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<div class="moz-cite-prefix">Ron, <br>
<br>
I agree that it is better to have some blockage of the central
part of the riser/combustion area. But in the burner called
"rectangular" (which could also be called "annular with
interruptions") Julien is forcing the combustible gases to the
periphery but then lets the flaming gases be pushed back into the
center. <br>
<br>
My preference (subject to further experimentation) is for the
ConcBelow to also have a buff body or other obstacle into the
center of the rising gases, keeping them forced to the periphery
where the secondary air is entering. The advantage of ConcBelow
is that IF pyrolysis is not uniform in the fuel chamber and is
sending more gases up one side than the other sides, those gases
should be required to go through a central concentrator hole.
And then be spread out as uniformly as possible to all of the
sides.<br>
<br>
Historical note: The original and famous Reed-Larson (1996)
natural draft TLUD did not have any effort at concentration, and
it can be faulted for having flames on one side without ability to
propagate flames on the rest of the annual ring of rising gases.
There is a "wick" (obstacle) in the riser. In contrast, the
major accomplishment of Paal Wendelbo was with the concentrator
disk (or hole) in the early 1990s, which I independently also
accomplished in 2005 with the Champion TLUD design. Some of us
did put buff bodies into the rising flames (I suspect Wendelbo
did), but we were always with the basic configuration that Julien
has called ConcAbove. <br>
<br>
The only person that I recall as advocating what would be a form
of ConcBelow is Crispin. He has pestered me about it, and doing
that research was on my list of things to do (but the list is far
to long). I thank Julien for doing that task on his own. It is
highly interesting that the work of Julien Winter was not done in
all those intervening years. <br>
<br>
And also, Alexis Belonio was advocating in January 2014 at the
Aprovecho Open House about some form of spreading the gases that
need to reach the secondary air that is coming in from the
sides. Alexis affirms that we should be able to have a blue
flame from woodgas. It is all about mixing (especially
pre-mixing if possible). <br>
<br>
***** change of topic ***********<br>
<br>
I comment on Ron's statement:
<blockquote type="cite">By looking closely, counterintuitively,
the flames seem attached NOT over the gas apertures, but rather
between them. I think this is true in all cases but can’t see
the case C “attachment” points. Except in private dialogs with
Paul O, I have not seen this stated before in print - and don’t
know if it should be encouraged or discouraged. <br>
</blockquote>
I think this has been considerably discussed or at least
observed. It relates to the phenomenon of the "inverted flame"
in which the air enters a zone of combustible gases instead of the
combustible gases entering a zone of air (which is the case of
common gas burners on stoves. In the TLUD gasifiers, the
secondary air holes are sufficiently close together that the
inverted flames are filling the space between the apertures of the
incoming gas (which is actually air).<br>
<br>
Paul A.<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
On 5/2/2014 7:44 PM, Ronal W. Larson wrote:<br>
</div>
<blockquote
cite="mid:C2BB825B-CB38-4517-AFCF-595FA6DE91A1@comcast.net"
type="cite">
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Julien, cc list:
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>Nice
report. Thanks for sharing. </div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span> 1.
My conclusion is that the best results were from what you call
the “rectangular hole design” - generally the right-most in your
figures. I put the difference down to the fact that you are
blocking the central part of the combustion area, so the
pyrolysis gases are much closer to the secondary air supplies.
Call this A.</div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>Next
best is what you called concentrator below (the left one -
which has 16 air ports (presumably smaller??). Call this B.
(Do you see any preference for 16 over 8 secondary air ports?</div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>It
seems very wrong to place concentrators above the secondary air
ports. Call this C.</div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>2.
In your Figure 3, this is B, C, A from left to right. (OK?)
The middle figure is the worst?</div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>My
criterion is the set of photos in Figure 4, with very clean
combustion for A, next best for B, and bad for C. In Figure 4,
in the top row, B is at the right, and th bottom row, you have C
left and A right. I see A as better than the open chimney - but
no videos or photos of the open chimney in action. Can you
compare A and open further?</div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>3.
In the still photo and the two videos, I perceive a
phenomenon I have seen before (with Paul Olivier’s deign). By
looking closely, counterintuitively, the flames seem attached
NOT over the gas apertures, but rather between them. I think
this is true in all cases but can’t see the case C “attachment”
points. Except in private dialogs with Paul O, I have not seen
this stated before in print - and don’t know if it should be
encouraged or discouraged. I believe if your large outer air
ports in A, were made narrower and longer in a circumferential
direction, there might be a more continuous flame, through which
little pyrolysis gas could pass without being combusted.</div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>My
guess is that you now have considerable excess air, and so could
get better het transfer to the cook pot, with less secondary air
aperture.</div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>4.
In the design A, all the holes cut be cut so as to create a
swirl - which might give improved combustion - and allow a
shorter chimney.</div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>5.
You would have a more “salable” design if you could control
primary air. A short piece (or two?) of electrical conduit (1/2
“ ID, 7/8’OD - or larger??) costs hardly anything and could be
fitted with a conical plug to control primary air. It would
have to penetrate the vertical walls of both cans, but wouldn’t
have to have a really tight fit - just a lot more control
through the pipe rather than air slipping around it. This
would replace your present multi-hole bottom, and you would have
to put in a different “holey” plate for the pellets to rest on.
Of interest to all would be how large a TDR (turn down ratio)
you could achieve (run for 1.5 hours??) </div>
<div><br>
</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>6.
So lots of suggestions that need not be on your plate. But I
think you are really on to something with A vs B or C.
Congratulations for what you have already accomplished.</div>
<div><br>
</div>
<div>Ron</div>
<br>
</blockquote>
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