need solution for airflow design

Hi to everybody, I am new in this forum and this is my first post.

I am trying to built a rocket stove for indoors heating and I have come up with a design that looks pretty good and functional. However I builted the stove and I realised that is not working properly. It needs redisgn but I dont know the causes and the mechanics around the problematic airflow.

So I am trying to introduce my design
Picture A shows the dimensions of the burner. I have installed a glass window in front but is always closed. The feeding of the wood comes from the top right
Picture B shows how the burner is supposed to work... and it works exactly like this (rocket effect).
Picture C shows the final design of my rocket stove with the outer shell installed.
Picture D shows how the rocket stove works with outer shell installed. The airflow operates completely in reverse.

Does anybody knows why this happen? It is all about physics and I don’t have too much knowledge on it.

Hi Nik,

DISCLAIMER: I have yet to build my own rocket mass heater, but I think I know how they're supposed to work. Hopefully someone with real experience will chime in.

I think the issue is your wood feed is a better chimney/riser than your heat riser. The classic "J" tube design yours seems to be modeled after is a J for a very specific reason, heat rises, which in turn creates a vacuum that needs to be replaced by more air. This is called a "draw".  In your case, you have more a "U" tube and the hot air takes the easiest path which is actually straight back up the wood feed instead of horizontally and then up the riser.

I think your fastest way to test this would be to plug the top of wood feed and instead feed material through the side, horizontally.  This would be more like the older "L" tube style rocket stoves.  Down the line, you could add a short, vertical wood feed outside of the shell if you wish to get the "J" tube shape back again.

What is the stove made of?

What insulation are you using?

Looks like you're wanting to make a pocket rocket:

The chimney pipe needs to be significantly taller than the intake and you usually put a piece of fire starter like paper or cardboard under the chimney at the start to get the draw going. Search for pocket rocket here on the site, and you should get more info. I wouldn't invest in a welded metal combustion chamber, that metal is all sacrificial. The normal pocket rocket can be cleaned out by taking the top lid off and pouring it out.

Nik Efs wrote:Hi to everybody, I am new in this forum and this is my first post.

I am trying to built a rocket stove for indoors heating and I have come up with a design that looks pretty good and functional. However I builted the stove and I realised that is not working properly. It needs redisgn but I dont know the causes and the mechanics around the problematic airflow.

So I am trying to introduce my design
Picture A shows the dimensions of the burner. I have installed a glass window in front but is always closed. The feeding of the wood comes from the top right
Picture B shows how the burner is supposed to work... and it works exactly like this (rocket effect).
Picture C shows the final design of my rocket stove with the outer shell installed.
Picture D shows how the rocket stove works with outer shell installed. The airflow operates completely in reverse.

Does anybody knows why this happen? It is all about physics and I don’t have too much knowledge on it.

Your dimensions are incorrect.  The heat riser should be a minimum of 3 times longer then your wood feed tube.  If your wood feed is 16 inches, your heat riser should be 48 inches minimum