DIESEL ENGINE SPEED, FUEL CONTROLS, AND PROTECTION

DIESEL ENGINE SPEED, DOE-HDBK-1018/1-93 Diesel Engine Fundamentals FUEL CONTROLS, AND PROTECTION DIESEL ENGINE SPEED, FUEL CONTROLS, AND PROTECTION Understanding how diesel engines are controlled and the types of protective instrumentation available is important for a complete understanding of the operation of a diesel engine. EO 1.7 DESCRIBE how the mechanical-hydraulic governor on a diesel engine controls engine speed. EO 1.8 LIST five protective alarms usually found on mid-sized and larger diesel engines. Engine Control The control of a diesel engine is accomplished through several components: the camshaft, the fuel injector, 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 governor regulates the amount of fuel that the injector is to inject. Together, these three major components ensure that the engine runs at the desired speed. Fuel Injectors Each cylinder has a fuel injector designed to meter and inject fuel into the cylinder at the proper instant. To accomplish this function, the injectors are actuated by the engine's camshaft. The camshaft provides the timing and pumping action used by the injector to inject the fuel. The injectors meter the amount of fuel injected into the cylinder on each stroke. The amount of fuel to be injected by each injector is set by a mechanical linkage called the fuel rack. The fuel rack position is controlled by the engine's governor. The governor determines the amount of fuel required to maintain the desired engine speed and adjusts the amount to be injected by adjusting the position of the fuel rack. Each injector operates in the following manner. As illustrated in Figure 26, fuel under pressure enters the injector through the injector's filter cap and filter element. From the filter element the fuel travels down into the supply chamber (that area between the plunger bushing and the spill deflector). The plunger operates up and down in the bushing, the bore of which is open to the fuel supply in the supply chamber by two funnel-shaped ports in the plunger bushing. ME-01 Rev. 0 Page 30