[Stoves] re-kindling stoves

Richard Stanley rstanley at legacyfound.org
Sat Dec 25 19:00:07 CST 2010


Aj, 
 
It looks like you have now come to the same conclusions of several hundred actual users !

Really though for real analysis, Rok Oblak <www.rokstoves.org> is the guy to talk to. He has menitoned different performance with different hole diameters --assuming of course, a constant briquette blend (which is  most likely not going to be the case from area to area...). 
I also know that some experimenters of the side-fed idea are extending the horizontal feed tube into the combustion  chamber a bit to assure more centralised combustion of the side fed briquette  within said chamber. 

I agree to that excess air can well quench the fire  but what is happening in the combustion of the hollow core Bq is a bit different.. It is picking up  radiated heat from the  burning core (at its combustion chamber-end) and that has the effect of heating the incoming feed air supply. The combustion zone if untended, tends to creep back out through the whole briquette. It is otherwise being contained  pretty much in the combustion chamber by  the insertion of a fresh bq which necessitates  pushing of the burning bq futher into the chamber. "combustion creep" is thus  contained. 
The art and craft of maintining combustion in a side fed stove is somewhat akin to managing a  thee stone fire with side fed sticks... bit hard to quantify but we have one heck of a lot of practical precedence to go on....   

I have not measured the temp of the incoming air  during its progression thru the feed tube, but from what I have seen of actual combustion in such a stove,  there is no blue smoke ---very little smoke at all for that matter.. Veteran stove designer on this list, Lanny Hansen has used a similar idea for ducting the heat to the center of the combustion chamber from its side-fed source for I think much of the same reason( Pls correct me Lanny, if I am way off base here...) 

Regards,

Richard Stanley 

On Dec 25, 2010, at 1:41 PM, ajheggie at gmail.com wrote:

> On Saturday 25 December 2010 20:43:14 Richard Stanley wrote:
>> er, what again, about side feeding... ???
> 
> As I said in my reply I don't know about this stove. 
> 
> For the general case I was waiting for some detail about briquettes from 
> you.
> 
> Consider that the 3 stone fire is a three legged side feeding stove with 
> no air control other than that provided by the unconstrained natural 
> convection around the fire and pot. Fuel control is by pushing sticks in. 
> Excess air around the burning fuel quenches the reaction and this is 
> where most blue smoke is generated.
> 
> The rocket is then one leg of the three stone fire with some containment 
> of the natural draught but as the fuel and air are fed concurrently 
> through the same hole there is still quenching from excess air.
> 
> A stove like the GTZ Crispin illustrated keeps the fuel feed separate from 
> the air feed and probably controls the rate of production of offgas ( the 
> bit that becomes the flame) by having a separate air supply to the 
> bottom, to burn char and drive off offgases, from the secondary air which 
> combines with the offgases to make the flame.
> 
> Now with a holy briquette being a uniform cross section there is probably 
> scope for using the hole as the primary air controll and having a 
> separate secondary air supply but it will depend on the rate at which the 
> briquettes burn .
> 
> Also Ronald pointed out that in the case of tlud it's the uniform rate at 
> which the pyrolysis front moves down that controls the power. Now there 
> may be a compromise somewhere between the vertical, char making, model 
> and the horizontal rocket model.
> 
> So yes I think a top lit  inclined side feeding briquette burner is 
> feasible and if the client is willing to discard a high carbon ash then  
> it should have low PMs.
> 
> AJH
> 
> 
> 
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