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

[Paul Anderson]

Julien and all,

The nozzle in Kevin Adair's design has the narrow neck of the hourglass 
at the level of the concentrator plate.   That means that the lower part 
extends downward into the reactor area.   The interpretation is that 
mixing will be better if the secondary air cannot move directly to the 
concentrator hole.

Observational research is needed to see the impact.   Note that one 
research variable is just how far down does the nozzele extend?   1 
cm?    2 cm?   5 cm?   This research topic is open to everyone.

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 1/11/2016 11:54 AM, Julien Winter 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
>
>
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