Dear spinning fire enthusiasts
There is a remarkable video of a fire spinning inside a vortex, in this case a tornado passing over a fire in Brazil. The tornado (or whirlwind as it is pretty small) was created by the updraft from the open fire. It seems natural for a spinning vortex to be self-sustaining once it gets going. The point of this is to observe that the central 'tube' of fire is rising much faster than the outer portion and as it is hotter, it rises faster, sustaining the updraft and pulls in more fuel and air. When such a vortex is deliberately created inside a tube of metal or ceramic (by for example introducing air in a manner that spins it) the effect is two-fold: the fire travels much farther through the system without cooling down (yet without heating the walls much), giving it time to burn fuels that have a relatively long chain oil content (like young coal or resinous wood). It is a good example of 'gas insulated' combustion taking place. The cooler part of the fire is the outside (normally against the wall of the tube or passage) and the centre is much hotter, faster moving, turbulent and cleaner burning. As products of incomplete combustion are pulled into the central region, they are entrained in the hotter flame which continues away from the wall. In the video, the wall is the outside of the tornado funnel. Creating such a vortex allows the use of materials that do not need to be able to survive high temperatures (like metals). The video is at: http://www.youtube.com/watch?v=F7D5jrWbppY <http://www.youtube.com/watch?v=F7D5jrWbppY&feature=player_embedded> &feature=player_embedded Regards Crispin
_______________________________________________ Stoves mailing list [email protected] http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org http://stoves.bioenergylists.org http://info.bioenergylists.org
