An investigation into diesel engine air-borne acoustics using continuous wavelet transform

Abstract

The emitted acoustic signals from diesel engines carry useful indicators about their operating conditions and health status. Unfortunately, those signals are very complex, contain numerous numbers of sources and corrupted by subnational amount of noise. This makes it difficult to extract those condition indicators via the use of conventional time and frequency domain analysis techniques. This paper studies the characteristics of diesel engine air-borne acoustic signals using time-frequency domain techniques. One analysis technique is investigated; continuous wavelet transform (CWT). First, some of the mathematical background of the CWT is reviewed. Second, the detection capabilities of this technique are evaluated using air-borne acoustic signals collected from diesel engine in acoustically untreated laboratory. Consequently, some engine operating conditions and faults are investigated using the CWT techniques. The achieved results prove the technique’s sensitivity to engine speed and load variations. More important the CWT shows excellent capabilities in detecting engine’s injection process and lubrication related faults at early stages.