Diagnostics and identification of injection duration of common rail diesel injectors

In this paper, we study the diagnostics and iden-
tification of injection duration of common rail (CR) diesel
pilot injectors of dual-fuel engines. In these pilot injec-
tors, the injected volume is small and the repeatability of
the injections and identification of the drifts of the injec-
tors are important factors, which need to be taken into ac-
count in achieving good repeatability (shot-to-shot with
every cylinder) and therefore a well-balanced engine and
reduced overall wear. A diagnostics method based on anal-
ysis of CR pressure signal with experimental verification
results is presented. Using the developed method, the rel-
ative duration of injection events can be identified. In the
method, the pressure signal during the injection is first ex-
tracted after the control of each injection event. After that,
the signal is normalized and filtered. Then a derivative of
the filtered signal is calculated. Change in the derivative
of the filtered signal larger than a predefined threshold
indicates an injection event which can be detected and
its relative duration can be identified. The efficacy of the
proposed diagnostics method is presented with the exper-
imental results, which show that the developed method
detects drifts in injection duration and the magnitude of
drift. According to the result, ≥ 10 µs change (2%, 500 µs)
in injection time can be identified.