Fuel Injection System Flashcards
fuel injection system requirements
meter or measure the correct quantity of fuel injected, time the fuel injection, control the rate of fuel injection, atomize or break up the fuel into fine particles according to type of combustion chamber, pressurize and distribute the fuel to be injected
desired condition is to create a homogeneous mixture in the combustion space, in the correct proportions, of the smallest possible fuel particles and Air
metering
the same quantity of fuel is delivered to each cylinder for each Power Stroke of the engine. Accurate metering causes the engine to operate at uniform speed with uniform power output
timing
the injection time ensures efficient combustion for maximum energy
rate of injection
rate of fuel injection determines rate of combustion
atomization
breaks up the fuel as it enters the cylinder into small particles which form a Mist like spray. helps to start burning process and ensures each particle of fuel will burn
pressurizing and distributing fuel
fuel pressure must be higher than that of combustion chamber to overcome combustion pressure. High pressure also ensures penetration and distribution of fuel in the combustion chamber
governor
regulates the flow of fuel
external fuel oil systems
fuel oil tank, fuel handling equipment
pumping of fuel
pumped from storage tank or day tank to fuel injection pumps on the engine
purifying fuel
centrifugal system. separates out heavy, solid contaminants
maintaining fuel pressure
fuel transfer pump ensures constant pressure to the injection system
fuel straining
filters large particles out of the fuel
original individual pump injection system
high pressure pumps and pressure operated spray valves are separate units
modified individual pump injection system
high pressure pump and injection nozzle for each cylinder are combined into one unit. Often referred to as a unit injector system
cetane number
rates a diesel fuel’s quality of ignition.
measures ignition delay, the time period between the start of the injection of the fuel and the start of the combustion of the fuel
In general, a higher cetane fuel will have a shorter ignition delay period than a lower cetane fuel.
