[Stoves] Premixing

[alex english]

Paul,
You asked what I might be able to do to shed light on the conditions for
achieving a blue flame.

This week I followed the evidence. It was clear from running a TLUD at
higher temperatures that the flame behaved differently than my original
example. The flame speed of the mix could attach at the point of secondary
air entrance in a 2 inch pipe ( all measures are inside diameter). Reducing
this to 1.5 inches moved the flame up to the transition back to 2 inches.
The flame speed was two slow for the higher speed in the 1.5 inch pipe.
However the 1.5 inch section was six inches long and it was clear that the
flame was not very well premixed because of tall orangey tails extending
from the lower blueish portion.  So a few increments of changes later  the
burner now has 18 inch mixing tube between the secondary air introduction
and the point of flame attachment. It steps down from 2 to1.5 to 1.25 and
up again to 1.5 to 2 to 2.5 which is the cone that expands to 6 inches.

This is the result;
https://www.youtube.com/watch?v=5sjOTHwDsWo

*It is quite different than the origional  slow continuous blueming flame
flower *
*Here again*

*https://www.youtube.com/watch?v=jnV1e60NTss
<https://www.youtube.com/watch?v=jnV1e60NTss>*

*There are a differences that are due to the fuel gasses, the temperature
of the gasses and perhaps the excess air values. All play a role. *
*The much longer mixing tube changes the net draft as well. Also I was
unable to light the mix from the secondary air entrance. Had to be lit top-
down.*

Here is a fun ignition shot. Talk about descending flame fronts:)
https://www.youtube.com/watch?v=X7JepJ1MdWg

You tube has a 'gear' icon in the lower right of the screen where you can
control the speed of the video replay (without sound). It is informative to
watch these at .25 speed. The glowing meteor sparks show up better.
Starting and stopping the videos freeze them in there tracks. If one knew
the frame speed of the camera you could almost calculate the velocity of
the sparks by the length of their paths.

Sorry to interrupt the very interesting discussion of charcoal.
Alex
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