Simulation And Experimental Study On Typical Faults Of Keymoving Parts Of Diesel Engine

Diesel engine is an important power source of social production and life.It has complex structure,harsh working environment and as a result frequent mechanical faults.Among these faults,the faults of key moving parts are very common.The faults of piston cylinder knocking,misalignment of shaft system,deviation of instantaneous speed measurement in misfire diagnosis,and abnormal valve clearance faults are typical.Aiming at these faults,simulation and experimental research is carried out in this paper as follows.Aiming at the cylinder knocking fault,the forces acting on piston are analysed,the vibration laws of piston knocking are explored by dynamic simulation.It is pointed out that the accelerations of four knocks in one cycle increase with the increase of diesel engine speed and piston clearance,and the vibration phases of knocks delay with the increase of diesel engine speed and piston clearance.Some results are verified on the diesel engine fault test bench.The research results pave the way for a better understanding of diesel engine cylinder knocking vibration and realizing online warning of cylinder knocking faults.Aiming at the misalignment fault of gear coupling,the characteristics of axial friction force produced by misalignment of gear coupling are analyzed,and the dynamic simulation model of shafting including gear coupling is established.Through dynamic simulation analysis,it is pointed out that the misaligned teeth coupling produces axial friction force,this force causes abnormal crankshaft axial movements.The simulation results through a case of wear fault of thrust bearing in practical engineering is validated in this paper.The purpose of this part is to provide a more accurate data analysis approach for the accuracy of fire fault diagnosis.For the deviation problem of instantaneous speed measurement in misfire fault diagnosis,the source of deviation is theoretically analyzed,and the influence laws of various factors on the deviation are investigated through dynamic simulation.Based on this,an optimized instantaneous speed measurement and calculation method is proposed.According to the simulation experiment of diesel engine misfire fault,the instantaneous speed obtained by the optimized instantaneous speed measurement method clearly shows the characteristics of misfire fault.The purpose of this part is to optimize the fault diagnosis method based on instantaneous speed.In addition,the cylinder head vibration signals of cylinder misfire and abnormal valve clearance faults simulated on the diesel engine fault test bench are analyzed.The experimental results are expected to provide relevant experimental experience for fault feature extraction of these two kinds of faults.