[Stoves] Organic Solid Fuel Classification System

[Kevin Chisholm]

Dear Jeff
----- Original Message ----- 
From: "Jeff Davis" <jeff0124 at velocity.net>
To: <stoves at listserv.repp.org>
Sent: Monday, September 25, 2006 12:59 AM
Subject: Re: [Stoves] Organic Solid Fuel Classification System


> Dear All,
>
> How about a stove that has an adjustable fuel to air ratio. First adjust
> the
> stove so that it is burning good. The emissions hood would also be nice
> here.
> How about an O2 sensor?
>
> Next start over with a new batch of fuel and measure the amount of air
> consumed (air fuel ratio), fuel consumed, remaining ash and how much water
> was boiled away.
>
> If we know the air/fuel ratio, how clean it burns, Joules/g (Btu's) and
> remaining ash what more do we really need?

The first thing that would be nice to know are the fuel properties for which
the stove was designed, and the properties of the fuel to be tested. If
there was a significant mismatch, then it could be a waste of time to even 
start the test. Clearly, it would not be worthwhile to try and burn rice 
husks in a
stove designed for forced air flow through a bed of wood chips, or in a
stove designed for pellets, or in a stove designed for split cordwood. For 
example, a Jotul Stove  that works well on split cordwood would probably not 
be the best stove for burning fireballs. Most
stoves that can burn anything would be expected to burn only few fuels well.

It would be nice to know the range of fuel moisture contents, for which the
stove is intended to burn. Relatively wet fuels with low unit surface area 
should probably have a fuel chamber with relatively large "floor area," to 
give the maximum potential for drying by back radiation. On the other hand, 
relatively dry fuels with large surface area should perhaps have a 
relatively low floor area exposed to flame radiation, to minimize runaway 
pyrolysis.

It may be advantageous or necessary to vary the air/fuel ratio, depending on
whether the fuel is wet or dry. Wet fuels may require a higher apparent 
primary air flow to bring the fire closer to the wet bed, as a way to assist 
in drying adequately so that combustion can be sustained.

It would be nice to know the permissible superficial velocity of Primary Air
into the fuel bed, to get a feel for whether fuel or ash would tend to
fluidize, or carry over to the secondary combustion zone. If particulate 
matter carryover is a concern because of the nature of the fuel or ash, it 
would be nice to know if the stove design contained a "settlement chamber 
effect" to allow the particulate carryover to settle out before it reached 
the living space.

It would be nice to know the characteristics of air flow through the bed, to
determine if the available fan pressure or natural draft was sufficient to
support effective primary combustion.

Once the low range Air/Fuel ratio was set, it would be nice to have a
secondary air control. Depending on fuel characteristics, it might be 
advantageous to have a variable Air Fuel Ratio. For example, a stove 
designed for burning wet fuel should perhaps have a high Air/Fuel Ratio, 
when operated at a lower percentage of rated capacity, but as the burning 
rate was increased, then it may be desirous to reduce the Air/Fuel ratio in 
the primary combustion zone, and increase the air flow to the secondary 
combustion zone.

etc....

As "The Fireball Man", you would be very aware of the differences that 
starting materials, size, smoothness, uniformity of size, and moisture 
content would have on burning characteristics.  You might be able to make 
Fireballs with 5 or 10 or 30 significantly different burning 
characteristics. Another way to say that is "Some fireballs are better than 
others." It would thus seem to me that some stoves would be better for some 
fireballs than others.

Does all that sort of hang together? :-)

Best wishes,

Kevin

>
>
> Jeff
>
>
>
>
> Tom wrote:
>> No, a calorimeter burns fuels in oxygen (and everything is consumed) and
>> measures the heat evolved as absorbed in a water bath.
>>
>> TOM REED
>>
>> steve wrote:
>> >> If we use a standard fuel to test stoves, why not use a
>> >> standard stove to test  fuels?
>> >
>> > Isn't that what a calorimeter is ?
>> >
>> > Steve
>
>
> Kevin wrote:
>>>That is similar to saying: "Lets use a standard engine to test fuels." If
>>>I
>>>give you a diesel engine and ask you to test #6 oil, you may or may not
>>>get
>>>good results. Or, if I give you a spark ignition engine set up for high
>>>octane gasoline, you will get very different results when you use
>>>hydrogen,
>>>low octane gasoline, CO, propane, Natural gas, biogas or kerosene.
>
>
> -- 
> Jeff Davis
> Somewhere 20 miles south of Lake Erie, USA
> http://www.velocity.net/~jeff0124
>
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