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About Diesel Fuel Injection Equipment

9/6/2013 12:59:12 PM | by Anonymous

Diesel Fuel Injection Equipment

Diesel fuel injection equipment is found in most diesel enginesnowadays except for some tractors and scale model engines, where diesel fuel is injected directly into the cylinder in a process known as direct fuel injection, and the combustion starts in a depression at the crown of the piston. A single mechanized plunger fuel pump operates at high pressure, driven by the engine crankshaft. Each engine cylinder has a corresponding plunger that measures the precise amount of fuel and the timing of the injection. The injectors are spring-loaded and are very precise, opening and closing at specific pressures and also have solenoids that are operated by an electrical control unit. This differs from other gasoline engines as most use port injection or a carburetor. For the former, the fuel is injected outside the cylinder, just before the intake stroke of the piston. In the latter, all the air and fuel is mixed before entering the cylinder.


Most modern diesel engines make use of Common Rail or Unit injector direct injection systems. For the former, a high pressure fuel rail feeds individual solenoid valves and for the latter, the injector nozzle and pump are combined to form a single component and the device is lubricated and cooled by the fuel itself. Another type of injection is the Swirl Injector, where diesel is injected in a way that forms a thin sheet of swirling liquid, to improve the efficiency of mixing and atomization.


Another form of diesel fuel injection equipment is the indirect diesel injection, where fuel is first delivered into a pre-chamber before the cylinder, before the turbulence created in the chamber causes the fuel to move into the cylinder. This allowed the pressure of the injector to be lower and made the engine quieter and cheaper to produce as compared to a direct fuel injection system. However, the efficiency of the system was also reduced due to the increased heat loss and restriction of the combustion burn caused by the pre-chamber. Thus, the direct injection system is still used for vehicles on roads. The indirect injection system is more commonly used in all-terrain vehicles.


The most complex piece of diesel fuel injection equipment is the injector, because it must be able to stand the high pressure and temperature inside and still deliver the diesel fuel in a fine mist. The mist must be evenly distributed in the cylinder so some engines use special induction valves or other devices to do this.


Larger diesel engines nowadays have advanced computer control systems that have sensors measuring a large variety of factors such as surrounding air temperature and oil temperature and thus can adjust the timing of fuel injections or compression so the ambient temperature does not affect the engine. Without a system like this, in cold weather, the engine might not be able to start as the engine is not hot enough to ignite the diesel fuel. For smaller diesel engines, a glow plug is used in situations like this. A glow plug is a wire, heated through electricity, which raises the temperature of the air and combustion chamber.


Diesel fuel is obtained from the refinement of crude oil, like gasoline, but unlike gasoline it is much heavier and oilier. Since it is heavier, it evaporates slowly – it has a boiling point above water’s. Diesel also has a higher energy density, so diesel engines nowadays have better mileage compared to similar gasoline engines. Diesel also produces much less global warming-causing emissions such as carbon monoxide, hydrocarbons and carbon dioxide. However, diesel produces large amounts of nitrogen compounds and soot when combusted, so diesel engines nowadays are equipped with catalytic converters and filters to reduce pollution.

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