Numerical Simulation On Loading And Regeneration Performance Of CDPF Of Heavy Diesel Engine

Catalytic Diesel Particulate Filter technology is widely used to reduce PM emissions of diesel engines.However,after long-term operation of diesel engines,the deposited ash will cause problems such as CDPF catalyst deactivation.Therefore,in order to meet the stricter PM limit requirements of emission regulations,this article focuses on the impact of ash amount on the working process of CDPF,and conducts an in-depth analysis of application issues related to capture performance and regeneration performance.This paper aims to accurately study the pressure drop and internal chemical reaction of CDPF,establish a one-dimensional reaction kinetic model of CDPF based on the experimental data of the reference,and calibrate and verify the parameters of the relevant pressure drop model and the regeneration reaction model.Based on the validated model,the influence of ash on the capture performance and regeneration performance of CDPF is studied.The simulation results show that the deposition of ash will increase the total pressure drop of CDPF and decrease the limit soot load;the formation of ash layer is beneficial to increase the filtration efficiency of the carrier,and the formation of ash blockage will reduce the filtration efficiency.When the permeability of the ash layer is greater than the wall permeability,the formation of the ash layer is beneficial to reduce the pressure drop of the system.Further analysis of the influence of ash on passive regeneration performance,comparison of DPF fuel additive regeneration and CDPF catalytic regeneration,found that the deposition of ash will cause the deactivation of the precious metal catalyst,inhibit the NO oxidation reaction,and cause the soot oxidation rate to decrease.However,for the DPF fuel additive regeneration method,ash deposition at the end can increase the temperature of the carrier,which is beneficial to increase the soot oxidation rate.This paper optimizes the structure of the CDPF in order to improve the capture performance,and studies the influence of exhaust parameters on the regeneration process.The results show that the reasonable combination of carrier pore density and pore size is beneficial to reduce pressure drop and improve filtration efficiency.The optimal range of pore density and pore size is about 260 to 300 cpsi and 10μm.The soot regeneration rate in CDPF is mainly affected by the concentration of reactants and the reverse diffusion capacity of NO₂.As NO₂ is used as an oxidant,the greater the concentration,the lower the regeneration equilibrium temperature;the increase in exhaust flow shortens the reaction time and increases the reverse diffusion resistance.The soot oxidation rate decreases and the equilibrium temperature rises;the greater the initial soot load,the greater the resistance to reverse diffusion of NO₂,the smaller the passive regeneration rate,and the greater the equilibrium temperature.The O₂ concentration affects the NO oxidation reaction and thus the soot oxidation rate.The equilibrium temperature decreases with the increase of the O₂ concentration;Analyzing the degree of influence of these factors on the balance characteristics,it can be known that NO₂ is the most critical factor,the influence of exhaust flow is greater than that of O₂ and the initial carbon loading has minimal impact on it.The outlet NO₂/NO_xratio is related to both the NO conversion rate and the soot regeneration rate.The outlet NO₂/NO_x ratio reaches its maximum at 340℃,and the initial soot loading has little effect on the outlet NO₂/NO_x ratio;at a given temperature,The NO₂/NO_xemission ratio increases with the increase of NO₂concentration and O₂concentration,and after340℃,NO₂ concentration has no effect on the NO₂/NO_x emission ratio;the increase in exhaust flow will make the NO₂/NO_x emission ratio reach the peak temperature Increase,and the ratio of NO₂/NO_x emissions decreases accordingly.