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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Dear Julien<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>First my compliments for demonstrating a series of constructions showing the progression of a changes to a particular aspect of the burn. <o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Second, without being a damper, I want to add some interpretations to your already well-constructed set of experiments that will help those adopting this approach to product development. They disagree in some ways with the interpretations provided by Jock and you, so maybe it will stimulate additional ideas.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>The split between primary and secondary is uncontrolled, for all intents and purposes, and should not be. In the same manner that you advocate at the end that reducing the area of holes through which the primary air can enter, this should be applied to the secondary air as well, arranged in such a way that the incoming has has to go to one or the other. It should not be controlling one and then the other is free to flow more or less depending on the riser height. In short, don’t use a macro structure as a fine tuning air control mechanism.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>There are several products that work in that ‘controlled split’ manner though they are hard to find. The point is to decide in advance what the pri/sec split should be, create it, test it to be sure it is correct, then scale the draft accordingly. If you were to conduct this test on a SeTAR type real time test bench, it would provide a very useful set of excess air and CO/CO2 ratio charts the quickly identify the ideal conditions for the pri/sec split. This will be <i>independent</i> of the riser height. In such a case the riser height will affect the power, not the split, then the power can be regulated by the gross control of the air entering. This is a different approach taken be nearly all the TLUD designers so far which is to regulate the primary and let the secondary run free according to flame temperature and architecture.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>If you have control over the entry and the correct split by construction, the riser height is used for total available draft, and for directing that energy (a risen has ‘power’) to the correct mixing of the air and gas, not the flow of secondary air.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Something I noticed throughout is how random the mixing is. That gives just about the lowest guarantee of good mixing at low power which worries me. If you have at the bottom of the inner riser vee notches, or square notches (bend a tab inwards) the secondary air would gain much more penetrating power to reach the centre whether the mixing was particularly or not. <o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Please see <a href="http://www.newdawnengineering.com/website/library/Stoves/grasifier/">http://www.newdawnengineering.com/website/library/Stoves/grasifier/</a> item 00 (the 100mm diameter Grasifier Stove). This is a fixed architecture version similar to what you are showing in your series but not identical in terms of the counter-flow. The point is to look at the videos: <a href="http://www.newdawnengineering.com/website/library/Stoves/grasifier/23%20Grasifier%20burning%20pistachio%20shells,%20high%20gas%20rate%20HRes.wmv">Item 23</a> (22 if you have a low speed connection) showing the high gasification rate without enough penetration of the secondary air into the gas stream (= tall diffusion flame). Then see <a href="http://www.newdawnengineering.com/website/library/Stoves/grasifier/24%20stable%20flame%20needs%20a%20plate%20or%20pot%20on%20top.wmv">Item 24</a> which shows the same device with a very low flow of primary air but the secondary air with a short riser provides excellent mixing all the way to the centre. This sort of contradicts your series of clips on low draft, but emphasizes what it could do if the secondary air were shaped and not so free to flow.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>The disturbance to the flame caused by removing the pseudo-pot is caused by the entry into the flaming chamber of cold air from above. We discussed this previously and I pointed to the same video. I suspect your large diameter risers in the experiments were experiencing this effect. If the tubes has been the same diameter as the chamber outlet the flaming appearance would have changed, and changed even more if there was some sort of breaking up of the secondary air into jets so they could reach the centre.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Yours is altogether an excellent piece and very useful for training about pri/sec splits. Used together with the Grasifier clips they would support a blackboard session on how to create good combustion across a range of gasification rates and approaches to secondary air provision.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>There are two stoves products both of which use a version of the two systems (combining aspects of Julien’s videos and mine) and both frustratingly not yet launched so you can’t see them. In both cases a good balance has been achieved across a range of conditions. Fundamentally, the riser height sets the maximum power level. A chimney does the same thing. The rest of the air controls allocate the distribution of air under different circumstances.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>I will bring this up again in a few weeks when I am in Tajikistan where I will continue to involve this Stoves group in the development of a couple of simple stoves for space heating, and they will be based on these same principles of construction, building on earlier conversations. <o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Julien I will refer to your videos. Many thanks for your contributions to the field. We need to find you (and others) some gas equipment. News in that regard coming separately. Yixiang and I have been tossing the back cupboards in China and Toronto and come up with some good sources.<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Best regards<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><div><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Julian,<o:p></o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Interesting video. <o:p></o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>1. I would try this with a flame retention disc rather than a central hole. I view central holes above fuel bed as a fundamental error. I know central holes are the given wisdom, but I view them as the source of problems that can not be overcome. They are a barrier to better achievements.<o:p></o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>2. I would strive for the maximum amount of blue flame. I did not see any in your video. People want to cook with blue flames. Aspirational.<o:p></o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>3. Perhaps an hour glass type device might work? Could be asymmetrical?<o:p></o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Cheers,<o:p></o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p></div><div id=ecxAppleMailSignature><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Calibri",sans-serif'>Jock<o:p></o:p></span></p><div><div><p class=MsoNormal><span style='font-family:"UICTFontTextStyleBody",serif'>Jock Gill<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"UICTFontTextStyleBody",serif'>P. O. Box 3<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"UICTFontTextStyleBody",serif'>Peacham, VT 05862<o:p></o:p></span></p></div></div><div><p class=MsoNormal><span style='font-family:"UICTFontTextStyleBody",serif'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><a href="https://plus.google.com/_/notifications/emlink?emr=02164940119180120523&emid=CIn6jOiavboCFcgLTAodARYAAA&path=/102260924343967128597/op/u&dt=1383089746165&ub=50" target="_blank"><b><span style='color:black'>google.com/+JockGill</span></b></a><o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p></div><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Extract CO2 from the atmosphere!<o:p></o:p></span></p></div><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Calibri",sans-serif'><br>On Jan 25, 2016, at 7:10 PM, Julien Winter <<a href="mailto:winter.julien@gmail.com">winter.julien@gmail.com</a>> wrote:<o:p></o:p></span></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Hi all;<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>I have posted a video on YouTube on Riser Height and a 'Counter-Current' burner that continues on the theme of discussions earlier this month about premixed flames.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><a href="https://youtu.be/KzYUzJPM3eQ" target="_blank">https://youtu.be/KzYUzJPM3eQ</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>The purpose of this video is to demonstrate the importance of riser height on the function of a natural draft, top-lit updraft gasifier using the “Counter-Current Woodgas Burner” (CCWB). Riser height affects the flow rate of both primary and secondary air, and the degree of turbulent mixing of woodgas with secondary air. Increasing riser height creates greater buoyancy forces that can improve the efficiency of stove combustion, and stove responsiveness for the operator, but it can lead to excessive secondary air, and excessive turbulence under some conditions.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>With a true counter-current burner, the fuel gas and oxidizer gas collide head-on. This is more-or-less what happens with the CCWB, because a downward laminar flow of secondary air is sent against the upward flow of woodgas. However, it is not a perfect counter-current burner, because a lot of the secondary air is pulled sideways by the buoyancy force created in the gas flame.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>The main objective of the CCWB is to get a much turbulent mixing of secondary air and woodgas at the base of the gas flame as possible. We are trying to approach an ideal of a pre-mixed flame at somewhat above (to be determined) the stoichiometric requirement for oxygen.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>The second objective of the CCWB is to locate the base of the flame over the fuel bed char. Some secondary air supports glowing char, and sustains a higher temperature in the fuel bed, from the ignition front up to the top of the char, than would be obtained if the secondary air and the gas flame were located at some distance above the fuel bed. Glowing char can help with cracking of tars, and provide heat to assist in the piloting of gas ignition. This helps maintain woodgas flame stability at low gasification rates.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Some modifications of the CCWB have been tried, but did not show much benefit. (1) A ring of small air holes (of various numbers and diameters) in the sidewall of the reactor were positioned just below the inner riser. It was thought that these holes would provide small flamelets that would keep the gas flame from extinguishing at very low gasification rates. It was found that these holes didn’t help, and functioned more to diminish the role of the counter-current air flow. (2) Various fins were made at the bottom of the internal riser to see if they would increase turbulence. Fins were found to be unnecessary.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>The stoves in this video are prototypes. They are working hypotheses that need scientific stove testing to optimize their geometry, and validate the counter-current approach. To become working stoves, they need a regulator for primary air, an insulated external riser, and mechanism to transfer the heat to the pot or other object of work.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>If the CCWB can be shown to improve combustion efficiency on diverse biomass fuels, and over a wide range of gasification rates, that would be good, because it is a very easy burner to build.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Cheers,<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Julien.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><br clear=all><br>-- <o:p></o:p></span></p><div><div><div><div><div><div><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'>Julien Winter<br>Cobourg, ON, CANADA<o:p></o:p></span></p></div></div></div></div></div></div></div></div></blockquote><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Calibri",sans-serif'>_______________________________________________<br>Stoves mailing list<br><br>to Send a Message to the list, use the email address<br><a href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</a><br><br>to UNSUBSCRIBE or Change your List Settings use the web page<br><a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br><br>for more Biomass Cooking Stoves, News and Information see our web site:<br><a href="http://stoves.bioenergylists.org/" target="_blank">http://stoves.bioenergylists.org/</a><o:p></o:p></span></p></div></blockquote><p class=MsoNormal><span style='font-family:"Calibri",sans-serif'><br>_______________________________________________ Stoves mailing list to Send a Message to the list, use the email address <a href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</a> to UNSUBSCRIBE or Change your List Settings use the web page <a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a> for more Biomass Cooking Stoves, News and Information see our web site: <a href="http://stoves.bioenergylists.org/">http://stoves.bioenergylists.org/</a><o:p></o:p></span></p></div></body></html>