Research On Diesel Particulate Filter And Its Regeneration System

Particulate matter is the most important pollutant emissions of diesel engines,great harm to human health.With the gradual implementation of national emission regulations,diesel engines must be equipped with a post-treatment system to meet the emission requirements.Diesel Particulate Filter(DPF)is the most effective technology to reduce particulate matter(PM)emissions.DPF can capture more than 90%of the particulate matter.With the gradual accumulation of soot in the DPF,gradually increased engine back pressure will reduce the engine efficiency,increase fuel consumption.So there must be periodic or continuous removal of soot,which is called regeneration.In this paper,the Diesel Oxidation Catalyst(DOC)and Diesel Particulate Filter(DPF)coupling system are studied by bench test and numerical simulation.The DPF pressure drop characteristics were studied by the engine bench test.Based on the theory of packed bed and Darcy’s law,the mathematical model of DPF trapping and pressure drop was established.The DPF pressure drop increases linearly with exhaust temperature.The pressure drop increases rapidly in the DPF deep bed filtration stage and slowly in cake filtration stage.The one-dimensional simulation model of DPF was established by AVL-BOOST software,and the model parameters were calibrated by using experimental data.The average error of the simulation results is less than 5%.The pressure drop of DPF was further studied by the corrected simulation model,and the influence of the deep bed soot layer on the total pressure drop was greater than that of the cake layer,which contributed more than 40%of the pressure drop.The temperature rise characteristics of DOC were studied by engine bench test.The effects of different fuel injection strategies,DOC inlet temperature and exhaust flow rate on the temperature rise were studied respectively.Increasing inlet temperature and fuel injection or decreasing exhaust flow can result in rise of DOC outlet temperature,but the higher injection rate may lead to thermal damage of DPF as well as the leakage of HC.Then,a one-dimensional discrete mathematical model is established on the MATLAB/Simulink software.Based on the experimental data,the least squares method is used to identify the model parameters.Further,the state estimator based on the Extended Kalman Filter is designed to estimate the unmeasurable state of the DOC.The estimation value of DOC outlet temperature tracks closely with the measured value with error less than 5%.Based on the conventional method of soot estimation,a DPF equivalent circuit model is proposed.the DPF model using the volume flow and pressure drop measurements accurately calculate the flow resistance caused by soot.Then the MAP of flow resistance-temperature-soot load is established to estimate soot load.Under the condition of large exhaust flow rate,the simulation value of model pressure drop can track the measured value,the relative error is less than 10%,and the absolute error is less than 0.1 kPa.