[Stoves] Studies of pressure variations in a TLUD - Pulsing Flame with Concentrator Rings

[Jaakko Saastamoinen]

Dear Julien and readers,

this pulsating phenomena could be related to similar pulsations occurring in a Rijke tube (see for example Wikipedia). About 25 years ago a researcher Joao Carvalho from INPE (Brazil) demonstrated this with a simple test when visiting our research laboratory in Finland. It was easy to build. It needs a vertical metal tube, a grate basket allowing air to go through hanging on a wire. The fuel (wood chips or pellets) on the grate were ignited and the grate was put into the tube hanging on the wire. Then when lowering the position of the grate, intense pulsations started at a specific location. As far as I remember, the location was about 1/4 of the total tube length from the bottom.  Prof. Carvalho has written some papers on this (for example: Definition of heater location to drive maximum amplitude acoustic oscillations in a Rijke tube,  Combustion and Flame, Vol.76, 1989, p. 17-27).

We built a test grate burner to study this, because pulsations can also have a positive effect by intensifying the combustion rate/grate area (heat and mass transfer between gas and fuel particles increases). Vibrations are also useful intensifying drying of particles. There are also other combustion devices creating pulsations as discussed for example in “Workshop on Pulsating Combustion and Its Applications,  2-5.8.1993, Lund University, Sweden (I have a coffee cup as a souvenir from this meeting in front of me now).

Regards

Jaakko

From: Stoves <stoves-bounces at lists.bioenergylists.org> On Behalf Of Julien Winter
Sent: perjantai 19. kesäkuuta 2020 2.27
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: [Stoves] Studies of pressure variations in a TLUD - Pulsing Flame with Concentrator Rings

Hi Folks;
I made another video so that you can see the relationship between above and below concentrator flames
https://youtu.be/0HBCHGQk1AU
Cheers,
Julien

--
Julien Winter
Cobourg, ON, CANADA
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20200619/c6f8a4c5/attachment.html>