Control of fuel through the injector, based on the observation of the electric current waveform

Abstract

The article discusses results of the laboratory experiment investigating the gas injector of the dual fuel engine supplied with diesel fuel and propane-butane mixture, mapping the real conditions of the injector operation. During generation of fuel doses, the current waveforms on the injector coil were registered. A detailed analysis of the variations of the function representing the current intensity and voltage, allows for determination of the lifting and closing points of the injector’s needle with the microsecond accuracy, based on the phenomenon of changes in injector core inductance during the needle movement. This enables optimation of the injector control. The coefficient of the fuel flow through the injector needle f_(c-s) has been developed, to be used in computations of the theoretical flow through the needle. Due to the above, the exponential increase in the fuel flow through the nozzle has been modelled, resulting from the exponential rise in the current pulse, performing the work of lifting the injector needle. The presented model is based on the analysis of the current waveforms. The authors do not analyse the mechanical forces counteracting the needle opening because change in the current and voltage at the injector coil defines precisely the actual position of the needle, and it determines the mass of the flowing fuel. On the basis of the presented paper, injector control (control of the solenoid valve) can be optimised and the losses resulting from the time shift in the injection pulse can be reduced.