[Stoves] Types of natural draft Re: Reports from ETHOS meetings: the future of TLUD research

Paul Anderson psanders at ilstu.edu
Sat Jan 31 23:32:04 CST 2015


Alex,

Please elaborate on
> I think "natural draft" is still too broad a term. There is a dramatic 
> difference in gas mixing potential of  30, 90 cm of buoyancy. 
Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 1/28/2015 9:45 PM, alex english wrote:
> Julien,
> Agreed. Its been a twenty year wait for basic in depth research on 
>  natural draft TLUDs.
> Natural draft mixing was my passion for a while. I think "natural 
> draft" is still too broad a term. There is a dramatic difference in 
> gas mixing potential of  30, 90 cm of buoyancy.
> It will be interesting to see the results shared, but I am inclined to 
> think the money would be better spent putting portable combustion gas 
> analysers in the hands of folks like you and Harris.
>
> My excess air for today,
>
> Alex
>
> On Wed, Jan 28, 2015 at 12:45 PM, Julien Winter 
> <winter.julien at gmail.com <mailto:winter.julien at gmail.com>> wrote:
>
>     I was at ETHOS this year presenting some of my basic
>     investigations of TLUD function, and I will circulate a copy of my
>     presentation shortly.  Kirk Harris presented his fascinating
>     burner design.
>
>     For me, one of the most interesting things at ETHOS was not what
>     was presented, but what is coming.  The Colorado State University
>     has received a very large grant from the US Department of Energy
>     to improve our scientific understanding of natural draft TLUDs. 
>     This year at ETHOS, they didn't present any results, but they
>     described the laboratory equipment that they have assembled.  They
>     will be able to measure the flow rates of primary and secondary
>     air, fuel bed and gas flame temperatures, gas flame structure, the
>     composition of the pyrogas as it exists the fuel bed, and exhaust
>     gas and particulate emissions.  They are able to test a variety of
>     gas burners to increase clean-burning --- the most pressing issue
>     today.  Knowledge gained on pyrolysis, combustion, and gas flows
>     will be systematized into computer simulation models.
>
>     This work is much needed.  Since the early 1980s, forced draft
>     systems have been extensively studied, however, except for a
>     couple of recent papers, natural draft systems, have not been
>     studied at all.  Research on forced draft has provided us with
>     some very important information, but it doesn't extrapolate
>     sufficiently well to natural draft systems.    Natural draft
>     systems different from forced draft systems, in three basic
>     ways: (1) they operate at lower gas velocities, near atmospheric
>     pressure, (2) operational temperatures cover a lower range, and
>     (3) and their processes, are interconnected through feed-back
>     mechanisms.  We have to understand how these feedbacks work for
>     designing ND-TLUD stoves.  For example, how does the size and
>     shape of the pyrogas flame affect draft for primary air -->
>     gasification rate --> size and shape of the pyrogas flame --> ...
>
>     It will be interesting to see what the workers at Colorado State
>     University come up with.  I expect they will be able to tell us
>     what the control or limiting points are in the TLUD reaction, such
>     as resistance to gas flow in the fuel bed, or heat production at
>     the pyrolytic front.  They should be able to tell us how the
>     thickness and temperature of the char layer above the pyrolytic
>     front changes the composition of pyrogas rising through it.  They
>     should be able to tell us how the composition of pyrogas changes
>     over a turndown curve.   Most importantly, I hope they
>     will provide guidelines for designing burners, reasons for why one
>     thing works and not another, and a computer program to simulate
>     design decisions.
>
>     The results from the Colorado State University lab can't come too
>     soon.
>
>     Cheers,
>     Julien.
>
>     ---------------------
>
>
>     -- 
>     Julien Winter
>     Cobourg, ON, CANADA
>
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