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<DIV><FONT size=2 face=Arial>Roberto,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Thank you for your excellent response.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Yes, it now has several tubes. This is to
increase the mixing capacity for a higher power flame. I forgot to mention
in the previous email that the Venturi works in addition to the draft to bring
in secondary air. The change in pressure is the main contribution of the
Venturi. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I am a fan of Alexis Belonio. We had a good
talk at Aprovecho after ETHOS 14. The pipe to conduct the wood gas to an
lpg like device is a exciting idea. I don't like the idea of cooling the
gas unless it is to be stored, because so much heat is lost. For
a TLUD, burning the gas while it is hot makes sense.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>A narrow pipe as you describe would work also to
create a Venturi effect. I can see how this would work. You write
that the holes are at the top of the central ring hole. I put
the tubes at the bottom of the combustor for two reasons: better
draft and more time for the gasses to finish burning. This works for my
needs. When the flame hits the pot, it cools and some of the fuel is lost
as PM, so I like to finish the burning before the flame hits the pot. The
pot seeing the entire flame will increase radiant heat to the pot surface but
also can loose some of the conductive heat transfer as I have heard
described at Aprovecho. I am not familiar with your arrangment, whether
this will happen or not. Which is best, radiant or conductive I don't
know, but your experience seems to add a vote for radiant.
I am happy that you are getting the good results that you want. This is
good. There are many ways to burn wood gas.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Some of us attending Stove Camp at Aprovecho this
summer, Steve, Cody, Ricardo, and myself tried using a second layer of
tubes. The test looked good at first until we realized that something
was wrong with the sensor/computer read out. When the filter was examined,
it was very dirty. This being said, some other thoughts need saying.
This combustor, as a 4 tube combustor had earlier tested at 1 mg/min, but
clean at only 3 kw. We wanted 5 kw, so we added the second row to this
combustor to try to increase its capacity to the higher power
level</FONT><FONT size=2 face=Arial>. Thus we ran the stove at a higher
power level. All we proved was that this particular combination did not
work at 5 kw. I have been trying variations of this combination
since, and the results are similar. It really doesn't seem to work.
The single layer is better. More tubes, as suggested by Cody Anderson at
stove camp, is the direction I am trying. It seems to work, but only if
the entire array can be used.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>The pipes themselves reduce the open area of the
combustor, so reducing the overall combustor opening higher up is not
needed. The combustor is left wide above the stationary fan to allow
room for the flame to finish burning. The rate of combustion does not need
to be increased. Improving on 1 mg/min would not be that meaningful.
1/2 mg/min is not too different from 1 mg/min. What I need to do
is increase the usable power level.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Pre-mixing with a TLUD is not possible since as
soon a it mixes, it burns. It is a mixed-while-burning device.
Venturi gas mixers used for fossil gasses can pre-mix because the gas is cool
and compressed. TLUD wood gas is hot and at near atmospheric
pressure. The TLUD Venturi gas mixer will look quit different than a
fossil gas Venturi mixer because of this. The TLUD Venturi mix is on a par
with a pre-mixed system, quite good. Actually, it is quite
excellent.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>To cool the gas, a complex cooling and filtering
system is needed, which would be expensive. All TLUDs mix the hot gasses
with various amounts of completeness. The TLUD Venturi mixer is capable of
mixing hot gasses, and doing it with a high amount of completeness. Using
a retort might be more appropriate for wood gas that is to be
cooled.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Burning some of the gas below the tubes is a good
topic. I have found that with no flame below the tubes, soot is deposited
on the bottoms of the tubes and the exhaust can be dirty. Too much
air below the tubes negates the value of the tubes and produces considerable
smoke. Probably because of too much air cooling and diluting the
flame. Allowing a moderate amount of flame below the tubes
keeps the tubes and exhaust clean, and does seem to help increase the
possible power level. The pre-tube secondary air can perform another
task, if it is done right. It can be used to blow the wood gas
evenly over the tube mixer array. This is very helpful because it avoids
over or under loading any part of the array, making better use of the entire
array. The simple Strata designs of a year ago using the 5 point star or
single tube arrangments seem to work better with various stoves. The
current design with more parallel tubes is more tempermental, and will need the
stove to be designed for the combustor.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Thank you, Roberto for your thoughtful response and
good ideas,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Kirk</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=roberto.poehlmann@gmail.com
href="mailto:roberto.poehlmann@gmail.com">Roberto Poehlmann</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=stoves@lists.bioenergylists.org
href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, September 14, 2015 12:25
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [Stoves] Strata combustor
general principles</DIV>
<DIV><FONT size=2 face=Arial></FONT><FONT size=2 face=Arial></FONT><BR></DIV>
<P dir=ltr>Hi Kirk,</P>
<P dir=ltr>Thanks for sharing this knowledge.<BR>I see that the Strata
combustor has evolved to a design with several secondary tubes. This remind me
the secondary tubes of some double combustion woodstoves, but without the use
of the venturi effect.</P>
<P dir=ltr>I always see the TLUD combustion chamber as a smoke or woodgas
generator. On top of the combustion chamber, exists multiple alternatives to
put different kind of combustors. One alternative is the Strata combustor, as
you propose. Another alternative is a pipe to conduct the woogas to a lpg like
burning device, as Alexis Belonio did in Phillipines.</P>
<P dir=ltr>With that in mind, i have constructed a combustor wich also
utilizes the venturi effect. Is a vertical tube with two rows of secondary
holes on top of the central ring hole. The diameter of the central ring hole
(and the tube) is smaller than a standar TLUD ring hole. Inside the tube,
because of the drop in pressure, it sucks secondary air to allow a good mixing
of the gases.<BR>Because of the small diameter of the tube (2 inches aprox.),
i can have a low consumption rate of pellets, without the risk of smoke
traspassing through the flame. Another advantage of this design, is that the
pot "see" the entire flame.<BR>With this design, i see that 2 or 3 rows of
secondary holes, generate a very good looking flame, without any perceptible
contamination.</P>
<P dir=ltr>Have you tried to put 2 layers or rows of secondary tubes in the
Strata combustor? Maybe you can also reduce the top hole of the combustion
chamber, and with the additional tubes, you can increase the rate of
combustion.</P>
<P dir=ltr>Another question or idea: have you tried to have a premixing
flame?<BR>I tried to do that, but when the air enter below the secondary
flame, the air reacts with the smoke and generate a pilot flame below the
principal flame.<BR>It is possible to cool down the smoke before mixing it
with air, to have a premixing flame? I see that in some woodgas generator to
feed internal combustion engines, so maybe is possible.</P>
<P dir=ltr>But, after the intend to have a premixing flame, i have had a new
idea. It is the increase of the pilot air below the principal flame or
terciary flame, to reduce it at very high combustion rates. Part of the smoke
will be burn inside the combustion chamber, before reaching the principal
flame.</P>
<P dir=ltr>Greetings<BR>Roberto Poehlmann</P>
<P>
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