Research On Fault Diagnosis Method Of Abnormal Injection In Electronic Fuel System

As one of the important components of high pressure common rail diesel engine,the working status of electronic fuel control system directly affect the working performance of high pressure common rail diesel engine.The injector is the core part of the electronic fuel system.The working environment of the injector is extremely harsh: the nozzle directly contacts with the fuel and is easily affected by the fuel quality.In addition,in the harsh environment of high temperature and high pressure during the combustion in the cylinder,it is very prone to failure.When the fuel injector has abnormal injection failure,it will directly affect the fuel injection quality,lead to the decrease of combustion efficiency and the aggravation of emissions,reduce the performance index of the high pressure common rail diesel engine,and even lead to the failure of other parts of the high pressure common rail diesel engine and endanger the safety of the machine and workers.Therefore,accurate prediction and diagnosis of electronic fuel system injection fault is great significance to ensure the work efficiency and safety of high pressure common rail diesel engines.The pressure waveform and fluctuation frequency in the high-pressure pipeline of the electronic fuel control system reflect the working state of the high pressure common rail diesel engine.When the abnormal injection failure occurs,the fuel injection volume is changed,resulting in the pressure fluctuation change.The use of pressure signal in fault diagnosis of electronic fuel system has been paid more and more attention by researchers.How to extract effective fault characteristic information from pressure signal to accurately identify the fault type and fault location of high pressure common rail diesel engine is the focus of diesel engine fault diagnosis research.In this paper,a fault feature extraction and diagnosis method based on pressure fluctuation is studied for abnormal injection caused by injector fault.Firstly,the causes and effects of common faults in the electronic fuel system are analyzed,and a fault mechanism analysis and diagnosis scheme based on simulation and experiment methods is designed for the fuel injector blockage and needle valve stuck failure.Secondly,according to a high pressure common rail system,a simulation model of electronic control fuel system based on AMESIM was established and tested.Based on this model,the fluctuation mechanism of normal and abnormal injection was studied,and the influence law of needle valve motion state and pressure fluctuation was obtained,and the influence of failure on the frequency component of pressure fluctuation is also analyzed.Thirdly,the fault feature extraction method of the Hilbert-Huang Transform is studied.This paper optimizes the endpoint effect and false mode in the Hilbert-Huang Transformation.The optimized Hilbert-Huang Transformation was applied to EMD decomposition and Hilbert Transformation of the pressure signals of common rail and high pressure tubing,obtaining the IMF component and corresponding Hilbert Marginal Spectrum.According to the components of pressure failure frequency,the normalized energy values of IMF3,IMF4,IMF5 and IMF6 of common rail pressure as well as IMF1,IMF2 and IMF5 components of high pressure tubing were extracted as the characteristic parameters of fault diagnosis.Finally,the experimental platform of electronic fuel control system was built to simulate the fault of injector,and the pressure data of different working conditions were measured.The method of Hilbert-Huang Transformation proposed in this paper was used to extract fault characteristics,and SVM classifier was used for training and pattern recognition,realizing fault diagnosis of fault injector in electronic fuel system.The experimental results show that this method can effectively diagnose the abnormal injection fault of electronic fuel system.