[Stoves] attempt at swirling secondary air

[David Young]

On Tue, May 13, 2014 at 09:26:39PM -0500, David Young wrote:
> My previous burner used 48 secondary inlets with sharp edges.  My
> current burner uses 32 inlets with radiused edges.  I'm not getting
> complete combustion (soot builds up on my kettle), so I'm going to try
> concentrating rings (both inner and outer) above the secondary air
> supply, since that is a simple and nondestructive experiment.  Then I
> may add more inlets.

I have experimented some with a central concentrating disk.  In my first
experiment, I cut out of a can top a disk 2/3rds the radius of the top.
I punched a length of 1/8-inch steel rod through the center of the disk
and then flattened the end of the rod slightly so that it held the disk.
Holding the steel rod with tongs, I lowered the concentrating disk into
the flames.

I found that if I could keep the flames from forming a column that rose
to the height of the chimney, without quenching the flames, if I held
the disk in the zone where the flame jets converged and tilted upward.
If the disk was not level, or if it was not centered, flame would slip
out the high side.  If the disk was too high, while a column would not
always form, flame would envelop the disk.  If the disk was too low,
flame jets would just skate over the top.  When the disk was in the
sweet spot, the flame burned completely within an inch of the secondary
air inlets.

In my second experiment, I cut a sheet metal disk with four tabs that
radiated from the circumference.  The radius was the same as in the
first experiment.  I bent the tabs slightly out of the plane of the
disk, just far enough that they held onto the chimney.  If the legs are
holding onto the bottom of the chimney, there are two settings for the
disk: disk low (legs above the disk) or disk high (legs below the disk).
I tried disk low, first.  The disk didn't hold the flame very well in
this setting.  My pot collected a lot of soot.  I tried disk high, next.
Much less soot accumulated, but there was still too much.  I could see
the stove emit smoke for a while shortly during the peak output period
right before the fuel has all converted to charcoal.

I'm going to try a position between disk high and disk low and see if
that works better.

Dave

-- 
David Young
dyoung at pobox.com    Urbana, IL    (217) 721-9981