[Stoves] Turn down on FA-TLUD and ND comments

Fri Feb 15 14:47:53 CST 2019

Thanks Paul

Something not mentioned is that when you have a fire burning under one of those perforated sheets, for example, the vertical height of that very hot zone can create quite a high pressure, relatively speaking, compared with a really open design. You can see from the flames that the velocity is quite high in those photos - that is the result of the high temperature (low EA) and pressure resulting from buoyancy.

That serves to drive the gases through those tiny slots. This is a completely different approach from that taken by Paul Olivier or Riaz Ahmad (at CAU in Beijing) where the burner is 'remote and the flames are above the holes. What that perforated plates is doing is acting as an ignition device for any gases that were not yet going to burn to completion.

I discovered this technique building down-draft coal burners. If the grate is "heavy" meaning cold even when the fire is large, the flames are extinguished if they contact the metal.  However if the metal is very thin, it gets yellow-hot and acts as an ignition source instead of as a quencher. Big difference. Obviously the metal has to be able to take those temperatures so it has limited usefulness as an updraft idea, but a lot of application for down-drafting.  Many models were made using Kanthal wire as the grate and ignition source.

Regards
Crispin

Crispin,

Your comments should help encourage everyone to continue the quest for cleaner combustion.   Much could depend on the velocity with which the created combustible gases are PRESSED (pushed) or DRAWN (pulled) through some configuration.

I think one point is clear:  constriction or limitation for the passageways for the gases can play a generally favorable role to get better mixing and combustion, but only to a certain point where overly-obstructed passageways hinder the flow (so put on more pressure or more pulling draft).

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu<mailto:psanders at ilstu.edu>       Skype:   paultlud
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