Untitled - Aerobib - Universidad Politécnica de Madrid

12.1. INTRODUCTION 285
which preceded blow-off. Region 7 corresponds to vortex flames. Finally, under given
conditions, flames similar to the manometric and singing flames were also observed
by Barr. This incomplete enumeration of the types of flames observed gives idea on
the complexity of the phenomenon. Further data can be found in Ref. [4].
100
10
Extinction
2
Smoke
6
Lifted flames
Butane flow (cm /s)
3
1
0.1
5
4
Smoke point
1
Laminar
diffusion
flames
7
Extinction
Meniscus flames
3
Vortex flames
Convective flames
Extinction
0.01
1 10 100
1000 10000
3
Air flow (cm /s)
Figure 12.4: Flow limits for formation of enclosed diffusion flames.
The case of an open diffusion flame where the fuel jet discharges and burns in
an atmosphere at rest has been experimentally analyzed, among others, by Rembert
and Haslam [7] , Cuthbertson [8] , Gaunce [9], Hottel and Hawthorne [3], Wohl,
Gazley and Kapp [10], Barr and Mullins [11], Parker and Wolfhard [12] and Yagi and
Saji [13]. The fundamental results of their experiments are as follows:
1) When the Reynolds number of the jet at the mouth of a burner is small, a laminar
flame establishes.
2) The length of the flame increases when the flow rate of the jet is increased.
3) When Reynolds number is larger than a given value a turbulent region initiates