Model-based Of Diesel Oxidation Catalyst Fault Diagnosis Research

The fault of Diesel O xidation Catalytic conve rter(DOC)have directly influence on the regeneration of Diesel Particulate Filter(DPF)and emission level.It as an important part of the aftertreatment system can not only get rid of the vast majority of carbon monoxide(CO)and hydrocarbons(HC)and soluble organic matter(SOF),but also can enhance the performance of the Selective Catalytic Reduction(SCR)and Diesel Particulate Filter(DPF).When DPF active regeneration,DOC can oxidate the high concentration hydrocarbon of the entrance makes the DOC outlet temperature reaches 550℃ to achieve the temperature of DPF active regeneratio n.When the DOC catalyst aging and poisoning.the conversion efficiency of DOC will drop,the DOC outlet temperature can achieve active regeneration needs and the emission of the diesel engine exceed the regulation limits.Therefore,this paper based the large temperature changes of the DOC outlet when the DPF active regeneration to bulid the DOC fault diagnosis strategy to evaluate the health of the DOC using the Matlab/Simulink.One dimensional DOC simulation model was established using AVL-BOOST software.Firstly,consulting a large of literature to study the mechanism of chemical reaction in the DOC confirmed the main chemical reactions of three kinds of gas composition: carbon monoxide(CO),nitrogen oxides(NOx)and hydrocarbons(HC)and the mass and energy transfer process of the three kinds of gas.Then,according to the mass conservation and energy conservation equations of gas phase and solid phase of the DOC to build the one-dimensional simulation model and using the genetic algorithm to identify the parameters of the chemical reaction kinetic model of the three chemical components in the chemical reaction.Finally,the simulation results of the DOC simulation model as follows: 1.The influence of the chemical composition on the DOC outlet temperature was analyzed in the DOC.2.The effects of different inlet temperature and volume flow rate of DOC inlet on the conversion efficie ncy of the DOC were analyzed.3.When the DPF active regeneration,the simulation of different fault conditions of the DOC by changing the conversion rate of hydrocarbon catalytic in the DOC to obtain the temperature variation of the DOC outlet.According to the AVL-BOOST simulation results,make the corresponding simplification of the DOC model.When DPF active regeneration,building a simplified model of the DOC using Matlab/Simulink.Then,using the least squares method to identify the parameters of the chemical reaction kinetics of the DOC by using the experimental data.Finally,by using the principle of the Kalman filter to build DOC state observer.Owing to the principle of the Kalman filter mainly aimed at the object who was a linear system,however,the DOC model is nonlinear.Therefore,according to the principle of Kalman filter to build DOC Extended Kalman Filter(EKF)after linearing the system of the DOC.The research of the DOC fault diagnosis strategy based on DOC extended Kalman state observer.The DOC model constructed by AVL-BOOST is regarded as the controlled object.DOC simplified model as reference model.Changing the hydrocarbon conversion rate in the AVL-BOOST simulation model to simulate the different failure degree of the DOC,then,using the obtained the temperature value of the DOC outlet with different fault degree as a signal of the temperature sensor to input the extended Kalman state observer.It can be concluded that the extended Kalman state observer can track the temperature signal and compare the observation and the reference value of the hydrocarbon conversion efficiency to monitor the failure of the DOC.