[Stoves] Role of secondary air on wood burning and charcoal stoves

[Sarbagya R. Tuladhar]

Hi Ron,

I am basically looking at natural draft front loading continuous feeding wood stoves and natural draft charcoal stoves. The reason I am investigating these is that for a wood stove, having secondary air component "really" did impact on the CO and PM production. The two stoves similar in design had the same thermal efficiency but then differed a lot with the emissions. The secondary air supposedly used was via the exterior gap ( I am guessing similar to the Philips TLUD). However, I am not talking about the TLUDs here but just normal front feeding wood cookstoves. 

Heard from Crispin regarding the role of secondary air in charcoal cookstoves. So it is used to burn the evaporated volatiles and the CO to CO2. Designs of the Benin charcoal stove have a simple concept of having holes on the bottom of the outer body which allows air to flow through it and then this pre-heated air is exited out to the combustion chamber to aid in the combustion of the volatile unburnt gases. Does this feature work?

Looking to hearing from you.

Cheers

Sarbagya
 
On 21/08/2013, at 1:25 AM, Ronal W. Larson wrote:

> Sarbagya:
> 
>    Can you narrow down the type of stoves you are looking at?  And why?  
> 
>    You seem to be talking of TLUDs, and when mentioning consuming char is that in a TLUD?
> 
>    We have seen some nice designs with secondary being preheated with a central pipe, not the exterior gap you describe.
> 
>    At least one stove developer (Kirk Harris) has argued for using that exterior space for added insulation.  A topic fairly easy to compare in the lab you appear to have available.
> 
> Ron
> 
> On Aug 20, 2013, at 6:44 AM, Sarbagya R. Tuladhar <sarbagya007 at gmail.com> wrote:
> 
>> Hi stovers,
>> 
>> The debate on the role of secondary air both for natural draft and forced draft has been raging for quite some time now. Obtaining secondary air in pre-heated form has been the research area for me in the laboratory for the past few weeks. However, one conclusion I obtained was that secondary air if not pre-heated would have the tendency to put off the fire by blowing in cold air. 
>> 
>> Hence my question is:
>> 
>> What is the role of secondary air for wood burning stoves ? Is there an optimum gap for the secondary air to travel between the jackets of the combustion chamber before ejecting out into the combustion chamber ? How does this effect the performance of the cookstove ? I know a few cookstoves which have secondary air concept included and which seemed to decrease the CO and PM up to some extent. 
>> 
>> What is the role of secondary air for charcoal burning stoves ? Quoting Crispin "Secondary air is necessary to burn charcoal in a low O2 environment at a high temperature." How does this effect the performance of the charcoal cookstove?
>> 
>> Waiting for the responses.
>> 
>> Cheers
>> 
>> Sarbagya Tuladhar
>> Pondicherry, INDIA
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