Determination of the response time of new generation electromagnetic injectors as a function of fuel pressure using the internal photoelectric effect

Very strict requirements referring to emission standards, the pollution of which is closely related to the quality of the combustion process, forces the manufacturers to introduce new solutions in the field of fuel injection, as well as adapt existing to more stringent standards. A noticeable trend in self-ignition engines is the return to injectors with electromagnetic control, due to the longer durability of the control element in relation to injectors with piezoelectric control. The use of electromagnetic injectors, however, required the introduction of numerous changes, resulting in a reduction in the number and weight of moving elements, which allowed to achieve greater precision of control and multiplication of the fuel dose. Due to the wide range of injector work pressures, it is necessary to determine the delay between the coil override and the beginning of the injection process, so that it is possible to precisely control the supply of fuel at each point of the engine's operation. In order to characterize the delay as a function of fuel pressure, the authors used the photoelectric effect. At the moment when the fuel stream interrupts the light source in the photoactive element, there is a voltage drop, on the basis of which it is possible to determine the actual start of the injection. The authors managed to show that the increase in fuel pressure in the reservoir significantly reduces the response time of the injector. Using the waveform curves, the relationship between the increase in the fuel dose for the measured cross section and the voltage drop in the photoactive element was also determined. It was also found, that the method basing on the use of a radiation source and a photoactive element can be used in the diagnostics of injectors to identify damaged friction pairs needle — body.