Page 113 - Boiler plant and distribution system optimization manual

98 Boiler Plant and Distribution System Optimization Manual

Figures 9.18 through 9.24 demonstrate vari-
ous problems that may develop with typical burn-
ers.

Figure 9.16—A governing reaction in flames and
burners is the diffusion of oxygen into the fuel rich
zone to sustain combustion. In low excess air opera-
tions the rate of evaporation may exceed the mixing
of fuel and oxygen by turbulent diffusion yielding a
process of rich limit ignition. Figure 9.18—Shows the flame pattern for a nearly
ideal flame geometry.

THE IDEAL FLAME

• Flame barely clears burner throat.
• Flame is bright and smooth with light smoke
wisps on the end.
• Problems, none.

PROBLEMS THAT CAN OCCUR IN A
BURNER FLAME OF IDEAL GEOMETRY
Figure 9.17—This graphic shows how nitric oxide
Flame contains ragged sparks
concentration changes with swirl patterns, the peak
• Excess oxygen too high.
point in this graph corresponds to the ball type flame
in figure 9.12. On the left we have the long luminous • Oil too hot.
or fire hose type flames and on the right the conical
• Ash in fuel.
and flat type flames.
Flame very smoky looking
• Excess oxygen too low.

Flame black and oily-looking with no burning
near throat.
• Air register closed.