Experimental Study On The Removal Of Ultrafine Carbon Particles And Regeneration Of DPF By Packed-bed Discharge Non-thermal Plasma

Carbon particulate matter（PM）emissions have always been the focus of control of exhaust gas aftertreatment technologies for various diesel engine power machineries.PM has a wide distribution of particle size,and the ultrafine particles are extremely harmful to the human body and the environment.Diesel particulate filter（DPF）can efficiently filter PM in the exhaust flow,but it must timely remove the carbon deposited in the DPF,that is,the regeneration of the DPF.Non-thermal plasma（NTP）has strong oxidizing properties and can oxidize and PM under conditions far below the ignition temperature.And it is a new type of exhaust purification technology.The packed bed dielectric barrier discharge（PB-DBD）can produce large-volume,high-density NTP,which is better than ordinary DBD.In this paper,a self-designed PB-DBD reactor is used to conduct discharge tests to explore the influence of different dielectric particle size and shape on the characteristics of DBD,and use the optimized PB-DBD reactor to remove ultrafine carbon particles and low-temperature regeneration of DPF applications for experimental research.The main research contents are as follows:（1）The discharge gap of the PB-DBD reactor was packed with dielectric particles of different sizes（glass beads or glass sand）,and the partial discharge equivalent circuit and simplified model of the discharge gap were established,and the effects of particle size and shape on the discharge characteristics of the reactor were explored.The research results show that as the packing particle size decreases,the suppression effect of the surface discharge on the filamentary discharge is enhanced,and the discharge sustaining voltage and partial discharge tendency increase.When a partial discharge occurs,the effective dielectric equivalent capacitance is always smaller than the dielectric equivalent capacitance,and the gas gap equivalent capacitance is partially retained.Compared with the empty bed reactor,the average electric field in the PB-DBD reactor is increased by 3 to 4 times,and the ozone energy efficiency and output are increased by more than 20%and 15%respectively.（2）The optimized PB-DBD reactor was used to carry out an experimental study on the removal of ultrafine carbon particles by NTP.The carbon particle generator（DNP digital 3000）outputs the exhaust gas flow with controllable PM particle size distribution,and the influence of different PM distribution characteristics,reaction zone temperature and reactor inlet flow on the removal effect were explored.The research results show that the removal rate of the total particle number concentration of different parameter setting groups by NTP reaches more than 30%at room temperature.Increasing the temperature in the reaction zone can improve the removal effect,but the temperature should not be too high.At 100°C,the removal rate of ultrafine particles in the setting group 3 by NTP is 77.7%,and the removal amount is more than twice that at room temperature.The inlet flow rate of the reactor affects the mixing ratio of the NTP active gas with the gas flow of the original machine.The inlet flow rate is increased from 2 L/min to 5L/min,and the ultrafine particle removal rate first increases and then decreases.At 3 L/min,the maximum removal rate is 81.1%.At this time,the ratio of the flow rate of the active gas to the original machine gas flow is 1:2.（3）The optimized PB-DBD reactor was used to carry out an experimental study on NTP low-temperature regeneration of DPF.The reaction products,the amount of carbon deposits removed,and the internal temperature field of the DPF were used as evaluation parameters to explore the effects of different nitrogen addition and different NTP intake directions on the DPF regeneration effect.The research results showed that when the volume ratio of discharge reaction gas was 95%O₂+5%N₂,the volume fractions of CO and CO₂ of the reaction products were slightly higher than that of pure oxygen source,and the amount of carbon deposit removed was higher than that of other gas sources,and it had a better effect of DPF regeneration.The change of the NTP intake direction affects the sequence of removing PM at different positions in the DPF filter element.The regeneration direction was opposite to that of the forward intake,but the mass of carbon deposits removed by the forward intake in the same time was more and the PM oxidation reaction was more complete than the reverse NTP intake.Therefore,the regeneration effect of forward NTP intake is better than that of reverse NTP intake.