[Stoves] Model II iCan -- update

[Jock Gill]

Ron,

I have arrived at the same conclusion as you.  As you increase the secondary air in an iCan you simultaneously reduce the up draft and thus the amount of primary air pulled into the system.  I expect the rate of primary air through the pyrolysis zone controls the temperature in the zone and thus the rate of pyrolytic gas formation.  Of course this effect will only show up if the primary air is not wildly over supplied, creating run away pyrolysis.

As for the hose clamp, it only acts as a sleeve.  The two cans interlock quite well so not too much secondary air enters there -- esp. when the secondary air holes are relatively large.  There is much less resistance for the incoming air at the secondary air holes.  This reduction in resistance also must apply to the primary air holes/supply as well.  It is easier to pull air through 5/16ths holes than through 1/8th inch holes.   I believe this accounts for the "decreased [in] the pressure difference across the fuel supply".

I look forward to learning more.

Thanks,

Jock

Jock Gill
P.O. Box 3
Peacham,  VT  05862
Carbon Negative Solutions
(G) (802) 503-1258



On Jun 7, 2011, at 11:00 AM, Ron Larson wrote:

> Jock etal (adding stoves list)
> 
>   If asked in advance, I would probably have guessed wrong.  Obviously you decreased the pressure difference across the fuel supply - but why is not clear to me.
> 
>   How much secondary air is entering at the hose clamp?
> 
>   Anyone reading this have a thermodynamic/flame model that would cover this very interesting question?
> 
> Ron
> 
> 
> 
> On Jun 7, 2011, at 7:47 AM, Jock Gill <jg45 at me.com> wrote:
> 
>> Doug,
>> 
>> [Update] When the 12 secondary air holes were enlarged to 5/16ths, but he primary air holes were unchanged,  the results from the modified two can system were good.  A load of 50 grams of fuel showed an increase of about 10% in the amount of time flammable gas was produced; the  post flame smoke was gone in less than 90 seconds; and the biochar passed all of the usual tests very well.  
>> 
>> Question for students:  Can you think of why the gas production time increased when the secondary air holes were enlarged from 1/4 inch to 5/16ths inch?
>> 
>> The above results increase my confidence level in my new secondary air design.
>> 
>> It is SOOO easy, I hope you will give t a try.
>> 
>> 
>> <Model II modified.jpeg>
>> 
>> 
>> 
>> Regards,
>> 
>> Jock
>> 
>> Jock Gill
>> P.O. Box 3
>> Peacham,  VT  05862
>> Carbon Negative Solutions
>> (G) (802) 503-1258
>>