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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Dear Julien<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>I also appreciate the well written report.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Because it is being discussed here, I want to draw the attention of the readers permanently to this point:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>See photo three which has three burners operating at the same time and there is a clear difference between the three combustor architectures:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><img width=604 height=362 id="Picture_x0020_1" src="cid:image003.png@01CF6767.677B25D0"></span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>My point is that NO COMBUSTOR operates with the pot off in the same manner as with the pot on. You simply cannot tell how the air and gases will mix, what the pattern is, what the penetration of air into the gas stream is, with the pot off. So please do not think that these flame patterns are ‘how these stoves work’ when there is a pot present. Just about everything changes.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>This is not a slap on the hand for Julien who provides a very good picture that contains some information of value. But please don’t think that this is ‘how the air flows and how the burner burn’. As soon as you put on a pot, two very important changes are made to all three fires:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l1 level1 lfo1'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>The cold air outside the combustion zone can no longer travel into the top of the burner and mix with the air that is coming through the walls, and exit up the centre along with the flame (now a chilled flame).<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l1 level1 lfo1'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>The pot adds substantial insulation/reflection/choking to the heat and airflow which can dramatically change the primary and secondary air flow rates and therefore (obviously) the quality of the burn.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>The pot is part of the stove. To know what to do in developing a combustor, the testing (observing) must be done in context – i.e. in a way that reflects use. This is not a fire pit, it is a cooker.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>The gap between the stove and the pot can be used as a total gas flow rate limiter. The Philips stove is a good example of one that does not because the gap is large enough to push fuel through into the combustion chamber while it is running. That is a design choice. It subjects the combustor to many influences such a light breeze, a periodic disturbance by people walking by, or any big changes in the way the wood happens to fall inside (which affects how the flames shoot up). That can cause the heat to preferentially go to one side because it is so open.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Changing the Keren stove in Indonesia from a pot support height of 25mm to 7mm increased the heat transfer efficiency from 17% to >30% - about double. It was able to do this because there was FAR too much air passing through the stove messing with the combustion and heat transfer. The pot went from a heat capture device to a gas flow regulator plus-heat-capturing-device. The flame pattern changed dramatically. Primary air could be added from behind the fire (like a Lion Stove) and the mixing much improved.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>All the stoves shown in Julien’s picture had clear effects of air entering the top where the pot would be, descending into and cooling the fire. Part, maybe all, of the flames being drawn together into a centre point is because of this.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>What to do to see how they really work?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>I have tried two things, not counting making a small peep hole in a plate.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo2'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Put a Pyrex casserole dish with water on it in place of a pot and look through the glass.<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo2'><![if !supportLists]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Put a metal plate on that represents a pot with lots of holes in it – about 8 to10 mm. This will effectively block the air entry even though one might think it would still allow air in. When ‘retained’ the flame or hot gases fill the space and prevent cold air entering. You can look through the holes. I used a shower floor disk when the stove is small.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Figure 4 shows the result of the different architectures, which is helpful because that is the result of the flame patterns you cannot see. Get the point? The photos of the fire are not what you get so you can’t use them to determine the flame pattern, but the pot bottoms are a test of the reality. You can of course mount a borosilicate glass window in the stove and look through. A 50 x 50mm piece is easily large enough to look through if there is a 20mm hole covered by it.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Conclusions<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>“</span><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>The Rectangular burner was promising because it had a lower flame height.”<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>That means the mixing was good, excess air had to be low (measure it at the pot-stove boundary).<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>“</span><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>However, when the secondary air enters as jets through air holes, a concentrator disk above the secondary air intake may be counter productive.”<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>There are sound reasons why, but another time.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>There is a lot of combustion that takes place in the transparent non-visible radiation zone away from and especially above the visible flame. Our eyes are not particularly broad-band. ‘Keeping the heat together’ provides burn-out conditions for CO in particular. Glowing particles make it easy to know if there are particles present. CO is burning late in the flame and above it without visibility (though more easily seen at night). In principle, a single large flame can burn cleaner that a large number of small flames in a large space.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>The development of the FSP paraffin stove was almost entirely done at night in order to be able to see the flame patterns that were invisible in the daytime. You have heard of ‘golf widows’. There are also ‘stove widows’.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext'>From:</span></b><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext'> Stoves [mailto:stoves-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Paul Anderson<br><br></span></p><div><p class=MsoNormal>Julien,<br><br>Thank you for such a wonderful and well organized report (that is attached to Julien's message yesterday). We need such studies of, in your case, the basic nature of the gas burners that are on the top of ND-TLUD stoves.<br><br>It is people like you and Kirk Harris and others who are doing some truly important work about TLUD gasifiers. <br> <br>With your permission, I would like to have your report posted at the drtlud.com website, but I think you should first add your name, contact info. and date of the report. Then it can go to the website administrator James Schoner <a href="mailto:jss@bitmaxim.com">jss@bitmaxim.com</a> for posting.<br><br>Please discuss your next steps. And I am sure that some of us would like to know more about you and your circumstances that relate to stove work, if you would please send such a message to the Listserv.<br><br>Paul<br><br><o:p></o:p></p><p class=MsoNormal>On 5/1/2014 10:22 PM, Julien Winter wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><div><p class=MsoNormal>Hello stovers;<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I have just finished some tinkering on natural-draft, TLUD gas burners. I expect that much, if not all of what I have done, has been done before, but it doesn't hurt to see some results to stimulate discussion. The results of my tinkerings are attached as a pdf.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I don't think my interpretations are complete, and I must revisit the paper by <span style='font-family:"Tahoma","sans-serif"'>Birzer et al. (2013). However, it is past my bedtime.</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'>Cheers,</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'>Julien</span><o:p></o:p></p></div><div><p class=MsoNormal><br clear=all><br>-- <o:p></o:p></p></div><div><p class=MsoNormal>Julien Winter<br>Cobourg, ON, CANADA<o:p></o:p></p></div></div></blockquote></div></body></html>