The primary filter is required to remove larger particles. Two stage filter system typically uses a primary filter on the inlet side of the fuel transfer pump and a secondary filter on the outlet side. In many cases, a course screen is also located at the fuel intake located in the fuel tank. As shown in Figure 1, fuel systems can contain one or more stages of filtration. Fuel filters help reduce damage and premature wear from contaminants by retaining very fine particles and water to prevent them from entering the fuel injection system. Trouble-free operation of a diesel injection system is possible only with filtered fuel. Also, the excess fuel that is heated by its contact with hot engine components can be returned to the tank or fuel filter to improve the vehicle’s low temperature operability. This extra fuel flow can serve a number of important functions including providing extra fuel to help to cool injectors, pumps and other engine components and maintaining a more constant temperature of the fuel in the entire fuel system. Some fuel systems, such as those based on a distributor type pump, incorporate a mechanically driven supply pump and the high pressure pump in one unit.įuel pumps are commonly sized to deliver more fuel than is consumed by the engine at any particular operating system. For example, so called tandem pumps are units that incorporate a fuel pump and a vacuum pump for the brake booster. Some fuel pumps may be incorporated into units that serve other functions. Pumps driven by the engine are attached to the engine. Using an electrically driven fuel pump allows the pump to be placed anywhere in the fuel system including inside the fuel tank. Modern day fuel pumps can be electrically or mechanically driven by the engine. The fuel supply pump, often referred to as the lift pump, is responsible for drawing fuel from the tank and delivering it to the high pressure pump. It must also use some means to prevent excessive pressure accumulation such as a vent or a safety valve. The fuel tank should be corrosion-resistant and leakproof to pressures of at least 30 kPa. The fuel tank also serves as an important means of dissipating heat from the fuel that is returned from the engine. The fuel tank is a reservoir that holds the fuel supply and helps maintain its temperature at a level below its flash point. Examples of Low Pressure Fuel Systems for Heavy-Duty and Light-Duty Diesel Vehicles Figure 1 illustrates two examples of schematics for low pressure fuel systems, one for a heavy-duty diesel truck and one for a light-duty diesel passenger car. In addition, many fuel systems contain coolers and/or heaters to better control fuel temperature. The low pressure side of the fuel system consists of a number of components including the fuel tank, one or more fuel supply pumps and one or more fuel filters. This is the role of the low-pressure fuel system components. In order for the fuel injection system to fulfill its purpose, fuel must be transferred to it from the fuel tank. Fuel Injector and Fuel Injection Nozzle.A number of injection nozzle designs and different actuation methods have been developed for use with different types of fuel injection systems. The high-pressure side components include a high pressure pump, accumulator, fuel injector and fuel injector nozzle. The low-pressure components include the fuel tank, fuel supply pump and fuel filter. Abstract: The fuel injection system can be divided into low-pressure and high-pressure sides.
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