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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>Dear Friends<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><p class=MsoNormal><b><span lang=EN-US style='color:#1F497D;mso-fareast-language:EN-CA'>></span></b>To visualize what Crispin is saying, think of the vortex created in a bathtub drain as the tub empties. <span style='font-size:12.0pt;mso-fareast-language:EN-CA'><o:p></o:p></span></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='color:#1F497D'>></span>A TLUD with a circular aperture for the exhaust gases is simply an upside down bathtub drain that just as surely creates a central spire of twirling flames. To be avoided if at all possible.<span style='color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Oohh…I didn’t meant to imply that. The deliberate creation of a vortex is very helpful in certain cases. Ibrahimo, a PhD student will present a paper at the DUE Conference in Cape Town in a month which is the result of building a CFD model of the BLDD6 downdraft coal stove. He has found a setup that reasonably matches the measured temperature profiles at several points along a flame path that is very deliberately filled with such a twirling of flames. The advantages of doing this were covered in earlier papers from the SeTAR Centre.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Jock, the advantage (if you have the space to do it) are that it preserves the wall material and provides an artificially temperature region in which to burn out the PM. The result is that ‘difficult’ coal like semi-bituminous Witbank coal can be burned with basically no smoke at all.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>I have a feeling this stove might burn jatropha seeds directly as well. Each fuel class requires its own circumstances. When the ‘oil’ chains are long, so too should the flame path be long. The layout increases [residence] Time, Turbulence and Temperature simultaneously.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Regards<br>Crispin<o:p></o:p></span></p></div></div></body></html>