[Stoves] scoping out a practical solid fuel stove igniter

Crispin Pemberton-Pigott crispinpigott at outlook.com
Fri Jul 11 20:22:33 CDT 2014


Dear Kirk

 

I appreciate that you are working on a common TLUD need and are willing to share what you can discover. Flameouts are a common problem particularly at the end when there is still a possibility of there being significant smoke from the remnant volatiles.

 

One of the activities noticeable at a TLUD convention is inventors tossing just-struck matches into a smoke bomb to re-establish the flame.

 

My own cure, after creating enough smoke to hide my embarrassed face, was to conduct the combustion of the gases as close as possible to the upper surface of the fuel.

 

This turned out to pretty much solve the problem because the secondary air entrance is low enough to the fuel that it keeps the top hot. This is not in line with many designs which have a gas burning zone that is away from the fuel. In my current view the move down burns some of the char and the payback is a product people are willing to use because the flame is reliable.

 

There is a new stove which was designed in Mongolia and produced in China that was submitted to the UB-CAP lab for testing which has what I consider the ‘right’ approach. The fuel bed is about 320mm deep which is typical of the breed. The secondary air is provided through very small holes (maybe 4 or 5mm diameter) around the ceramic combustion chamber. They are at least 125mm below the top of the fuel, were the available space to be completely filled. The secondary air is preheated to a high degree and limited in volume by a restricted entrance. 

 

It is extremely clean-burning. It has no controls at all – it just runs and burns out. The PM2.5 reduction against the baseline is over 99%. 

 

I have used the same approach and recommend it. Secondary air should not be spread out over the fuel chamber, not vertically at least. It should be lower than the fuel top when ignited as it serves little purpose right at the beginning. The fuel shrinks considerably as it burns and drops to uncover the ports which are not blocked in the meanwhile, they allow air to enter, but later they are clear of the fuel.

 

In the end the flame is hot enough to brighten and maintain a hot upper surface that resists the flameout at the tail end.

 

Regards

Crispin

 

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