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| Stoves Archive for October 2001 |
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| 135 messages, last added Tue Nov 26 17:31:02 2002 |
[Date Index][Thread Index]
Re: No requirement of chips
On Sat, 27 Oct 2001 09:16:50 -0600, "Thomas Reed" <tombreed@home.com>
wrote:
>The purpose of the blower is to get "micromixing" of th ecombustion air and
>the woodgas. It would be most desirable - and impossible - to cool the
>woodgas to room temperature, mix it with air and have a nice "blue flame"
>gas similar to propane-air combustion. However, that would greatly
>complicate the stove.
Why should it be necessary to cool the gas before mixing, to prevent
spontaneous combustion? I saw an earlier post to the list that
suggested preheating primary air for an idd stove, this can quite
easily turn the idd into an updraught burner. I have also fed
commercial oxygen as primary gas, this too rapidly produces a flash
over to the bottom of the fire.
>
>Typically a diffusion flame of fuel gas in air or air in fuel gas goes
>through a luminous "soot" phase before combustion is complete, as in
>
>refinery flare
>candle
>match
>log fire
>
>Unfortunately, the slow mixing of air and fuel gives a very LOW intensity
>flame, often many cm or meters high. Interfere with that flame and you get
>incomplete combustion, black pots etc.
>
Yes this is the dilemma of allowing complete combustion without
artificial turbulence, now your mention of "refinery flare" is
interesting, I had earlier had a correspondence in arranging a meeting
with Ronal which I have pasted below, refinery flares also use coanda
burners.
>The purpose of the blower is to micromix the air and fuel gas to provide the
>maximum "Micro mixing" geometry. This has been used in kerosene stoves for
>150 years. (Go buy and study one). In particular the Argand lamp and
>kerosene mantle lamps have beautiful air-gas mixing passages.
Yes this came up in an earlier thread.
To: Ron Larson <ronallarson@qwest.net>
Sent: Tuesday, October 02, 2001 3:17 PM
Subject: Re: Air!! My stove needs air!!
On Mon, 1 Oct 2001 17:56:20 -0600, you wrote:
>On your just prior message to the list on supplying air - please keep it
up.
>I think there is a lot to be gained by external forcing - maybe even
>electrically. But we need to explore more options.
I read the list but seldom comment now. I remember a long time ago I
told you I thought natural draught was a difficult route to travel.
The major reason for pursuing this is that your "clients" are so poor,
in fact so poor that I have never come to grasp the problem properly.
Since my very first experiments after I read "stoves list" I felt
control was needed to have a clean burn and, in my case, modify the
charcoal produced. I had not conceived how visibly cleanly I could
flare the charcoal making before I tried the idd stove. Once I had
done it I sat down to see what was happening.
The first requisite was dryness, idd does not readily occur with the
wood we were making charcoal from. The steam dryer was the quickest,
most compact and cheapest way of getting dry wood. This probably only
got us to "denver dry" anyway. yield experiments soon made me realise
idd burn inevitably cost us some carbon yield.
In playing with a heat source for the drier I made a turbulent burner,
this works well and if I have time I will rig it up for you. However
it made me think back to David Beedie's early advice that for clean
burning you need Turbulence, Temperature and Time.
I saw that I was achieving my clean burn but at the expense of using a
powered fan. I was maintaining temperature by not taking heat out of
the system before combustion was complete.
Things that have interested me are
1) the use of non woody biomass in a prilled or pelletted form, this
to meter in fuel as and when needed (even by a crude clockwork device)
2) turbulent air flow. To my mind this needs to be a secondary airflow
which itself entrains the primary air. This could be achieved by
a: clockwork, after all we probably only need 3 watts
b: a mechanical turbine, which I have thought too expensive
c: an aspirator, eductor or ejector using steam, this will have an
energy cost which I cannot calculate. If used on primary air it could
well consume charcoal in the idd stove but this would require a
substantial flaming pyrolysis zone and the steam would have to be
injected directly into it. Being endo thermic it would work to cool
the zone.
d: the same using pyrolysis products.
What is never discussed in the list about idd stoves is the way they
make a batch loaded device act like a continuously fed device and
hence they do not suffer the difficulties in other batch fed devices
of the fuel load reaching pyrolysis temperature and then "running
away" and subsequently the residual char burning away with poor CO
emissions.
I have looked at
1 venturi effect as used in a carburetor
2 ejector as used in primus or gas burner
3 coanda effect
I can show you a version of d:+3 that a friend made for use with
paraffin but which may work with sawdust.
AJH
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