COMBUSTION AND FUELS 85 



Amount of Steam Used for Atomizing. During 1902 and 

 1903 the Bureau of Steam Engineering of the U. S. Navy 

 Department made an extensive series of tests of oil burners 

 using steam and air as atomizing agents. From the results of 

 these tests it is found that the atomization of each pound of oil 

 required the use of from .15 to 1 Ib. of steam, the average value 

 being about .55 Ib. For good performance, the value should lie 

 between .3 and .5 Ib. The amount of steam used for atomiza- 

 tion, expressed as a percentage of the total amount of steam 

 generated by the boiler, ranged from 1 to 10%, but the aver- 

 age was approximately 2%. The foregoing values refer to the 

 steam used for atomization only, whether directly or through 

 the medium of the compressor, and are representative of aver- 

 age practice. They do not include the steam required for the 

 oil-pressure pumps, which amounts to another 2%, approxi- 

 mately. Hence, in calculating capacities for an installation, 

 it will be safe to assume that 5% of the steam generated will 

 be utilized by the atomizing and pressure systems. 



Effect of Steam on Combustion. The steam that is used 

 for the purpose of atomizing the oil does not increase the total 

 heat resulting from combustion, although it may affect the 

 character of the chemical changes in certain parts of the 

 flame so as to produce a higher temperature at those points. 

 An impression that seems to have gained credence is that the 

 steam, under the effects of the high furnace temperature, is 

 dissociated into its elements, oxygen and hydrogen, and that 

 the combustion of the hydrogen thus set free increases the heat 

 of combustion. The impression is wrong, for it takes just as 

 much heat to break the steam up into its elements as is obtained 

 by the subsequent uniting of those elements. Consequently, 

 if the combustion is perfect, the steam that enters the furnace 

 passes up the stack as steam, carrying away heat with it, and 

 the greater the amount of steam introduced, the greater will 

 be the heat loss. Thus, the introduction of steam into the 

 furnace decreases the available heat rather than increases it. 



Excess of Air in Oil Burning. A pound of oil fuel of average 

 composition requires about 13 or 14 Ib. of air for its complete 

 combustion; however, a greater amount must be admitted to 

 the furnace to insure complete combustion, as the mixture of 



