[Stoves] Adding a fan

[Boll, Martin Dr.]

Dean,
Congratulation for your fan-blown rocket-stove!
I saw the pictures. What dimensions does the bucket have?
I am not familiar with those.

In my opinion (no specialist) one cannot reach an as big turbulence as you
need to mix burning gasses sufficiently with fresh air only by the simple
draft. 
If you want to use not much air for best combustion, you need a real "blow",
as you do. 
Remind my posting "Blow by draft". To get this blowing effect by draft, one
must have a high chimney, and a tight stove. Nobody of the here intended
users has such chimney- and stove conditions. All the proposals for doing
the good job by a simple chimney will not work sufficiently.

But I would think about a low-tech-blower without electricity, 
(Though an electrically fan is the simplest way in "advanced!" countries;
- Even in a cooling-box there is a fan to blow-)

Blowing is not necessary during all the running time by a rocket-stove, as
you mentioned. That will make it far easier to find a simple
low-tech-solution for your new fanned rocket-stove.
I am thinking quite a while about different simple blower-solutions without
electricity, but had not the time to work out my different ideas.
How about to try a belly with a non-return valve and an air-reservoir, to
get a continuously blow?

I think, people don't like to cut wood, if they have uncut sticks to burn.
Therefore a rocket-stove has a handling-plus, compared by batch-loaded
stoves, when only such fuel is available and used.

Best wishes for your project

Martin


> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Sat, 20 May 2006 09:38:52 -0700
> From: "Dean Still" <dstill at epud.net>
> Subject: [Stoves] Adding a fan
> To: "'STOVES'" <STOVES at LISTSERV.REPP.ORG>,	"'Paul van der Sluis'"
> 	<paul.van.der.sluis at philips.com>
> Message-ID: <20060520163853.C3C65D at telchar.epud.net>
> Content-Type: text/plain;	charset="us-ascii"
> 
> Dear STOVES,
> 
> I have had some luck adding a fan to a Rocket stove. Preliminary results,
> photos and a chart are posted on the REPP site.
> 
> The combustion chamber is made from insulative firebrick inside a 20 liter
> bucket. The fan blows air into a sealed annulus between the outside of the
> firebrick and the inside of the metal container. Drilled holes through the
> brick blow jets of air into and above the fire. The holes are all pointed
> up
> a bit so that the direction of flow is up the L shaped Rocket combustion
> chamber. The long sticks enter the stove from the side as usual.
> 
> Batch fed fan stoves like the ones built by Dr. Tom Reed and Dr. Paul van
> der Sluis are remarkably clean burning. I wondered if it would be possible
> to do the same thing in a side-feed stove. Stoves without fans often do
> not
> have good mixing of wood gases, air, and flame so uncombusted gases
> escape.
> 
> The World Food Program Rocket stove is made from used metal food
> containers.
> It is low mass and pretty much represents the cleanest burning Rocket type
> stove. Time to Boil 5 liters is 22.7 minutes. Fuel used to boil one liter
> and simmer it for 45 minutes is 68.1 grams. CO produced during this task
> is
> 0.8 grams. PM produced is 162.4 micrograms. Firepower is 5532 watts.
> 
> Adding a fan that blows air into and above the fire improves performance
> in
> this type of stove. Time to Boil in the firebrick fan Rocket is 14.0
> minutes. Fuel use is 56.9. CO is 0.3. PM is 9.7. Firepower is 5954.
> 
> The air is not preheated except that it goes through 3 inches of
> insulative
> .6g/cc firebrick in the drilled 1/8th inch holes. The fan is 10 watts on
> full speed. A 3 watt fan did not seem to do as well.
> 
> I'll keep on changing things to try to lower PM.
> 
> Adding an inexpensive fan even to a sidefeed stove is an effective way to
> increase performance.
> 
> Dr. Tami Bond said to us yesterday that the permanent brown cloud over
> India, China, etc. is caused in large part by the burning of biomass. I
> was
> just in India for 6 weeks and away from the cities in the countryside the
> sky is no longer blue. The work that we are doing here on STOVES etc. is
> to
> change back the color of the sky to its intended color!
> 
> Best,
> 
> Dean
> 
> PS
> 
> By the way Stove Camp is August 18-22 here in Oregon. Hope that you can
> come!
> 
> Shall we concentrate on $5 fan stoves?
> 
> ------------------------------