lehpron
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Flameholders?

Thu Nov 03, 2005 4:54 am

For some reason, I have always akin the burn of fuel out of an injector to a pilot light in a commercial heating furnace. That it would always be lit unless the fuel flow stopped, but needed to be re-lit by an ignition source every time.

What are flame holders, what do they look like and how do they work? Do they store heat, so to speak.
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MD11Engineer
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RE: Flameholders?

Thu Nov 03, 2005 6:01 am

Quoting Lehpron (Thread starter):
What are flame holders, what do they look like and how do they work? Do they store heat, so to speak.

Flameholders create localised turbulence in the combustor (or the tail pipe of an engine with reheat / afterburner), which locally slows down the airflow and prevents the flame from getting blown away from the vicinity of the injector nozzles.

In afterburners they often look like rings of v shaped sheetmetal (high heat resistant steels, opening of the V faces aft) around and just downstream of the injector.

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TripleDelta
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RE: Flameholders?

Thu Nov 03, 2005 6:32 am

Quoting MD11Engineer (Reply 1):
Flameholders create localised turbulence in the combustor (or the tail pipe of an engine with reheat / afterburner), which locally slows down the airflow and prevents the flame from getting blown away from the vicinity of the injector nozzles.

I found this nice shot of the rear end of an F-16 engine in the db. Is this ring with the "fingers" and corrugated inner and outer radius the flameholder?

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FredT
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RE: Flameholders?

Thu Nov 03, 2005 6:35 am

Quoting TripleDelta (Reply 2):
I found this nice shot of the rear end of an F-16 engine in the db. Is this ring with the "fingers" and corrugated inner and outer radius the flameholder?

From experience with other types: Yes.
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IFIXCF6
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RE: Flameholders?

Thu Nov 03, 2005 10:29 am

From my experience with this exact type: Yes
 
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HAWK21M
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RE: Flameholders?

Thu Nov 03, 2005 1:28 pm

http://rds.yahoo.com/S=96062883/K=flame+holders/v=2/SID=w/l=IVS/SIG=11mok292n/EXP=1131078262/*-http%3A//www.fb-111a.net/OJT6-14.jpg
http://www.laugle.com/J57%20Flame%20Holders.jpg
regds
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lehpron
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RE: Flameholders?

Mon Nov 07, 2005 3:42 am

From all those who described, from my point of view, I see two things:

The flow just aft of the injector and prior to the flame holder looks like it would slow to zero just before flowing to either side of the ring. Is there much stagnation from the injector to the ring itself? Would that pressure increase help the burn?

I would probably see a localized reverse flow behind the ring that is 'U' or 'V' shaped like a twin local vortex solenoid spool, so to speak. Not that there is a vacuum on the back side, but wouldn't the pressures be significantly lower to cause this flow disturbance?
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