[Stoves] TLUD pellets stove with a venturi burner.

[Roberto Poehlmann]

Hi Kirk,

Maybe i have named the top of the combustion chamber with the wrong word
(concentrator ring). The combustion chamber has on top a 3 inch hole, and
no secondary holes inside the combustion chamber below the concentrator
ring.
The 3 inch hole "concentrate" the smoke to the tube burner.

When the primary air control is wide open, i can obtain a good flame with a
taller internal chimney to increase draft. Another way to increase
secondary air flow without a chimney is to add a fan.
The experiment, with a taller chimney, also make me doubt about the
importance of the venturi effect versus the draft of a chimney. With a
normal TLUD burner (Peko Pe or Champion stove for example) you can also
have a short flame with a taller chimney.

Another way, as you say, is to add more than one burner.
I have made sometime ago, an experiment with 4 similar burners on top of a
18 liter chamber. The problem i had, is that always a burner draft "lose"
vs a stronger draft of another burner. The weakest burner acts like a
primary air control, and i never had a "positive" draft for all of the
burners at the same time. If i restrict the weakest burner, another burner
take the place with negative draft.

The solution is to put a fan at the primary air control, like Paul Olivier
did, or with the subdivision of the combustion chamber in 4 independent
chambers, each with his own burner on top. All of the 4 independent
chambers can "share" the same primary air control below.

I have no equipment to test particulates or gases.  The equipment are very
expensive for me. I am not a stove constructor (yet). But i thing the stove
would have very good results. Maybe you, Julian or Crispin can contruct
this burner and make some measurments to test it.
I have made some variations of the tube, with distinct sizes and holes
configurations, and i found this is the best configuration for now (best
looking flame).

Thanks for the photos of the control valve. Maybe i will construct
something similar.

Here are some photos of the same burner (tube and cone) and the same beer
barrel, in another similar configuration stove:

https://www.dropbox.com/sh/af6b6gfihhw4psj/AAD6cuP8q4PMGTCDSMJqfXDGa?dl=0

This is a video of this stove with a taller chimney:

https://youtu.be/j6BfGrPsvt8


Greetings
Roberto Poehlmann


"
Roberto,

Nice.  I would like to see test results for particulates.  It should
be very clean.  It looks like it is loosely based on Crispins flame
tube design with holes added in the tube where the Venturi low
pressure area is.  The holes are at the bottom of the burner, so there
is better draft and a good burning area above.  If I understand
correctly Crispin is using the tube differently, to concentrate the
heat and increase the dwell time for the flame in that hot
environment.  His secondary air is all added before the flame tube.
Your design looks more compact and perhaps would be a better choice
for a TLUD.

There is a limit to how much gas the burner can handle.  When the foil
is removed and more primary air is added the burner is overloaded with
gas and a tall diffusion flame forms.  I have been trying to handle
this problem by adding more mixing capability, and have had some
improvment, but further work is needed.  The problem with the mixing
tubes I am using is that along the edges of the combustor, the air
exiting the tubes exits at an angle instead of straight out.  This
holds the gasses below the burner along the edges, and adds to blowing
them to the center, overloading the center of the mixer and wasting
air at the edges of the combustor.  This would not be a problem with
your design.  You might be able to use two or three of theses mixers
side by side to gain a clean higher fire power.

The concentrator ring is intended to mix the wood gas and air, and the
Venturi mixer is intended to mix the wood gas and the air, so you have
a duplicate mixing system.  I am not saying good or bad, just
something I notice.

I see Julian has expressed some doubts about the Venturi concept.
Good for him.  I would be very happy if someone with adiquate
equipment and technical ability proved or disproved the TLUD Venturi
concept, either way.  I perhaps will have to bite the bullet and buy a
manometer with the ability to measure down to .001 inch of water
column.  My rather primative home made manometer did show a slight
pressure drop at the mixer, but not enough to get any measurments.
Our local college science department didn't seem to be interested.

Attached are some photos of the primary control valve I am currently
using very successfully.  It looks like something similar might work
for you.

Good work Roberto,

Kirk

"
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