DEVELOPMENTS IN OIL BURNING. 



253 



CONTROL OF CAPACITY. 



This matter of adjustability of an oil burner, that is, the ability to change 

 the quantity of oil delivered in a given time without changing the oil pressure 

 or the velocity of the liquid through the tip, while attractive in idea and per- 

 haps well sustained in theory, has no particular value in practice. It is a 

 fact that the simpler forms of burners which do not possess this feature are 

 quite, if not more, successful in regular operation on shipboard. The manip- 

 ulation of the oil pressure acting on all burners at once presents in itself a 

 simple means for the control of output through a wide range ; a good burner 

 will atomize moderately heavy oil with an oil pressure as low as thirty pounds, 

 and from that up to two hundred or above. If this range is insufficient to 



Enlarged Views of Spindlb. 



Fig. 7. — Thornycroft Burner. 



meet the variable steam requirements, then it is easier and better to shut 

 down a portion of the burners entirely than to attempt to adjust each indi- 

 vidual burner separately, particularly as it is important to regulate the quan- 

 tity of air for combustion admitted to the furnace at the same time the quan- 

 tity of oil is varied. This air supply can easily be controlled for all burners by 

 regulating the draft pressure, and the air can be closed off entirely when a 

 burner is shut down. This puts the question of proper air supply more into 

 the hands of the designer, requiring the operator to determine only the proper 

 conditions of draft pressure for the plant as a whole, at the required capacity. 



