Hi Crispin and Paul,
Bluff bodies (BB) are refered to in fluid dynamics generally for which
combustion of gases is a subset. The definition of a BB
"a solid obstruction in a fluid stream, having a broad flattened front
and providing a shelter for small scale turbulence and zones of low
velocity; a stability assister."
(from the North American Combustion Handbook (Vol 2))
So does a screen qualifies as a bluff body? It can be a flame holder as
can a single wire in the path. We have a screen burner on our propane
refrigerator but the flame is down sream of the screen. I don't think
the screen glowed.
Paul's burner appears to have good flame holding at the holes in the
burner head. He mentions the screen protects these flames from the wind
and that combustion is below the screen. So in this case it is not
clear that there is any combustion happening in or on the outer surface
of the screen although it could be invisible to our eyes. So you could
say that there are two screens, the holes in the burner head being the
first screen, the BB perhaps, and the second is simply a radiator/wind
screen. The small pressure drop across the screen also helps distribute
the flow evenly.
All in all, great result= great design.
Alex
On 04/03/2012 8:26 AM, Crispin Pemberton-Pigott wrote:
Paul, what you are describing are the effects of a 'bluff body'. It is why they
are sometimes used above a flame.
Crispin
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