On Sun, 11 Mar 2012 07:30:24 +0700, Paul Olivier wrote: >> > >It is impossible to light the burner with the strainer in place. >So in lighting a burner, I have to run it for a short while without the >strainer. >And when I put the strainer on the burner, I always have to turn down the >fan.
Does the fan simultaneously supply primary air ( for the gasifier) and the secondary air to burn the offgas? You mention the initial flame pyrolysis/gasification in the primary chamber migrates to the burner holes after some time. > >To get full and uniform ignition at all burner holes without the strainer, >a certain fan speed is required. >But to get full and uniform ignition at all burner holes with the strainer, >a lesser fan speed is required. Difficult to judge without seeing things but my guess this is to do with air:fuel mixture rather than flame speeds. Initially the burn in the primary chamber using more air than necessary for gasification (secondary burn happening to some extent in the primary chamber}. >With the strainer the flames are far more consistent and stable. >The flames acquire structure and are not easily influenced by the wind. >This gives me reason to believe that the transfer of convective heat is >much more efficient when a dome is present. >So with a more efficient transfer of heat by convective means > and with the whole new dimension of thermal radiation that comes into play, > a lot more heat makes it into the pot. We'd need comparative (i.e. they don't need to be exact, given the problems with thermocouples in a gas stream) temperature readings both above and below the dome and in the same positions with the dome removed. I can see the strainer/dome acting as a means of shielding, mixing and providing turbulence. I can't see what effect it would have in changing the flue gas characteristic to change the way the gases reaching the pot are transferred to it. The fact that you lower the fan rate when the dome is in position makes me think that with the fan dome you supply less excess air, this increases the flue gas temperature and thus the delta T twixt flue gas and pot increases heat transfer. AJH _______________________________________________ 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/
