PRINCIPLE OF NAVAL ENGINEERING 



developed within an engine. Since the tempera- 

 ture of combustion alone is about twice that at 

 which iron melts, it is apparent that, without 

 some means of dissipating heat, an engine would 

 operate for only a very limited time. Without 

 proper temperature control, the lubricating-oil 

 film between moving parts would be destroyed, 

 proper clearance between parts could not be 

 maintained, and metals would tend to fail. 



Of the total heat supplied to the cylinder of 

 an engine by the burning fuel, only one-third, 

 approximately, is transformed into useful work: 

 an equal amount is lost to the exhaust gases. 

 This leaves approximately 30 to 35 percent of 

 the heat of combustion which must be removed 

 in order to prevent damage to engine parts. The 

 greater portion of the heat which may produce 

 harmful results is transferred from the engine 

 through the medium of water; lubricating oil, air, 

 and fuel are also utilized to aid in the cooling of 

 an engine. All methods of heat transfer are uti- 

 lized in keeping engine parts and fluids (air, 

 water, fuel, and lubricating oil) at safe operating 

 temperatures. 



In a marine engine, the cooling system may 

 be of the open or closed type. In the open sys- 

 tem, the engine is cooled directly by saltwater. 



In the closed system, fresh water (or an anti- 

 freeze solution) is circulated through the engine. 

 The fresh water is then cooled by salt water. 

 In marine installations, the closed system is 

 the type commonly used; however, some older 

 marine installations use a system of the open 

 type. The cooling systems of diesel and gasoline 

 engines are similar mechanically and in func- 

 tion performed. 



The cooling system of an engine may include 

 such parts as pumps, coolers, engine passages, 

 water manifolds, valves, expansion tank, piping, 

 strainers, connections, and instruments. The 

 schematic diagrams in figure 22-27 and 22-28 

 show the parts and the path of water flow in the 

 fresh- and sea-water circuits of one arrange- 

 ment of a closed cooling system. 



Even though there are many types and models 

 of engines used by the Navy, the cooling systems 

 of most of these engines include the same basic 

 parts. Design and location of parts, however, 

 may differ considerably from one engine to 

 another. 



ENGINE LUBRICATING SYSTEMS. -It is 

 essential to the operation of an engine that the 

 contacting surfaces of all moving parts of an 



FRESH WATER PUMP 



DUPLEX PRESSURE 

 GAGE 



CONNECTION 



LUBE OIL HEAT 

 EXCHANGER 



THERMOMETER 



FRESH WATER HEAT 

 EXCHANGER 



FRESH WATER PUMP- 



EXHAUST MANIFOLD EXTENSION 

 ATMOSPHERIC VENT 



^EXPANSION TANK 

 SUPERCHARGER 



TEMPERATURE INDICATOR-^ MhERMOSTAT 



ADAPTER 



RESTRICTION 



NOZZLE 

 BOX 



COUPLING 



75.208X 



Figure 22-27.— Fresh water circuit of a closed cooling system. 



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