[Stoves] Heat to sustain TLUD process

[Paul S. Anderson]

Crispin and all,

Your details about the improved Vesto [semi]-gasifier version are interesting
and appreciated.

Much snipped, but my comments are below:

Quoting Crispin Pemberton-Pigott <crispinpigott at gmail.com>:

> It can choke the air to
> the bottom of the combustion chamber almost completely so I have control of
> the pyrolysation rate.

Please verify that you are igniting at the bottom as in the standard 
Vesto, not
at the top as in a TLUD gasifier.  If bottom lighting is the case, you have
some very different conditions, especially during the first 3 to 8 
minutes when
the heat from the bottom is drying out the fuel above it, sending much more
moisture in those early minutes.  More details please.
>
> Unlike the Anderson type gasifiers, it is close coupled in that the
> temperature of the gases is high when ignited and there is usually some or
> other lick of flame to re-light the gas should it happen to blow out from
> transient air movement.

:-)   Do I know __that__ Anderson guy?  :-))   I believe that all of MY TLUDs
are close coupled with the temperature of the gases as high as I can keep them
in a TLUD.  Do you have something different as "close coupled"?

> The combination of features means the upper flame
> is stable.  This as accomplished with natural draft in a total stove height
> (with nested pot) of 440mm.  I don't think it is optimised yet.

With bottom lighting, you have the full height (440 mm) to act as a chimney to
create natural draft.  What aspects are you wanting to optimize?
>
> When the volatiles start to run out, it is wise to open the primary air a
> bit, increasing it to full open when there is not much but charcoal left at
> which point it becomes a charcoal stove.

Do you (or can you) also restrict the in-flow of secondary air so that the
fullness of the draft is pulling on the primary air during the char-burning
stage?

> I am not sure of the total CO emissions from the whole 'cook'. The charcoal
> burning phase has much high CO than the gasifying stage, which has nearly
> none.

Please watch your terminology.  The charcoal burning is the "char-gasifying"
stage.  And what you called "the gasifying stage" is actually the "pyrolysis
stage."  The "purists of gasification" would refer to the charcoal burning (or
char-gasification) as simply "gasification" and they do not usually refer to
the pyrolysis as gasification.  But the lay-persons see the smoke-making
(pyrolysis) and the char-burning as both together being "gasification".  That
is why I always refer to "char-gasification" and "pyrolysis" as the 2 
processes
of turning solid wood into combustible gases.

> The main purpose of this whole design was not to produce a gasifier,

:-)  and maybe you did not produce one, but actually have a better 
semi-gasifier
or perhaps a true gasifier that is truly different from the known forms of
up-draft gasifiers.  Without seeing it and operating it, I reserve my opinions
until later.  But we know it is not a TLUD.

> it [Crispin's main purpose] was to have a high turn-down ratio with 
> the ability to refuel it [the improved Vesto] at any
> time with either charcoal or wood, and to control the power without having
> to use only a certain size of wood.  This approach it does better than
> anything else I have tried.

That last sentence is important.  You and I know and we want all the 
other stove
makers to know that air control is so extremely important.  The collective WE
have not yet learned all there is to know about how to maximize these small
cookstoves.

snipped

Paul

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