[Stoves] diy TLUD flame / Laminar Flow

[Jock Gill]

Crispin,

I find I have no problem with my tin can "wall materials" with my deflectors set above a secondary air gap.  This appears to prevent laminar flows in the exhaust gases and to keep the flame more contained for longer periods [residence time in your parlance].  This may be because I use a secondary air slot rather than holes.  The use of the slot may tend to force the hot gases away from the wall materials?

The best way to see this is to simply make one of my units as described and illustrated in the Pyro-Grilling PDF on Greater Democracy.

I will try the experiment below when I get back from vacation [Anguilla].

Fill a TLUD with water and watch what happens when you invert it and allow the water to flow out thru a concentrator hole [bathtub drain]

Next, fill a draft can with deflector washers at one end with water, invert it, and watch the water flow out thru the deflectors.

What differences does this reveal? I will be most curious to see what I can see.

Cheers,

Jock

Jock Gill
P.O. Box 3
Peacham,  VT 05862

Cell: (617) 449-8111

google.com/+JockGill

:> Extract CO2 from the atmosphere! <:

Via iPad

> On Feb 27, 2014, at 9:11 AM, Crispin Pembert-Pigott <crispinpigott at outlook.com> wrote:
> 
> Dear Friends
>  
> >To visualize what Crispin is saying, think of the vortex created in a bathtub drain as the tub empties. 
>  
> >A TLUD with a circular aperture for the exhaust gases is simply an upside down bathtub drain that just as surely creates a central spire of twirling flames. To be avoided if at all possible.
>  
> Oohh…I didn’t meant to imply that. The deliberate creation of a vortex is very helpful in certain cases. Ibrahimo, a PhD student will present a paper at the DUE Conference in Cape Town in a month which is the result of building a CFD model of the BLDD6 downdraft coal stove. He has found a setup that reasonably matches the measured temperature profiles at several points along a flame path that is very deliberately filled with such a twirling of flames. The advantages of doing this were covered in earlier papers from the SeTAR Centre.
>  
> Jock, the advantage (if you have the space to do it) are that it preserves the wall material and provides an artificially temperature region in which to burn out the PM. The result is that ‘difficult’ coal like semi-bituminous Witbank coal can be burned with basically no smoke at all.
>  
> I have a feeling this stove might burn jatropha seeds directly as well. Each fuel class requires its own circumstances. When the ‘oil’ chains are long, so too should the flame path be long. The layout increases [residence] Time, Turbulence and Temperature simultaneously.
>  
> Regards
> Crispin
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