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<DIV><FONT size=2 face=Arial>Alex, </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Thank you for your excellent responses. You
pose some very good ideas and concerns.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>On the question of obstruction, I have to disagree
with you. </FONT><FONT size=2 face=Arial>The Venturi mixer I am working on
reduces the open area to .5 that of the fuel reactor
chamber. Your design reduces the open area from 12 inch dia
to 2 inch dia which is 113 sq in to 3.14 sq in. That is .028 the open
area of the fuel reactor chamber, which is much more restriction than I am
using. You must be getting an incredible velocity through the 2 in pipe,
which would be giving you a substantial drop in pressure via the Venturi
effect. It would be very interesting to get pressure measurements
throughout your stove (with the secondary air entrance open/closed, and
compared to a straight wall stove of the same height for a control). Your
placement of the secondary air entrance is perfect to use the Venturi pressure
reduction for mixing. I have not found tangential secondary air mixing to
work very well, but I am guessing that the increased pressure difference makes
it work for you. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I very much like the way you have found to
<STRONG><U>pre-mix</U></STRONG> the wood gas with the secondary air. I had
thought it would be much more difficult to achieve this. You have cleverly
increased the wood gas velocity so it is faster than the flame
can burn back, and thus give the gasses time to pre-mix before they
burn. When the mixture ignites in the mixing area, the high
gas velocity just pushes the flame out. Or perhaps there is
always a small amount of flame in the mixing zone, but the gasses are moving so
fast that the majority of gas doesn't burn until it reaches the burning
area. Or perhaps the gasses mix and begin combusting, but because of the
gas velocity they don't have time to burn completely in the mixer area.
Even well mixed gasses take time to burn. The only way I can see that
there would be no flame in the mixing area is if the mixture is below ignition
temperature.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>It appears to be a rapid mixing technique,
though you have designed for narrow and tall whereas I designed for wide and
short. Both will find their place. The height of the
cone that accelerates the wood gas plus the height of the mixer
plus the height of the cone to decelerate the mixture and hold the flame adds up
to some height. That is not a negative if it works for the
application. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>How do you use the flame for cooking? A grill
over the top? A sunken pot?</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>What is the fire power? The constriction must
be creating a back pressure that is slowing pyrolysis, and thus fire
power. This might be countered by the large diameter fuel reactor chamber
providing a large pyrolysis front and lots of wood gas. It is natural
draft and with how much turn-down?</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I agree with you on the concern for material
life. Your design allows the materials some cooling by giving off
heat to the outside. My design holds the material in the heat. The
only cooling I get is from the secondary air entering and picking up some of the
heat. Things often glow red hot. Material life will be a serious
concern for my design, but this is the twenty-first century, and materials
science has progressed. Possible solutions include making the mixers
from ceramics or other heat resisting material, and designing for cheap and easy
replacement of the heat stressed parts.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Very nice concept! Thank you for
sharing.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Kirk H.</FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"
dir=ltr>
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=aenglish444@gmail.com href="mailto:aenglish444@gmail.com">alex
english</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=stoves@lists.bioenergylists.org
href="mailto:stoves@lists.bioenergylists.org">Discussion of biomass cooking
stoves</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, September 29, 2016 4:22
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Stoves] Rapid mixing</DIV>
<DIV><BR></DIV>
<DIV dir=ltr>Kirk,
<DIV>Its quite wonderful what you have demonstrated. A holy grail of sorts.
The durability and complexity, and ultimately this is the cost, of the
structure you have placed in the flame/gas path will determine its future
usefulness. Interesting solution none the less.</DIV>
<DIV><BR></DIV>
<DIV>Here is a recent video of my premixed blue tlud-gas flame. Its all
geometry, no obstruction.</DIV>
<DIV><A
href="https://www.youtube.com/watch?v=jnV1e60NTss&feature=youtu.be">https://www.youtube.com/watch?v=jnV1e60NTss&feature=youtu.be</A></DIV>
<DIV><BR></DIV>
<DIV>Alex<BR>
<DIV class=gmail_extra><BR>
<DIV class=gmail_quote>On Wed, Sep 28, 2016 at 12:05 PM, kgharris <SPAN
dir=ltr><<A href="mailto:kgharris@sonic.net"
target=_blank>kgharris@sonic.net</A>></SPAN> wrote:<BR>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote><U></U>
<DIV lang=EN-CA bgcolor="white">
<DIV><FONT face=Arial>Crispin and All,</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>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. </FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Your techniques are what I was looking for, ideas for
rapid mixing.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Kirk H.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(0,0,0) 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"
dir=ltr>
<DIV style="FONT: 10pt arial; font-stretch: normal"><FONT size=3>-----
Original Message ----- </FONT></DIV>
<DIV
style="BACKGROUND-COLOR: rgb(228,228,228); FONT: 10pt arial; font-stretch: normal; background-size: initial; background-origin: initial; background-clip: initial"><FONT
size=3><B>From:</B> </FONT><A title=crispinpigott@outlook.com><FONT
size=3>Crispin Pemberton-Pigott</FONT></A><FONT size=3> </FONT></DIV>
<DIV style="FONT: 10pt arial; font-stretch: normal"><FONT
size=3><B>To:</B> </FONT><A title=stoves@lists.bioenergylists.org><FONT
size=3>'Discussion of biomass cooking stoves'</FONT></A><FONT size=3>
</FONT></DIV>
<DIV style="FONT: 10pt arial; font-stretch: normal"><FONT
size=3><B>Sent:</B> Tuesday, September 27, 2016 8:09 PM</FONT></DIV>
<DIV style="FONT: 10pt arial; font-stretch: normal"><FONT
size=3><B>Subject:</B> Re: [Stoves] Rapid mixing</FONT></DIV>
<DIV><BR></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT size=3>Dear
Kirk<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT size=3>I
think your conclusion is correct – that you can shorted the height of the
combustion zone with radial or helical
mixing.<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT size=3>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.<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><IMG style="MIN-HEIGHT: 2.833in; WIDTH: 3.145in"
src="cid:09FB0192762A4BDA9EACFDD25FC626DC@phyllisPC" width=302
height=272><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><U></U></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT size=3>The
material is a low chrome stainless steel. The production is in three
stages: blanking, punching the cuts, then
forming.<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><FONT size=3><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt">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</SPAN><SPAN
style="FONT-FAMILY: tahoma,sans-serif; FONT-SIZE: 11pt">˚</SPAN><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt">C works
well.<U></U><U></U></SPAN></FONT></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><IMG style="MIN-HEIGHT: 3.145in; WIDTH: 3.145in"
src="cid:55273154DB1C4F3FA2B12AA3BD463CD8@phyllisPC" width=302
height=302><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><U></U></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT size=3>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.
<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT
size=3>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.<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT
size=3>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.
<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT
size=3>Everyone should try these approaches and report what works well.
<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT
size=3>Regards<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><FONT
size=3>Crispin<U></U><U></U></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: calibri,sans-serif; FONT-SIZE: 11pt"><U></U><FONT
size=3></FONT><U></U></SPAN> </P>
<DIV>
<P class=MsoNormal> ……<U></U><U></U></P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3><SPAN
style="FONT-FAMILY: arial,sans-serif; FONT-SIZE: 10pt">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 <STRONG><U><SPAN
style="FONT-FAMILY: arial,sans-serif">high and low</SPAN></U></STRONG>
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.</SPAN><U></U><U></U></FONT></P></DIV>
<DIV>
<P class=MsoNormal><U></U><U></U> </P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3><SPAN
style="FONT-FAMILY: arial,sans-serif; FONT-SIZE: 10pt">List, keep writing
about wood stoves, don't be
distracted.</SPAN><U></U><U></U></FONT></P></DIV>
<DIV>
<P class=MsoNormal><U></U><U></U> </P></DIV>
<DIV>
<P class=MsoNormal><FONT size=3><SPAN
style="FONT-FAMILY: arial,sans-serif; FONT-SIZE: 10pt">Kirk
H.</SPAN><U></U><U></U></FONT></P></DIV></DIV>
<P></P>
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