PRINCIPLES OF NAVAL ENGINEERING 



TOP CENTER 





Figure 22-1.— Relationship of events and strokes in 



54.19A 

 a 4 -stroke cycle diesel engine. 



event in some 2-stroke cycle diesel engines ends 

 a few degrees after the intake event ends.) When 

 the scavenging event ends, the cylinder is 

 charged with the air which is to be compressed. 

 The compression event (2) and (2') takes place 

 during the major portion of the upstroke. The 

 injection event (3) and (3') and ignition and com- 

 bustion (4) and (4') occur during the latter part 

 of the upstroke. (The point at which the injection 



ends varies with engines. In some cases, it ends 

 before TDC; in others, a few degrees after TDC.) 

 The intense heat generated during the compres- 

 sion of the air ignites the fuel-air mixture and 

 the pressure resulting from combustion forces 

 the piston down. The expansion (5 and 5') of the 

 gases continues through a major portion of the 

 down stroke. After the force of the gases has 

 been expended, the exhaust valve opens (6') and 



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