Diesel Engine FundamentalsDOE-HDBK-1018/1-93DIESEL ENGINESFigure 7 Diesel Engine Crankshaft and BearingsFlywheelThe flywheelis located on one end of the crankshaft and serves three purposes. First,through its inertia, it reduces vibration by smoothing out the power stroke as eachcylinder fires. Second, it is the mounting surface used to bolt the engine up to its load.Third, on some diesels, the flywheel has gear teeth around its perimeter that allow thestarting motors to engage and crank the diesel.CylinderHeadsandValvesA diesel engine's cylinder heads perform several functions. First, they provide the topseal for the cylinder bore or sleeve. Second, they provide the structure holding exhaustvalves (and intake valves where applicable), the fuel injector, and necessary linkages. Adiesel engine's heads are manufactured in one of two ways. In one method, eachcylinder has its own head casting, which is bolted to the block. This method is usedprimarily on the larger diesel engines. In the second method, which is used on smallerengines, the engine's head is cast as one piece (multi-cylinder head).Diesel engines have two methods of admitting and exhausting gasses from the cylinder.They can use either ports or valves or a combination of both. Ports are slots in thecylinder walls located in the lower 1/3 of the bore. See Figure 2 and Figure 3 forexamples of intake ports, and note their relative location with respect to the rest of theRev. 0ME-01Page 9
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