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Assignment 5-2-3

Gas Turbine Engines Review

QuestionAnswer
What is the purpose of the Engine inlet? Act as a diffuser and provides a turbulent-free supply of air to the face of the compressor.
Why should the inlet duct be constructed with straight section? Smooth out turbulent airflow.
What are the advantages of a single-entrance duct? Simplest and most effective at providing smooth airflow.
What is the shape of a subsonic inlet duct? Why? Divergent, decrease velocity and increase pressure.
What is the shape of a supersonic inlet duct? Why? Convergent/Divergent, decrease velocity and increase pressure .
What is the purpose if a variable geometry inlet duct? To allow a supersonic aircraft to fly in all flight regimes (supersonic and subsonic).
What are the advantages and disadvantages of a centrifugal compressor? Centrifugal Advantages: Rugged, Low cost, Good power output and wide range of RPM's, High pressure increase per stage. Disadvantages: Large frontal area required, Impractical for multiple stages
What are the parts of a centrifugal compressor and what is the function of each? Impeller-increase velocity, pressure and total pressure. Diffuser-decrease velocity, increase pressure. Manifold-route air mas to the burner.
What are the components of an axial flow compressor? Rotors, stators
Why do the rotor and stator vanes within an axial compressor decrease in length for the front to rear of the compressor? The cross sectional area decrease within the compressor from fore to aft to allow the velocity to remain fairly constant as pressure increase. Therefore, the rotor and stator length requirements will decrease.
What do inlet and exit guide vanes do? Redirect the airflow.
What is the function of the diffuser? Final decrease in velocity and increase in pressure prior combustion.
Describe a dual-spool axial flow compressor. Why is it used. Two separate compressors, driven by its own turbine, to obtain higher compressor rations.
Where is fuel introduced within a gas turbine engine? In the burner.
What are the criteria for a good burner section? Minimum pressure loss. 2. High combustion efficiency. 3. Flame must not blow out. 4. Contain the total combustion process.
What are the three types of combustion chambers? What are the advantages and disadvantages of each? Can- ease of maintenance, cause cold spots on turbine. Annular-even heat, complicated maintenance. Can-annular-even heat, ease of maintenance, expressive .
What is primary and secondary air? Primary air = 20 to 25 % mixed fuel for combustion Secondary air = 75 to 80% cooling and flame cone control.
What is the purpose of the turbine section? To turn the compressor and accessories.
How mush of the energy produced is used to turn the compressor and accessories? 75 t0 80% for the total heat energy produced prior the turbine section.
What aer the main parts of the turbine? Stators and rotors.
What is creep? Turbine blade elongations and deformation.
What is the purpose of the exhaust duct? To increase velocity and decrease turbulence.
Describe a subsonic and supersonic exhaust duct and how each operate? Subsonic-convergent Supersonic-convergent/divergent. Both will maximize the increase in velocity at the expense of pressure.
Describe the four parts of an afterburner. Spray bars, flame holder, screech liner, variable exhaust nozzle.
Describe how an afterburner operates Secondary air form burner section along with bypass air (turbofan) is mixed with fuel and ignited in the afterburner dust to augment thrust.
What controls the amount of thrust augmentation an afterburner will produce? The more fuel introduced, the more thrust produce.
What is the function of the spray bars? The flame holder? Spray bars spray fuel. Flame holders hold the flame and they create local turbulence (eddies) to enable a better fuel/ air mixture for combustion.
What is a screech liner and how dowee it operate? it acts as a shock absorber to guard against pressure fluctuations or cycle vibration sometimes associated with After Burner AB .
What type of exhaust nozzle is used on an afterburner equipped aircraft? Variables exhaust nozzle
How does subsonic airflow react through a convergent opening? Airflow velocity will increase and pressure decrease
How does subsonic sonic airflow react through a divergent opening. Airflow pressure will increase and velocity will decrease.
Created by: Rudyrm
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