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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US'>Dear Kirk<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;mso-fareast-language:EN-US'>I think your conclusion is correct – that you can shorted the height of the combustion zone with radial or helical mixing.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;mso-fareast-language:EN-US'>I provide two photos with this in mind, though accomplished in completely different ways. The first is (for a wood burner, not pellets) is to put the mixed below the fuel, to continuously create a series of ¡®induced vortices¡¯ a few of which pass through the fuel and provide mixing by spinning. A vortex tends to perpetuate itself so all that is needed is to get a few going all the time.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><img width=302 height=272 style='width:3.1458in;height:2.8333in' id="Picture_x0020_1" src="cid:image001.png@01D21912.CECC31C0"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;mso-fareast-language:EN-US'>The material is a low chrome stainless steel. The production is in three stages: blanking, punching the cuts, then forming.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;mso-fareast-language:EN-US'>The second method of shortening the flame is to use the secondary air entering the fire as a method of driving the flames horizontally. This should be done in a ¡®divided¡¯ manner, not a ring of air, so that it breaks up the rising gases into manageable jets. This kind of short clean burn can only be done with preheated secondary air – 300-500</span><span style='font-size:11.0pt;font-family:"Tahoma",sans-serif;mso-fareast-language:EN-US'>¢ª</span><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US'>C works well.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;mso-fareast-language:EN-US'><o:p> </o:p></span></p><p class=MsoNormal><img width=302 height=302 style='width:3.1458in;height:3.1458in' id="Picture_x0020_2" src="cid:image002.jpg@01D21914.42194B80"><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;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;mso-fareast-language:EN-US'>The fire above is burning pellet gas (as a TLUD) though it also works for wood if the gas generation is consistent. Consistency requires very good air control. The amount of is required to achieve this is so low that it pretty much rules out having an open bottom with fuel sticking out. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;mso-fareast-language:EN-US'>Readers may recall Julien in Coburg combined the injection of air and placement of the air feed in the gas stream. A problem commonly reported with that approach is the cooling of the metal by the air can interfere with the combustion.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;mso-fareast-language:EN-US'>Readers may also recall Dr Nurhuda in Indonesia achieved a downward turning flame consistently in his recent stoves reducing the flame height basically to zero. All of these approaches can assist the provision of lower height stoves – a major challenge for typical Indian rural households where cooks won¡¯t compromise on the cooking height. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;mso-fareast-language:EN-US'>Everyone should try these approaches and report what works well. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;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;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;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;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;mso-fareast-language:EN-US'><o:p> </o:p></span></p><div><p class=MsoNormal> ¡¦¡¦<o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>Not to be distracted from the purpose of this list, I have a thought about wood stoves. A small natural draft wood burning cook stove that mixes the wood gas with secondary air in 2 cm has a considerable advantage over a stove that may take 20 cm or more. It's a little like transistors, which gave advantage over vacuum tubes in electronics. Rapid mixing can enable a small wood stove to burn quick and clean at both <strong><u><span style='font-family:"Arial",sans-serif'>high and low</span></u></strong> power levels. Witness the excellent numbers for the Wonderwerk TLUD-ND stove which uses a rapid Venturi mixing technique. Combined with the user friendly power level controls, the principles used in the Wonderwerk stove hold considerable potential. Rapid mixing seems to me to be a very good area for research. I wonder how many rapid mixing techniques will be found over the next few years? I intend to contribute.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>List, keep writing about wood stoves, don't be distracted.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial",sans-serif'>Kirk H.</span><o:p></o:p></p></div></div></body></html>