[Stoves] Basics: about self-ignition-temperature/ flash-point-temperature

[Boll, Martin Dr.]

There are a lot of burning principles we all think they are very trivial, but I think, it is worth thinking/meditating about.

The advantage is,they are well known, the disadvantage is, all of us are not every time aware of the aspect they give, seen out of the most different angles of view.
Happily the stovers are a very inhomogenous community, so that the personal angle of view differs a lot. And each other telling combined gives a more "three-dimensional" view; -very happily!

 My first attempt about:
1. Self-ignition temperature  ( further as: SIT)

To get a sustaining burn, there must be _always_ a temperature above the SIT of the fuel.
By burning wood we have to deal first with the high SIT of woodgas and then with the low SIT of charcoal.
Therefore it is "hard" to start a wood/woodgas fire, but easy to maintain a charcoal-glow.

Appliance: 
-Starting a fire by friction is first making charcoal-dust, to have a fuel with low SIT, so low that we can reach it by friction.
We could never reach the SIT of/for woodgas by friction.


2. The flash-point-temperature: (further as: FPT)

Appliance:
- Starting fire with a spark (-high temperature-), we can use a very fine "split" fuel as cotton-wool, or some wool-like seeds (Common dandelion, Taraxacum officinale;	
Canadian Poplar, Populus Canadensis; Field thistle, Cirsium arvense ) . That tends to be very similar to a gas-air cloud, which is above burnable liquids, with low evaporation temperature.


Different fuel; how to rise its flame temperature:

Charcoal ( has low SIT): Simply blow cold air onto the charcoal, -even excessively blow does work.
Woodgas ( has high SIT ): Make a good gas-air-mixture, but avoid too fast air-stream (blow-out)
		 even important ore more: Reduction of overflow air, pre-warming of used air, ideally prewarmed to or near SIT.
		But the other advantage; woodgas has a low FPT, and can therefore be lit/relit with a spark ( e.g. woodgas driven engines) 

All those thoughts are basics to help to succeed or fail in appliance, and now worth to combine with the discussion, about turning-down-ratio in progress.
The very good reported turn-down experiments, are good examples of applied basics.

Because of the different SITs, we are aware of: It is more difficult, to run a _very_ small woodgas-fire in comparison with an even-powered  _very_ small charcoal-fire.

And these thoughts lead to the questions about, how small/less-powered a wood- or a wood-gas-stove can be constructed.
Thoughts and solutions about the heat-loss by radiation will come into compilation, as well as fuel size and shape.

Interested to see your ideas and angles of view about in discussion, to get a more "three-dimensional" view for all of us.

Regards
Martin

 








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