[Stoves] [Fwd: Superficial Velocities of Power gasifiers and WoodGas Stoves]

[Robert Penn Taylor]

Frank,

I have a few questions for you about your setup:

1. What are the details of the flow measurement, especially what type of 
flowmeter?
2. Are you monitoring pressures in the system? If so, where and what are 
they?
3. When the CO2 is injected, is it via a pressurized pulse or are you 
relying on a venturi effect to pull a measured volume of CO2 into the 
system passively? If it's a pulse, what is the timing on it? Either way, 
what is its pressure?
4. I assume your analyzer measures CO2 concentration. If you integrate 
the concentration the analyzer reads over the time of the experiment, do 
you end up with the same amount of CO2 you put into the system?

I suspect you've set up a constant volume flow rather than a constant 
mass flow. Your hypothesis of faster movement in the restricted setup is 
based on the assumption of constant mass.

-Penn Taylor

--

Robert Penn Taylor
Graduate Research Assistant
Department of Mechanical Engineering
Iowa State University
(515) 294-5311

frank wrote:
> Stovers,
> 
> Trying to understand the movement of air through small fuel I set up a 
> simple experiment (see below) where I measured the time air took to pass 
> through an empty one liter chamber and again with the chamber filled 
> with plastic balls (fuel). Thinking the time of travel would be faster 
> with the balls due to reduction of void space by ~50%.causing the air to 
> rush faster past the balls.
> Flow was constant at 0.5 LPM.
> 
> I found just the opposite! It took about 18 seconds without the 'fuel' 
> and about 56 seconds with the 'fuel' between the injection of CO2 and 
> the peak height. ????
> 
> Crispin mentioned awhile back he thought Surface Area was an important 
> factor to know.
> A) I am wondering if this increased surface with the balls is the cause 
> of the increased time it took for the air to pass?
> B) Can we determine the surface area of a small fuel doing this 
> experiment (standardized against beads).
> C) Can we calculate the speed air is going past the fuel surface with 
> this experiment?
> D) Am I (once again!) way off base?
> 
> 
> Thanks for any enlightenment.
> 
> Frank
> 
> 
> 
>> EXPERIMENT
>> Purpose:
>> To show that when fuel fills a container the air travels faster 
>> through the fuel than in the same container without fuel due to the  
>> reduced void space.
>>
>> Set-up:
>> I used a one liter squeeze water bottle for the fuel container and 140 
>> plastic spheres that each are 3.7657 cm3 for the fuel.
>>
>> Train from back end to front:
>> flow meter and needle valve set for 0.5 LPM
>> Aquarium air pump sucking air from up stream and flow controlled by 
>> needle valve. Steady flow.
>> CO2 analyzer
>> Out flow of the water (fuel) container piped to analyzer. Fuel 
>> container (A) not filled and (B) filled with total 527 cm3 plastic 
>> balls (fuel) leaving 47.3 % of total void space.
>> Two hole stopper fitted where the cap was. One hole for injecting in 
>> CO2 and the other with continued flow of CO2 free air being drawn 
>> through the train
>> CO2 free air comes from head space at the top of a large bottle of 
>> water with NaOH to remove the CO2 from supply line
>> Compressor on roof supplying air to the NaOH scrubber.
>>
>> Procedure:
>> (A)
>> System run until CO2 meter indicated a steady baseline with CO2 free 
>> air and *no fuel in the fuel container*.
>> 250uL CO2 injected
>> Time from injection to high point of peak.
>>
>> (B)
>> System run until CO2 meter indicated a steady baseline with CO2 free 
>> air and fuel container *filled with fuel* .
>> 250uL CO2 injected
>> Time from injection to high point of peak
>>
>> Results:
>> (A)
>> Time (seconds) from injection to high point of peak (NO Fuel)
>> 18
>> 17
>> 18
>> 16
>> 20
>>
>> (B)
>> Time (seconds) from injection to high point of peak (Fuel)
>> 63
>> 56
>> 58
>> 56
>> 50
>>
>> Conclusion:
>> It takes longer for air to pass through the restricted flow (due to 
>> fuel) than with an open fuel container.
>>
>>
>> Frank
>>
>>
>>
>>
>>