[Stoves] Loss of flame from a fire

[Crispin Pemberton-Pigott]

Dear Friends

 

This is a classic demonstration of what happens when there is a dwindling
fire in a hot stove and suddenly the flame goes out (usually making a lot of
smoke).

 



 

The vertical yellow bar indicates when the water in the pot reached 30 C and
the blue when it reached 70 C. The black line is the CO/CO2 ratio. It goes
from wonderful (much less than 1%) to 9% in a few seconds.

 

Looking at the excess air (green line) you can see that it was creeping up
as the fire got smaller. That is a bad sign and can be prevented (well,
considerably delayed) by using counter-flowing preheated primary and
secondary air as discussed a couple of days ago. Marc, this is a good
lesson. If the EA had not risen so much the flame would have kept going a
lot longer. Because it went out, the average COr for this pot heating
efficiency test was 6.5% instead of perhaps 1.5%. When the EA jumps up like
that (as the air is no longer being used by the flames) the heat transfer
efficiency takes a big knock.

 

The stove's air is supplied to the fire from below and the fuel was black
wattle, though this late in the fire it was mostly char.

 

Regards

Crispin

 

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