Chapter 12 Internal Combustion Engine

l l l l l CHAPTER 12 INTERNAL COMBUSTION ENGINE CHAPTER LEARNING OBJECTIVES Upon 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. The engine that moves it is one of the most fascinating and talked about of all the complex machines we use today. In this chapter we will explain briefly some of the operational principles and basic mechanisms of this machine. As you study its operation and construction, notice that it consists of many of the devices and basic mechanisms covered earlier in this book. COMBUSTION ENGINE We define an engine simply as a machine that converts heat energy to mechanical energy. The engine does this through either internal or external combustion. Combustion is the act of burning. Internal means inside or enclosed. Thus, in internal combustion engines, the burning of fuel takes place inside the engine; that is, burning takes place within the same cylinder that produces energy to turn the crankshaft. In external combustion engines, such as steam engines, the burning of fuel takes place outside the engine. Figure 12-1 shows, in the simplified form, an external and an internal combustion engine. The external combustion engine contains a boiler that holds water. Heat applied to the boiler causes the water to boil, which, in turn, produces steam. The steam passes into the engine cylinder under pressure and forces the piston to move downward. With the internal Figure 12-1.-Simple external and internal combustion engine. 12-1