Unit 3:Gas Turbine Flashcards
Lecture 8-16 (37 cards)
What thermodynamic cycle underpins gas turbine operation?
The brayton cycle, involving compression, combustion at constant pressure and expansion.
What are the main components of a gas turbine?
Compressor, Combustor, turbine and Nozzle.
What is the main role of compressor?
To raise the temperature and pressure of the intake air before combustion.
What is the benefit of increasing turbine inlet temperature and it limitation?
Higher turbine inlet temperature improves engine efficiency and power output.
Material temperature limit and cooling capability
What is thrust in terms of gas turbine function?
Thrust is generated by expelling high velocity exhaust gases applying Newton’s third law.
What is propulsive efficiency?
Efficiency of converting fuel energy to useful KE
How to increase thrust in gas turbine?
Increase exhaust velocity or mass flow rate.
What engine type offers better propulsive efficiency at subsonic speed?
Turbofan engines.
What are the key losses in real gas turbines?
Pressure losses, friction and non ideal combustion.
What is ram drag?
The resistance due to air entering the intake at flight speed.
What is the main cause if pressure loss in combustion?
Friction and turbulence as air flows through the burner.
What factor affects real cycle efficiency the most?
Component efficiencies, especially the compressor and turbine.
What are the two main types of compressors?
Axial and centrigual.
Why are axial compressors preferred in large engines?
They offer higher pressure ratios and greater efficiency for large mass flow.
What limit compressor performance?
Flow separation and stalling due to adverse pressure gradient.
What is compressor surge?
A condition of flow reversal that can damage the engine.
How is stable compressor operation maintained?
By matching pressure rise to flow angle and using variable stator vanes.
What components follow each rotor in an axial compressor?
A stator, which straightens and redirects the airflow.
What is the main role of a turbine in a gas turbine engine?
To extract energy from exhaust gases to power the compressor and fan.
Why are turbine blades cooled?
To prevent material failure at high operating temperature.
What is a nozzle guide vane (NVG).
A stationary components that redirects flow onto the turbine rotor blades.
How does the turbine affect overall engine performance?
Efficient turbines enable higher compressor pressure ratios and better cycle efficiency.
Why is turbine blade material selection critical?
Because they must withstand extreme temperatures and mechanical stress.
What are common materials used in turbine?
Nicked- based superalloys, often ceramic coating.
