Pang -
Luminous flames are flames that have less access to oxygen than the
non-luminous ones. Bunsen burners make a great example. The barrel of
the burner has small holes at the base of it that you can open or close
with the knob. If you close the holes, the only place the flame can get
oxygen is at the top of the tube, giving you a luminous flame. But if
you open the holes, the flame can get oxygen from the top and the
bottom both, making it burn better - a non-luminous flame.
The reason that we see so many luminous flames is that most fires
don't have the convenient 'back-entrance' for oxygen that the bunsen
burner does. It's hard for most flames to get oxygen because there's so
much flame in between the source of the fire and the air. So most
flames don't get as much oxygen as they need to burn efficiently.
-Tamara
(published on 10/22/2007)
