[Stoves] Pressed biofuel - and Fire balls. Testing
frank at compostlab.com
Fri Jan 9 13:36:30 CST 2009
Crispin Pemberton-Pigott wrote:
>If you come with a big eraser, you are going to make progress. You should
>see my junk pile! Wish I could erase that....
"erase and start over" Its the most important part of the oencil.
>>I believe there is a lot yet to learn regarding optimum air flow for a
>>type of fuel and void space.
>Yes, and there is a lot of difficulty getting meaningful direct
>measurements. I am watching your method with interest. It seemed whacky to
>start with but might work well for obtaining certain information.
I think first we need to develop simple test procedures that will
quantify differences in air movement etc.. Once we have a collection we
can see if one of these measured values correspond to a change we
observe and want to control. For example CO release or WBT results. Now
we can formulate fuel or adjust air flow based on test results to meet
these improved conditions. First we need a collection of test methods in
a manual to pick from.
>I have managed to obtain two 8mm diameter velocity measuring probes that are
>0.1 m/s accurate. At least it is a start. I suspect that chip/nugget cooling
>is a major consideration when it comes to slow burners like gasifiers and
>top loaded, downdraft stoves - basically continuous burners. The specific
>challenge is how to predict the maximum time a stove can burn for based on
>its dimensions. 6-8 hrs is needed for a space heating stove.
The probe is one tool. Knowing particle density and weight and volume of
combustion chamber you now have the void space and can determine air
volacity in the void space of the fuel. It will calculate the same be
it Richard Stanley single pressed fuel with a hole in the center or
fine wood chips with lots of small void spaces. So how do we quantify
the difference? I am thinking injecting CO2 at the bottom of the fuel
chamber and timing the time it takes to get to the top and compare that
to what was calculated it should based on total flow and void space will
give us an idea of what the void space is like. Air moving in a zig zag
because of many small voids or way the fuel is placed in the chamber
(shape and orientation of voids) will be useful info. The quick tests
done in my spare time needs the eraser.
>>We stovers work at such small scale that
>>test methods for coal and other procedures designed for large combustion
>>chambers do not apply and we need to develop our own methods.
>This is an enormous part of the problem. I was looking at the stove
>standards of a country in Asia for ideas and the standard covers domestic
>stoves up to 80 KW (!) which is hardly realistic for a 4 kw cooker. It
>called for on-site inspection every 5 years.
As you say - "an enormous part of the problem"! We need our own
book. Some how we need to get money to set up a group that will take
it on to organize such a methods manual. A University will be perfect.
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