[Stoves] Nozzles for TLUDs Re: venturi system -ratios of air and gas?

[Julien Winter]

Hi Folks;

It seems that I attached the first photo of the pervious email twice.
Here is the second photo

Cheers,
Julien.

On Mon, Jan 11, 2016 at 12:54 PM, Julien Winter <winter.julien at gmail.com>
wrote:

> Hi Paul, Frans and all;
>
> When you talk of Kevin Adair's nozzle, are I assume you describing a
> hourglass riser above the concentrator ring?  Something like the hourglass
> comes to mind following Frans' comments on the coanda effect.  However, I
> expect that the dominant force at the bottom of the hourglass would be
> buoyancy, straight up.
>
> A rough type of 'hourglass' venturi burner was invented by Dave Yarrow
> (ca. 2013) for barrel type TLUDs.  I built one myself, and it roars.  I
> have attached a couple of photos
>
> 1) shows the whole unit.  There is a 130 L reactor barrel inside the 200 L
> barrel, so secondary air was being preheated, and passed over the top of
> the 130 L barrel where woodgas ignited under the concentrator.  The flame
> then went up into the chimney burner.
>
> 2) shows the bottom of the chimney burner, which constricts to accelerate
> the gases, then expands.  Where it expands, there are tertiary air holes
> that are cut at an angle to get rotational turbulence (supposedly).  The
> idea is to create a bit of a venturi suction for the tertiary air.
>
> This unit is designed for a high gasification rate.  At low gasification
> rates, the flame is below the concentrator.  I haven't done any more work
> on this idea, because I have been focusing attention at on the initial
> mixing of woodgas and secondary air.  I have yet to move upstream.
>
> I don't have this unit any more.  I gave it to a friend who lives in the
> countryside, and does not fear being shut down by the town's fire
> department.
>
>
>
> Of course, anything said about a natural draft, wood gas burner is
> dependent on the supply rate of woodgas, because that can change its mode
> of operation (as above).  The big problem for any burner is to get it to
> work over a wide range of woodgas supply rates.  What works great at a
> medium gasification rate, can be the cause of smoke at a high gasification
> rate.
>
> Premixing air and woodgas under natural draft would be a nice thing to
> achieve.  The challenge under natural draft is to get the flow of the
> mixture to be faster than the flame speed of H2, CO, CH4, so there is no
> flash back.  We may be able to achieve that at higher gasification rates.
> At low rates, the flame will likely flash back to the top of the char,
> which may not be a bad thing for low turndown.
>
> Cheers,
> Julien.
>
>
>
> --
> Julien Winter
> Cobourg, ON, CANADA
>



-- 
Julien Winter
Cobourg, ON, CANADA
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