Internal combustion engine lubricating oil condition monitoring based on vibro-acoustic measurements

Modern internal combustion engine maintenance programmes incorporate various methods and techniques for early fault detection and diagnosis to maintain efficiency, low pollution and high reliability and to avoid catastrophic failures. Lubrication oil related faults are among those faults that may lead to such consequences. This research has been conducted aiming at engine lubrication oil condition monitoring intrusively by analysing the engine airborne acoustic signals. The structure-borne acoustic signals were measured using an accelerometer mounted on the thrust side of the 1(st) cylinder and the airborne acoustic signals were recorded using a microphone placed 0.5 m away from the engine block facing the 1(st) cylinder and I m high from the floor. The signals are then band-pass filtered and transformed to the frequency domain, where the amplitudes of the frequency components of these signals are analysed and compared to the base-line signals. The mean amplitudes of the spectral components in the frequency band 1 kHz to 3 kHz werefound directly proportional to the engine speed and load. It was also found that the RMS values of this frequency band are affected by the lubricating oil conditions. These results show that it is possible to use airborne acoustic signals to evaluate the quality of lubrication.