Rocket Stove Experiments – The importance of the chimney

In the last posting, I introduced you to my experiments with Rocket Stoves.  I started with the most basic, 4 brick rocket stove to introduce the concepts of the air and fuel intake chambers, the combustion chamber, and the chimney.  It is a simple burn process, input, combustion, output.

In this posting, I want to talk about the role of the combustion chamber and the chimney, because that is where all the real work gets done.  The combustion chamber is of course where the burning happens, and the chimney is where the smoke and flames go as the air rushes through the system.

It is important to understand at this point that a rocket stove works as efficiently as it does because it allows enough air to go through the system, and burns hot enough, to allow the fuel and the smoke to get burned in the combustion chamber.  The chimney is an extension of the combustion chamber, and it is essential to the process because it gives the fire enough time to consume the energy released in the smoke by burning it.  This process requires a very hot combustion chamber and chimney to be successful.

4 brick rocket stove with chimney
This is an experiment to see how adding a metal chimney affects the burning of the rocket stove.

This video shows what happens in the combustion chamber of the 4 brick rocket stove when the chimney is removed, when it is added back to the system, and when it is improved.

So from the video you can see that the enhanced chimney significantly increases the air flow and allows the smoke to burn off before exiting the chimney.  These are two crucial factors in creating an efficient rocket stove.

Since having a hot combustion chamber and chimney as extension of the combustion chamber is so important, the next thing to consider is finding a way to insulate around the combustion chamber and chimney so that the heat can remain in the chamber instead of leaching off through the surrounding materials.  I will explore this in later posts.

In the next post, I graduate from the 4 brick rocket stove to using a J shaped feed, combustion, chimney approach that is very common with rocket stoves.  The next posting is the last of the articles on testing, then in the article after that I proceed to an actual prototype.