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CHRISBA777ER
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Why Are Some Afterburners Blue And Some Orange?

Wed Jan 30, 2008 2:38 pm

Simple question really -



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I mean, I know Concorde's were blue and I've seen a pic of the Blackjack and hers were blue as well - is it a large aircraft thing?
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
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moo
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RE: Why Are Some Afterburners Blue And Some Orange

Wed Jan 30, 2008 2:40 pm

Temperature at which they are burning at and whether the burn is complete or not - and they can change colour as well.

Quoting CHRISBA777ER (Thread starter):
I mean, I know Concorde's were blue

There are numerous videos where they are orange as well.
 
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Stitch
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RE: Why Are Some Afterburners Blue And Some Orange?

Wed Jan 30, 2008 2:40 pm

Could it be temperature-related? Larger engines with higher operating temperatures creating bluer exhausts?
 
Ceph
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RE: Why Are Some Afterburners Blue And Some Orange?

Wed Jan 30, 2008 4:00 pm

Blue or non-luminious flame are produced when there is complete combustion. Orange or luminious flames are produced when there are incomplete combustion as there are still carbon around.

As far as I know, it could be due to the amount of oxygen feeding the flames.

And yes, the blue flame is much hotter then the orange flame.
 
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Starlionblue
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RE: Why Are Some Afterburners Blue And Some Orange

Wed Jan 30, 2008 4:33 pm



Quoting Ceph (Reply 3):
And yes, the blue flame is much hotter then the orange flame.

Just like gas stoves. Methane fueled tend to be much bluer, thus cleaner combusting. Propane and such has a yellow flame and leaves more residue.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
BAE146QT
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RE: Why Are Some Afterburners Blue And Some Orange?

Wed Jan 30, 2008 5:03 pm



Quoting Ceph (Reply 3):
Blue or non-luminious flame are produced when there is complete combustion. Orange or luminious flames are produced when there are incomplete combustion as there are still carbon around.

Unrelated to aviation, but this information has saved lives.

Some years ago, a young girl had learned the above fact at school. At home that evening, she looked through the little window of her parent's gas heating boiler and noticed that it was burning yellow. Thinking it odd, she pointed it out to her dad who in turn called a repairman.

Turned out that it was pumping out Carbon Monoxide by the bucket load because of blocked filters reducing airflow.

So, yes, it probably is nothing more than varying degrees of combustion.
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KELPkid
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RE: Why Are Some Afterburners Blue And Some Orange?

Wed Jan 30, 2008 11:54 pm



Quoting Starlionblue (Reply 4):
Just like gas stoves. Methane fueled tend to be much bluer, thus cleaner combusting. Propane and such has a yellow flame and leaves more residue.

Actually, in my experience, natural gas appliances converted to run on propane burn with blue flames, too. But you are right, they will leave behind a little bit of carbon residue on your pots and pans, whereas natural gas (methane) won't.

Come to think of it, my Coleman camping stove (propane-powered) burns with a blue flame, although you get the occasional flicker of orange when it's cooking  Wink
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
MQTmxguy
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RE: Why Are Some Afterburners Blue And Some Orange?

Thu Jan 31, 2008 6:00 am

Quoting Ceph (Reply 3):
Blue or non-luminious flame are produced when there is complete combustion. Orange or luminious flames are produced when there are incomplete combustion as there are still carbon around.

As far as I know, it could be due to the amount of oxygen feeding the flames.

And yes, the blue flame is much hotter then the orange flame

I think you hit it the closest. My guess would be that the blue AB flame front is a product of a lower AB setting (AB1 AB2) or just an AB that dumps less fuel than others. While you may get more thrust from AB2, I could see where a lower setting would burn hotter due to using less O2 out of the gas stream for combustion, thus having a leaner, hotter mixture

[Edited 2008-01-30 22:01:05]

[Edited 2008-01-30 22:02:08]
Well at least we can all take comfort in the fact that NW will never retire their DC-9s
 
avt007
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RE: Why Are Some Afterburners Blue And Some Orange?

Thu Jan 31, 2008 8:08 pm

Somewhere I still have a tool called "something-tune" I can't remember the whole name, but it is a see through sparkplug. You install it in the engine, and by observing the colour of the flame, you can judge the mixture ColourTune, that's it! And as I recall, orange indicated rich, and a deep blue was best. Same applies here.
 
CF188A
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RE: Why Are Some Afterburners Blue And Some Orange?

Thu Jan 31, 2008 9:45 pm



Quoting Ceph (Reply 3):
Blue or non-luminious flame are produced when there is complete combustion. Orange or luminious flames are produced when there are incomplete combustion as there are still carbon around.

As far as I know, it could be due to the amount of oxygen feeding the flames.

And yes, the blue flame is much hotter then the orange flame.

does this mean Russian jets are better than American jets :P:P:P
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grandtheftaero
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RE: Why Are Some Afterburners Blue And Some Orange?

Fri Feb 01, 2008 3:26 am



Quoting Ceph (Reply 3):
Blue or non-luminious flame are produced when there is complete combustion. Orange or luminious flames are produced when there are incomplete combustion as there are still carbon around.

Sho-nuff. Flame color has a lot to do with adiabatic flame temperature and the presence of carbon. These kinda go hand-in-hand. If you mix the right portions of fuel and air well you well get good combustion with little or no unused fuel. Your flame will be very hot and the corresponding black-body radiation will be toward the blue side of the spectrum. Furthermore if you have completely burned all of the hydrocarbons your flame will free of yellow-flame-producing soot. Mess this up and have an over-rich or poorly "stirred" mixture and your flame temp will decrease, moving the black-body emission closer to the orange/yellow side of the spectrum. More soot will be present creating yellow flame as well.

WARNING: SELF GLOSS! Do a good job and all you will see is blue flame regardless of power setting or flight condition. During testing, the F136 augmentor operates from min AB all the way to max AB thrust with a deep-blue to whitish-blue flame the entire time. I have video... but I can't show it here. You'll just have to take my word that my colleagues and I did an awesome job.  Silly

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