Dear Bjarne,
I think you have not told us the duration of the operation of the
gasifier stove with your pellets (or I missed it in the messages).
Please tell us that.
And what is the depth of the pile of pellets in the stove? Depth often
relates closely to length of burn time.
Paul
Paul S. Anderson, PhD aka "Dr TLUD"
Email: [email protected] Skype: paultlud Phone: +1-309-452-7072
Website: www.drtlud.com
On 1/25/2013 1:20 AM, Bjarne Laustsen wrote:
Dear Crispin
The secondary air enter into the combustion through 3 rows of holes in
the bottom part of the internal chimney in the top part of the stove.
We have designed this internal chimney to have a height allowing the
gasses to burn without going over the top of the stove. So the flame
will not reach the pot if the stove is operated in the right way.
We have earlier tried to bring in the secondary air closer to the fuel
bed, however it was not very successful. For me to see it is necessary
to have a separation of of the fuel bed and the burning of the volume
where the gasses are burnt if you operate gasification stove, else it
does not work satisfactory.
The burning of the gases in the internal chimney gives heat enough to
keep the pellets hot enough to release the gasses so that is not a
problem.
A problem with this separation of the two is that in strong winds the
flames can be blown out, if this happens the stove stops operating and
a lot of smoke will develop. This is not a big problem here as most
households cook in sheltered places, so we have not got complains on
that. The stove can also get started again if a light match are
dropped down into the internal chimney, this will get the gases to
burn again.
Yours
Bjarne Laustsen
On 1/24/2013 5:04 PM, Crispin Pemberton-Pigott wrote:
Dear Bjarne
It is now clear - there are two sections of the stove - a gas making
unit
and a mixing/burning unit.
I am still missing one critical piece of information: where does the
secondary air enter the upper unit? It seems to have all the basic
parts in
place.
There is a feature, not in the positive sense, that man gasifiers
have which
is to separate the gas burning from the fuel bed. There is no essential
reason for doing this. It actually introduces two new problems that
should
not be there which are: separating the radiated heat from the
underside of
the flame from fuel bed and the addition of the problems related to the
flame going out and not re-lighting.
Thus, where you add the secondary air is critical. It can prevent both
problems. It would be unfortunate if you were spending money and
effort to
create a problem that should not be there.
I did not realise without the photos that you had a removable upper
section.
The photos helped a lot in clearing that up. If the secondary air were
pushed into the gas at the top of the fuel containing section and the
plate
with the triangular holes were not present, what happens? If there
was the
same top round disk placed at the top if the fuel container - or
better, at
the bottom of the upper unit so it is removable - it would push the
secondary air into the gas near enough to the fuel to help keep it
hot. The
'disk' could have any of a number of complex shapes to promote
mixing, but
the point is that the secondary air should not be added near the top
because
it means the flames will be running against the pot spoiling the CO
and PM
burn. That is why I am asking about where (am perhaps how) the
secondary air
is introduced.
The stove looks quite strong.
Regards
Crispin
Dear Crispin
Here is some pictures of the Jiko Bomba casification cookstove.
The first shows the two part of the stove with pellet as fuel in the
firebox
before fire is lit.
Second show the stove burning.
The third the same, in the end of the gasification.
The forth shows the charcoal stage where the pellets remains as glowing
carbon. A pot can be put on top of the bottom part of the stove,
there are
three supports for that.
Yours
Bjarne Laustsen
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