[Stoves] Rapid mixing

Wed Sep 28 11:05:10 CDT 2016

Crispin and All,

Some clarification:  By radial mixing I assume you mean the method in the lower photo where the air travels inward, radially.  By helical mixing I assume you mean swirling gasses by using fan blades like in the top photo.  Neither of these represents a conclusion on my part.  Your opening sentence put me on guard immediately because it defines your techniques as my conclusion.  A more accurate starting sentence for your response would have been 'Here are two techniques to look at that have worked for me'.  My thinking is not limited to these two ideas.  

Your techniques are what I was looking for, ideas for rapid mixing.

Kirk H.

  ----- Original Message ----- 
  From: Crispin Pemberton-Pigott 
  To: 'Discussion of biomass cooking stoves' 
  Sent: Tuesday, September 27, 2016 8:09 PM
  Subject: Re: [Stoves] Rapid mixing

  Dear Kirk

  I think your conclusion is correct – that you can shorted the height of the combustion zone with radial or helical mixing.

  I provide two photos with this in mind, though accomplished in completely different ways. The first is (for a wood burner, not pellets) is to put the mixed below the fuel, to continuously create a series of ‘induced vortices’ a few of which pass through the fuel and provide mixing by spinning. A vortex tends to perpetuate itself so all that is needed is to get a few going all the time.

  The material is a low chrome stainless steel. The production is in three stages: blanking, punching the cuts, then forming.

  The second method of shortening the flame is to use the secondary air entering the fire as a method of driving the flames horizontally. This should be done in a ‘divided’ manner, not a ring of air, so that it breaks up the rising gases into manageable jets. This kind of short clean burn can only be done with preheated secondary air – 300-500˚C works well.

  The fire above is burning pellet gas (as a TLUD) though it also works for wood if the gas generation is consistent. Consistency requires very good air control. The amount of is required to achieve this is so low that it pretty much rules out having an open bottom with fuel sticking out. 

  Readers may recall Julien in Coburg combined the injection of air and placement of the air feed in the gas stream. A problem commonly reported with that approach is the cooling of the metal by the air can interfere with the combustion.

  Readers may also recall Dr Nurhuda in Indonesia achieved a downward turning flame consistently in his recent stoves reducing the flame height basically to zero. All of these approaches can assist the provision of lower height stoves – a major challenge for typical Indian rural households where cooks won’t compromise on the cooking height. 

  Everyone should try these approaches and report what works well. 

  Regards

  Crispin

   ……

  Not to be distracted from the purpose of this list, I have a thought about wood stoves.  A small natural draft wood burning cook stove that mixes the wood gas with secondary air in 2 cm has a considerable advantage over a stove that may take 20 cm or more.  It's a little like transistors, which gave advantage over vacuum tubes in electronics.  Rapid mixing can enable a small wood stove to burn quick and clean at both high and low power levels.  Witness the excellent numbers for the Wonderwerk TLUD-ND stove which uses a rapid Venturi mixing technique.  Combined with the user friendly power level controls, the principles used in the Wonderwerk stove hold considerable potential.  Rapid mixing seems to me to be a very good area for research.  I wonder how many rapid mixing techniques will be found over the next few years?  I intend to contribute.

  List, keep writing about wood stoves, don't be distracted.

  Kirk H.

------------------------------------------------------------------------------

  _______________________________________________
  Stoves mailing list

  to Send a Message to the list, use the email address
  stoves at lists.bioenergylists.org

  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://stoves.bioenergylists.org/

------------------------------------------------------------------------------

  No virus found in this message.
  Checked by AVG - www.avg.com
  Version: 2016.0.7797 / Virus Database: 4656/13096 - Release Date: 09/27/16
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20160928/c20e8cdb/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 175915 bytes
Desc: not available
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20160928/c20e8cdb/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.jpg
Type: image/jpeg
Size: 17127 bytes
Desc: not available
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20160928/c20e8cdb/attachment.jpg>