[Stoves] TLUD gasification rate research ....

Julien Winter winter.julien at gmail.com
Fri Feb 20 19:14:30 CST 2015


Hello Frans and all;

What was fixed in my experiments was the grate aperture.  You are right
that the primary air flow in a natural draft TLUD was not fixed.  The
system is continually changing, and there is one very important feed-back
loop:

gasification rate --> flow rate of pyrogas --> size of gas flame --> effect
of gas flame draft on flow of primary air --> gasification rate --> ...

With a forced draft system, we can override feedbacks by setting the rate
of primary air.  In studying a natural draft system, we MUST allow these
feedbacks to operate, and accept that our system is continually changing
during the coarse of a trial, and from one fuel to the next.  If we want to
measure the flow of gases, we must use ways that don't change them.

I monitored the rate of fuel mass loss with a manual overhead balance.
That showed me that the gasification rate did not change that much during
the course of a run so calculating the overall gasification rate was good
enough for my purposes.  Most importantly, overall gasification rate is
something other people can measure in the field, so they can compare their
observations to mine.

My objective was to get some very basic information; the kind of
information that would be of practical use to stove builders and users.
The measurements I was making were ones that many people could make on a
low budget.  People can see how small adjustments in grate aperture between
1-3% can make a big difference in gasification rate.  They can see what
range of gasification rates and temperatures are possible in a ND-TLUD.


Frans, you make some important points about better measurements.  If I
wanted to more precise, I would have had the whole stove on top of a
data-logging balance, and I would have continuously measured primary air
flow rate with a hot wire anemometer.  I would have conducted all the work
indoors at the same temperature and humidity.  I would have sent my fuel
away for analysis, including thermogravimetry.

What I think my research does is to set the ground work for detailed and
precise research.  It demonstrates the amplitude of changes, and poses
questions that need answering.  That kind of research is being done at
Colorado State University.   From their presentation at ETHOS, I would
guess they have a million dollars.

I think a good argument can be made for doing simple research before doing
complex research.  "Walk before you can run" is the expression.  A very
good example of this is in studying TLUD gas burners by building small
TLUDs out of food cans.  Sometimes we can test an idea with a food can
burner in less than one hour.  If we want to run a replicated experiment
with treatments, we can have up to 45 trials in one day, so an experiment
with 120 trials can be over in three days.   With a full-sized TLUD, we may
only get 6 to 8 trials in a day.  If we do the simple experiments first, we
can be more focused and economical when we come to do the major
experiments.  I designed my gas burner using food can prototypes.

My research was unfunded.  It was something that needed to be done.

All the best,
Julien.

-- 
Julien Winter
Cobourg, ON, CANADA
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