[Stoves] Airflow For Biomass Fired Appliances- Natural Draft Stoves

[Dean Still]

Dear Lanny,

Hope you get better soon!

Here are the design principles I use to tune a stove (same for Rocket,
TLUD, Fan stoves).

I imagine that to get clean combustion all of the gases and smoke are
forced to enter the flame.

Then the gases and smoke stay in the flame long enough to be burned up.

The very hot yellow/white flames easily make black carbon.

The less hot deeper yellow/red flames make less/no black carbon.

Draft is decreased or increased until the right amount of gas and smoke is
delivered to the flame for the right amount of time.

Draft has a lot to do with the correct metering of fuel (gas and smoke)
into the flame: how fast gas and smoke is made and how much flame is made.
I think we want lots of flame but only the right metered amount of gas and
flame to enter the flame.

Lengthening the time for combustion in the flame is good when: the metering
of fuel stays right,  the air/fuel ratio stays right, and losses through
the stove body do not increase too much (good insulation.)

Flame is needed to combust smoke and gas.

Something like that.

Best,

Dean



On Sun, Apr 14, 2013 at 11:25 AM, Alex English <english at kingston.net> wrote:

>  Lanny,
> I understand the comment below but I think flame height can be shortened
> with excessive excess air. The lowest emissions CO/CO2 and highest
> temperatures, at some power levels, in appliances that I have tested has
> often been when there is a significantly taller tail of flame.
>
> However, don't believe  all tall tails :)
> Alex
>
> On 14/04/2013 1:51 PM, Lanny Henson wrote:
>
>
>  The combustion air needs to be focused on the combustion zone in a way
> that shortens the flame height. More like the way a TLUD with a fan works.
>
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