See comments.<br><br><div class="gmail_quote">On Sun, Mar 11, 2012 at 6:19 PM, <span dir="ltr"><<a href="mailto:ajheggie@gmail.com">ajheggie@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On Sun, 11 Mar 2012 07:30:24 +0700, Paul Olivier wrote:<br>
<br>
>><br>
><br>
>It is impossible to light the burner with the strainer in place.<br>
>So in lighting a burner, I have to run it for a short while without the<br>
>strainer.<br>
>And when I put the strainer on the burner, I always have to turn down the<br>
>fan.<br>
<br>
</div>Does the fan simultaneously supply primary air ( for the gasifier) and<br>
the secondary air to burn the offgas? </blockquote><div><br>The fan only supplies primary air.<br>Secondary air is drawn in between the burner housing and the burner.<br>Some secondary air also come in through the dome.<br>
</div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">You mention the initial flame<br>
pyrolysis/gasification in the primary chamber migrates to the burner<br>
holes after some time.<br></blockquote><div><br>At a normal fan speed, most of the gas is burned at the burner holes.<br>The gases that comprise the diffusion tail are burned within the dome.<br> </div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div class="im">><br>
>To get full and uniform ignition at all burner holes without the strainer,<br>
>a certain fan speed is required.<br>
>But to get full and uniform ignition at all burner holes with the strainer,<br>
>a lesser fan speed is required.<br>
<br>
</div>Difficult to judge without seeing things but my guess this is to do<br>
with air:fuel mixture rather than flame speeds. Initially the burn in<br>
the primary chamber using more air than necessary for gasification<br>
(secondary burn happening to some extent in the primary chamber}.<br>
<div class="im"><br>
>With the strainer the flames are far more consistent and stable.<br>
>The flames acquire structure and are not easily influenced by the wind.<br>
>This gives me reason to believe that the transfer of convective heat is<br>
>much more efficient when a dome is present.<br>
>So with a more efficient transfer of heat by convective means<br>
> and with the whole new dimension of thermal radiation that comes into play,<br>
> a lot more heat makes it into the pot.<br>
<br>
</div>We'd need comparative (i.e. they don't need to be exact, given the<br>
problems with thermocouples in a gas stream) temperature readings both<br>
above and below the dome and in the same positions with the dome<br>
removed.<br></blockquote><div><br>Yes, this needs to be done.<br> </div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
I can see the strainer/dome acting as a means of shielding, mixing and<br>
providing turbulence.<br></blockquote><div><br>The dome definitely shields.<br>It allows for an input of additional secondary air.<br>I do not think that it provides turbulence.<br> </div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
I can't see what effect it would have in changing the flue gas<br>
characteristic to change the way the gases reaching the pot are<br>
transferred to it. The fact that you lower the fan rate when the dome<br>
is in position makes me think that with the fan dome you supply less<br>
excess air, this increases the flue gas temperature and thus the delta<br>
T twixt flue gas and pot increases heat transfer.<br></blockquote><div><br>More primary air means more gas.<br>It does not necessarily mean more excess or secondary air.<br>My simple understanding of what is happening here is that<br>
wind does not disturb what is happening within the dome.<br>Wind does not dissipate heat so easily.<br>This gives a better transfer of convective heat,<br> and it also gives more thermal radiation.<br><br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div class="HOEnZb"><div class="h5"><br>
AJH<br>
<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Paul A. Olivier PhD<br>27C Pham Hong Thai Street<br>Dalat<br>Vietnam<br><br>Louisiana telephone: 1-337-447-4124 (rings Vietnam)<br>Mobile: 090-694-1573 (in Vietnam)<br>
Skype address: Xpolivier<br><a href="http://www.esrla.com/" target="_blank">http://www.esrla.com/</a><br>