Flame in a background atmosphere of fuel

[hilbert2]

In combustion science, typical flames that are studied are premixed or diffusion flames, where a stream of methane, propane or some other fuel is released to an atmosphere of air or oxygen and ignited. Another scenario is a "pool fire", where a puddle of volatile solvent is burning in air and there's a balance between energy consumption by evaporation and energy production by oxidation.

Have there been any combustion experiments where the setting is the opposite - a stream of oxygen gas released from a gas tank to a background atmosphere of fuel (propane gas, etc...) and ignited? An equivalent of a pool fire in such a situation would be a pool of dinitrogen pentoxide or other liquid oxidizer "burning" in a hydrocarbon atmosphere. I wasn't able to find any examples of this kind of experiments myself, but intuition tells that in such an experiment there would be a lot more soot and other pyrolysis products formed than in an ordinary combustion, because there would always be an excess of fuel available.

Of course, this kind of situation is very improbable in practice, but doing such a test could be interesting from the viewpoint of combustion theory.

 

[Bystander]

http://www.fireengineering.com/articles/2005/03/flashover-and-backdraft-a-primer.html

 

[hilbert2]

Thanks, I forgot about the backdraft phenomenon. In that case the reducing atmosphere is pre-heated, though, so it's not exactly what I was thinking about.

 

[Bystander]

... , and, there's https://nfa.usfa.fema.gov/pdf/efop/tr_95ck.pdf , also related, but not quite "there." An interesting question.

 

[hilbert2]

Looks like this kind of burning is called an inverse flame: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040053527.pdf . Probably difficult to experiment with, because of the explosion risk from having a large chamber filled with a fuel atmosphere.

 

[snorkack]

Looks like this kind of burning is called an inverse flame: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040053527.pdf . Probably difficult to experiment with, because of the explosion risk from having a large chamber filled with a fuel atmosphere.

Only if there is enough oxidant in the tank.

For example, gasoline is said to have upper explosive limit of just 7,6 %. So if you have a gasoline tank and the large gas volume inside is 10 % gasoline vapours, 90 % air, it cannot ignite. Only the small volume of mixture in the mouth of the tank can sustain fire.
What happens if you then withdraw gasoline from the tank, pulling air and fire into the tank (still too fuel rich to sustain an explosion through the headspace)?

 

[hilbert2]

For example, gasoline is said to have upper explosive limit of just 7,6 %. So if you have a gasoline tank and the large gas volume inside is 10 % gasoline vapours, 90 % air, it cannot ignite. Only the small volume of mixture in the mouth of the tank can sustain fire.
What happens if you then withdraw gasoline from the tank, pulling air and fire into the tank (still too fuel rich to sustain an explosion through the headspace)?

I was thinking about the possibility of the reaction compartment leaking and therefore producing an explosion risk.