Andrew, Crispin, I recall that in the Vesto Crispin very successfully demonstrated the challenges of creating and using a vortex in low energy, low velocity flames for heat recycling. http://www.bioenergylists.org/vestoheatrecycle You can take advantage of this centrifugal separation when you supply cold, dense, combustion air downward in an outer annulus. It mixes with the fuel and creates an inner vortex flame in the opposite direction. Particles or droplets that are heavy fly to the outer vortex and re-circulate. This makes for good mixing and complete combustion. Like the quarl in a gas or oil burner, it increases residence time in the high temperature zone. We have called this a "concentric vortex" or double vortex in our designs. It has also been called an "aerodynamic flame holder" (e.g. RH Essenhigh, 1970, MM Kamal, 2008). We have used the recirculation in burning wood gas efficiently. Vortex flames require a certain mass flow to be efficient. In the 1980s the French burner company, Pillard, re-circulated flue gas to increase mass flow and reduce excess air. Dick Wright's 1985 Biomass Suspension Burner patent has a pretty good description of vortex suspension burning. http://www.google.com/patents/about?id=1F82AAAAEBAJ&dq=4565137
Tom -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of andrew heggie Sent: Sunday, August 29, 2010 7:57 AM To: Discussion of biomass cooking stoves Subject: Re: [Stoves] Fire in a vortex On Sunday 29 August 2010 15:05:55 Crispin Pemberton-Pigott wrote: > Dear Andrew > > I agree re pipe walls - they definitely run cooler with a vortex. You > mention the region of higher EA. Is that at the centre or the > periphery? We measured at the top of a flue stack via a long pipe to lose temperature, there was no heat exchanger so all the flue heat was direct. The flue was 250mm and the vortex 1200mm so there was a lot of mixing going on after the combustion, which is why it was impossible to differentiate excess air that had passed through the combustion and dilution air that had passed up the outside of the vortex (because it was cool and more dense) and into the flue. When playing with smaller stoves (without the benefit of flue gas analyser) I formed the opinion that the heat exchange to a Kelly kettle must be inhibited by this effect. I experimented by putting some "fins" in the central tube to disrupt the vortex but never came to any conclusion. AJH _______________________________________________ Stoves mailing list [email protected] http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org http://stoves.bioenergylists.org http://info.bioenergylists.org _______________________________________________ Stoves mailing list [email protected] http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org http://stoves.bioenergylists.org http://info.bioenergylists.org
