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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoPlainText>Dear Paul<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>For what it is worth (saving time for others who try) I have looked at both types of solutions. Do you remember me showing you a conical version of this in Matsapha in about 2003 on the Vesto stove converted to burn coal with a chimney and a sunken pot? That was a drop-in concentrator though it was not fixed. The idea was that it could be dropped into place after fuelling or refuelling. That resolved the problem of access and still brought the gases together with the flames, if any, to burn everything.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Design principle: the flames need to meet the smoke. This is best accomplished by not creating problems in the first place. <o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Don't spread the burning fuel out over a large area like a Jiko which is very difficult to get to burn clean at anything other than one power level.<o:p></o:p></p><p class=MsoPlainText>Don't accomplish with hardware things that can be done with air and flames. For example don't use a catalytic converter on the exhaust gases to react unburned gases, burn them properly in the first place.<o:p></o:p></p><p class=MsoPlainText>Don't feed air into a place where there is no space to burn. After the secondary air enters, there has to be a place for the reaction to take place.<o:p></o:p></p><p class=MsoPlainText>Don't let flames touch pots - it kills the combustion and creates a lot of soot. Finish the burn first.<o:p></o:p></p><p class=MsoPlainText>All the TLUD's with natural draft, well, nearly all of them, introduce secondary air too late and put in too much. The result is often a central yellow flame (glowing particles) emerging from the burner surrounded by copious excess air doing nothing but robbing heat. <o:p></o:p></p><p class=MsoPlainText>If you have a central diffusion flame gasping for air emerging from the centre of your TLUD, you have failed to bring the secondary air to the middle, and it has no chance of ever burning cleanly. It is already too late.<o:p></o:p></p><p class=MsoPlainText>If you choose to bring in secondary air high in the stove (all pyrolysers need separately provided secondary air) you are going to have to deal with a flame that is outside the burner, chilling in the open air, subject to the cold surface of the nearby pot.<o:p></o:p></p><p class=MsoPlainText>If you choose to bring in secondary air well below the top of the stove you face the possibility that it will get the materials so hot they will not last. This is a problem with a concentrator disk. If they work well if the air is brought in low enough to burn the gases well, the plate gets so hot it disintegrates. Cooling it by using the heat/disc as a preheater for secondary air works.<o:p></o:p></p><p class=MsoPlainText>That is why I settled eventually for using the air jets themselves as the concentrator. <o:p></o:p></p><p class=MsoPlainText>Energy imparted to the air flow is driven by convention pulling from above and to a lesser extent from below if it is a vertical concentric sleeve. <o:p></o:p></p><p class=MsoPlainText>The hole size and shape are important. A sharp edged hole is not as effective as imparting velocity (kinetic energy) to the air as a shaped one. There is only so much energy available. Fans are a substitute for this draft power. The exercise is aimed at getting the air jets to penetrate the rising gas stream far enough to reach the middle. Here is a picture of a successful result:<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><span style='mso-fareast-language:EN-CA'><img width=303 height=282 id="Picture_x0020_1" src="cid:image005.jpg@01CEC288.8CDDA5C0"></span><o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Note: this is not a great flame, but it is a demonstration of the principle that the secondary air should reach the middle. This was burning pistachio nut shells with too much primary air.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Here is the same stove (showing the design is right) burning switchgrass pellets with the correct amount of primary air:<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><span style='mso-fareast-language:EN-CA'><img width=302 height=289 id="Picture_x0020_2" src="cid:image006.jpg@01CEC288.8CDDA5C0"></span><o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>You can see the burning deck of blue at the level of air entry, you can see the air entering and cooling (initially) the hot clear gas stream creating particles that glow, then they burn in the centre as there is enough time and temperature to complete the reaction. <o:p></o:p></p><p class=MsoPlainText>This could have been accomplished with a concentrator disk, but that might not have created the disrupting secondary air mix needed to break up the vertical flow of gases from below into combustible portions.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>The ring of air idea (instead of jets) entering the space was implemented on the POCA with some good success but remember that is a charcoal stove and the primary air requirement is much higher (5-6x), meaning there was a lot less need to disrupt the gases to penetrate the flow with additional air. My guess is that all pyrolysers that make char will burn cleaner and shorter using air than using metal, and will last longer as well. A conical device might with well. A conical (pyramidal) structure was used on the GTZ-7 coal stove with a very small amount of secondary air. It relied on the ceramic (chamotte) to last at high temperature. The combustion chamber below was shoe-box shaped, a square exit and an opening pyramidal flame space above. As has been reported before, the PM was, most of the time, net negative after ignition was fully established. So it was a ‘concentrator ring’ approach but using ceramic which could take the heat and might even have offered a catalytic function (because it was rough).<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>So, there are some considerations for researchers.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Regards<o:p></o:p></p><p class=MsoPlainText>Crispin<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><span lang=EN-US style='mso-fareast-language:EN-CA'>-----Original Message-----<br>From: Paul Anderson [mailto:psanders@ilstu.edu] <br>Sent: Sunday, October 06, 2013 10:19 AM<br>To: Jock Gill<br>Cc: Discussion of biomass cooking stoves; crispinpigott@gmail.com Pemberton-Pigott; Ron Larson; Paul Olivier; Tom Miles; Paul Olivier; Sarah Uof IL Haiti stove; James S. Schoner<br>Subject: Research topic: Increasing turbulence at the level of combustion of TLUD gases.</span></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Jock, Crispin, and all Stovers, (James, for my website listed/tagged as R&D work to be done.)<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>As far as I know, there has not been much study of the impact of variations and options for increasing turbulence (using natural draft, <o:p></o:p></p><p class=MsoPlainText>not force air) at the level of the top of the TLUD fuel cylinder. This <o:p></o:p></p><p class=MsoPlainText>is certainly a topic that merits attention and could have significant impact on improving stove performance.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>The same TLUD stove (for purposes of need to control variables) to be tested with only changes to the combustion area of the pyrolysis <o:p></o:p></p><p class=MsoPlainText>gases. And what is found to be better, then also needs to be tested on <o:p></o:p></p><p class=MsoPlainText>other TLUD designs.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>However, even with rigorous observations and controls, ultimately emissions data will be required, and for that, equipment will be needed.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>This would be a fine topic for some student group to undertake, or for a <o:p></o:p></p><p class=MsoPlainText>master's thesis, or any of the many Stovers. I and probably several <o:p></o:p></p><p class=MsoPlainText>other Stovers would gladly facilitate/assist anyone undertaking this very interesting task.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Paul<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Doc / Dr TLUD / Prof. Paul S. Anderson, PhD<o:p></o:p></p><p class=MsoPlainText>Email: <a href="mailto:psanders@ilstu.edu"><span style='color:windowtext;text-decoration:none'>psanders@ilstu.edu</span></a><o:p></o:p></p><p class=MsoPlainText>Skype: paultlud Phone: +1-309-452-7072<o:p></o:p></p><p class=MsoPlainText>Website: <a href="http://www.drtlud.com"><span style='color:windowtext;text-decoration:none'>www.drtlud.com</span></a><o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>On 10/5/2013 7:37 AM, Jock Gill wrote:<o:p></o:p></p><p class=MsoPlainText>> Crispin,<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> When I read your "In the time-temperature-turbulence equation" lights went off. I expect this is why my iCans with three washers as deflectors, in contra distinction to a "concentrator ring", burn cleaner. The deflectors increase both turbulence and residence time in the combustion zone. Secondary air slots also contribute to the turbulence. At least my iCans with secondary air slots burn much cleaner than those with various holes used for secondary air. My current system burns cleanly enough to deposit very little soot on cooking utensils or food. They are essentially soot free. Perhaps "soot free" should be a goal?<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> Cheers,<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> Jock<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> Jock Gill<o:p></o:p></p><p class=MsoPlainText>> P.O. Box 3<o:p></o:p></p><p class=MsoPlainText>> Peacham, VT 05862<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>> Cell: (617) 449-8111<o:p></o:p></p><p class=MsoPlainText>><o:p> </o:p></p><p class=MsoPlainText>><o:p> </o:p></p></div></body></html>