Keywords: diesel engines, vibration diagnosis, main journal bearings, wear detection, oil film pressure, oil film thickness, bearing load, crankshaft centre, simulation, strain, bearing wear
Vibration diagnosis of main journal bearings for diesel engines
A comprehensive summary of the vibration diagnosis techniques used to detect the wear of the main journal bearings in a diesel engine is presented. The load of the main journal bearing, the minimum thickness of the oil film, the oil film pressure and the locus of the crankshaft centre have been calculated based on the measured thermal parameters. Simulated wear experiments for the main journal bearing have been carried out in laboratory conditions. The strain and vibration on the main journal pedestals in the vertical direction were measured under various working conditions. The strain signals on the main journal bearing pedestal are related to the oil film forces, damped by the lubricant oil. The excitation sources and the vibration characteristics of the main journal bearing pedestal system were analysed by measuring the vibration signals. The relationships between the feature parameters of the vibration signals and the wear conditions of the main journal bearing have been obtained. It is promising, therefore, to develop and apply the vibration diagnosis technique further to detect the wear conditions of the main journal bearings online.