<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div>Paul, list and Julien (who I addressed last message to but failed to send to; apologies)</div><div><br></div><span class="Apple-tab-span" style="white-space:pre"> </span>See inserts<div><br></div><div><br><div><div>On May 2, 2014, at 7:38 PM, Paul Anderson <<a href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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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. </div></div></blockquote><div><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: Maybe your are arguing for a second upper blockage? I hope someone will try that but the fact that the no-blockage case looked pretty good doesn’t encourage me on that.</b></div><div><b><span class="Apple-tab-span" style="white-space:pre"> </span>I think it OK that the flames are centered - as they hit the pot where you want them to (in the center).</b></div><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix"> <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></div></div></blockquote><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: It has been a long time since I did any testing, but my recollection is that the pyrolysis front only very rarely did not go downward extremely uniformly. If your pyrolysis front doesn’t behave that way, you are in a degree of trouble that a blockage can’t help. With a fuel as uniform as pellets, there much be some physical phenomenon that keeps the pyrolysis front uniform.</b></div><div><b><span class="Apple-tab-span" style="white-space:pre"> </span>So I am not yet ready to agree on the uniform spreading theory of your last sentence. Julien’s results says otherwise, as did all my early work.</b></div><div><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix">
<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.
</div></div></blockquote><div><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: I’m not understanding “on one side”. The flames were certainly started only on the outside and traveled up the chimney on the inside. Also not understanding anything on the last part of the sentence. There was generally an unbroken “cone” - because I rarely used holes for secondary air - usually just a slit where two cans of equal size were “cobbled” together some way (often paperclips). This slit could be an eighht to a quarter inch wide. Pertinent to comments below, the flame was (I recall) usually attached to both the upper and lower can. The paper was ’96, but the work was first on Tom Mile’s “bioenergy” list in 1995, and people saw early work I think even in ’93.</b></div><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix">There is a "wick" (obstacle) in the riser. </div></div></blockquote><div><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: I have never used the term wick - and only vaguely recall obstacles in the center. That was Tom’s word and approach. The central object I am not objecting to at all, but the “Concabove” (washer shape above) now seems to be questionable. I hope many others can replicate Julien’s tests.</b></div><span class="Apple-tab-span" style="white-space:pre"> </span><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix">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></div></div></blockquote><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: But that is now being called into question. That is Julien's C design, which gave a lot of soot. Until Julien’s message I had no idea this would be wrong - but I never tried that approach. I have no idea why the difference in soot should be so profound.</b><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix">
<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></div></div></blockquote><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: Can you (or Crispin) give a cite for that design. In general Crispin has been discouraging about making char, so I wonder what he did. This also brings up the issue of using concentrators with Rockets - to the best of my knowledge, not done.</b></div><div><b><span class="Apple-tab-span" style="white-space:pre"> </span>With Kirk Harris, I have been exploring other options - but it is premature to discuss that since the ideas haven’t been tested. </b></div><div><b><span class="Apple-tab-span" style="white-space:pre"> </span>One of the best looking flames I have seen had a secondary air interior pipe, with radially oriented flames butting into each other. Had wonderful turbulence. But that group disappeared - from my view at least.<br></b><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix">
<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. </div></div></blockquote><div><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: That would seem to be Julien’s design “C”. But to the best of my knowledge Alexis is not working in this type of TLUD. See Paul Olivier’s site for a description of the flamelets, which are unchanged from Alexis designs.</b></div><span class="Apple-tab-span" style="white-space:pre"> </span><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix"> Alexis affirms that we should be able to have a blue
flame from wood gas. </div></div></blockquote><div><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: I confess to not understanding either how to obtain blue or how much advantage there is to it. I only saw yellow. But the yellow is/was quite clean. The advantage of yellow is radiant heat transfer to where there is a mixture ready to ignite. Also radiant heat going to the cook pot. I’d like to hear more from anyone on how to achieve blue.</b></div><div><b><span class="Apple-tab-span" style="white-space:pre"> </span>In Julien’s short nighttime video, the design “C” is blue at the the base, but mostly is yellow.</b></div><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix"> It is all about mixing (especially
pre-mixing if possible). <br></div></div></blockquote><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: To my knowledge the only char-making stove that has pulled pre-mixing off is Nat Mulcahy’s World Stove “Lucia”. We met in 2008 - and I stopped thinking much about stove design thereafter. Pre-mixing should be the “Holy Grail”. But yes mixing is essential - Turbulence - to go with two other T’s: Time and Temperature.</b><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix">
<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. </div></div></blockquote><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: If anyone can provide a link, that would be much appreciated. Paul Olivier and I never found a write-up - and it still baffles me. Are there other TLUD photos around I can look at, that show the flame appearing between secondary air holes - not over them?</b><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix"> 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. </div></div></blockquote><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: Well, I think there is another explanation. Paul Olivier has his gas flamelets enter into air - not the "inverted flame”, which I agree is or could be substantially different. But the Olivier/Belonio flamelets (very short - not the typical long flames of most TLUDs) look remarkably similar to small match or candle flames. I think the diffusion process is substantially similar, in both normal and “inverted” flames. I think the results obtained by Jim Jetter showing low particulates and CO with many TLUD tests indicate the regular and inverted flames can’t be widely different. The emissions are arguably superior with TLUDs - and (maybe) independent of whether these flames seem to originate from over or between holes.</b><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix"> 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).</div></div></blockquote><span class="Apple-tab-span" style="white-space:pre"> </span><b>[RWL: As noted above, I mostly operated with a continuous circumferential narrow slit - and never saw this - which is why I used “counterintuitively” Has anyone ever seen this with a natural gas multi-hole burner? My discussions with Paul Olivier centered on the importance of radiation - possibly coupled with the fact that pyrolysis gases have a chemistry (not try for methane) which gives you a smaller number of reaction particles at the end than going in. Makes for a helpful pressure difference. (This holds for whether there is gas entering air or air entering gas.)</b></div><div><b><span class="Apple-tab-span" style="white-space:pre"> </span>Re the last clause <i>("which is actually air")</i> needs more discussion. There has to be some gas there in order to have a flame. If there were still eight input ports, but appreciably smaller, would we see the same thing? Does it have to do with a big air speed through the input ports?</b></div><div><b><span class="Apple-tab-span" style="white-space:pre"> </span>I think there is a doctoral thesis lurking in here somewhere. There may be some optimum of hole diameters, spacings, shapes, separations, etc - to get the best flames (better “flamelets”).</b></div><div><b><br></b></div><div><b>Ron<br></b><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix">
<span class="Apple-tab-span" style="white-space:pre"> </span><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>
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<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>
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<br>
</div>
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