<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><style> body { font-family: "Calibri","Slate Pro",sans-serif,"sans-serif"; color:#262626 }</style> </head> <body lang="en-US"><div>Dear TLUD lovers</div><div><br></div><div>This one should warm you. </div><div><br></div><div>I left a design and working example of the TJ3B stove (see my website under Tajikistan) in the town of Muminabad which is where Caritas has a regional office focused on stove production and other projects. </div><div><br></div><div>A sample arrived in Dushanbe without the essential seven secondary air holes. The reason is that the producer feared that CO would energy from the holes rather than air going in. As this fear is real and people don't understand what risks that faced in the past or now, and from what. I decided to test the stove as is and see what would happen. Thanks to Paul Anderson for teaching me not to live on assumptions about what does and doesn't work. Prove it. </div><div><br></div><div>So I filled it with about 5 kg of Kyrgyz coal lit with mostly soft wood. The coal size was under 27mm. <span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">Because of the nature of the test goal I was careful to leave out the duff smaller than 6mm. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">After ignition the fire was normal because the bottom door was open as usual for 10-15 minutes. There was never any smoke at all from the start. Nothing seen even during early ignition. Part of the explanation was the use of the lid to allow some air into the top hole on the opposite side from the chimney creating a cross draft fire right from the start. Otherwise I don't have a comprehensive explanation for why it burned clean the entire time. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">The fire then burned in a normal manner as a coal gasifier with combustion above the fuel relying on air supplied through the fuel bed rather than above the fuel as usual. This is how the Turkish TLUD's work. Generally they rely heavily on the fuel particle size and hardness to get an appropriate air/fuel ratio. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">I had to leave the door open at least a little or else the stove would go into a very low power mode because the control arm only uncovers three 12.7mm holes. I settled on 3mm open on one side and zero on the other. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">Apart from having an extremely low excess air level in the coke burning phase, it did remarkable well. Obviously it needed the air below but it followed the usual burn pattern of pyrolysing the fuel bed, about 350mm deep, in 2 hrs and then completed a slow burn of the coke over the next five hours. Five hours after ignition the coke was again burning on top with an outsde temperature (stove body radiation) of 490 C. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">The excess air level in that condition was 1.5% but the CO/CO2 ratio was only 3% which is remarkable. In this condition the system efficiency was >80. During pyrolysis it was as high as 7%, obviously because of a lack of air. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">So the challenge is how to improve the combustion without offending the ideas of the customers and their well grounded fears (people die from chimney malfunctions).</span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">After some measurements and math the plan is:</span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">Drill one hole 20mm in diameter at the height of the original secondary air holes. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">Weld a 40x40 angle iron against the steel body creating a triangular cavity inside it going from almost the bottom of the body to just above the hole. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">Cap the angle iron with a triangle of steel. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">Weld a 45 or 90 degree steam pipe elbow to the inside to lead the air coming through the hole downwards into the stove body. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">This will provide preheated secondary air most of the time, but especially when the ash is packed into the coke and the air supply is most limited. It will direct the air downwards so as to reach the top of the collapsed pile of fuel. Any tendency for CO to emerge from the hole in very low draft conditions will be overcome by heat raising the air in the channel by buoyancy. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">The plan is to raise the excess air to at least 45%, preferably 60% in the late fire. A second change will be increasing the stove height to bring the burn time to 9 hours so it can heat a school classroom for a whole day on a single load</span><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"></span><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">There is a picture of the stove in the Model 3 folder under Tajikistan. In the attached photo the top number is the efficiency as a space heater. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">We will test this product in some school classrooms this winter. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">The lesson is that it worked far better than I expected, the secondary air holes did not render the combustion 'terrible'. It never smoked that we could see from beginning to end. The final version will address the evident fear of the customers. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">It is worth noting that this solution was recommended to the Turkish stove producers after lab tests showed they were all short of air for great periods of time, hours, during which PM bursts were seen at very low EA levels. None adopted it. </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">Regards </span></div><div><span style="font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;">Crispin </span></div><br></body></html>