[Stoves] Fwd: Simplified TLUD design

[Crispin Pemberton-Pigott]

Dear Jock

My suggestion is to send a couple of photos of the fire working, say, one the fuel bed is well developed, and about 15 minutes before the end. At the end the flame should be burning a fairly large amount of carbon which will change the dominant flame colour from yellow to blue. I would like to see how the mixing below the cover plate is happening. If there is a substantial difference in the flame colour between the outside and centre, then the mixing isn't too good. 

If it is very similar across the plate, then mixing is good. 

Based on the flame appearance and height we can then see if the secondary air is over or under-supplied.

What do you think? You could observe the flames and decide when it would be best to take a pic, so as to demonstrate changing conditions.

When gas production starts it is rich in oxygen, and this drops dramatically towards the end of the burn. Thus the secondary air requirement is variable. You can tune it to supply the 'right amount' through most of the early burn and let the late fire starve, or a whole variety of other options.

Did you try inverting the top plate and putting a pot above it? I am interested to know how that would affect the 'breathing' at the outer edge of the diameter.

Regards
Crispin




From: Jock Gill
Date: 4 May 2017 at 23:59
Subject: Simplified TLUD design
To: stoves-owner at lists.bioenergylists.org



Stovers,

I have just today started to explore a simplified TLUD design that is new to me. Has this been done before? Is it a well known variant?




The bottom can is the only can. It only has primary air holes.

The object on top is a 4 inch stove pipe cap with a dozen holes drilled in its top. The secondary air rises up through the gap between the can and the cap. This forms a circular source of secondary air. It also appears to create a circular flow of burning gases above the fuel bed and below the cap.




In the photo above, the unit was suspended inside a 3 pound coffee can. Makes for less constrained primary air flow.

Photos of flames emerging from the holes in the cap in a day or two.

Lots of work to optimize the variables.

When placed inside my big green egg, a wind free environment, there were long periods of blue tipped flames coming up through the holes in the cap.  The size of the holes in the cap appears to be an important variable.

Not sure of the utility of this approach, but it's interesting and possibly in time a good use for this approach will be discovered.

Of course larger stove pipe caps will allow working with larger cans.
So this is expected to be a scalable design.

BTW: after several adjustments, the third run produced some very nice biochar.

Please feel free to explore this approach as you see fit. Please share any thing you learn/discover.

Thoughts? Suggestions?

Good stoving,

Jock

Jock Gill
P.O. Box 3
Peacham
VT 05862