See comments. On Fri, Aug 31, 2012 at 1:25 AM, Crispin Pemberton-Pigott < [email protected]> wrote:
> Dear Phil**** > > ** ** > > That was valuable info. The problem is not so much the volume of air > needed, it is the pressure required to force some air through the fuel to > maintain a pyrolysing bed. > There are two important factors here. The first is the open area of the reactor grate. If the open area is not enough, the pressure resistance and power requirement of the fan increases a lot. I had to increase the open area of what Belonio had originally specified. This made a big difference. The second is the pressure resistance of the fan (40x40x28mm). For a gasifier of a 150 mm diameter, the pressure resistance has to be at least 0.87 InAq. I tried 0.55 InAq. This works well in the beginning of the burn, but is not quite enough toward the end. I tried 1.5 InAq, but this is far too powerful. The 1.5 InAq fan is OK for the 250 gasifier. Keep in mind that I do all of my testing at an elevation of 1,500 meters. > **** > > ** ** > > If you could stack fans running at a lower speed, it might give you the > pressure. You sometimes see that on high end computer cases. The fans > already have holes to allow this, it is so common. > The fans that I use are computer fans, and they are not cheap. They are guaranteed to run for 65,000 hours. So it might be best to have but one fan per gasifier. To have a good turn down ratio, the speed of the fan has to be adjustable in very small increments. As the burn proceeds, one must turn up the fan at least two or three times to maintain the same output of heat. Thanks. Paul Olivier > **** > > ** ** > > But it is probably better to use a lower voltage fan that is running at > the right tip speed for its blade density. **** > > ** ** > > During an earlier discussion on fans a few years ago we pointed out that a > squirrel cage fan is better for stoves because it so easily provides the > pressure needed.**** > > ** ** > > Do you have access to a DC-DC inverter chip to get the voltage up to 5?*** > * > > ** ** > > Regards**** > > Crispin**** > > ** ** > > ** ** > > Amazing as it may seem, this off-grid Nicaraguan resident has some of > those fans. So, I just gave one a test run. > > It starts rotating at 3.22V but the speed is very slow at anything less > than 4V. Even at 4V I would guess 25% or less of the air flow that you get > at 5V. So, it is possible to use one but not directly from a single LiIon > cell.**** > > On Thu, Aug 30, 2012 at 9:42 AM, Phil Hughes <[email protected]> wrote:*** > * > > > > **** > > _______________________________________________ > Stoves mailing list > > to Send a Message to the list, use the email address > [email protected] > > to UNSUBSCRIBE or Change your List Settings use the web page > > http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org > > for more Biomass Cooking Stoves, News and Information see our web site: > http://www.bioenergylists.org/ > > > -- Paul A. Olivier PhD 27C Pham Hong Thai Street Dalat Vietnam Louisiana telephone: 1-337-447-4124 (rings Vietnam) Mobile: 090-694-1573 (in Vietnam) Skype address: Xpolivier http://www.esrla.com/
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