THE THERMODYNAMICS OF THE MARINE OIL ENGINE. 



By John F. Wentworth, Esq.^ Visitor. 



[Read at the twenty-second general meeting of the Society of Naval Architects and Marine Engineers, held in 



New York, December 10 and 11, 1914.] 



This paper is intended to present certain experimental data obtained by the 

 writer as well as to reintroduce certain old and well-established facts in a new garb 

 in order that the oil engine may be looked at from a new viewpoint. 



The marine oil engine is discussed because in the marine plant every condi- 

 tion must be considered. The marine plant, in its perfect form, must be capable 

 of running at full load with a maximum of power or of running at partial load with 

 a maximum efficiency; and last, but most essential at times, is the ability to run 

 at extreme slow speeds. The marine oil engine, to meet all conditions and take its 

 place as a perfect prime mover at sea, must be capable of being built in large single 

 units, which means that extreme pressures must be avoided. It is not intended to 

 go into all phases of this problem at length in the text, but rather to state the facts, 

 and in the plates accompanying this paper these facts may be studied more in de- 

 tail. It is true that the fundamental principles of the oil engine even to-day are not 

 widely known. A glaring example of the general misconception of these general 

 principles is found in the brief description of the Diesel oil engine published in 

 Technical Paper No. 37, issued by the Bureau of Mines, Department of the In- 

 terior, on the subject of Heavy Oil as a Fuel for Internal-combustion Engines, 

 1913. On page 8 of this paper we find this statement: — 



"The cycle of the Diesel engine, therefore, is to compress air to 450 or 500 

 pounds pressure per square inch, thereby generating a temperature of approxi- 

 mately 540° C. Into this highly heated air the fuel is injected during the return 

 or second stroke of the engine, in a finely atomized form, at such a rate as will 

 maintain an approximately constant temperature while burning and in such quan- 

 tity as will yield the required work for that stroke." 



Also: — 



"This high elevation of temperature by compression is a necessary part of 

 the improved method of using heat. It also causes the spontaneous ignition of the 

 charge of fuel, although that is not the chief reason for the high compression." 



Also, on page 9 : — 



"In general appearance these engines are like explosion engines, although not 

 built so heavily." 



