[Stoves] Controlling the Primary / Secondary Air Split in ND-TLUDs

[Julien Winter]

Hi Crispin;

If I understand your splitter, it looks schematically something like this.


    ===== stove turntown control valve
      |
      |
      | _______________
      |                |
 ———>                     ———> primary air
 ———> variable         |
 ———> aperture            ———>
 ———> for incoming        ———> secondary air
 ———> air                 ———>
 ———>                  |
      | _______________|


Given that formulas for air flow through an orifice are not hard to find,
if one knows the buoyancy force in a TLUD reactor, and the buoyancy force
in the gas burner, as well as air flow rates, it should be possible to
simulate this, and see if it is possible for this system to create the
change in secondary/primary air from 6:1 to 3:1 as primary air increases
from 0.017 to 0.062 m/s over an increasing gasification rate increases
(Reed et al., 2000).  Even if we don't have good data, it may be possible
to make a theoretical prediction.  However, ...

For anyone interested in a quick illustration on the effect of orifice size
on gas flow, one can be found here:
http://www.engineeringtoolbox.com/orifice-air-volume-leakage-d_1191.html

One can see from the chart that the resistance to air flow increases
logarithmically.  As one would expect, the resistance to air flow will
increase faster for smaller holes than larger holes as air velocity
increases.

Does that raise a problem if we want the proportion of primary air vs
secondary air to increase as the stove's power is turned up?


Cheers,
Julien.



-- 
Julien Winter
Cobourg, ON, CANADA
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