[Stoves] Are we being bluffed....or no?

Richard Stanley rstanley at legacyfound.org
Sun Mar 4 11:57:07 CST 2012


Andrew Crispin,

And this (bluff body) in itself: Is it  is enough to explain Paul's noted reduction of boiling time by half ? 
 
Richard

On Mar 4, 2012, at 8:23 AM, Alex English wrote:

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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