[Stoves] venturi system -ratios of air and gas?

[Paul Medwell]

Sorry to protract this discussion, but...

It is not entirely fair to call a nonpremixed flame "dirty". A 
nonpremixed Bunsen burner flame is typically yellow, caused by the 
presence of in-situ soot. However, very little of that soot is released 
from the flame. There are enormous differences between soot in a flame 
and soot emitted from a flame.

The candle is a classic example. Its primary purpose is to generate soot 
-- without soot in a candle flame it would emit very little light. 
Comparatively little of the soot that is generated is actually emitted 
from the flame. Next time you are at a fancy dinner, place you spoon 
above the flame and see how much soot is released: there will be some, 
but surprisingly little. Put your spoon in the flame for the same amount 
of time and you'll soon see how much soot is within the flame.

Soot within flames is often highly desirable: it is one of the primary 
mechanisms for heat release. A typical furnace runs nonpremixed flames 
for the sole purpose of generating as much in-situ soot as possible to 
radiatively heat the furnace.


On 9/1/16 5:18 PM, Philip Lloyd wrote:
>
> There is quite a good pic of flames at various mixed levels in 
> https://en.wikipedia.org/wiki/Bunsen_burner. When there is no 
> premixing, the flame is yellow and dirty (not all carbon is combusted, 
> as in a candle flame). When you get to a stoichiometric flame, all the 
> combustion takes place at the blue cone – the almost invisible “flame” 
> above it is mainly hot gas radiating; minimal combustion takes place 
> there.
>
> Prof Philip Lloyd
>
> Energy Institute
>
> Cape Peninsula University of Technology
>
> PO Box 1906
>
> Bellville 7535
>
> Tel: 021 959 4323
>
> Fax: 086 778 0257
>
> Cell: 083 441 5247
>
> PA: Nadia 021 959 4330
>

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