Experimental Investigation of Vibration Signals from an On-Rotor Sensing for Diesel Engine Crankshaft Lubrication Monitoring

Engine vibrations associated with crankshaft bearing lubricity and asperity friction tends to be characterized by weak signatures, modulated in high frequency resonance and signals are often contaminated by other complex engine excitations, structural vibrations and background noise. The effects lead to a challenging diagnostics and detection procedure due to weak features even amidst interferences. To resolve the problem of poor signal resolution and complex modulation, an on-rotor sensing (ORS) method composed of a tri-axial MEMS accelerometer was implemented to fully capture the rotational dynamics of the engine crankshaft. In this work, the crankshaft lubrication performance is experimentally studied using ORS MEMS accelerometer installed directly to the end of the rotating crankshaft. Vibrational signals acquired from engine are analysed to study the effect of lubricant rheological properties and temperature on engine crankshaft vibrations. It has found that kurtosis variations with oil temperature show good agreement with classic stribeck characteristics, allowing the identification of different lubrication regimes. In the meantime, engine body vibrations acquired by conventional accelerometer show little correlations with lubrication changes. These findings confirm ORS signal possess rich information to indicate engine crankshaft lubricity.