[Stoves] A Premix Burner

[Andrew Heggie]

  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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