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</o:shapelayout></xml><![endif]--></head><body 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'>Dear Peter<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Good to hear from you, I was thinking of you last week testing a downdraft stove using chunks of wood the same size you use on your DD BBQ (barbie). The chunks of wood provide quite a bit of excess air so the way the heat transfer takes place it affected a lot.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>></span>As far as I know the difference between kerosene (paraffin) and higher hydrocarbon fractions, including vegetable oils is the fact that they are not distillable under atmospheric pressure.<span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The stove must work then by boiling something in the veggie oil that boils at a temperature achievable in the evaporator tube. Perhaps that is why there is so much gunk left behind. A completely different approach (and an old one) is dripping oil onto a flat plate that is completely contained inside the combustion chamber. People burn old engine oil that way, and for similar reasons.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>></span>Undistillable hydrocarbons are fed into the fire as a spray of very fine droplets that burn completely. <span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>With the residence time in the flame matching the burnabilty of the droplet, right? When a droplet of diesel burns, has it been evaporated by radiant heat under that increasing pressure of the pressure wave?<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>The same could be done with vegetable oils at the combustor end. However, most vegetable oils tend to react slowly with oxygen to form gunk which eventually blocks the passages it has to flow through.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Is this process dramatically accelerated by heating the oil? In other words, is the depositing cause by O2 already in the fuel? That bodes badly for the future of burning raw oil.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>So for a stove that burns vegetable oil, the piping from the storage to the burner should be of very simple shape and easy to clean.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Daily, as I understand it.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Realising that producing a spray of fine droplets is out of the question for domestic stoves, we have to find something that feeds the oil to the combustion zone where the carbon, resulting from the decomposition of the oil is burnt as well. <span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>How about using one of those spinning disks with a spiky periphery that are used in greenhouses to make as fine a mist as possible? They are very small (50-75mm) and use only a small amount of power. It is conceivable they could be driven by electricity, heat or draft.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Possibly something like a perforated disk where the oil burns in updraft mode and where the holes occupy a sufficient part of the disk area that all the char comes in contact with air.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Good idea. A variation on the drop-onto-plate idea might do.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Does the Protos stove have any relation to Siemens. <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Yes it is a Bosch-Siemens product.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div></body></html>