On Sun, 4 Mar 2012 17:50:46 +0700, Paul Olivier wrote: > >I am not sure if I understand what you are saying here. >From what I observed, the gases have to burn below the wire mesh. >If they go through the wire mesh and then burn, then the wire mesh turns >from red to black.
This is understandable and points to the same effect as the gauze in the Davey lamp, is the black sooty deposits? Or just lower temperature? My inference is that there would be higher products of incomplete combustion above the wire in this scenario. >Most of the gases burn close to the burner holes. >But there are always gases that rise in the dome and hug the underside of >the dome. >There they burn right on the underside of the dome. >The wire mesh dome gives structure to the diffusion tail > and does not allow it to be so easily influenced by the random movement of >air or wind. It's hard to see what's happening here, how the dome is acting as a shield, whether the dome is passing unburnt gas, just as in the gauze and Bunsen burner demonstration. > > > >> I wonder how >> this sits compared with the wire gauze in a Davey Safety lamp, which >> is there specifically to remove the source of ignition from the gases >> outside? >> > >Again, I do not understand your point. In the beginning of the industrial age coal was the driving energy source and with the lack of large machines it was "won" by men tunneling into the seams with pick axes and candles on their heads. Apart from the obvious dangers of rock fall there was the danger from gases seeping into the mineshaft, they were given different names from their consequences, black damp was CO2 and water vapour from the newly exposed coal reacting with air which caused asphyxiation (damp derives from the german for vapour). Canaries are sensitive to reduced O2 in the atmosphere and were used to indicate black damp. Firedamp was an explosive mixture , mostly now known to be methane, and candle flames could set off an explosion. Humphrey Davey produced a lamp that was safe to use because it was not an ignition source, like a naked flame. The principle he used was to enclose the flame in a glass cylinder to let the light out but all the combustion air and flue gases passed through a mine gauze, this gauze conducts the heat away from a flame such that the flame is quenched, just like lowering a cold spoon over a candle flame. So even though the lamp was hot it was below the auto ignition temperature of methane:air mixture and because the flame is quenched there is no flame or spark to trigger the explosion. You seem already to have observed that the flame needs to complete under the gauze. I just worry that what you observe of the dome giving the flame structure is not just that the dome is quenching and unburnt gases are thus not seen above the dome. If you have access to a Bunsen burner you can readily demonstrate this effect by placing the gauze 1cm above an ordinary gas burner before it is ignited and then light it above the gauze, not the flame dances on the gauze and does not jump back to the burner, at least until the gauze gets bright red hot, if ever. First hit on Goggle http://www.minerslamps.net/homepage/safetylamphistory.htm >Please clarify. >So sorry. Paul all of your questions are sensible, my struggling to answer them in a way you understand is the problem, this often troubles me when I see no responses. 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/
