CHAPTER 22 



DIESEL AND GASOLINE ENGINES 



Much of the machinery and equipment dis- 

 cussed in the preceding chapters utilizes steam 

 as the working fluid in the process of converting 

 thermal energy to mechanical energy . This chap- 

 ter deals with internal combustion engines, in 

 which air (or a mixture of air and fuel) serves 

 as the working fluid. The internal combustion 

 engines considered are those to which the 

 thermodynamic cycles of the open and heated- 

 engine types^ apply. In engines which operate 

 on these cycles, the working fluid is taken into 

 the engine, heat is added to the fluid, the 

 energy available in the fluid is utilized, and 

 then the fluid is discarded. During the process, 

 thermal energy is converted to mechanical 

 energy. The purpose of this chapter is to pre- 

 sent the basic theory and the fundamental 

 principles underlying the energy conversion 

 in internal combustion engines, and the functions 

 of the engine parts, accessories, and systems 

 essential for the conversion. No attempt is 

 made to describe design, construction, models, 

 etc., except as necessary to make the theory of 

 operation and the function of components readily 

 understandable. 



Internal combustion engines are used ex- 

 tensively in the Navy, serving as propulsion 

 units in a variety of installations such as ships, 

 boats, airplanes, and automotive vehicles. Eh- 

 gines of the internal combustion type are also 

 used as prime movers for auxiliary machinery. 

 Internal combustion engines in a majority of 

 the shipboard installations are of the recipro- 

 cating type. In relatively recent years, engines 

 of the gas turbine type have been placed in Navy 

 service as power plants. Gas turbine engines are 

 discussed in chapter 23 of this text. 



Thermodynamic cycles are discussed in chapter 8 of 

 this text. 



RECIPROCATING ENGINES 



Most of the internal combustion engines 

 in marine installations of the Navy are of the 

 reciprocating type. This classification is based 

 on the fact that the cylinders in which the 

 energy conversion takes place are fitted with 

 pistons, which employ a reciprocating motion. 

 Internal combustion engines of the reciprocating 

 type are commonly identified as diesel and gaso- 

 line engines. The general trend in navy service 

 is to install diesel engines rather than gasoline 

 engines unless special conditions favor the use 

 of the latter. 



Most of the information on reciprocating 

 engines in this chapter applies to diesel and 

 gasoline engines. These engines differ, how- 

 ever, in some respects; the principal dif- 

 ferences which exist are noted and discussed, 



Basic Principles 



The operation of an internal combustion 

 engine of the reciprocating type involves the 

 admission of fuel and air into a combustion 

 space and the compression and ignition of the 

 charge. The resulting combustion releases gases 

 and increases the temperature within the space. 

 As temperature increases, pressure increases 

 and forces the piston to move. This movement is 

 transmitted through a chain of parts to a shaft. 

 The resulting rotary motion of the shaft is 

 utilized for work; thus, heat energy is trans- 

 formed into mechanical energy. In order for 

 the process to be continuous, the expanded 

 gases must be removed from the combustion 

 space, a new charge admitted, and then the 

 process repeated. 



In the study of engine operating principles, 

 starting with the admission of air and fuel and 

 following through to the removal of the expanded 

 gases, it will be noted that a series of events 



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