In some cases, rail pressures can reach 300 MPa. ![]() The rail pressure can be controlled to a value that depends on the needs of any particular engine operating condition. In most cases, a metering valve at the high pressure pump controls the high pressure fuel delivery to the rail. The volume of the rail varies from only a few cubic centimeters in passenger cars, to as much as 60 cm 3 in heavy-duty applications. The rail is a thick walled tube designed to act as an accumulator to prevent significant pressure drop at the full fueling rate by providing hydraulic capacitance to the high pressure circuit. With increased use of multiple injections and the need to accurately control small fuel injection quantities starting at about the Euro 4 phase, manufacturers have paid more attention these seemingly mundane components. The sizing of these components has a significant impact on critical fuel injection variables such as the dwell time between multiple injections and the minimum fuel injection quantity. In modern common rail systems, the injector supply pipe dimensions and rail volume are critical parameters that can affect injection system dynamic performance. Several types of injectors can be used in common rail systems, including servo controlled electrohydraulic injectors and direct acting injectors. High pressure pump designs are evolving to achieve higher efficiency of the fuel injection system and to facilitate accurate rail pressure control. Radial, unit and in-line pumps are used in commercial common rail systems. The thermal expansion compensator of the spreader body of the injector and the piezo ceramic, which operates on a hydraulic principle, is mounted above the piezo actuator, thus providing fuel flow.Abstract: The components of a common rail fuel injection system include the rail, a high pressure pump and fuel injectors. The sand activator directly pushes the needle of the injector, so that very precise injection is achieved without stopping. ![]() The injector consists of three parts, the injector servo valve, the piezo actuator and the compensation element, which are arranged in a row one after the other. In a piezo injector, a multi-layer ceramic element is used as a so-called piezo pole of interconnected elements. in case they are exposed to electrical voltage, they have mechanical displacement. To increase precision, the operating pressure is increased to 2000 bar, and the mechanism that drives them is based on a piezo system that provides high speed and accuracy. The role of injectors is to inject a certain amount of fuel very precisely into the chamber. ![]() The CRDI system operates at high pressures with flexible fuel delivery control.īecause the injection is fully electronically controlled, multiple injections can be made and high injection pressures can reduce exhaust emissions and fuel consumption, with excellent driving performance and low noise. The main advantage of CRDI systems over traditional fuel injection systems is that high injection pressures are always available and the fuel injection time is independent of the crankshaft angle position. Therefore, precise injector control is one of the most important parts of CRDI engine control. The operational performance of injectors in CRDI diesel engines have an impact on exhaust emissions. In CRDI diesel engines, piezo injectors have gradually replaced electromagnetic injectors, due to the speed of reaction of the injectors.
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