[Stoves] Smoke, tar and soot-free biomass pellet stove UB with toroidal vortex combustion

[Andrew Heggie]

On 19 May 2017 at 20:20,  <neiltm at uwclub.net> wrote:

> I would love to understand how you have managed to direct the secondary
> air downwards to create the toroidal vortex, and the vortex itself if you
> have anything you can share.  This is a new departure from your previous
> stoves from what I can see.

Neil I suspect this is a flame (aka air) curtain device. The fuel
container has a bottom and  all the air enters from the top, the angle
of the air holes causes a downward vortex and the shearing between the
upward exiting flaming gases gives good mixing and keeps the flame
short. As the fuel burns away from the air supply it gets to the stage
where fresh primary air reaches the fuel, hence the shorter fuel
canister used to burn out the char. I was happy to extinguish the fire
and keep the residual char.

I made many similar devices from around 1995 which we discussed here
but eventually simplified the idea into a device I threw together for
an off grid café in 2009.

Essentially I ended up with a piece of old insulated 150mm flue, a
short tube  tangentially and slightly downward pointing some 200mm
below the top and a Panaflo 12V 0.16A centrifugal server fan powered
by a booster pack via a DC-DC pulse modulated  converter, which gave a
very good turn down. Picture shows it burning flat out and too
fiercely, the flame shouldn't be above the pot stand.

It burned pallets or dry wood, in this case it was using kindling
sized pieces cut and split from old pallets.

It was one of those serendipitous builds that just worked well from
day one but it was lost when the mobile café was stolen.
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