases entering the turbine should be closeto the temperature limit of the burnermaterial.


Performance requirements of combustion


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Easy starting: low pressure and high velocity in

the burner make starting difficult .Poorly designed burner will start within only a

small range of flight speed and altitudes.Well designed burner permit easier air restart.Small size: large burner results in large frontal

area, increase in aerodynamic drag, decreasein flight maximum speed, high engine weight,low fuel capacity.



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Low smoke burner: smoke is annoying on theground. It allows easy tracking of high flyingmilitary aircraft.

Low carbon formation: Carbon deposits blockcritical air passages and disrupt air flow alongthe liner walls, causing high metaltemperatures and low burner life.

C i f l


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Construction of nozzlesNozzle vanes are cast or forged.

Nozzle vanes are made hollow to allow a degreeof cooling.

Nozzle is made of very high strength steel to

withstand the direct impact of the hot, highpressure, high velocity gas flowing from thecombustion chamber.

Transpiration cooling


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Impulse turbine and reaction turbine


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Exhaust system


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Sound suppression


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Thrust reversal


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Methods of thrust augmentation


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Afterburner System

2. Gtt - Engine Parts

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