Page 111 - Boiler plant and distribution system optimization manual

96 Boiler Plant and Distribution System Optimization Manual

Figure 9.9—The combustion re-
circulation pattern established
by main flame swirl to recircu-
late combustion products for
more complete and stable com-
bustion.

• It has an over-all color that may change The combustion problems which typically occur
as excess oxygen is decreased. Natural gas will be due to one or more of the following.
flames for instance, become more visible Observing oil flames provides important
or luminous with yellow or slightly hazy, information concerning the combustion process.
portions. Coal and oil flames become darker The combustion problems which typically occur
yellow and orange and may appear hazy in will be due to one or more of the following.
parts.
Sources of Problems
Although low excess-air operation is import- 1. Excess oxygen level.
ant, it is sometimes not possible to operate this 2. Oil temperature or pressure.
way because of combustion related problems. 3. Oil gun tip.
Observing oil flames provides important 4. Air register setting.
information concerning the combustion process. 5. Oil gun position.

Figure 9.10—Conventional feather or “jet” flame for
all purpose combustion chambers.
Figure 9.11—Headpin flame in which some slight
swirl is introduced for stability especially at low
firing rates.