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<div class="moz-cite-prefix">Crispin,<br>
<br>
Thanks for your efforts at Servals and for your insights and
comments. I am sending this and your message to others who are
working on the rice husk gasifier, and TLUDs in general. We all
need to evaluate your comments and make and test adjustments.
Your combustion analyzer is such a great tool !!!!<br>
<br>
Note to all: Crispin is the only stove developer that I know who
regularly and consistently uses a combustion analyzer (about $3K
or $4K). There is not one at Aprovecho, CREEC or any other
testing center as far as I know. I suspect that Alex English
might have one available to him, and others who who work on
furnaces (not stoves). <br>
<br>
Note: The mentioned rice husk gasifier is a reconstruction at
Servals of the design provided by Joe James. As we all know,
things made from the same set of plans are not necessarily the
same. Strict comparisons are not easy, especially when the two
units are 10,000 miles apart.<br>
<br>
The comment about the sleeve of secondary air surrounding the
column of rising woodgases seems quite valid. We (Wendelbo,
Anderson, and all who subsequently implement the concentrator disk
in TLUD stoves) have tended to think that the concentration to the
center was sufficient to get sufficient mixing. It is certainly
more mixing than without a concentrator, but mixing can almost
always be improved (with some trade offs in price, production,
etc.)<br>
<br>
The work of Jock Gill, Kirk Harris, Julien Winter and others is
giving new attention to alternatives for improved mixing. Much
work remains to be done. <br>
<br>
And we do not know (and are not told because of proprietary
restrictions) if the technical stove studies funded by millions of
dollars from the GACC and US DOE are looking at such topics.<br>
<br>
Paul<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 9/23/2014 1:15 PM, Crispin Pemberton-Pigott wrote:<br>
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<p class="MsoNormal">Dear Paul<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I tested a large rice hull gasifier today
at Servals with a combustion analyser and made some changes to
the amount of secondary air. They have already made a large
change in the design because if very high excess air values
(from too much secondary air). This they did by inverting the
combustion chamber and closing all the 5mm holes with bolts.
Later they removed some of them (now at the bottom) and
drilled some 2mm holes near the top. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">With the 5mm holes a little open at the
bottom and the 2mm’s at the top, there is still 180% EA
meaning they should remove about 1/3 of the total secondary
air still getting in.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The result of the
as-much-restricted-as-possible condition (for the
secondary/primary split) was a CO/CO2 ratio of 0.14% which is
very good. When the EA went down occasionally to 150% it
dropped to 0.13% which means it would drop still further if
further secondary air reduction was possible.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It seems, and this is the purpose of my
note, that whatever model you have for calculating the need
for secondary air is putting in far too much. The volume that
wold have gone in (as designed) was about 10 times what was
needed, but my guestimation (had to assume some things in that
then calculate based on hole size). <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The penetration of the secondary air into
the gas stream is a serious issue with the their regular
Champion. The flame is unable to burn because there is air
entering as a sheet through a ring gap just below the top cap.
This is not a good place, and that is not a good way to let it
come it. It never mixes with the gas and only provides a
sleeve around the central flame then moves away below the pot.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">So…I have suggested they try capping the
preheater and installing a roughly calculated 16 x 16mm
secondary air holes – large enough to get impetus towards the
centre of the gas column and about right to supply the
Champion with adequate secondary air (it too was much too
high).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The CO/CO2 ratio was about 0.6% for the
Champion. Good enough for government work, as they say. It was
quite smoky but did not make much CO. The smoke was directly
caused by the long flame sheathed in secondary air, then the
flame hitting the pot and chilling against it. Surprised there
as not more CO. I think the instrument is working fine so it
really is making lots of smoke while not making much CO – Alex
English said it was possible and demonstrated it to me once.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I also tested the Servals kerosene burner
head and the other one in the market against each other in the
same stove. They have about the same performance but the one
in the market definitely over-heats the fuel on high power,
causing it to decompose thermally leaving free carbon in the
gas stream – blocks the nozzle. Reproducible effect. They
definitely have a better product.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am heading to Dubai tonight. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Stay well<o:p></o:p></p>
<p class="MsoNormal">Crispin<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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