[Stoves] Fan-blaster Combustors, Stove Camp 2006, and the Dell-Point Pellet Stove

[Tom Miles]

Paul,

The term "fan-blast" does not adequately describe the operation of these
forced draft, or fan, stoves. There are conventional terms for what you are
describing so there is no need to invent new terms. A combustor is either
natural draft or "forced draft". When a fan is used to supply air under
pressure to the fuel it is called a forced draft fan. There are many
variations of forced draft burners. 

"Combustion air" is air used for all stages of combustion whether it is used
to promote gasification or combustion. Gasification air is sometimes called
primary air. Air supplied to burn off the volatiles is often called
secondary air. If primary air is delivered to a furnace/burner through
openings in furnace walls(s) below the main fuel it is called underfire air.
Secondary air, which is usually supplied in the zone of gaseous combustion,
is sometimes called overfire air.  

Air is supplied through openings, nozzles or tuyeres. The arrangement of the
air supply depends on how the designer wants to control the fire. While
Dell-point appears to have gotten a (1998) patent on a spiral pattern for a
cup-type pellet stove there is really nothing unique about this. I have been
working with burners with this kind of tuyere arrangement for more than 30
years. We use the tuyere geometry and the air pressure to control the
combustion. You'll find this kind of arrangement in Crispin's discussions as
well. Tom Reed is correct in concluding that the arrangement of air holes in
the burner is intended to stage the combustion, partly to reduce slagging.
There is a well known industrial version of this kind of burner that
performs in the same way.

Air impingement on the fuel is not unique or characteristic of the group of
burners you call top fed. Air impingement is a common combustion technique
to remove the boundary layer of gases at the surface of the wood, like
blowing on a fire. The blowtorch effect can also be created using an induced
draft stack or fan in which the energy for pulling the air onto the fuel is
from a stack or fan that exhausts the hot gases from the furnace. This was a
basic part of Richard Hill's stickwood furnace design. I don't think the
blowtorch effect is necessarily common to all the burners you describe. You
have not shown us the specific locations of air and fuel and the volumes of
airfow to the fuel in each case. If you look closely at the designs of all
four stoves you will find significant differences in their design and
operation. I think the tuyeres in Tom Reed's woodgas stove or the Phillips
stove are intended to burn gases above the fuel not solids at the fuel
surface. (You claim that the woodgas stove in the Stove Camp test was not
operated in a normal manner. Perhaps the people who tested it can explain
how and why.)

I am not ready to accept a "fan-blaster" classification for forced or induce
draft burners that employ air impingement as a combustion technique. But it
does make a catchy tag that you might use to describe the behaviour in your
Juntos fan stove. 

Regards,

Tom Miles                               

-----Original Message-----
From: stoves-bounces at listserv.repp.org
[mailto:stoves-bounces at listserv.repp.org] On Behalf Of Paul S. Anderson
Sent: Monday, September 18, 2006 8:30 PM
To: GASIFICATION - Listserve; STOVES - Listserve
Subject: [Stoves] Fan-blaster Combustors, Stove Camp 2006,and the Dell-Point
Pellet Stove

Dear Stovers and Gas-L readers,

I have sent to Tom Miles for posting to the Bioenergylist.org website a
5-page document about the topics in the Subject line above.  I place here
only the first few paragraphs.  Tom Miles will inform us when and where the
full document is available on the Internet.

I hope you enjoy it.

Paul
*******************
Fan-blaster Combustors, Stove Camp 2006, and the Dell-Point Pellet Stove
                 Paul S. Anderson
        Submitted to the Bioenergy.org website on 18 September 2006

	I have used this Title / Subject name "Fan-blaster Combustors, Stove
Camp 2006, and the Dell-Point Pellet Stove" because all three are related
and are topics of recent messages on the Stoves and Gasification Listservs..

1.  What is a "fan-blaster"?
	Perhaps there is a better name for the combustion technology found
in pellet stoves, but I do not know what it is.  Essentially a controlled
stream of focused air is directed onto a small amount of fuel that is being
continually replenished.  It is not simply "a fan stove" because that could
apply to any stove that uses a fan.  This type of combustion is related to
the blast of air that is perhaps similar to "blast furnaces" where extra air
is forcefully injected and does good things.  So I have called it
"fan-blaster" technology. 
It is not sufficiently clear to say "pellet stove" because other combustion
technologies can and do burn pellets; and some of the same technology is
used in corn burners and where small pieces of wood are used as fuels.
Names other than "fan-blaster" are welcome as long as they are clearly
defined and do not overlap onto other combustion technologies.

2.  What stoves are "fan-blasters"?
	A.  Standard pellet stoves, corn stoves, etc.
	B.  The Dell-Point pellet stove.
	C.  The "Woodflame Gusto" stove

            	Forced-air T-LUDs when they are NOT used as T-LUDs!!!!!
	D.  Reed's Woodgas Campstove, when NOT used as a T-LUD.
	E.  Phillips stove, when NOT used as a T-LUD.
	F.  Anderson's "Juntos B," when NOT used as a T-LUD.

(what follows in the full document will inform you about Stove Camp 2006
experiences and the "Cat Pee" results.)
--
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone:  USA-309-452-7072 (residence and office) Internet site:
www.ilstu.edu/~psanders For my gasifier stoves info, go to:
http://bioenergylists.org/contributors#Paul_Anderson





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