I'm working with a nonprofit to design rocket stoves to replace the filthy 3-stone cooking used by billions. Our goal is a rocket stove that is ultra-affordable and can be made everywhere with local material. We want any brick maker to be able to easily make these stoves.
While I'm sure we are far from the final designs, I'll give our latest designs below.
L Rocket Stove Attached is the latest design. We are limited to materials that are cheap and locally available everywhere. So no insulation, no steel, no firewood rack, no .... Just the clay mix used by local brick makers. We use a broken brick to elevate the firewood into the fire chamber. We have tested prototypes of this design and they work pretty well. Not as well as commercial rocket stoves but much better than 3-stone.
We are testing different sizes for the center hole, different brick heights and additional air holes at the bottom of the bottom brick.
If we are successful in this design, we should be able to give brick makers the pipes for their molds and quickly teach them how to make the 2-brick stoves. They should be able to make and sell the stoves for under US$1.
J Rocket Stove We haven't yet tested a prototype of the J rocket stove. The design is attached. This is designed for the 11cm pvc pipe and 25x25x10 cm brick mold that one of our volunteers in Africa already has. I expect that 11cm is too narrow. I have a number of other concerns about this design, but we'll test it out. Other volunteers should have access to larger pipes so we can test them later.
All suggestions are welcome. Again, we hope these can be made without metal, without insulation, without firewood racks, etc.. (Adding insulative material to the clay is preferable but for now we want a design that can be used universally. Depending one what is available locally, brick makers can add insulation (rice hulls, sawdust) to their clay.)
Aprovecho have done lots of work on stove design, also donkey32.proboards.com where you probably know you can find much information. One point is, have you asked the potential users what they want? Is a heavy brick structure going to provide for their needs. Can they get suitable wood for running a J tube? There are lots of questions to ask and unless you have the answers to work with, success may be difficult.
I am faced with a similar problem. I've become associated with an orphan school in Kenya that is currently using the traditional three stone hearth. I want to advise my African partner on how improve this. We have almost no funds for this and so I am asking about local material like stones. (I need him to send me a picture of the stone kilns they use for pottery.) I've been researching the technology behind rocket stoves and how best to adapt to local conditions.
A note for Kevin: I have found in my research that a smooth chimney throat is less effective. Turbulence in the fire column gives more complete combustion, a square stack of bricks will give a more complete burn than round stovepipe.