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Julien and all,<br>
<br>
The nozzle in Kevin Adair's design has the narrow neck of the
hourglass at the level of the concentrator plate. That means that
the lower part extends downward into the reactor area. The
interpretation is that mixing will be better if the secondary air
cannot move directly to the concentrator hole.<br>
<br>
Observational research is needed to see the impact. Note that one
research variable is just how far down does the nozzele extend? 1
cm? 2 cm? 5 cm? This research topic is open to everyone.<br>
<br>
Paul<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>
<div class="moz-cite-prefix">On 1/11/2016 11:54 AM, Julien Winter
wrote:<br>
</div>
<blockquote
cite="mid:CALv4xTxgoLPAMs5Hb5_FvaPJ6+EwA+Zy=EVPJ8Ei3624aYW4cA@mail.gmail.com"
type="cite">
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<div>Hi Paul, Frans and all;<br>
<br>
</div>
<div>When you talk of Kevin Adair's nozzle, are I assume you
describing a hourglass riser above the concentrator ring?
Something like the hourglass comes to mind following Frans'
comments on the coanda effect. However, I expect that the
dominant force at the bottom of the hourglass would be
buoyancy, straight up.<br>
<br>
A rough type of 'hourglass' venturi burner was invented by
Dave Yarrow (ca. 2013) for barrel type TLUDs. I built one
myself, and it roars. I have attached a couple of photos<br>
<br>
</div>
<div>1) shows the whole unit. There is a 130 L reactor barrel
inside the 200 L barrel, so secondary air was being preheated,
and passed over the top of the 130 L barrel where woodgas
ignited under the concentrator. The flame then went up into
the chimney burner.<br>
<br>
</div>
<div>2) shows the bottom of the chimney burner, which constricts
to accelerate the gases, then expands. Where it expands,
there are tertiary air holes that are cut at an angle to get
rotational turbulence (supposedly). The idea is to create a
bit of a venturi suction for the tertiary air. <br>
<br>
</div>
<div>This unit is designed for a high gasification rate. At low
gasification rates, the flame is below the concentrator. I
haven't done any more work on this idea, because I have been
focusing attention at on the initial mixing of woodgas and
secondary air. I have yet to move upstream.<br>
<br>
I don't have this unit any more. I gave it to a friend who
lives in the countryside, and does not fear being shut down by
the town's fire department.<br>
</div>
<div><br>
</div>
<div><br>
<br>
</div>
<div>Of course, anything said about a natural draft, wood gas
burner is dependent on the supply rate of woodgas, because
that can change its mode of operation (as above). The big
problem for any burner is to get it to work over a wide range
of woodgas supply rates. What works great at a medium
gasification rate, can be the cause of smoke at a high
gasification rate. <br>
<br>
</div>
<div>Premixing air and woodgas under natural draft would be a
nice thing to achieve. The challenge under natural draft is
to get the flow of the mixture to be faster than the flame
speed of H2, CO, CH4, so there is no flash back. We may be
able to achieve that at higher gasification rates. At low
rates, the flame will likely flash back to the top of the
char, which may not be a bad thing for low turndown.<br>
<br>
</div>
<div>Cheers,<br>
</div>
<div>Julien.<br>
</div>
<div><br>
<br>
</div>
<div>
<div><br>
-- <br>
<div>
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<div>
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<div>
<div dir="ltr">Julien Winter<br>
Cobourg, ON, CANADA<br>
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<br>
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