| In the context of increasingly strict emission regulations and greater emphasis on energy efficiency and emissions reduction in ship power,the utilization of common rail fuel systems in diesel engines has become widespread.While offering precise fuel injection control and flexible injection control strategies,the complex structure and cumbersome working process of the common rail fuel system have led to reduced reliability of high-pressure common rail diesel engines,necessitating regular operation,and maintenance as well as health management.However,given the high costs and risks associated with experimental operations and the difficulties in acquiring various fault data,the establishment of an accurate common rail fuel system model for fault simulation has become crucial to obtain difficult sensor data,revealing fault mechanisms,and performing fault diagnosis.Against this background,this paper aims to conduct the following research:In this study,a simulation model for a common rail fuel system is developed using the AMESim simulation software.To establish boundary conditions,the electrical components and fuel characteristics are analyzed based on the composition and principle of the common rail fuel system.The simulation model is built using fundamental mathematical equations,including the plunger motion continuity equation,the fuel compressibility formula,and the bond graph principle,along with boundary conditions.The accuracy of the simulation model is verified by comparing the fuel supply flow characteristics,fuel injection flow characteristics,and rail pressure characteristics obtained from the simulation with experimental data.The results show that the accuracy errors are all within 10%,indicating the reliability of the developed common rail fuel system simulation model.Secondly,the failure mechanism,operation process,and impact of fuel injectors,highpressure oil pumps,and common rail pipes are analyzed to design the Failure FMEA table of the common rail fuel system.The FMEA table is used to sort the risk order number and select the more harmful typical faults.The common rail fuel system simulation model is utilized to simulate three typical faults,namely injector nozzle hole blockage,nozzle hole wear,and plunger pump plunger wear,and to analyze the results of the simulated fuel injection pump pressure and injector cavity pressure.Subsequently,a common rail fuel system test bench is constructed to simulate two typical faults of nozzle clogging and needle valve wear.The rail pressure data is measured and recorded,and the same fault is simulated in the common rail fuel system simulation model under the same working conditions,with the rail pressure value also recorded.By comparing the experimental value and the simulated value,it is observed that the feedback on the impact of the fault is consistent,with an average error of less than 10%.Additionally,the common rail fuel system response to the same fault at different stages is accurately captured,thus verifying the capability of the common rail fuel system simulation model to effectively simulate the impact of different degrees of faults.In conclusion,this study proposes a reliability evaluation model for the common rail fuel system based on the degradation failure theory.The proposed model can acquire the degradation characteristic quantity through the common rail fuel system simulation model and fit it with an appropriate degradation trajectory model to estimate the corresponding expected failure time.Furthermore,the K-S test is conducted to obtain the reliability function of the system and perform reliability evaluation at the critical node.Based on the obtained results,this study puts forward recommendations for the operation,maintenance,and health management of the common rail fuel system to enhance the reliability of the common rail diesel engine. |
