Lecture 11 - Aero and Industrial Gas Turbines Flashcards
When are emissions regulated for aircraft
during landing and takeoff situation - causes development to make gas turbines bigger diameter - more efficient at low amplitude
What is the emissions trade off faced in engine design
high pressure ratios = more efficient but need higher take off temp which increases smoke and NOx
NOx emissions are dependent on
Temperature of engine
Why is there such a small range of temperature for engines
minimum point - if you increase temp NOx increases
if you decrease temp CO increases
can we use water to reduce emissions
technically yes - reduce temp reduce NOx emissions - have to be careful where you input - cant do before compressor as cant compress, difficult to do after compressor as you require a lot of water
Why do fighter jets inject water in through combustor
when performing fast maneuvers - more mass flow rate from nozzle
Can we use steam to reduce emissions
yes technically - inject in combustor to reduce temp and reduce NOx but difficult to do pracitcally
What is the advantage variable geometry combustors
proposed concept to reduce NOx, pass more air through combustor or round outside
more air in combustor - high altitude, reduce temp reduce NOx
more air outside - stable flame, more thrust, for takeoff
What are catalytic Combustors
Combustors with catalysts in, not used as pressure drop too high
What would premixing fuel do
premixing fuel with air - better combustibility - burn leaner - lower temp - lower NOx
What is a rich burn quick quench combustor
RQL combustor - currently working on - burn very rich then burn very lean, need to closely control temperatures and inject air very quickly to prevent massive jump in temperatures
Intention to keep temperature very low
Options for improving combustor efficiency
variable geometry catalytic premixing rich burn quick quench Staged Combustor
What is a staged combustor
combust in stages - keep low temperatures
What type of aircraft uses twin spool GT
military
What type of aircraft uses triple spool
standard passenger jet