Research On Model-based Particulate Matter Load Estimation In Diesel Particulate Filter

The sustainable development of domestic automobile industry faces thechallenges of energy crisis and environmental pollution.With more frequentatmospheric smog and stringent vehicle emission regulation，which puts forward strictrequirements of diesel soot emission，the higher purified performance of diesel engineaftertreatment is necessary for soot emission control. Now diesel particulate filter(DPF) is recognized as one of the most effective technology to reduce soot emission.In order to reduce the influence of the increasing of back pressure on diesel enginefuel economy and power performance,which causes by particulate matter load in theDPF sustainedly,it needs to be regenerated regularly.DPF regeneration faces theproblems of incomplete regeneration and unsafe regeneration（DPF burning-out andrupture，etc）.Accurately judging the regeneration time of DPF becomes the key tosolve these problems.The essence of accurately judging regeneration time needs toaccurately estimate particulate matter load in DPF.Traditional method to estimateparticulate matter load is difficult to apply in real-time,and its precision needs to befurther improved.Therefore,this paper establishes a DPF particulate matter load modelbased on MATLAB/Simulink platform,which can be applied to real-time computingof ECU,then carry out the research on Model-based particulate matter load estimationin diesel particulate filter.Considering the complex characteristics of one-dimension and three-dimensionDPF modeling, this paper builds particulate matter load model based on packed bedtheory and zero-dimensional lumped parameter method.First of all, DPF wall isdivided into several discrete layers based on the packed bed filtration theory,deep bedfiltration process is built based on the Brownian diffusion deposition mechanism andinterception deposition mechanism.Then,a distribution coefficient is introduced,whichrealizes particulate matter load distribution between on-the-wall and in-the-wall.Thus,particulate matter load process modeling is realized without considering passive regeneration.Finally,combining with global heterogeneous chemical reaction(NO2assisted oxidation, etc) which may happen in particulate matter load process,fourmodes of zero-dimensional DPF lumped parameters mass and energy balance modelare built based on the starting reaction temperature,and thus particulate matter loadprocess modeling is realized,considering the effect of passive regeneration.For control parameter of DPF particulare matter load estimate model, parameteridentification method is put forward based on linear fitting and least squares.Theidentification of the DPF filtration parameters and chemical kinetic parameters inselected steady-state loading conditions is realized based on the experimental data.The DPF particulate matter load estimation model is validated through bench test,and the simulation results of the DPF particulate matter load estimation model arealso analyzed. Validation experiment includes two groups of experiments:one group isdiesel engine aftertreatment system with only DPF,the other one with both DOC andDPF.Experiments in each group separately include clean DPF pressure drop test andDPF steady-state load test.DPF particulate matter load estimation model is validatedindirectly by comparing clean DPF pressure drop,DPF steady-state load pressure dropcharacteristics predicted from the model and from the test.The results show that theprediction of clean DPF pressure drop and DPF steady-state load from the model andtest results has good aggrement.The DPF particulate matter load estimation model proposed above is carried outthrough Simulink simulation software.The simulation results show that the estimationprecision of particulate matter load is increased,for that the influence of the passiveregeneration on particulate matter load is considered in model-based DPF particulatematter load estimation. And this model realizes the track of DPF particulate matterload and pressure drop characteristics in different time during the particulate matterloading process.Also,the establishment of mathematical model of DPF particulatematter load estimate contributes to the development of model-based regenerationcontrol strategy for diesel particulate filter.