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<div class="moz-cite-prefix">Dean,<br>
<br>
My comments here are about tuning of TLUD stoves.<br>
<br>
I view the "tuning of the combustion" as being done mainly with
the secondary air. The primary air is mainly for the "turn-down
of the combusiton" (that is, the quantity of gases that are to be
produced.)<br>
<br>
Control of secondary air in NATURAL DRAFT TLUD stoves is rare to
non-existent. Usually the objective is to just have low
emissions, and to get that seems to mean having plenty of
secondary, often in excess (which can result in lower
efficiencies, but we are discussing the emissions issues.)<br>
<br>
In the FA (Forced Air or Fan Assisted) stoves, "tuning of the
secondary air for combustion" is really great!! and is not yet
well studied. Examples/comments:<br>
<br>
1. Reed's Woodgas Campstove (TLUD-FA) has a carefully determined
number and diameter of hole sizes, with a set balance for primary
and secondary air. Two speeds for the fan, but no change in the
ratio of P and S air. But the unit comes with 3 small screws
and instructions that say that when operating the unit at higher
elevations (such as 5000 feet or more above sea level), then use
the screws to block off some of the 11 primary air holes. Great
that such impact has been noted, but not great that nothing more
has been done about that "tuning" issue.<br>
<br>
2. With the exception of the Rua/HOS TLUD-FA from Hanoi, the Rice
Hull TLUD-FA designs by Belonio (and by those he has influenced)
all use a special burner head that seems to be very well tuned.
(Alexis and I spoke at ETHOS and Aprovecho Open House about
variations that can still be considered.) It is notable that
those stoves have FA for only Primary air. Therefore, there is
no way to change the secondary air supply, that is being drawn in
by natural convective forces.<br>
********** IMO, the reason it is working so well is that the
stove is designed specifically for rice hull fuel. And as a
stove made for use with a SPECIFIC fuel, it can be manufactured
with a single specific burner head. (that is along the same
lines as the burner heads on LPG and natural gas stoves where
tuning is not needed.)<br>
*********** Alexis says that his stoves can also burn other dry
biomass fuels. I am sure that they can, but I am not sure that
the existing combustion head is optimal for the other fuels.
This is another research topic to examine, and it will require
testing under an emissions hood to see what the impacts will be.<br>
<br>
Paul<br>
<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
On 3/6/2014 3:57 PM, Dean Still wrote:<br>
</div>
<blockquote
cite="mid:CA+tShZuS6tSmvh5M8Bqtme-B5WKTtVrb6=0dT_KK9ho1tu7MEw@mail.gmail.com"
type="cite">
<div dir="ltr">Hi Paul,
<div><br>
</div>
<div>I think that the denser pellets might not maintain the
flame as easily as the .56g small pellets described by Tom. I
wonder if for clean emissions the TLUD has to be tuned to burn
the fuel even if the tuning is easily accomplished by
adjusting primary and secondary air. </div>
<div><br>
</div>
<div>Best,</div>
<div><br>
</div>
<div>Dean</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Thu, Mar 6, 2014 at 11:35 AM, Paul
Anderson <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:psanders@ilstu.edu" target="_blank">psanders@ilstu.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Stovers,<br>
<br>
Crispin wrote, in agreement with Dean, and I have added
the emphasis on Crispin's words:<br>
<blockquote type="cite"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The
air flow through the pellets strongly affects the
way they burn<b><big><i><u> if the device is
constructed such that the fuel contributes a
significant element of air control.</u></i></big></b></span></blockquote>
Simply, stove devices should NOT be constructed for a
specific fuel UNLESS that fuel is specified and can be
supplied. The issue is just like using an incorrect
grade of gasoline in your automobile. LEADED gas will
not burn like unleaded. Super premium is different
from regular. And pellet sizes are different from
each other (assuming that the pellet materials were also
the same, which might or might not have been the case in
what Dean has mentioned.)<br>
<br>
Most of the TLUD stoves that have been tested have not
been the ones with serious control of the primary air
supply. Hence the problem that Dean mentions. <br>
<br>
I do not know of any tests of emissions from different
pellet sizes that have been conducted in TLUD stoves
that have serious control of primary air. One more
research topic to add to the list of things to do.<br>
<br>
Personal comment: I have had my hand involved with the
development of the "Champion Family" of TLUD stoves:<br>
1. Champion TLUD that won the first Cat Pee Award at
Aprovecho Stove Camp 2005. We just had a blocker on
the primary air inlet.<br>
<br>
2. Champion by Servals (India): Still with a rather
rudimentary control of primary air (a disk into a cone).<br>
<br>
3. Mwoto (for BEIA project by CREEC in Uganda): It
has a slider control of primary air directly on the fuel
cylinder, but we had not perfected it then and did not
make much of an issue about closing off the primary air
through tiny gaps such as at the ends the strips that
hold the slider in place.. <br>
<br>
4. Quad (by Awamu in Uganda): We made a better slider
door and placed it onto a "snout" for primary air.
But we did not seal with great care. Also, the
tab-and-slot construction left tiny air leaks that
proved to be too much uncontrolled air. This was
discovered at the July 2013 Stove Camp at Aprovecho
where we progressively sealed better and better the
stoves being tested. The best sealed stove won one of
the Cat Pee Awards. That was seven months ago, and we
have stopped production of the Quad stove with
tab-and-slot construction (and have sealed better the
existing units.)<br>
<br>
5. Troika Bingwa (by Awamu in Uganda): This stove is
just getting out to the users. It has a tightly sealed
fuel chamber with a slider over the primary air entry.<br>
<br>
Note: Do not underestimate the impact of even a very
very very small leak of primary air if you expect to
have turn-down of a TLUD stove.<br>
<br>
Of all the other TLUD stoves, most have no attempt to
control the primary air. The unit by Prof. Nurhuda
does seem to have excellent primary air control (but I
do not have one of those stoves, and there are
additional issues to be considered.)<br>
<br>
I hope that these comments are useful for everyone
dealing with natural draft TLUD stoves. Comments pro
or con are most welcome.<br>
<br>
Paul<br>
<br>
<pre cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a moz-do-not-send="true" href="mailto:psanders@ilstu.edu" target="_blank">psanders@ilstu.edu</a>
Skype: paultlud Phone: <a moz-do-not-send="true" href="tel:%2B1-309-452-7072" value="+13094527072" target="_blank">+1-309-452-7072</a>
Website: <a moz-do-not-send="true" href="http://www.drtlud.com" target="_blank">www.drtlud.com</a></pre>
On 3/6/2014 11:38 AM, Crispin Pembert-Pigott wrote:<br>
</div>
<blockquote type="cite">
<div>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Dear
Friends</span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I
agree with Dean on this score. The air flow
through the pellets strongly affects the way they
burn if the device is constructed such that the
fuel contributes a significant element of air
control.</span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">These
devices</span></p>
<p class="MsoNormal"><br>
<span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Are
‘cubers’ in that they are producing densified
lumps that can be put into a stove. But they will
work best in a large stove such as is used in
China for space heating and cooking. The input
material is straw and other stover.</span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The
mechanism is an eccentric roller running inside a
perforated cage at maybe 60-100 RPM. As Tom notes,
power consumption is about 110 kW.</span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">So
far I don’t think the product is economically
viable as there is a subsidy involved. What we
need is a breakthrough technology that will make
densified fuel without the need for heat.</span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Regards</span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Crispin</span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><b><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif""
lang="EN-US"> </span></b></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<div>
<p class="MsoNormal">Hi Paul,</p>
<div>
<p class="MsoNormal"> </p>
</div>
<div>
<p class="MsoNormal">I have seen the very small
pellets sold for heating stoves in the US burn
very cleanly. Larger sized pellets did not burn
as cleanly. </p>
</div>
<div>
<p class="MsoNormal"> </p>
</div>
<div>
<p class="MsoNormal">Best,</p>
</div>
<div>
<p class="MsoNormal"> </p>
</div>
<div>
<p class="MsoNormal">Dean</p>
</div>
</div>
</div>
<br>
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