[Stoves] My current project - very unfinished

Wed Apr 9 05:42:57 CDT 2014

Dear Ron and list,

My pellets tests were  with my mini stove, combustion chamber of  11cmx11cm,
total height 30 cm, PA door 11cmx3cm (a lot larger than all can stoves,
probably). For other large biomass such as wood, corn cobs,. adjusting PA
door give noticeable change in flame level. When using pellets (saw dust
pellets, 6m diameter), the PA door gave almost no change in flame level at
most of the time, the flame just burn in the area about 5-8cm above the
secondary air holes. Toward the end the flame go a bit higher and the PA
door started to have a bit effect in adjusting flame level. 

About the metal net, it was a fine mesh, similar to the insect screen net
(1mm maybe, will measure it next week when I come back to workshop). It was
a unbranded stainless steel net, I picked up a few types from local shops
for testing. I already tried to put the net above or below the concentration
cap and moving it up, down a bit and here are some results:

-          Putting net on top of concentration cap is more feasible as it is
easier to move, can remove it easily to add fuel. 

-          Too large open net >3mm: no change.

-          3mm net reduce the fire level a bit, but not much.

-          1mm net: putting up too soon will kill the fire, only put on when
the flame is stable. 

It's a good idea to do WBT with and w/o the net, I will try it and also
measure the total cook time and char creation too.

Please note that my above observation is for wood stick on our medium stove
(combustion chamber 16x16x35cm).

Regards,

Anh

From: Ronal W. Larson [mailto:rongretlarson at comcast.net] 
Sent: Wednesday, April 09, 2014 11:05 AM
To: Discussion of biomass; Anh
Cc: Julien Winter; revjcsd at juno.com
Subject: Re: [Stoves] My current project - very unfinished

Anh, list, ccs

1.  Re your first point on primary air (PA) supply needing to change toward
end of the burn - I'd like to hear more on this.  Anyone monitoring weight
loss in real time should be able to say whether this is flat or increasing
(meaning higher power output or burn rate).  My experience from visual
observations of a boil rate - has been that the power stays remarkably
constant during a run.  Others?  (Maybe there is some compensating effect on
fuel packing as it settles?  We need more experimental data.)

2.  I am very intrigued by your observations on a "metal net".  Radiant heat
transfer can be much more efficient that convective.  Can you describe the
net used in more detail?  What mesh size? a measured "openness" ? -  a
company name and model?   I hope you have access to more mesh sizes and can
report back.  Could be a major help for char-making stoves.   It would be
interesting to just use a simple water boiling test (WBT) to compare
efficiencies with and without a net - even if power level went down and time
to boil went up.  Maybe different nets could give different power rates -
one just right for simmering after no net gave a rapid boil.

Ron

On Apr 7, 2014, at 3:40 AM, Anh <ntanh at greengenvn.com> wrote:

Dear Jock and Julien,

As per my observation with pellets, as pellets are small size, the space
between them is small and it limit the PA from coming up to pyrolysis zone,
even fully open PA may not be enough. Towards the end, when there is less
pellets left, more PA will come up and may need to reduce it a bit.

I tried another way similar to with Julien did. I placed a metal net on top
of the cap (concentration cap), it keep the flame lower, less soot and the
net glowing red look quite nice. But it have some problem too, at some early
time, it may reduce the airflow too much and not enough PA get in so I can
only put on when the fire is stable.

Anh

From: Stoves [ <mailto:stoves-bounces at lists.bioenergylists.org>
mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Jock Gill
Sent: Monday, April 07, 2014 7:47 AM
To: Julien Winter
Cc:  <mailto:revjcsd at juno.com> revjcsd at juno.com; Discussion of biomass
cooking stoves
Subject: Re: [Stoves] My current project - very unfinished

Julien,

Glad you like the looks of Trash Can School of Pyro-Grilling ;-)

I do not have any instrumentation.  I can tell you, however, that I have not
problem with the pyrolysis front stalling once it gets going.  I have some
thoughts on this initial phase problem. I will try starting the unit with no
restrictions on access to primary air.  Then once things are HOT, I will
restrict access for the rest of the burn.  I will report back on this.

The oxygen supply may be a problem vis the secondary air:  not enough to get
good clean combustion.  It might be good to raise the top of the draft can
above the top of the outer can to avoid any combustion gases being sucked
back down into the system?  I will also try this tomorrow.  Thanks for the
tip!

Cheers,

Jock

Jock Gill

P.O. Box 3

Peacham,  VT 05862

Cell: (617) 449-8111

 <http://google.com/+JockGill> google.com/+JockGill

:> Extract CO2 from the atmosphere! <:

Via iPad

On Apr 6, 2014, at 8:24 PM, Julien Winter < <mailto:winter.julien at gmail.com>
winter.julien at gmail.com> wrote:

Hi Jock et al;

That is a nice rig you have in the garbage can, and I like the burner.

I once tried heating the primary air, from the sidewalls of a TLUD, and I
found that it reduced the buoyance effect within the fuel bed.  As the
reaction progressed and the TLUD became hotter, the flaming pyrolysis front
stalled to a smolder.  Besides a lower temperature gradient within the fuel
bed, there may also be a problem with oxygen supply, because the density of
air decreases as it expands according to Charles's gas law: V1/T1 = V2/T2

To me, it doesn't look like that will be a problem in your garbage can,
because of its size relative to the stove, but it is something to think
about.

In my last email to "Stoves" I almost included a picture of my Jack Russell
Terrier guarding a TLUD.  She likes cat.

Cheers,

Julien

On Sun, Apr 6, 2014 at 6:09 PM, Jock Gill < <mailto:jg45 at icloud.com>
jg45 at icloud.com> wrote:

Here is what I am working on. Still figuring things out.

<IMG_3155.JPG>

The idea is to use a large outer can, in this case a 20 gallon unit, to do
some pre-heating, but not so much as to create a run away retort effect,
capture some hot air for warming, a pseudo turn down effect, keep breezes
out of the air system, contain the fire and charcoal for safety.  Cook on
high heat over the "fire", slow cook or warm, on the hot air  around the
edges.  The air there gets so hot you can not pick up a pot by its handle.

It would be possible to mount a removable grill a bit below the top of the
outer can.

Above, I  have used a gas stove grate to support a pan over the fire in a
unit made from two coffee cans -- about 6 inches in diameter.  More on the
cans latter.

Note:  There are no holes in the outer can at all.  it is working by down
drafting air for both the primary and secondary air ports.  The primary air
is supplied by thirty eight 3/32 inch holes in three rings.  The secondary
air is currently a single row of 3/8th inch holes about 1 cm above the
bottom plate of the FXJ burner.  It is very clear that I need more secondary
air in just the right place.

So far,  I can get flamelets, but also quite a bit of very soft soot.  There
appears to be no creosote.

<image.jpeg>

I've cut the primary air supply gap way down.  Next I will try a second row
of 3/8s inch secondary air holes.  This configuration is hard to start, but
once it gets going, it really gets going.

A pyrolysis process with a 6 inch diameter produce an awful lot of gas.  I
am finding it a challenge to achieve a favorable fuel to air ratio.  If I
can find it, I am hoping the soot deposits will vanish, or at least become
minimal.

More as it is.

Jock

Jock Gill

P.O. Box 3

Peacham,  VT 05862

Cell:  <tel:%28617%29%20449-8111> (617) 449-8111

 <http://google.com/+JockGill> google.com/+JockGill

:> Extract CO2 from the atmosphere! <:

Via iPad

--

Julien Winter
Cobourg, ON, CANADA

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