The analysis of acoustic emission signals from the cylinder head of a diesel engine for fault detection

There are many acoustic emission (AE) sources in a diesel engine. During an engine cycle, fuel injection, onset of combustion, valve impacts and piston slaps all produce AE effects. Because these events happen around the top dead centre, it is difficult to separate them for the purpose of combustion monitoring. This study focuses on characterising AE signals measured on the cylinder head of a diesel engine for injection fault diagnosis. Firstly, AE signals are analysed to understand AE signals in association with engine operating conditions and sensor placement. Then, faulty injectors are tested to evaluate AE based injection fault detection. The results from joint angular and frequency analysis has shown that AE can clearly monitor the changes in the combustion process due to its high signal to noise ratio in the high frequency range from 10kHz to 45kHz where other vibro-acoustic sources have little influence.