DIESEL ENGINE SPEED,DOE-HDBK-1018/1-93Diesel Engine FundamentalsFUEL CONTROLS, AND PROTECTIONDIESEL ENGINE SPEED, FUEL CONTROLS,AND PROTECTIONUnderstanding how diesel engines are controlled and the types of protectiveinstrumentation available is important for a complete understanding of theoperation of a diesel engine. EO 1.7DESCRIBE how the mechanical-hydraulic governor on adiesel engine controls engine speed.EO 1.8LIST five protective alarms usually found on mid-sized andlarger diesel engines.EngineControlThe control of a diesel engine is accomplished through several components: the camshaft, the fuelinjector, and the governor. The camshaft provides the timing needed to properly inject the fuel,the fuel injector provides the component that meters and injects the fuel, and the governorregulates the amount of fuel that the injector is to inject. Together, these three major componentsensure that the engine runs at the desired speed. FuelInjectorsEach cylinder has a fuel injector designed to meter and inject fuel into the cylinder at the properinstant. To accomplish this function, the injectors are actuated by the engine's camshaft. Thecamshaft provides the timing and pumping action used by the injector to inject the fuel. Theinjectors meter the amount of fuel injected into the cylinder on each stroke. The amount of fuelto be injected by each injector is set by a mechanical linkage called the fuel rack. The fuel rackposition is controlled by the engine's governor. The governor determines the amount of fuelrequired to maintain the desired engine speed and adjusts the amount to be injected by adjustingthe position of the fuel rack.Each injector operates in the following manner. As illustrated in Figure 26, fuel under pressureenters the injector through the injector's filter cap and filter element. From the filter element thefuel travels down into the supply chamber (that area between the plunger bushing and the spilldeflector). The plunger operates up and down in the bushing, the bore of which is open to thefuel supply in the supply chamber by two funnel-shaped ports in the plunger bushing.ME-01Rev. 0Page 30
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