Greetings, First post to the list. Has anybody measured the combustion wall temperature for a stove where the combustion takes place in a vortex vs. one where it does not?
Sam On Sun, 2010-08-29 at 12:00 -0700, [email protected] wrote: > Send Stoves mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Stoves digest..." > > > Today's Topics: > > 1. Fire in a vortex (Crispin Pemberton-Pigott) > 2. Re: Fire in a vortex (andrew heggie) > 3. Re: Fire in a vortex (Crispin Pemberton-Pigott) > 4. Re: Fire in a vortex (andrew heggie) > 5. Re: Fire in a vortex (Tom Miles) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Sun, 29 Aug 2010 06:35:33 +0800 > From: "Crispin Pemberton-Pigott" <[email protected]> > To: "'Discussion of biomass cooking stoves'" > <[email protected]> > Subject: [Stoves] Fire in a vortex > Message-ID: <01bc01cb4701$54a35200$fde9f6...@com> > Content-Type: text/plain; charset="us-ascii" > > 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 > > > ------------------------------ > > Message: 2 > Date: Sun, 29 Aug 2010 10:38:49 +0100 > From: andrew heggie <[email protected]> > To: Discussion of biomass cooking stoves <[email protected]> > Subject: Re: [Stoves] Fire in a vortex > Message-ID: <[email protected]> > Content-Type: text/plain; charset="utf-8" > > On Saturday 28 August 2010 23:35:33 Crispin Pemberton-Pigott wrote: > > Creating such a vortex allows the use of materials that do not need to > > be able to survive high temperatures (like metals). > > Even metals survive well because the centrifuge throws denser, cooler, > gases to the outside keeping the core hot and the walls cool. It seems to > lead to some segregation of incoming air such that dilution air ends up > as a high excess air value. I say this only from observation of > experiments where I have measured excess air in the flue with low (30ppm) > CO levels where I expected lower excess air measurements for a pre mixed > flame. > > AJH > > > > ------------------------------ > > Message: 3 > Date: Sun, 29 Aug 2010 14:05:55 +0000 > From: "Crispin Pemberton-Pigott" <[email protected]> > To: "Stoves List" <[email protected]> > Subject: Re: [Stoves] Fire in a vortex > Message-ID: > > <1331265718-1283090745-cardhu_decombobulator_blackberry.rim.net-3179517...@bda2277.bisx.prod.on.blackberry> > > Content-Type: text/plain > > 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? > > It is worth sampling them separately before the heat exchanger mixes > everything - something we did not do. > > Thanks > Crispin > -----Original Message----- > From: andrew heggie <[email protected]> > Sender: [email protected] > Date: Sun, 29 Aug 2010 10:38:49 > To: Discussion of biomass cooking stoves<[email protected]> > Reply-To: Discussion of biomass cooking stoves <[email protected]> > Subject: Re: [Stoves] Fire in a vortex > > On Saturday 28 August 2010 23:35:33 Crispin Pemberton-Pigott wrote: > > Creating such a vortex allows the use of materials that do not need to > > be able to survive high temperatures (like metals). > > Even metals survive well because the centrifuge throws denser, cooler, > gases to the outside keeping the core hot and the walls cool. It seems to > lead to some segregation of incoming air such that dilution air ends up > as a high excess air value. I say this only from observation of > experiments where I have measured excess air in the flue with low (30ppm) > CO levels where I expected lower excess air measurements for a pre mixed > flame. > > AJH > > _______________________________________________ > Stoves mailing list > [email protected] > http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org > http://stoves.bioenergylists.org > http://info.bioenergylists.org > > > _______________________________________________________ > Unlimited Disk, Data Transfer, PHP/MySQL Domain Hosting > http://www.doteasy.com > > ------------------------------ > > Message: 4 > Date: Sun, 29 Aug 2010 15:57:13 +0100 > From: andrew heggie <[email protected]> > To: Discussion of biomass cooking stoves <[email protected]> > Subject: Re: [Stoves] Fire in a vortex > Message-ID: <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > 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 > > > > ------------------------------ > > Message: 5 > Date: Sun, 29 Aug 2010 08:59:34 -0700 > From: "Tom Miles" <[email protected]> > To: "'Discussion of biomass cooking stoves'" > <[email protected]> > Subject: Re: [Stoves] Fire in a vortex > Message-ID: <001f01cb4793$2ee4c3e0$8cae4b...@com> > Content-Type: text/plain; charset="us-ascii" > > 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 > > End of Stoves Digest, Vol 50, Issue 26 > ************************************** _______________________________________________ Stoves mailing list [email protected] http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org http://stoves.bioenergylists.org http://info.bioenergylists.org
