[Stoves] Rapid mixing

[alex english]

No, but it is produced with a pyrolysis front at a temperature (500c ish)
at the low end of normal for a TLUDs filled with wood pellets. There are
some unanswered ( or demonstrated) questions here. To match burn rate with
a higher py-fr-tp I need to use a smaller fuel chamber and increase the
superficial velocity. This will perhaps produce a different gas
composition. We'll see...

Alex

On Sep 29, 2016 9:00 AM, "Crispin Pemberton-Pigott" <
crispinpigott at outlook.com> wrote:

> Dear Alex
>
> is that flame produced late in the pyrolysis? ‎By that I means in a carbon
> 'evaporating' stage.
>
> Thanks
> Crispin
>
>
> Kirk,
> Its quite wonderful what you have demonstrated. A holy grail of sorts. The
> durability and complexity, and ultimately this is the cost, of the
> structure you have placed in the flame/gas path will determine its future
> usefulness. Interesting solution none the less.
>
> Here is a recent video of my premixed blue tlud-gas flame. Its all
> geometry, no obstruction.
> https://www.youtube.com/watch?v=jnV1e60NTss&feature=youtu.be
>
> Alex
>
> On Wed, Sep 28, 2016 at 12:05 PM, kgharris <kgharris at sonic.net> wrote:
>
> Crispin and All,
>
> Some clarification:  By radial mixing I assume you mean the method in the
> lower photo where the air travels inward, radially.  By helical mixing I
> assume you mean swirling gasses by using fan blades like in the top photo.
> Neither of these represents a conclusion on my part.  Your opening sentence
> put me on guard immediately because it defines your techniques as my
> conclusion.  A more accurate starting sentence for your response would have
> been 'Here are two techniques to look at that have worked for me'.  My
> thinking is not limited to these two ideas.
>
> Your techniques are what I was looking for, ideas for rapid mixing.
>
> Kirk H.
>
>
>
>
> ----- Original Message -----
> *From:* Crispin Pemberton-Pigott
> *To:* 'Discussion of biomass cooking stoves'
> *Sent:* Tuesday, September 27, 2016 8:09 PM
> *Subject:* Re: [Stoves] Rapid mixing
>
> Dear Kirk
>
>
>
> I think your conclusion is correct – that you can shorted the height of
> the combustion zone with radial or helical mixing.
>
>
>
> I provide two photos with this in mind, though accomplished in completely
> different ways. The first is (for a wood burner, not pellets) is to put the
> mixed below the fuel, to continuously create a series of ‘induced vortices’
> a few of which pass through the fuel and provide mixing by spinning. A
> vortex tends to perpetuate itself so all that is needed is to get a few
> going all the time.
>
>
>
> The material is a low chrome stainless steel. The production is in three
> stages: blanking, punching the cuts, then forming.
>
>
>
> The second method of shortening the flame is to use the secondary air
> entering the fire as a method of driving the flames horizontally. This
> should be done in a ‘divided’ manner, not a ring of air, so that it breaks
> up the rising gases into manageable jets. This kind of short clean burn can
> only be done with preheated secondary air – 300-500˚C works well.
>
>
>
>
>
> The fire above is burning pellet gas (as a TLUD) though it also works for
> wood if the gas generation is consistent. Consistency requires very good
> air control. The amount of is required to achieve this is so low that it
> pretty much rules out having an open bottom with fuel sticking out.
>
>
>
> Readers may recall Julien in Coburg combined the injection of air and
> placement of the air feed in the gas stream. A problem commonly reported
> with that approach is the cooling of the metal by the air can interfere
> with the combustion.
>
>
>
> Readers may also recall Dr Nurhuda in Indonesia achieved a downward
> turning flame consistently in his recent stoves reducing the flame height
> basically to zero. All of these approaches can assist the provision of
> lower height stoves – a major challenge for typical Indian rural households
> where cooks won’t compromise on the cooking height.
>
>
>
> Everyone should try these approaches and report what works well.
>
>
>
> Regards
>
> Crispin
>
>
>
>
>
>  ……
>
> Not to be distracted from the purpose of this list, I have a thought about
> wood stoves.  A small natural draft wood burning cook stove that mixes the
> wood gas with secondary air in 2 cm has a considerable advantage over a
> stove that may take 20 cm or more.  It's a little like transistors,
> which gave advantage over vacuum tubes in electronics.  Rapid mixing can
> enable a small wood stove to burn quick and clean at both *high and low*
> power levels.  Witness the excellent numbers for the Wonderwerk TLUD-ND
> stove which uses a rapid Venturi mixing technique.  Combined with the user
> friendly power level controls, the principles used in the Wonderwerk stove
> hold considerable potential.  Rapid mixing seems to me to be a very good
> area for research.  I wonder how many rapid mixing techniques will be found
> over the next few years?  I intend to contribute.
>
>
>
> List, keep writing about wood stoves, don't be distracted.
>
>
>
> Kirk H.
>
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