DIESEL ENGINE SPEED,
Diesel Engine Fundamentals
FUEL CONTROLS, AND PROTECTION
DIESEL ENGINE SPEED, FUEL CONTROLS,
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.
DESCRIBE how the mechanical-hydraulic governor on a
diesel engine controls engine speed.
LIST five protective alarms usually found on mid-sized and
larger diesel engines.
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.
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.