[Stoves] Stoves Digest, Vol 108, Issue 12

Sun Aug 25 23:49:13 CDT 2019

Crispin;

Thank you so much for the explanation. Very interesting. In my latest TLUD
design, I have a lot of sharp corners. Later on I plan to test emissions at
Aprovecho. Perhaps I could test for this as well.

Thanks again. Most appreciated.

Norm

On Sun, Aug 25, 2019 at 10:01 AM <stoves-request at lists.bioenergylists.org>
wrote:

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> Today's Topics:
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>    1. TLUD Design and operation (Norman Baker)
>    2. Re: TLUD Design and operation (Crispin Pemberton-Pigott)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Sat, 24 Aug 2019 10:59:34 -0700
> From: Norman Baker <ntbakerphd at gmail.com>
> To: Discussion of biomass <stoves at lists.bioenergylists.org>
> Subject: [Stoves] TLUD Design and operation
> Message-ID:
>         <
> CAEZw-BCaYK9GDZLooq6va3d0GdaJ7hwM6i3rzYegiy_W45Ti5w at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Recently we had some discussion about TLUD design and cookstoves. The TLUD
> Summit was very beneficial. Currently building version 24.
>
> One recent comment from someone discussing TLUD design was that (as I
> recall) "sharp corners result in the formation of soot in the exhaust
> stream". I assume this means sharp corners in the metals used in the stove.
> My interpretation is the metal sunflower or turbulator used in many TLUD
> cookstoves.
>
>  Or is it sharp corners in the spaces where combustion and/or pyrolysis
> occurs?
>
> Does anyone have any ideas or comments or experience on that issue?
>
> Thanks,
>
> Norm
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> ------------------------------
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> Message: 2
> Date: Sat, 24 Aug 2019 18:56:14 +0000
> From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> To: Stove Discussion <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] TLUD Design and operation
> Message-ID:
>         <
> BN6PR22MB00499A54E25CB75F61F9B2AEB1A70 at BN6PR22MB0049.namprd22.prod.outlook.com
> >
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>
> How's this, Norm:
>
> A sharp edge, two soot formation paths. One is electrical and the other is
> temperature.
>
> Sharp edges are used to dissipate electrical charges (aircraft, for
> example). As combustion involves separating atoms from molecules, there are
> charges roaming all over the show. Ions, charged particles...
>
> So the most likely place a charge will be noticed is at the tip of
> something sharp.  The most likely thing to be attracted to the points is
> charge-bearing free carbon because there is simply so much of it.
>
> This phenomenon is also noticed inside the evaporators of kerosene stoves.
> Heating the fuel evaporates it and there is thermal decomposition creating
> free carbon with one or two charges. At the the entrance or exit of the
> jet, there is high velocity gas creating a static charge on the metal. The
> carbon tends to deposit on the sharp edges to dissipate the charges. This
> accumulates as soot, builds, breaks off and flows with the gas, and blocks
> the nozzle.
>
> This problem requires the user to use a thin wire to unblock the nozzle.
> The tool is known as a "pricker".  Sometimes this has to be done quite
> frequently to keep it burning. This problem can be minimized by polishing
> the edges inside - so generally the jet and holder are polished to remove
> all internal points and sharp edges.
>
> On the TLUD, the sharp corners can be radiused as well as can be managed,
> and the effect will be limited to some extent.
>
> The second cause could be temperature. The metal next to the sharp edge
> probably has little gas contact, which means the area around the "sharp" is
> radiating while not being so much heated. The edge will be cooled by the
> nearby material, placing a chilled contact point in a passing evaporated
> stream of volatiles almost in the gas stream.
>
> The result is an accumulation of carbon and carbonaceous particles on the
> "corner" due to condensation alone.
>
> Clearly these two effects may also be combined.
>
> Regards
> Crispin
>
> From: ntbakerphd at gmail.com
> Sent: August 24, 2019 2:01 PM
> To: stoves at lists.bioenergylists.org
> Reply to: stoves at lists.bioenergylists.org
> Subject: [Stoves] TLUD Design and operation
>
> Recently we had some discussion about TLUD design and cookstoves. The TLUD
> Summit was very beneficial. Currently building version 24.
>
> One recent comment from someone discussing TLUD design was that (as I
> recall) "sharp corners result in the formation of soot in the exhaust
> stream". I assume this means sharp corners in the metals used in the stove.
> My interpretation is the metal sunflower or turbulator used in many TLUD
> cookstoves.
>
>  Or is it sharp corners in the spaces where combustion and/or pyrolysis
> occurs?
>
> Does anyone have any ideas or comments or experience on that issue?
>
> Thanks,
>
> Norm
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> End of Stoves Digest, Vol 108, Issue 12
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