| Diesel engine is an important source of power for social production and life.It is widely used in ships,nuclear power,chemical industry,and transportation.The structure of the diesel engine is complex and there are many excitation sources.The unbalanced inertial force and the detonation impact force caused the frequent failure of the moving parts and the wearing parts.At present,there are many research results on diesel gear faults and crank linkage faults,but the research methods are relatively traditional and there is a lack of accurate analysis methods for the faults caused by other related parts.Therefore,faults often cannot be solved once and for all.If a diesel engine fails,it will require downtime and maintenance,which brings huge economic losses to enterprises and the society.It will even become out of control and endanger personal safety and affect the reputation of the company.Therefore,it is of great social and economic value for the diesel engine to improve the diagnosis level,develop on-line fault monitoring and diagnosis technology,and realize fault early warning to reduce the probability of malignant faults and reduce the probability of fault losses.This paper focus on the frequent occurrence crank connecting rod mechanism and gear train failure during the actual operation of the diesel engine,which seriously affects the safe and stable operation of the unit.Taking into account the lack of actual fault data,some fault simulation experiments are difficult,high-risk,and costly,simulation technology is used to study on the crank connecting rod mechanism and gear train failure monitoring and diagnosis,combined with experimental and practical project case verification.The main research content of the paper is as follows:(1)Study on the fault of gear teeth broken caused by crankshaft axial motion,a multi-body dynamic simulation was conducted to investigate the effect of crankshaft axial motion on the dynamic load of the transmission gear.The dynamic change law of gear load was obtained.On this basis,the influencing factors of thrust bearing wear rate were studied,and the change law of thrust bearing wear rate was obtained.The research results lay a foundation for the analysis,monitoring and diagnosis of diesel crankshaft axial motion and broken tooth faults.(2)Aimed at the faults of clearance abnormality and wear defects in the pressure zone of the bigend bearing,the study is carried out based on elastohydrodynamic lubrication simulation of the bearing.The variation law of bearing lubrication parameters and the bearing bush temperature distribution characteristics in the fault condition were obtained.The research results lay a foundation for the bearing fault analysis,and diagnosis based on temperature monitoring.(3)Aimed at the problem that influence of crankshaft axial motion on the dynamic load of the gear is difficult to verify through experiment.The fault case of camshaft gear teeth broken,which is caused by crankshaft axial motion is used to verify it.Based on the characteristic of temperature change after the failure of the conrod bigend bearing,an experiment was carried out to simulate the wear of the bigend bearing,and the measured results of the bearing temperature change were used to verify the simulation results.Combined with the fault of the seawater pump gear teeth broken,the vibration signal characteristics of the unit under different fault conditions were compared and analyzed in detail.The result lays the foundation for such fault monitoring and diagnosis based on vibration monitoring.The results in this paper reveal the failure mechanism of diesel gear train and crank connecting rod mechanism and the characteristics of the monitoring signal changes.It has been applied to the actual fault monitoring and diagnosis of diesel engines,improved the efficiency of fault analysis and diagnosis and optimized diesel engine fault monitoring and measuring points location.The result of this paper formed a theoretical guidance and achieved good results. |
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