[Stoves] Strata combustor general principles

Crispin Pemberton-Pigott crispinpigott at outlook.com
Wed Sep 16 08:52:52 MDT 2015


Dear Martin

 

Here is the technique. It was used as a way to operate a cross draft fire in
a bottom-lit updraft stove. The fuel is always piled to the same depth. For
different fire-powers, the width of the channel is changed, not the fuel
depth. The operating time is always about the same.

 

This technique - End-Lit Cross Draft (ELCD) is being copied around the
country here and there without no one pushing it at all. I heard that in
January. It reduces emissions about 80%, a little more, without replacing
the stove. It involves the insertion of a flame tube into the end wall,
60-70mm diameter. That costs about $1.

 

The fuel saving is perhaps 10-20%. It runs far smoother - no big peaks of
heating and followed by fire collapse.

 

Regards

Crispin

 

.The big space can be narrowed temporarily.

Here the space is only 110mm wide.

The space is filled with fuel.

The wood is in a hole so air can come up through the grate below.

The flame tube is visible on the left. It is made from sheet metal and set
in clay.

After the metal burns away the clay hole will remain.

All smoke and flames have to pass through the hole so there is an active
fire inside the tube leading to the heat exchanger.

 

 

Kirk,

 

first of all, your stoves and thoughts about TLUD's are very interesting.
And in my opinion

 

 the venturi-concept, you are talking about, -how ever managed- will be
generally the next important step for better burning; - and for less blacked
pots!!! 

 

A presumption I made a year or two ago: 

The (nominal-) power rate of a good working stove has a more or less narrow
relation to the grate-surface, and/or the burning-chamber-volume.

 

 I calculated the given numbers of some different commercial stoves.  My
calculations confirmed my guess.

I dont remember the numbers, but it is easy to calculate the numbers out of
available commercial data.

 

Additional I remind to Crispin's postings, some time ago:

He reported, that he made the burning-chamber of some coal stoves in
Ulanbaator smaller, by just filling some space of the burning-chamber-space
with bricks. And some surface of the grate. In combination with special
incending-procedure, that gave better burning; even by transforming the may
of stoves there, there was an enormous reduction (more than 90%) of
air-pollution. 

So I suspect, if you would use the right-balanced amount of
burning-chamber-volume, you could get a step forward.  The volume within the
venturi-riser-burner-tube should be included in the calculation; but in the
tube there will be, -hopefully- a burning some similar to a LPG or NG flame,
which will afford less volume. 

You could take the power-rate which you achieve with low emission, for
extrapolating the stove dimensions for your desired 5 kW output.

 

 

Regards

 

Martin

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