Research On Soot Accumulation And Continuous Regeneration Characteristics Of Diesel Particulate Filter From Diesel Engine

Diesel particulate filter（DPF）has been seen as an indispensable aftertreatment device to reduce the PM and PN emissions of diesel engine.Continuous regeneration technology（CRT）has advantages of simple structure and wide regeneration temperature range.Gas conversion,pressure drop,soot accumulation and regeneration performance are the main characteristics of CRT.In this study,ash distribution factor and new cell structure were put forward.The main characteristics of DPF were comprehensively studied by utilizing AVL software code,as well as the effects of exhaust and structural parameters on CRT performance.The goal of this paper is to provide theoretical reference for CRT research and structure optimization.The effects of exhaust and structural parameters on DOC gas conversion performance were studied.With increase of temperature,the conversion rates of CO and C₃H₆ increase,while that of NO increases first and then decreases.With increase of mass flow rate,the conversion rates of CO,C₃H₆ and NO show descending trend.The O₂ and NO concentrations in exhaust gas are of great advantage to the conversion of NO.CPSI has little influence on NO conversion at higher exhaust temperature.The soot accumulation performance of DPF was studied.The soot distribution in DPF filter is nonuniform,and both ends of DPF filter contain higher soot load than the middle part.In radial direction,soot load of DPF center is the largest.Ash deposited as plug has lower pressure drop at higher soot capacity and lower ash load.Moreover,ash deposited as cake layer is not conducive to soot accumulation and pressure drop performance.The effect of exhaust parameters on CRT pressure drop and regeneration performance was studied.The maximum temperature and soot regeneration position move toward to the end of DPF along filter direction.The exhaust temperature of CRT balanced regeneration state is within the range of 250-350℃and the regeneration rate is not linear with exhaust temperature.Smaller mass flow rate is beneficial for lower pressure drop and higher soot capacity ability.With increase of mass flow rate,soot regeneration rate grows up gradually.The soot load has little influence on regeneration process at lower temperature,but is of great significance when at higher temperature conditions.The regeneration rate increases with the increased NO₂ concentration,which is conducive to the DPF regeneration at lower temperature.At higher temperature conditions,O₂ has greater influence on DPF regeneration than NO₂.The effect of c_m（NO₂）/c_m（PM）on soot regeneration exists critical value.The CRT characteristics were studied under different DPF structural parameters.Wall thickness has big influence on pressure drop in DPF regeneration process.At higher soot and ash load,the ACT structure and hexagonal DPF can reduce pressure drop,promote soot capacity and decrease regeneration frequency,which is beneficial for engine fuel economy performance.The ACT structure can accelerate regeneration rate,but has larger pressure drop at lower soot load.Furthermore,the ratio of inlet and outlet diameter should not be in excess of 1.4.The regeneration rate of hexagonal DPF is bigger than that of square structure regardless of exhaust temperature.The filter temperature of hexagonal DPF is smaller than square cell structure,which has better thermal durability and longer lifetime.On the basis of results above,a CRT structure optimization scheme was proposed to apply the ACT and hexagonal cell structures at last.