[Stoves] air for gazification

[Kevin Chisholm]

Dear Frank

frank at compostlab.com wrote:
> Dear Martin and stovers,

...del...
> 
> Can anyone give me the pressure produced from a computer fan? I have
> compressed air but would like to simulate a computer fan blasting up the raw
> fuel chamber to the primary. 
> 
There is no specific answer to this question. Any given fan is able to 
develop a range of pressures, depending on the flow it is delivering, 
OR, any given fan is able to develop a range of flows, depending on the 
pressure the fan is developing.

What you need is a Fan Curve for the particular fan that you are using, 
or wish to use.

Fan Curves are a plot showing the relationship of Fan Pressure Generated 
versus Air Flow Delivered.

Note also that a fan of "larger" diameter does not necessarily deliver a 
higher pressure, or a larger flow, than a fan of smaller diameter. 
(within limits) For example, the larger fan may be designed for quiet 
operation, and the smaller diameter may have been designed for an 
application where noise was not important, but compactness was.

Note also that Computer Fans are typically "Axial Flow" fans, which 
deliver relatively large flows at relatively low pressures. On the other 
hand, a "Squirrel Cage Fan", (as one would find in  the heater system of 
a car) would deliver much higher pressure at reduced flow. A "Radial 
Flow Fan" (as one would find in a vacuum cleaner) would deliver still 
higher pressure. These three fan wheel configurations are perhaps best 
compared by power drawn, rather than wheel diameter. For example, a 4" 
diameter Axial Flow fan might deliver 100 CFM against a pressure of 0.1 
inches of water gage, while a 4" diameter vacuum cleaner fan (probably 2 
stage) might deliver the same volume, but at a pressure of 10" water 
gage, ie, 100 times the pressure with the same flow.

There are two ways to get Fan Curves:
1: Ask the Seller to get the Fan Curve from the Manufacturer.
2: Get a Fan, and make your own Fan Curve.

To make your own Fan Curve, you need facilities for measuring air flows 
and air pressures. This is not a trivial task, especially when flows are 
small, and pressures are low.

Unless you have Fan Curves, you cannot "design" a stove... all you can 
do is "try one" and see if it gives you the results you want.

I think that is a "reasonably complete non-answer" to your question. :-) 
  Hopefully, you can see why your question has no simple answer.

Best wishes,

Kevin


> Thanks
> Frank  
> 
> 
> 
> 
> 
> 
>> Let us have fun!
>>
>> Best wishes!
>>
>> Martin
>>
>>> -----Ursprüngliche Nachricht-----
>>> Von: Kevin Chisholm [mailto:kchisholm at ca.inter.net]
>>> Gesendet: Samstag, 9. Juni 2007 01:59
>>> An: boll.bn at t-online.de
>>> Betreff: Re: [Stoves] air for gazification
>>>
>>> PERSONAL TOP SECRET INSIDER INFORMATION!!! :-)
>>>
>>> Dear Martin
>>>
>>> One cubic foot of air, under stoichiometric conditions will support
>>> combustion that releases 100 BTU
>>>
>>> If you want 1 kw in 1 hour, ie, 1 kwh, you have to liberate 3412 BTU
>>>
>>> Therefore, you need, in theory, 34.12 cubic feet of air.
>>>
>>> Be\cause of poor mixing, etc, you will probably need about 15% top 25%
>>> excess. Say 20% excess, or say a total of roughly 40 cubic feet of air
>>> per hour.
>>>
>>> Now, roughly 1/2 should be blown in below the grate, as primary air, to
>>> make gas, and the other half should be blown in above teh fuel, as
>>> secondary air, to burn the gas to completion.
>>>
>>> That will be our little secret!! :-)
>>>
>>> Best wishes,
>>>
>>> Kevin
>>>
>>> Boll, Martin Dr. wrote:
>>>> Dear all,
>>>>
>>>>
>>>>
>>>> where can I find a rough and ready-number, of the needed air (oxygen)
>>> amount
>>>> for e.g. the release of 1kw heat-making wood-gas-amount in a T-LUD-type
>>>> burner?
>>>>
>>>> - I am aware that moisture will make differences.
>>>>
>>>> - How many litres air per minute?
>>>>
>>>>
>>>>
>>>> Regards
>>>>
>>>>
>>>>
>>>> Martin
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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> 
> 
> --
> Frank Shields
> Soil Control Lab
> 42 Hangar Way
> Watsonville, CA  95076
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>