[Stoves] A Premix Burner

[Aaron Wingle]

https://youtu.be/p_01Uy6sEl4
FA - Secondary Combustion Chamber

https://youtu.be/25GRrEi9u74
ND-TLUD with Secondary Combustion Chamber

https://youtu.be/J5jJcpvNuRY
ND - TLUD with Secondary Combustion Chamber and a strong vortex

Yes, the secondary (delayed) Combustion almost always offers a very clean
burn.  I have seen those very nearly invisible Flames using wood chips of
unknown origin on several of my designs using the Secondary Combustion
chamber. I not been able to afford insulation on the Secondary Combustion
chamber either but I suspect insulation would be very helpful on top.
Anyway, my YouTube channel is chock full of Secondary Combustion Chamber
videos.  It’s been difficult to fully prevent backfiring if these stoves by
sizing the openings properly but I do have at least 1 that works
dependable.

I’m happy to find others working on similar designs, your use of small
pipes would probably be much easier to work with than my small vortex
vents. The forced air version does not have backfire issues cause the
primary burn chamber has a bit of flame in it.

On Sat, Mar 16, 2019 at 2:41 PM Andrew Heggie <aj.heggie at gmail.com> wrote:

>   forwarded a message from wmknauss
>
> The two short video clips were too large for the list server but I
> have included a screenshot.
>
> Andrew
> >
> > Subject: A Premix Burner
> >
> >
> >
> > I have tried everything I can think of to add some very short video
> > clips as a reply to all from either my iPhone or tablet.  Nothing
> > seems to work so I am sending my videos and comments directly to you.
> >
> > Before I read Gordon`s email I burned my 7 year old barrel TLUD in the
> > shop shop side by side with the new barrel TLUD I had recently
> > completed. This was the first time I had burned the old TLUD inside.
> > Outside in the daylight the only indication that it is burning is the
> > heat waves rising from the top.
> >
> > The design of both TLUD's is very similar except the old one has a
> > secondary combustion chamber that is made from 20ga stainless steel,
> > no insulation, and is about a quarter of the size of the new one.  The
> > primary difference with the  new one is that the larger seconddary
> > combustion chamber is lined with refractory fiber insulation.
> >
> > Much to my surprise the videos clearly show a nice blue turbulent
> > flame in th old TLUD and a light yellow flame in the new one.  The
> > pecan shell feedstock was identical in both units with around 13%
> > moisture.
> >
> > I have no idea if one of the TLUD's was burning cleaner than the
> > other, but if anyone has any ideas what is going on I would sure would
> > like to hear it. My first thought is that Paul Olivier has the most
> > experience with controlling the flame color and has probably done some
> > testing that suggests it is a cleaner flame.
> >
> > On the subject of premixing the pyrolysis gas with air it occurs to me
> > that the premixer must be separated from the combustion chamber with a
> > tube or orifice that is small enough to increase the velocity of the
> > cooler mixture and long enough to prevent the premixed from becoming
> > too hot, for the purpose of prevent the secondary flame from
> > backfiring into the premixed chamber.  A good illustration of the
> > problem is when you try to adjust an acetylene torch to a low
> > intensity flame and it backfires into the torch. That is not something
> > you want to happen in a TLUD or a torch.
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