[Stoves] basics: Need different flame-speeds different mixture-procedures?

[frank]

Dear Martin,

About this 'flame speed' when using the 'string soaked in a fuel' method 
and measure the speed it burns down to the other end and get a flame 
speed. If you were to add two liquid fuels soaked into the string I 
would think the speed would be the faster one then the other burns 'in 
place'. Then the cotton string will burn 'in place'. Perhaps this is how 
mixed gases works. The one having the faster flame speed sets the pace 
(as long as the concentration is high enough) and the other gas burns 
'in place' as it is carried to the secondary?

Frank





Boll, Martin Dr. wrote:

>Dear all,
>
>            reeding the the comments in the stoves-list, mentioning the
>different flame speeds for H2 and woodgas  "a coin dropped in my mind".
>
>There are "worlds" between the two different speeds.
>
>-When you think of the draft of an open flame and a _real_  jet-blow, there
>are also "worlds" between both in speeds too
>
>So I come to basic thoughts for burning.
>
> 
>
>- For H2:  
>
>There is good chance for retro-burning under normal conditions. There must
>be a small nozzle hole, that this does not occur (in other words there must
>be a point of _very high_ speed; faster then the flame speed (of 3 or 4
>meters per second?)
>
> 
>
>- For wood-gas:
>
>There is a good chance that the flame blows out itself, because the speed of
>the outstreaming woodgas is too high.(Higher than 40cm per second?)
>
> 
>
>Conlusion: By woodgas the jet-speed must be _very_ different to fit
>comfortely for a constant flame.
>
> 
>
>My question:
>
>For H2 and other fast flame-speed stuff the jet is high and so there is a
>good turbulence to mix gas and air.
>
>For woodgas the gas-jet _must be_ slow for not blowing out. Therefore the
>turbulence is _far less_.
>
> 
>
>Is this small turbulence big enough to make a comparable good mixture for
>clean burn??
>
>-Even by a normal kitchen gas-burner there is a gas-air premixture. Is this
>premixture not more necessary by a slower jet-speed coming out of the
>nozzle?
>
> 
>
>I guess:
>
> There must be at least a jet-blow against a baffle to get a stable flame.
>
>_and_  there must be a _premixing_ before the balanced woodgas-air-mixture
>passes through the nozzle _and_ then against a baffle to form a stable _and_
>clean flame.
>
> 
>
>-What is the good range of speed for that? Or:
>
>-What are good combinations for pressure difference  and diameter of the
>nozzle, for a given gas/woodgas?
>
> -What is the good premixing ratio of woodgas and air? And has the premixing
>air to be preheated? (For: quicker reaction time; and/or no precipitation
>out of the woodgas?)
>
>- Would a static-mixer be helpful te reach a good gas/air mixture with low
>speed instead of a high-speed-jet? 
>
> 
>
>I hope not to ennoy you too much with simplicities.
>
> 
>
>Regards
>
> 
>
>Martin
>
> 
>
> 
>
> 
>
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>
>  
>

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Frank Shields
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