DEVELOPMENTS IN OIL BURNING. 257 



firmly in place. This has a hole in the center corresponding with the 

 diameter of the central chamber of the tip, and small slots or ducts, extending 

 tangentially from the edges of the central opening outward toward the per- 

 iphery of the washer, long enough to overlap the annular channel of the nozzle 

 and put it in communication with the central chamber. The effect is that 

 when the burner is assembled with the washer in place, oil is delivered through 

 the ducts tangentially to the central chamber where it rapidly revolves and 

 almost immediately is discharged through the orifice in the tip. 



CHARACTER OF MECHANICAIv SPRAY AND EFFECT ON COMBUSTION. 



In order to correct a popular fallacy I beg to call attention here to the 

 fact that no mechanical atomizer produces a revolving spray, but the particles 

 of oil fly off in straight lines under the influence of centrifugal force, thus 

 forming a hollow, conical spray. The fineness of this spray, i. e., the minute- 

 ness of the particles forming it, has a most important bearing on the results 

 obtained in the furnace. It is possible with some forms of steam atomizers 

 to atomize oil so finely that no flame at all will be produced, the incandescent 

 combustion chamber being filled merely with a clear, invisible gas and every 

 brick being discernible. I doubt if this condition of flameless combustion 

 can be produced with mechanical atomizers and heavy oil, nor is it desirable 

 under any circumstances for the simple reason that it costs too much. 



With the production of flame, however, furnace design assumes an added 

 importance, for the flame must be distributed evenly and without localizing 

 on the heating surfaces of the boiler, and the gases must be given time and 

 space in which to expand and burn as nearly as possible to completion before 

 being cooled and the flame extinguished by contact with the tubes of the 

 boiler. These points become exceedingly vital when the boiler is forced to 

 the requirements now demanded in naval service. 



FURNACE DESIGN. 



Having an atomizer, therefore, that will produce a fine spray with heavy 

 oil and which is simple, reliable and easily handled, the problem becomes 

 one, not of oil burner, but of furnace design and air distribution. Our 

 work has been carried on, until recently, entirely with the Babcock and 

 Wilcox marine boiler, a design having a furnace ideally suited for any volatile 

 fuel and particularly for oil. A longitudinal section through this boiler fitted 

 with mechanical atomizers is shown in Fig. 10. It will be seen that the 

 characteristics of this furnace are : Large volume in proportion to the heating 

 surface of the boiler; upward slope of the roof toward the rear, resulting in 



