[Stoves] Trials on TLUD Gas Burners - Burner Diameter

[Julien Winter]

Hi Stoves;

In May, I reported to this listserv on some tests I had done with a
menagerie of gas burners.
http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/2014-May/008665.html

My tinkering has continued, and some results are attached as a pdf that
show some interesting features of ND-TLUDs.  For example, the best I could
do for a turndown was about 2x, and turndown is very sensitive to primary
air supply.

These tests follow from the earlier work were is was shown that placing a
concentrator disk below the secondary air inlets did not result in a flame
concentrated above the aperture in the disk.  Instead, pyrogas moved
radially outward to the underside of the secondary air holes, and became
entrained in the jets of secondary air.
In addition, I was using gas burners that were 1.2 x larger than the
diameter of the TLUD combustion chamber so as to get more space to
manipulate secondary air, and more space for the gas flame to develop.
This work suggested that is was possible to increase the diameter of the
gas burner even further.  The current trials put this to the test.  Here is
an abstract of the study:

ABASTACT
Gas burners for a natural draft, top-lit updraft gasifier (ND-TLUD) were
assessed for visible flame characteristics and their effect on gasification
rate.  Two main design options were tested: diameter of the burner and
preheating secondary air. Burners were tested on wood chip fuel that varied
in moisture content, and primary air was adjusted to get very low to
maximal rates of gasification.  Preheating secondary air had no visible
effect on the gas flame nor did it alter gasification rate.  Increasing the
size of the gas burner from 1x to 1.2x the diameter of the TLUD
significantly improved gasification rate, reduced flame height, and reduced
visible smoke production.  Further increasing burner diameter to 1.5x TLUD
diameter didn’t cause a further increase gasification rate, and made the
reaction unstable at low rates of primary air and high fuel moisture
contents.  Increasing the diameter of burners to at least 1.2x looked very
promising for improving TLUD operation.  Burners of 1.5x may be suitable
for TLUDs that only run at high gasification rates.  Larger diameter
burners will likely cause less air pollution, and should be tested for CO
and particulate emissions.


Increasing the size of gas burners could be tested with some of Jock Gill's
ideas for increasing flame temperature in the burner.
http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/2014-May/008843.html


All the best,
Julien.



-- 
Julien Winter
Cobourg, ON, CANADA
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