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Dear Paul and All</div>
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Aprovecho has an Enerac 500 which is pretty good. We are using Enerac 700's in the YDD lab in central Java. There is an article in Boiling Point 53 on how to use one for developing stoves. It is free to download. </div>
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The stove Servals is selling is quite well made. There is considerable capacity to manufacture in Chennai. </div>
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Regards </div>
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Crispin </div>
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BBM 2B990AFA</div>
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<div><b>From: </b>Paul Anderson</div>
<div><b>Sent: </b>Wednesday, September 24, 2014 02:09</div>
<div><b>To: </b>Crispin Pemberton-Pigott; Joe JAMES - Cambodia & Ohio; Dave James; Discussion of biomass cooking stoves</div>
<div><b>Reply To: </b>Discussion of biomass cooking stoves</div>
<div><b>Subject: </b>[Stoves] Useful Crispin comments at Servals</div>
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<div class="x_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="x_moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="x_moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="x_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="x_MsoNormal">Dear Paul</p>
<p class="x_MsoNormal"> </p>
<p class="x_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.
</p>
<p class="x_MsoNormal"> </p>
<p class="x_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.</p>
<p class="x_MsoNormal"> </p>
<p class="x_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.</p>
<p class="x_MsoNormal"> </p>
<p class="x_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).
</p>
<p class="x_MsoNormal"> </p>
<p class="x_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.
</p>
<p class="x_MsoNormal"> </p>
<p class="x_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).</p>
<p class="x_MsoNormal"> </p>
<p class="x_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.</p>
<p class="x_MsoNormal"> </p>
<p class="x_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.</p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">I am heading to Dubai tonight. </p>
<p class="x_MsoNormal"> </p>
<p class="x_MsoNormal">Stay well</p>
<p class="x_MsoNormal">Crispin</p>
<p class="x_MsoNormal"> </p>
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