Crispin cc list Thanks for both the cutaway and the added information below. I think we all recognize that you were designing a stove with an intent to consume char - not produce it, although the latter was possible in part with appropriate timing of extinguishment. Your objective seems to have been well met - especially with the reduced amount of secondary air in the latest mods..
Would you agree that if one is striving for char production, that the amount of primary air flow can/should be much reduced over the present design? The only remaining design feature I can't see in the cutaway or your comments is how you are controlling secondary air flow with the right hand slide control. A similar (unshown) angular rotation slide? Ron ----- Original Message ----- From: "Crispin Pemberton-Pigott" <[email protected]> To: "Discussion of biomass cooking stoves" <[email protected]> Sent: Monday, January 21, 2013 10:07:29 AM Subject: Re: [Stoves] is this new? Dear Alex Well spotted. That combustion chamber was changed some years ago. There are no holes near the top of the current version (which works better as a TLUD when desired). I was able to reduce the number of holes. The Vesto being manufactured in the Gambia uses the new version as well. The number of holes below the secondary air lines was also changed to provide 2 or 3 char-burning pilot flames in case the main flame goes out for some reason (it gets unstable when the charcoal is nearly gone). This solution is one way to get the charcoal to burn more or less concurrently with the gases, or if it was operated in a char-making mode, to burn the char without losing the fragile flame at the secondary stage. I was always unhappy with the way gasifiers are going out with any slight disturbance and found that if the secondary fire is close-coupled to the pyrolysing zone and there is a pilot flame from below, the top (big) flam re-lights automatically if some gust of wind blows it out. When burning ball-shaped fuel with a lot of air flowing through (like perhaps the jatropha seeds) too much air passes through the primary zone. I think this is part of the cause of the problems reported re smoking excessively or smoking too much of the time when burning oily seeds. There is just too much primary air and one ends up with a tall diffusion flame with no hope of getting enough secondary air mixed into it in the (usually very) short space provided for the flame. The simplest cure is to put a paper disk on the bottom of the combustion chamber to block the air. It will catch fire later one and provide the needed primary to that will burn the char (if that is desired). If there are some jatropha seeds available in Yogyakarta I will try some to see what happens. I took a new combustion chamber to them on the past trip. (That stove is ancient). Regards Crispin hitting -14 C today and what about that 40 cm of snow?? L Crispin, Its been a while since I saw the Vesto. It looks from the pictures like there are secondary air holes all the way up the central tube. Is that current? Seems like the top rows would just be adding tramp air (unemployed air). Alex _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/
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