Study On Control Strategy Of Regeneration System Of Dieselparticulate Filter

Diesel particulate trap(DPF)is one of the most effective means to deal with exhaust pollutant emissions.Relatively speaking,the catalyst coating technology of DPF carrier is very complete.At present,the biggest bottleneck of this technology is regeneration control technology.DPF regeneration timing is judged too early,the regeneration frequency is too high,it will accelerate the aging of the carrier and reduce the fuel economy of the engine;the timing of regeneration is too late,the carbon load accumulated in the carrier during regeneration will be too much,and the regeneration temperature will be too high.The carrier is prone to burning.In addition,after determining the regeneration timing,it is also necessary to manage the temperature during the regeneration process,both to prevent the regeneration temperature from being too high,to damage the post-treatment system,and to avoid the temperature at the inlet of the post-treatment system being too low.The fuel cannot be fully oxidized,causing secondary pollution.Therefore,in this paper,the DPF regeneration control strategy is designed for the DPF regeneration technology problem,and the effectiveness of the control strategy and model algorithm is verified by simulation experiments.The main contents and results of this paper are as follows:(1)Construct a post-processing system controlled model.It mainly includes engines,catalytic oxidizer(DOC)and particle trap(DPF)models.Through the bench test,the exhaust temperature and exhaust back pressure of the engine and after-treatment system are obtained under partial working conditions.The controlled model is off-line calibrated based on the bench test to ensure that the controlled model can accurately reflect the physical output characteristics of the research prototype..Considering the use of the engine gantry for the verification of the control strategy,the soot loading cycle is long and the cost is too high,so the above-mentioned controlled model will be used later in this paper to quickly verify the control strategy.(2)Design a carbon load estimation model for the particle trap.The relationship between the exhaust back pressure and the loading of soot particles in the particle trap carrier is derived,and the carbon load estimation model based on exhaust back pressure is established.Based on the soot collection,active regeneration and passive regeneration process in the carrier.Based on the relationship between the consumption of particulate matter,a carbon loading estimation model based on chemical reaction was established.In addition,in the process of establishing the carbon load estimation model,the effects of diesel transient conditions such as EGR rate,transient airfuel ratio,ash and exhaust volume flow on the exhaust pressure difference are considered.Designing two carbon load estimation models can improve the accuracy of the carbon load estimation in the particle trap and compensate for the lack of measurement accuracy of the differential pressure sensor when the small exhaust flow is small.(3)Design the exhaust temperature feedback controller at the outlet of the catalytic oxidizer.In order to make the exhaust gas temperature control at the outlet of the catalytic oxidizer more accurate,the mathematical model of the DOC heat transfer process is established according to the law of conservation of energy and the temperature feedback controller is established according to the PID theory.(4)Co-simulation using MATLAB/Simulink and AVL BOOST to verify the effectiveness of the control strategy and control model.Firstly,the basic parameters of the regeneration control system are determined through simulation test.The parameters mainly include the lowest exhaust gas temperature at the DOC inlet,the target value of the outlet exhaust temperature and the oxygen content required for the active regeneration reaction.Threshold and verification stages were selected as representative of medium and high load conditions and WHTC test cycle as boundary conditions.In addition,the regeneration interruption strategy in the control strategy was verified.