Chapter 22. -DIESEL AND GASOLINE ENGINES 



2- START 

 INJECTION 



3-END 

 INJECTION 



4-EXPANSION 5-SCAVENGING 6-SUPERCHARGE 



Figure 22-10.— Events in operating cycle of an opposed-piston engine. 



75.10 



combustion possible, and those which minimize 

 and dissipate heat created by combustion and 

 friction. Since combustion requires air, fuel, 

 and heat (ignition), systems providing each may 

 be found on some engines. However, since a 

 diesel engine generates its own heat for com- 

 bustion within the cylinders, no separate ignition 

 system is required for engines of this type. The 

 problem of heat, created as a result of combus- 

 tion and friction, is taken care of by two separate 

 systems— cooling and lubrication. The functions 

 of the parts and systems of engines which operate 

 on the principles already described are dis- 

 cussed briefly in the following paragraphs. 



MAIN STR UCTUR AL PAR TS. -The main pur- 

 pose of the structural parts of an engine is to 

 maintain the moving parts in their proper rela- 

 tive position. This is necessary if the gas pres- 

 sure produced by combustion is to fulfill its 

 function. 



The term frame is sometimes used to identify 

 a single part of an engine; in other cases, it 

 identifies several stationary parts fastened to- 

 gether to support most of the moving engine 

 parts and engine accessories. For the purpose 



of this discussion, the latter meaning will be 

 used. As the load-carrying part of the engine, 

 the frame of the modern engine may include 

 such parts as the cylinder block, crankcase, 

 bedplate or base, sump or oil pan, and end 

 plates. 



The part of the engine frame which sup- 

 ports the engine's cylinder liners and head 

 or heads is generally referred to as the cyl- 

 inder block. The blocks for most large engines 

 are of the welded-steel type construction. Blocks 

 of small high-speed engines may be of the en 

 bloc construction. In this type construction, the 

 block is cast in one piece. Two types of cylinder 

 blocks coming to Navy service are shown in 

 figures 22-11 and 22-12. The block shown in 

 figure 22-11 is representative of blocks designed 

 for some large engines with in-line cylinder ar- 

 rangement. The block illustrated infigure 22-12 

 is representative of blocks constructed for 

 some engines with V-type cylinder arrangement. 



The engine frame part which serves as a 

 housing for the crankshaft is commonly called 

 the crankcase. In some engines, the crankcase 

 is an integral part of the cylinder block (see 

 fig. 22-11), requiring an oil pan, sump, or base 



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