Research On The Influencing Factors Of Exhaust Heat Assisted NTP To Regenerate DPF

Diesel particulate filter?DPF?regeneration can be implemented by non-thermal plasma?NTP?technology at low temperatures.However,the oxidation reactions between NTP and PM are significantly weakened by the high-speed exhaust flow during on-line DPF regeneration,reducing the DPF regeneration efficiency.In this paper,a strategy of DPF regeneration after engine flameout was proposed.DPF regeneration was performed using NTP technology aided by exhaust waste heat,avoiding the influence of exhaust flow.The main studies and results are as follows:?1?An experimental system of DPF regeneration was constructed to investigate the regeneration effect in which DPF was not heated by an external heat source.Aided by the exhaust waste heat after engine outage,an experimental study on DPF regeneration was conducted.The DPF regeneration effect was evaluated by the exhaust backpressure change before and after regeneration.The oxidation process of PM was investigated through analyzing the volume fraction of CO_x and the temperature variation inside DPF.Thermogravimetric analysis was also performed to study the influence of NTP treatment on physicochemical properties of PM.The results showed that a good DPF regeneration effect was implemented using NTP technology aided by exhaust waste heat with a 69%reduction in the backpressure of DPF.The oxidative reactions released heat,causing the internal temperature of DPF rising instead of dropping.In the regeneration process,the oxidation area extended from the front of DPF to the back.The soluble organic fraction?SOF?in the remnant deposit reduced after DPF regeneration.NTP treatment reduced the activation energy of SOF and dry soot?DS?.?2?DPF regeneration was implemented at different initial regeneration temperatures using NTP injection system.In the process of PM collection,engine exhaust particle sizer was used to measure the particle size distribution before and after DPF,in order to analyze the DPF trapping efficiency at different trapping times.The emission level of PM was evaluated by mass addition of the filter paper after PM sampling.Combined with the DPF trapping efficiency,the mass of PM deposited in DPF was computed.Comparison analysis of deposit removal mass,backpressure drop,and internal temperature variation was then implemented to investigate the influence of initial regeneration temperature on DPF regeneration.The results showed that 12.5 g of PM was deposited in DPF with a high filtration efficiency of about 90%.The strategy of100°C initial regeneration temperature showed the better DPF regeneration effect,as the deposit removal rate and percentage drop of the backpressure both maximized at the initial temperature of 100°C.?3?On the basis of optimizing the initial regeneration temperature,DPF regeneration was investigated with different carbon deposit masses.DPF regeneration process and effect were evaluated by monitoring the volume fraction of regeneration products,the residual O₃concentration and the internal temperature of DPF.The heat durability of the regeneration method was also assessed by the temperature peak and gradient inside DPF.The results revealed that the residual O₃ concentration decreased and the utilization efficiency of NTP increased as the carbon deposit mass increased.Without influence of exhaust backpressure on the engine normal operation,DPF regeneration efficiency could be improved through postponing regeneration.Temperature peak and gradient were both much lower than the failure limitation,indicating the outstanding heat durability of this regeneration method.