[Stoves] is this new?

Crispin Pemberton-Pigott crispinpigott at gmail.com
Sun Jan 20 20:42:51 CST 2013


Dear Marc and Ron and All interested in air flows

 

This is a response to questions about air and Marc's tube.

 

Here is an old photo of secondary air entering the combustion chamber of a
Vesto pushing the flame to the centre. This accomplishes the following:

 

Keeps the fire away from the wall, reducing the temperature it has to
survive (a lot)

Keeps the flame going

Not allowing it to spread to one side away from the smoke on the other side
that might otherwise 'get away'.

Provides turbulent mixing of flame, hot secondary air and smoke

Allows for preheating to a significant degree (250-500 C)

 

cid:image001.jpg at 01CDF756.FE0F8310

 

Here is an example (hard to see of course because it is a still taken from a
video) of the spinning of the flame caused by the shaped grate at the
bottom.

 

cid:image006.jpg at 01CDF756.FE0F8310

 

The fire is circular because it is spinning rapidly, though pushed to the
side by the way the fuel happened to be sitting. The spin adds turbulence
without a fan and assists in keeping the flame away from the combustion
chamber wall.

 

Here is a Vesto burning switchgrass pellets operating as TLUD, showing that
there is nothing special about a TLUD in the sense of it having to operate
in a particular fashion. The air flow through the fuel is reduced by the
fuel and it operates as a TLUD. The secondary air is send across the surface
to keep a deck of flame going at the height of the holes. This obviates the
need for adding a circular disk at the top to 'keep the flame going'. Adding
a 'concentrator' as Paul calls it takes more material and moves the fire too
far away from the heat of the pyrolysis bed leading to unwanted flame-outs
from time to time. A major issue with all pyrolysing TLUD's. It is simply
not necessary. Just keep the fire near the fuel. This also provides
additional vertical space for the flame to finish burning before getting to
a cold pot surface.

 

Here is a really cool picture of a Vesto burning walnut shells in TLUD mode.

 

cid:image009.jpg at 01CDF756.FE0F8310

 

Finally, here is a photo of a Vesto cutaway showing the inside parts in
their correct positons.

 

cid:image010.jpg at 01CDF756.FE0F8310

 

The primary air controller is the ring with holes in it. When the handle is
moved to the side the holes are closed.

 

Regards

Crispin

 

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