Acoustic Emission Investigation on an Electronically Controlled Two-Stroke Low-Speed Marine Diesel Engine: in Axial and Vertical Directions

An experimental method in a real-working condition was conducted to collect acoustic emission (AE) signals emitted from cylinders of a large two-stroke low-speed marine diesel engine. Measurements were performed in an axial direction of the cylinder in medium-frequency (20–80 kHz) and high-frequency (100–900 kHz) ranges and in a vertical direction only in the medium-frequency range under two engine operating modes. The collected AE signals were analyzed in crank angle and crank angle–frequency domains. kurtosis and root mean square (RMS) parameters were employed to identify engine operating modes based on the obtained AE signals as well as investigate their characteristics. A fast Fourier transform (FFT) algorithm was also utilized to discover the frequency range of the AE signals. The results showed that only the AE signals generated by combustion processes, friction and wear, and exhaust valve opening (EVO) were partially detected. However, the AE signal radiated by the friction phenomenon was not apparent in the high-frequency range. Also, the combustion process had a strong influence on the remaining AE’s sources, especially in the axial direction of the medium-frequency range. Furthermore, the measurements should be implemented for the AE signals due to friction and wear in the medium and low frequencies; meanwhile, the combustion should be investigated in the frequency range of 200–300 kHz