[Stoves] About "inverted flames" ......was Re: Trials on TLUD gas burners

[Paul Anderson]

Stovers,

I have left below the previous discussion by Ron and me.   And I thank 
him for his thoughtful comments.

  But to keep things short, here is a reply to some issues raised (much 
snipped and with order sometimes changed:

1.  Ron wrote:
> *I think the diffusion process is substantially similar, in both 
> normal and “inverted” flames. *
> *Are there other TLUD photos around I can look at, that show the flame 
> appearing between secondary air holes - not over them?*
Inverted flames are conical just like regular flames.   Looking downward 
at them, the parts that are over and below the air coming in are the 
thinnest and the flame can appear to be absent.   But it certainly is 
there.   Meanwhile, the parts of the flame on the two sides of the cone 
are seen as much more yellow because of looking downward through 
side-wall of the cone, which can appear to be "thicker."  AND, because 
the sidewall flames of two adjacent inverted cones are close together, 
the flames are joined and appear to be attached to the walls of the fuel 
canister.

2.  Paul A. Wrote:
>  In the TLUD gasifiers, the secondary air holes are sufficiently close 
> together that the inverted flames are filling the space between the 
> apertures of the incoming gas (which is actually air).
I should have written ".... the incoming /_NON-combustible_/ gas (which 
is actually air). "      Sorry for the confusion.   The INVERTED flame 
is still the mixing of two gases (air and combustible gas), but with the 
air in the center of the cone.

3.  Alexis Belonio's most known stoves are with "natural flames" with 
the combustible gases being injected vertically into a zone of air, with 
his burners looking much like a regular burner of gas fuel.   But Alexis 
was discussing with me the inverted flame situation, so my comment was 
correct when I wrote:
> And also, Alexis Belonio was advocating in January 2014 at the 
> Aprovecho Open House about some form of spreading the gases that need 
> to reach the secondary air that is coming in from the sides. 
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 5/3/2014 2:34 PM, Ronal W. Larson wrote:
>> ***** change of topic ***********
>>
>> I comment on Ron's statement:
>>> By looking closely, counterintuitively, the flames seem attached 
>>>  NOT over the gas apertures, but rather between them.  I think this 
>>> is true in all cases but can’t see the case C “attachment” points. 
>>>  Except in private dialogs with Paul O, I have not seen this stated 
>>> before in print  - and don’t know if it should be encouraged or 
>>> discouraged.
>> I think this has been considerably discussed or at least observed.
> *[RWL:  If anyone can provide a link, that would be much appreciated. 
>  Paul Olivier and I never found a write-up - and it still baffles me. 
>  Are there other TLUD photos around I can look at, that show the flame 
> appearing between secondary air holes - not over them?*
>> It relates to the phenomenon of the "inverted flame" in which the air 
>> enters a zone of combustible gases instead of the combustible gases 
>> entering a zone of air (which is the case of common gas burners on 
>> stoves.
> *[RWL:  Well,  I think there is another explanation.  Paul Olivier has 
> his gas flamelets enter into air - not the "inverted flame”, which I 
> agree is or could be substantially different.  But the Olivier/Belonio 
> flamelets (very short - not the typical long flames of most TLUDs) 
> look remarkably similar to small match or candle flames.  I think the 
> diffusion process is substantially similar, in both normal 
> and “inverted” flames.  I think the results obtained by Jim Jetter 
> showing low particulates and CO with many TLUD tests indicate the 
> regular and inverted flames can’t be widely different.  The emissions 
> are arguably superior with TLUDs - and (maybe) independent of whether 
> these flames seem to originate from over or between holes.*
>> In the TLUD gasifiers, the secondary air holes are sufficiently close 
>> together that the inverted flames are filling the space between the 
>> apertures of the incoming gas (which is actually air).
> *[RWL:  As noted above, I mostly operated with a continuous 
> circumferential narrow slit - and never saw this - which is why I 
> used “counterintuitively”  Has anyone ever seen this with a natural 
> gas multi-hole burner?  My discussions with Paul Olivier centered on 
> the importance of radiation - possibly coupled with the fact that 
> pyrolysis gases have a chemistry (not try for methane) which gives you 
> a smaller number of reaction particles at the end than going in. 
>  Makes for a helpful pressure difference.  (This holds for whether 
> there is gas entering air or air entering gas.)*
> *Re the last clause /("which is actually air")/ needs more discussion. 
>  There has to be some gas there in order to have a flame.  If there 
> were still eight input ports, but appreciably smaller, would we see 
> the same thing?  Does it have to do with a big air speed through the 
> input ports?*
> *I think there is a doctoral thesis lurking in here somewhere.  There 
> may be some optimum of hole diameters, spacings, shapes, separations, 
> etc - to get the best flames (better “flamelets”).*
> *
> *
> *Ron
> *
>>
>> Paul A.
>> Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
>> Email:psanders at ilstu.edu    
>> Skype: paultlud      Phone: +1-309-452-7072
>> Website:www.drtlud.com
>>

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