In-depth diagnostics of electrohydraulic injectors for battery-powered fuel injection system of vehicle powertrain

Introduction. The technical condition of electro-hydraulic injectors of the fuel injection system has a significant impact on the efficiency and reliability of power units in diesel vehicles. To promptly detect and eliminate any injector failures during operation, it is necessary to follow periodical control and diagnostics procedures. Diagnosing injectors removed from the power unit with special stands is characterized by the highest accuracy, though it allows checking general technical condition of the injectors, without specifying particular faults. In-depth diagnostics with fault localization will affect optimal decisions to be made regarding technical measures during injector repair. The research objective is to evaluate the possibility of increased in-depth failure detection during bench diagnostics of injectors by analyzing the nature of relations between diagnostic parameters and the values of test fluid pressure at the bench liquid accumulator inlet with constant time of control pulses.
Materials and methods. A mathematical model of an electrohydraulic injector is presented in the form of a system of differential equations describing the dynamics of the processes in the injector. During numerical experiments, the pressure of the test liquid at the battery inlet and the following structural parameters were changed within specific ranges: multiplier plunger sleeve gap, needle guide nozzle, and the leakage of the control valve and that of the sealing ring. The time of the electrical control pulses remained constant.
Results. The graphs demonstrating relations between the diagnostic parameters (cyclic delivery, average flow rate of test fluid in the return line and delay time in the end of injection) and the pressure of the test fluid have been presented for different values ​ ​of the structural parameters.
Discussion and conclusion. As a result of the conducted research, differences were revealed in the nature of the relations between some diagnostic parameters and the accumulator inlet pressure with deviations in particular structural parameters. The additional information obtained during diagnostics will allow us to identify deviations in certain structural parameters, which will increase the level of detecting failures. The paper presents a block diagram of the proposed diagnostic algorithm.

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