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<DIV><FONT size=2 face=Arial>Ron and All,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I do use swirl in the Wonderwerk Strata test
combustors. The swirl is not for mixing. Mixing is done first
by the Venturi gas mixer arrangement, which uses both draft and Venturi vacuum
to mix the gasses. Thank you Ron Larson for your suggestion of using a
pipe across the wood gas column, which eventually led to an adaptation of the
Venturi gas mixer for the TLUD stove. This gas mixer does a supurb job of
mixing the gasses, so when the flame enters the swirl, it is already thoroughly
mixed. The swirl is for three purposes: first to give the flame a
longer path to finish burning, second to concentrate the heat for better burn,
and three to shorten the height of the flame.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I did some experimenting with using tangential
secondary air entrances to create swirl to mix the gasses. It sort of
worked at low speeds, but at higher speeds it seperated the cooler, heavier air
from the hotter, lighter wood gas by acting like a centrifuge. The air
moves to the outside and the wood gas to the inside. This is why the
Strata combustor mixes the gasses first, and then swirls the resulting
flame second. This combination works very well. The Strata
combustor that I took to stove camp in July turned in one run at 1mg/min
particulates, which is good. This was at about 3 kw but above this the
particulates and CO went up rapidly. I am now testing an upgraded design
(using some ideas those who helped me at stove camp came up with) which
seems to make it to my target 5 kw, (It boiled 5 liters of water in 14.5
minutes. The flame looked quite clean, blue and yellow.). I
will know for sure when Aprovecho tests it. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>The stationary fan which creates the swirl resides
directly above the Venturi mixer array. I have found that the closer the
fan is to the mixer, the better it works, so the lower tips of the fan
touch the mixer array. The blade design is very simple. It is a disk
of sheet metal, with six radial slits located evenly around the disk. The
blades formed are each curved into a smooth, gentle curve. This smooth
gentle curve can make use of the Coanda effect. This effect is that a gas
moving along a surface tends to stay close to the surface. It does not
work if there is a sharp bend in the blade or if the blade is too tightly
curved. The flame stays close to the gently curved blade all along its
length and leaves the blade at its trailing edge at a very flat angle.
This gives a very high quality swirl. If the flame is too large
it can overload the mixer and fan. The buoyancy (draft) becomes so
strong that it overcomes the Coanda effect and pushes the flame away from the
blade early, giving a steeper, less desirable swirl angle. As a result of
this I have been thinking about Rons idea of using a helix shaped blade, which
would hold the flame into a spiral. This would be more complex to build
and may increase flow resistance. I have also been thinking of Julian
Winters widening of the combustor, with a wider stationary fan, which would
lower the flow resistance. I have tried this before with good
results. Both arrangments will need testing.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>The mixer array is at the bottom of the combustor,
the stationary fan is just above the mixer array. This leaves the rest of
the combustor for the swirling flame. The combustor I am testing now is 5"
(13cm) tall. This is great for the 3kw flame, but a little short for a 5
kw flame as it is exiting the combustor. I will need to add a
little height, perhaps another inch (2.5 cm) will work. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I hope this adds to the discussion.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Jon Andersen gave me my battle cry,</FONT></DIV>
<DIV><FONT size=2 face=Arial>"Watch out propane!!!"</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>My best wishes to all,</FONT></DIV>
<DIV><FONT size=2 face=Arial>Kirk</FONT></DIV>
<DIV><FONT size=2 face=Arial></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=rongretlarson@comcast.net
href="mailto:rongretlarson@comcast.net">Ronal W. Larson</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</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, August 04, 2015 6:13
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Stoves] Request to get
partners in a possible TLUD stoveimprovement project</DIV>
<DIV><BR></DIV>Dean:
<DIV><BR></DIV>
<DIV><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN>I want to
emphasize - no making of a new stove intended. This is to be only an
addition to stoves that (hopefully, but not necessarily) have already been
tested. Looking for a breadth of existing designs. Hopefully these
are already in the best “balance” they could achieve. This is to see
whether that can be improved.</DIV>
<DIV><BR></DIV>
<DIV><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN>What have you
seen in swirl approaches?</DIV>
<DIV><BR></DIV>
<DIV><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN>What have you
seen in turbulence enhancers?</DIV>
<DIV><BR></DIV>
<DIV><SPAN style="WHITE-SPACE: pre" class=Apple-tab-span></SPAN>Thanks for the
quick feedback.</DIV>
<DIV><BR></DIV>
<DIV>Ron</DIV>
<DIV><BR></DIV>
<DIV><BR>
<DIV>
<DIV>On Aug 4, 2015, at 6:52 PM, Dean Still <<A
href="mailto:deankstill@gmail.com">deankstill@gmail.com</A>>
wrote:</DIV><BR class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
<DIV dir=ltr>Hi Ron,
<DIV><BR></DIV>
<DIV>In my opinion, reducing emissions in a TLUD or any stove requires
testing with emissions equipment. The great stove combines many factors
working together. "Swirl" is only one part. Kirk gets good results when
everything is in balance. "Swirl" is not powerful enough to overcome
problems in the balance.</DIV>
<DIV><BR></DIV>
<DIV>I completely agree that anyone with tin snips and emission equipment
and perseverance can make low emission stoves. If you are lucky it
takes a shorter time. So what? Even if you are unlucky it happens
eventually. Drink more coffee.</DIV>
<DIV><BR></DIV>
<DIV>Best,</DIV>
<DIV><BR></DIV>
<DIV>Dean</DIV></DIV>
<DIV class=gmail_extra><BR>
<DIV class=gmail_quote>On Tue, Aug 4, 2015 at 5:40 PM, Ronal W. Larson <SPAN
dir=ltr><<A href="mailto:rongretlarson@comcast.net"
target=_blank>rongretlarson@comcast.net</A>></SPAN> wrote:<BR>
<BLOCKQUOTE
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>Stove list cc Kirk<BR><BR>
From what I can understand, the lowest emission (particulates, CO
is easy) values from TLUDs have been from stoves designed and tested (last
week) by Kirk Harris. One reason seems to be that he has achieved a
swirl, using (as described on this list often) a fan blade
shape.<BR><BR> I recall a few other uses of the
term “swirl”, but know of no significant tests like those by
Kirk.<BR><BR> In recent conversations, Kirk has
agreed to be part of an off-list TLUD stove group to investigate a
different means of achieving swirl. It seems to be cheap and applicable to
most TLUD stoves.<BR><BR> The main advantage of
a swirl is more flame time spent in the stove; to get low emissions,
hot gases, not flames, need to be hitting the cook pot.<BR><BR>
The proposed approach also should increase
turbulence. I do not recall any TLUD that tried to achieve
turbulence (to get the mixing needed for shorter path lengths and
more complete combustion). Anybody know of designs to achieve
turbulence other than added disk or washer shapes?<BR><BR>
The reason for not saying much now is to save list members’
time and energy. This is not a guaranteed approach.<BR><BR>
Anyone joining should want to see this open-source (no
patents).<BR><BR> Anticipated time commitment
for a first design - a few hours with tin snips. Metal cost a buck
or two. Probably can work with clay as well.<BR><BR>
If anyone knows of past swirl or turbulence experiments (or
modeling) in TLUDs, your input now could save Kirk and I (and anyone else
wanting to join) a lot of time - especially if those results were
negative.<BR><BR>Ron<BR><BR> feel free to call
<A href="tel:303-526-9629" value="+13035269629">303-526-9629</A>, if that
would help.<BR>_______________________________________________<BR>Stoves
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clear=all>
<DIV><BR></DIV>-- <BR>
<DIV class=gmail_signature>
<DIV dir=ltr>
<DIV>Dean Still</DIV>
<DIV dir=ltr>Executive Director
<DIV>Aprovecho Research Center</DIV>
<DIV>PO Box 1175</DIV>
<DIV>76132 Blue Mountain School Road</DIV>
<DIV>Cottage Grove, OR 97424</DIV>
<DIV>(541)
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