[Stoves] Designation of TLUD gasifier devices.

[Julien Winter]

Hi All;

I have to agree with Paul Anderson on having a clear definition of a TLUD.
It is essential for the science of cookstoves, and combustion science, that
terminology is clear and unambiguous.

It is very clear to me what Paul means by the TLUD process.  There is a
migrating pyrolytic front, and two phases of combustion can be identified:
(1) flaming pyrolysis, followed by (2) bottom-up char combustion.

It is a process that has under fed air at a rate slow enough that the
ignition front is a flaming pyrolysis front, and not so fast that it is a
complete combustion front.  It is a process that is burning a type of fuel
that supports a migrating ignition front (and doesn't channel the fire to
the grate).

In science, the TLUD, as Paul describes it, is called a "paradigmatic
example".  It is a special theoretical model against which other cases can
be compared and contrasted.  These exemplars are vital to scientific
discourse, hypothesis testing, and developing theories.

When I search through the Web of Science, I will not find much on the
keyword "TLUD" (yet), but I can find articles with close synonyms "pot
stove" or "underfed batch combustion".   I haven't done a count, but I have
about 50-75 articles where laboratories have experimented with what are
ostensibly forced draft TLUDs.  I can trace the articles back to 1946.  I
found these articles because the definitions of terms (although there are
synonyms) are clear.  If that clarity didn't exist, the scientific
literature would be impenetrable.  "TLUD" is not common in the academic
literature yet, but it is a good synonym that is clearly understood in the
general stove community.  When papers are published on TLUD stoves, they
should include the close synonyms (above) in the list of key words below
the abstract, so the article can be found.

As for the stove world in general, there are "TLUD-like" stove/fuel
combinations that may not fit the ideal description of a TLUD, but their
mechanism can be usefully compared and contrasted with the paradigmatic
TLUD.

Trying to classify cookstoves in general is a bit of a challenge.  One may
come up with other paradigmatic exemplars.  In general, however, people are
faced with the fact that, most of the time, things in the world and human
words don't match up unambiguously.  The world around us, language, and
minds are such variable crazy things, that it is surprising that we can
actually speak to one another.

In the first half of 20th century, analytic philosophers tried to come up
with language based on definitions with "necessary and sufficient
conditions".  They failed.

What are the necessary and sufficient conditions of being a "sport" such
that it includes skiing, baseball, underwater hockey, hula hoops and
tiddlywinks.

What are chairs?  If the definition of a "chair" is "that which supports
human buttocks", then if I am sitting on an elephant, it must be a chair.
Are all elephants chairs by virtue of my having sat on one?

Except for a few very useful exemplars like TLUD, trying to put all stoves
into categories faces the same general problem of trying to match up words
(concepts) with groups of things.

In 1953, Ludwig Wittgenstein published his "Philosophical Investigations".
In it he argued that most categories denote things grouped because they
have "family resemblances" rather than definable essences (see the attached
cartoon).  Somehow, we seem to more-or-less agree on what is a chair, or a
sport, even if our language if vague.  We still manage to communicate.
(Amazingly, because no two human minds have ever contain exactly the same
"chair" thoughts.)

In the face of this fog, science needs TLUDs.

Soon, I hope, I am going to write a paper on my experiments on gasification
rate and TLUD reaction temperature.  My experiments were conducted to make
sure that I got TLUD conditions.  My paper is not about a TLUD-like stove;
is about a TLUD!!!   My job as a scientist is conduct experiments that will
contribute to building detailed TLUD theories.  That way, we can make
predictions.



Cheers,
Julien

-- 
Julien Winter
Cobourg, ON, CANADA
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