lllllCHAPTER 12INTERNAL COMBUSTION ENGINECHAPTER LEARNING OBJECTIVESUpon completion of this chapter, you should be able to do the following:Explain the principles of a combustion engine.Explain the process of an engine cycle.State the classifications of engines.Discuss the construction of an engine.List the auxiliary assemblies of an engine.The automobile is a familiar object to all of us. Theengine that moves it is one of the most fascinating andtalked about of all the complex machines we use today.In this chapter we will explain briefly some of theoperational principles and basic mechanisms of thismachine. As you study its operation and construction,notice that it consists of many of the devices and basicmechanisms covered earlier in this book.COMBUSTION ENGINEWe define an engine simply as a machine thatconverts heat energy to mechanical energy. The enginedoes this through either internal or external combustion.Combustion is the act of burning. Internal meansinside or enclosed. Thus, in internal combustionengines, the burning of fuel takes place inside theengine; that is, burning takes place within the samecylinder that produces energy to turn the crankshaft. Inexternal combustion engines, such as steam engines, theburning of fuel takes place outside the engine. Figure12-1 shows, in the simplified form, an external and aninternal combustion engine.The external combustion engine contains a boilerthat holds water. Heat applied to the boiler causes thewater to boil, which, in turn, produces steam. The steampasses into the engine cylinder under pressure andforces the piston to move downward. With the internalFigure 12-1.-Simple external and internal combustion engine.12-1
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