Principles of naval engineering - Historic Naval Ships Association

Chapter 22. -DIESEL AND GASOLINE ENGINESI. MAIN BEARING JOURNAL- FRONT2. COUNTERWEIGHT3. MAIN BEARING JOURNAL-INTERMEDIATE4. CONNECTING ROD JOURNAL- NO. 35. MAIN BEARING JOURNAL- REAR6. BOLTING FLANGE -TIMING GEAR7. DOWEL- FLYWHEEL8. RING GEAR9. RETAINING BOLT HOLE10. DOWEL HOLEI I. PULLER SCREW HOLE12. FLYWHEEL13. LUBRICATING OIL HOLESFigure 22-19.— One-piece six-throw crankshaft with flywheel.75.81Xare finished, are commonly referred to as theintake and exhaust systems . These systems areclosely related and, in some cases, are referredto as the air systems of an engine. A crosssectionalview of the air systems of one typeof high-speed diesel engine is shown in figure22-20.The following information on air systemsdeals primarily with the systems of diesel engines;nevertheless, much of the informationdealing with the parts of diesel engine air systemsis also applicable to most of the partsin similar systems of gasoline engines. However,the intake event in the cycle of operationof a gasoline engine includes the admission ofair and fuel as a mixture to the cylinder. Forthis reason, the intake system of a gasolineengine differs, in some respects, from that ofa diesel engine. (See subsequent section on fuelsystems.)A discussion of the air systems of deiselengines frequently involves the use of two termswhich identify processes related to the functionsof the intake and exhaust systems. These termsscavengingand supercharging— and the processesthey identify are common to many moderndiesel engines.In the intake systems of all modern 2-strokecycle engines and some 4-stroke cycle engines,a device, usually a blower, is installed to increasethe flow of air into the cylinders. Thisis accomplished by the blower compressing theair and forcing it into an air box or manifold(reservoir) which surrounds or is attached tothe cylinders of an engine. Thus, an increasedamount of air under constant pressure is availableas required during the cycle of operation.The increased amount of air available as aresult of blower action is used to fill the cylinderwith a fresh charge of air and, during theprocess, aids in clearing the cylinder of thegases of combustion. This process is calledscavenging . Thus, the intake system of someengines, especially those operating on the 2-stroke cycle, is sometimes called the scavengingsystem. The air forced into the cylinder565