[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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