[Stoves] Excess air

[Andrew Heggie]

> I think stove testing needs to be comparable between both stoves and fuels.

I agree the above.

> I need, for instance, to be able to compare a
> single stove burning either wood or charcoal.  I have to be able to take the
> oxygen present in the cellulose and other constituents of the wood into
> account in calculating the excess air,

I disagree. Stoichiometric air is the amount of air needed to cmobine
with the fuel if combustion goes to completion and there is no fuel or
oxygen left over. Excess air is that air over and above the
stoichiometric air that is supplied in order for all the fuel to be
able to "meet" and combine with oxygen from the air. It thus follows
that there will be oxygen in the exhaust that is equal to the excess
air supplied. The fact that the fuel is already partially oxidised
makes no difference to the excess air value.

It does make a difference to the total oxygen in the exhaust
constituents but that is an entirely different matter.





> because it contributes to the
> combustion, whereas with charcoal there is essentially no oxygen present in
> the fuel.  The difference is real, measurable, and has an impact on the
> efficiency of combustion.

This statement needs some clarification, as oxygen in wood is
essentially combined with hydrogen or carbon it does not contribute to
further oxidation.

I agree its very presence does have an impact on combustion in that it
probably makes it harder to approach stoichiometric ratios as is
possible with high carbon or hydrocarbon fuels.

AJH