[Stoves] Increasing ND-TLUD riser height accelerates gasification and increases bed temperature

[Paul Anderson]

Julien,

I am not sure that I said it that way, but I will try to answer
> Paul Anderson made an interesting comment to me the other day.  
> He wondered if as the size of the gas flame increased, the flame 
> became more fuel rich.  Perhaps he will elaborate on this for us.
As the gas flame increases because of adding more draft (chimney), at 
the start the flame will be more fuel rich.   Then it tries to get more 
secondary air (to become "normal"), but that means more flame, and more 
draft, etc.    So it can take a while for the system to normalize after 
a change (such as adding more chimney) takes place.

If that comment does not address what I said earlier, please clarify the 
question.

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 12/12/2014 9:07 AM, Julien Winter wrote:
> Hi Jock;
>
> Thanks for your comment "Tweak one [design parameter] and you tweak 
> them all".  The interactions in ND-TLUDs are interesting.  We don't 
> see them so much in FD-TLUDs because the fan overrides all.   
> I developed the burner I am using with prototype tin-can TLUDs and 
> found that the gasification rate was higher over the whole power curve 
> with moderately large secondary air holes.  The size of the air holes 
> can't be too large, however, because as they become larger they 
> structure the air jets less and less, and you also end up with big 
> gaps between the holes.  I have found that round holes are better than 
> rectangular holes, because the round holes are better at 
> self-regulating the flow of secondary air as the flame size changes.
>
> Geometry and placement of secondary air holes can affect the 
> distribution of burner draft between primary and secondary air.  Paul 
> Anderson made an interesting comment to me the other day.  
> He wondered if as the size of the gas flame increased, the flame 
> became more fuel rich.  Perhaps he will elaborate on this for us.
>
> The burner I am using is simple and robust.  There are, of course, 
> other approaches to burners, as you and Kirk Harris have shown.
>
>
> All the best,
> Julien.
>
> On Fri, Dec 12, 2014 at 8:19 AM, Jock Gill <jock at jockgill.com 
> <mailto:jock at jockgill.com>> wrote:
>
>     Julien,
>
>     If you increase draft  you will increase the "pull" on both
>     secondary air and primary. This should allow you to reduce the
>     size, amount, of the primary air holes.
>
>     If you increase the amount of secondary air you will reduce the
>     amount of primary air. It is easier to pull in secondary air than
>     primary. The draft, primary and secondary air are all tightly
>     coupled in a non linear system.  It might be linear if the
>     resistance in the fuel bed were a constant, but as the fuel is
>     pyrolized the resistance is constantly changing.  And of course
>     the variable amount of heat as the process progresses also
>      contributes to the non linearity of the system.
>
>     Tweak one and you tweak them all.
>
>     Cheers,
>
>     Jock
>
>     Jock Gill
>     P. O. Box 3
>     Peacham, VT 05862
>
>     google.com/+JockGill
>     <https://plus.google.com/_/notifications/emlink?emr=02164940119180120523&emid=CIn6jOiavboCFcgLTAodARYAAA&path=%2F102260924343967128597%2Fop%2Fu&dt=1383089746165&ub=50>
>
>     Extract CO2 from the atmosphere!
>
>     On Dec 11, 2014, at 7:20 PM, Julien Winter
>     <winter.julien at gmail.com <mailto:winter.julien at gmail.com>> wrote:
>
>>     Hi All;
>>
>>     Attached is an "experimental vignette".  It is a report on a
>>     small experiment conducted to get a better understanding of
>>     natural draft TLUD design.
>>
>>     The height of the riser above a gas burner was doubled.  The
>>     resulting increase in draft in the burner resulted in faster
>>     gasification rates and higher temperatures in the TLUD. Besides
>>     riser height, I have found that a number of design elements of
>>     the gas burner can increase gasification rate such as the size of
>>     secondary air holes.
>>
>>     I have a few more of these experimental vignette to come, such as
>>     how creating a vortex flame may not be a good idea, and how heat
>>     is lost from the side walls of the reactor, and a reasonable heap
>>     on reactor temperature for different fuels.  Now that snow is on
>>     the ground in Southern Ontario, I have more time to analyze data.
>>
>>     All the best
>>     Julien
>>
>>     -- 
>>     Julien Winter
>>     Cobourg, ON, CANADA
>>     <Height of gas burner riser.pdf>
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>
>
>
> -- 
> Julien Winter
> Cobourg, ON, CANADA

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