Zhu J.

Using vibration monitoring and fault diagnosis can improve the reliability and efficiency of diesel engines. The working conditions of diesel engine components can be detected by monitoring the cylinder cover vibration signals. This paper conducts an investigation on diesel engine condition monitoring using cylinder cover vibration signals. In order to analysis these vibration signals, both time series analysis and Fourier spectrum method are adopted. The characteristics of cylinder cover vibration signals excited by valve impacts and combustion forces are discussed, and some criteria suitable for diesel engine vibration monitoring and fault diagnosis are proposed. The experimental investigations were carried out on a medium speed four-stroke 6-cylinder marine diesel engine. The cylinder cover surface vibration signals are measured and analyzed for diagnosing the working conditions of valve clearances and engine cylinder loads. The analytic and experimental investigations indicate that the variations in valve clearance and engine load can be distinguished by use of cylinder cover vibration signals. The results show that it is viable and effective to detect the variations in valve clearance and engine cylinder load from cylinder cover vibration signals. Furthermore, this investigation shows that autoregressive spectrum is smoother than Fourier spectrum, with more accurate frequency location, so it is more suitable to diesel engine condition monitoring and fault diagnosis.