Fault detection of injectors in diesel engines using vibration time-frequency analysis

In CI engines, injector spraying into the combustion chamber has extreme importance in fuel atomization and knocking control in the CI engines. Knocking and malfunction of engines due to faulty injectors can lead to efficiency reduction, damages, and acoustic noise. Much research is developing methods of engine knock detection. Hence, injector fault detection has not been addressed specifically, this research is focused on the subject and corresponding vibration amplitudes and frequencies, likely to cause the knock phenomenon. Welch test, Short-Term Fourier Transform (STFT), Wigner-Ville Distribution (WVD), and Choi-Williams Distribution (CWD) were employed for detailed scrutiny of vibrations generated by an under-load engine. For an ideal combustion, the acceleration peak values should be placed in the range of 0-10 kHz in time-frequency (TFR) diagram. While a faulty injection unit can cause components at higher frequency, between 10 and 25 kHz, in TFR diagram for each cylinder, and this can effects on the engine performance. Regarding the results which are presented in this research it infers that, in real-time performance monitoring of an engine, the STFT technique is more efficient for fault diagnosis of fuel injection nozzles and knock detection. By comparing vibration response of healthy and faulty injectors, the RMS and kurtosis of the faulty injectors showed an increase of 12.9% and 20.6% respectively.