[Stoves] TLUD pellets stove with a venturi burner.

Crispin Pemberton-Pigott crispinpigott at outlook.com
Wed Oct 7 23:17:35 CDT 2015


Dear Kirk

 

At 1:25 of the video there is some separation of the flames on the right
indicating the fire is right on the edge of having too much air and too
little gas - maybe cold air from above. I presume this is at the lowest
power setting.

 

Following this the central flames comes up with a lot of PM in it (bright
yellow). This seems to indicate that there is a shortage of secondary air
and an excess of gas in the centre.  It looks as if the addition of more
primary air may have weakened the draft available for the secondary air.
This is solvable. 

 

How about dropping into the space where the flame is, a tube that reduces
the diameter? The space is really empty of flame. There doesn't seem to be
any advantage to that. 

 

Something else to check is: lower the pot rest height so there is no
possibility of air entering from the top into the upper chamber. When
filming with the pot off, the combustion is strongly affected by the absence
of the pot. It is hard to say for sure but it looks around the 2 minute mark
that there air entering from the top in a downward running tube and then
scooping the outside of the flame near the secondary air holes, the pushing
it up again without much mixing into the gas core. Putting on the pot (but
with much lower stands) might change what is happening inside the chamber. 

 

The flame coverage is very good at low power - full deck of flame, but that
doesn't last when it is turned up. The secondary air can't reach the centre
either because of lack of pressure, holes are too many and small, or the
venturi is not doing what you want. You might be ahead to put some downward
angled holes running into the gas below the venturi. What you have works
well (tending to the edge of stability as mentioned above) at that power
level. It is possible that the flame instability is entirely caused by the
cold air coming from above. Try putting a perforated metal plate over the
top so you can see through, the gas can get out, but air can't get in.

 

Like this:



 

If you want to get the effect of a chimney, akin to what I was doing, the
secondary air should be added under the bottom if it will go in there. It
has more chance to mix on the way up. 

 

I will send you a video of the effect pot on/pot off directly to your
address.

 

Regards

Crispin

 

 

 

Kirk,

Nice work!!!!   Kevin Adair is doing some venturi additions also.   

Paul



Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD  
Email:  psanders at ilstu.edu <mailto:psanders at ilstu.edu>    
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com <http://www.drtlud.com> 

On 10/7/2015 5:09 PM, kgharris wrote:

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

----- Original Message ----- 

From: Roberto Poehlmann <mailto:roberto.poehlmann at gmail.com>  

To: stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org>


Sent: Tuesday, October 06, 2015 5:53 PM

Subject: [Stoves] TLUD pellets stove with a venturi burner.

 

Hi,

 

This is a video of one of my prototypes of a TLUD pellet stove.

 

The difference with a "normal" TLUD burner, is that it has a 3 inch tube
with secondary air holes after the concentrator ring.

On top of the the tube, i put a cone to expand the path of the gases, to
shorten the flame, and to have a little internal chimney for draft.

 

One advantage of this burner, is that you can also burn all of the charcoal
made at the pyrolysis stage, with a nice secondary blue flame (if you wish)
.

 

https://youtu.be/uXMeGcZEYX0




Greetings
Roberto Poehlmann

Valdivia, Chile.

  _____  

 

 

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