[Stoves] ND-TLUD Burners at ETHOS -- What Works Best?

[David Young]

On Fri, Feb 05, 2016 at 04:41:33PM -0500, Crispin Pemberton-Pigott wrote:
> Julien wrote:
> “The burst of wood gas that we often see just before the end of
> primary pyrolysis is because we are beginning to get char oxidation
> at the grate.  I have measured a sharp increase in temperature 5 cm
> above the grate (sometimes rising from 750 °C to 1000 °C) when
> that happens.  The rise in temperature accelerates pyrolysis of the
> residual raw fuel.”
>
> The bottom layer has no air restriction below it and the char tends to
> burn. That plus the lack of moisture and endothermic volatiles in the
> fuel that is not below the last layer means the burn rate in the first
> few layers rises.
>
> You can demonstrate the influence of the moisture on this process –
> the more moisture, the closer the heat gets to the plate before the
> flash burn starts. The effect is less noticeable with TLUD’s that
> do not rely on the fuel to restrict the airflow. This was noticed
> in testing at the YDD Lab in Yogyakarta.  Some stoves have the fire
> expire without much smoke at all (if any) at the end. Others have a
> clear flash. Those with very well controlled primary air and no easy
> way for air to evade the controller (by entering from a hole above
> then flowing downwards through the char, for example) either have no
> puff or it is small.

We may be talking about different phenomena.  By "puff," "flash," and
"burst," do you mean a momentary increase in wood gas?  Seconds?  Less
than a second?  Or a minute or longer?  Also: are you noticing smoke or
a long flame?  I notice a long flame.

Dave

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