Principles of naval engineering - Historic Naval Ships Association

Chapter 22. -DIESEL AND GASOLINE ENGINESTHERMOMETER-- OVERBOARD DISCHARGERESTRICTIONPRESSUREGAGESEA WATER INTAKE THRUHULL FITTING AND STRAINERFigure 22-28.— Salt water circuit of a closed cooling system.75.209Xengine be kept free from abrasion and that therebe a minimum of friction and wear. If slidingcontact is made by two dry metal surfacesunder pressure, excessive friction, heat, andwear result. Friction, heat, and wear can begreatly reduced if metal -to-metal contact isprevented by keeping a clean film of lubricantbetween the metal surfaces.Lubrication and the system which supplieslubricating oil to engine parts that involve slidingor rolling contact are as important to successfulengine operation as air, fuel, and heatare to combustion. It is important not only thatthe proper type of lubricant be used, but alsothat the lubricant be supplied to the engine partsin the proper quantities, at the proper temperature,and that provisions be made to removeany impurities which enter the system. Theengine lubricating oil system is designed tofulfill the above requirements.The lubricating system of an engine may bethought of as consisting of two main divisions,that external to the engine and that within theengine. The internal division, or engine part,of the system consists principally of passagesand piping; the external part of the systemincludes several components which aid in supplyingthe oil in the proper quantity, at theproper temperature, and free of impurities. Inorder to meet these requirements, the lubricatingsystems of many engines include, externalto the engine, such parts as tanks and sumps,pumps, coolers, strainers and filters, and purifiers.These parts and their relative locationfor one type of engine are shown in figure 22-29.The engine system which supplies the oilrequired to perform the functions of lubricationis of the pressure type in practically all moderninternal combustion engines. Even though manyvariations exist in the details of engine lubricatingsystems, the parts of such a system andits operation are basically the same, whetherthe system is in a diesel or a gasoline engine.Any variance between the systems of the twotypes of engines is generally due to differencesin engine design and in opinions of manufacturersas to the best location of the component parts ofthe system. In many cases, similar types ofcomponents are used in the systems of dieseland gasoline engines.TRANSMISSION OF ENGINE POWERThe fundamental characteristics of an internalcombustion engine make it necessary,in many cases, for the drive mechanism to577