Simulation And Experimental Study On The Performance Of DPF For Commercial Vehicle Diesel Engine

As particulate matter（PM）requirements of China VI emission regulation increasingly being more and more stringent,the diesel particulate filter（DPF）,as the most effective method of controlling PM emission,has become the indispensable device for commercial vehicle heavy duty diesel（HDD）exhaust aftertreatment system.After a certain amount of soot captured in DPF,the exhaust pressure will be increased,which affect the operation of the engine,so the DPF needs to be periodically regenerated.The diesel is injected into the exhaust pipe behind the turbocharger to generate heat.The active regeneration technology that removes soot from the DPF is one of the key technologies for HDD to meet the China VI emission regulation.Therefore,the research and simulation analysis of DPF work process has great significance and engineering practical value.Based on the national key research and development plan“Research on the evaluation and industrialization of key components for diesel aftertreatment system”,in this paper an engine test bench and a three-dimensional simulation model of DPF have been built.The temperature field,flow field and backpressure characteristics of DPF active regeneration have been studied by experimental and simulation methods.The research content mainly includes four parts:DPF regeneration test research,theoretical description and mathematical modeling of DPF backpressure and regeneration process,DPF internal temperature field influence factor analysis,DPF mass flow and backpressure characteristics simulation analysis.Through the engine test bench experiment,the back pressure characteristics of DPF with different soot loading and the temperature characteristics during active regeneration are studied.The results show that the DPF soot loading has a certain correspondence with the DPF pressure drop.The soot captured by the DPF can be estimated by the pressure drop value.The DPF regeneration temperature rises with the order of exhaust flow and soot combustion.The front part is warmed up earlier than the rear part,and the middle part is heated up earlier than the edge.The highest temperature appears in the outlet plane,and the radial temperature gradient is larger than the axial temperature gradient.The DPF back pressure and regeneration process are mathematically modeled based on soot capture theory,Darcy’s law,and mass,energy,and chemical dynamics equilibrium equations.The DPF 3D simulation model is established by AVL-FIRE software.Firstly,the back pressure calibration of the DPF is carried out,and the wall permeability turns out to be k_w=2.555e-12.Secondly,the error of the experimental data compared with the results of the 3D simulation model is less than 8%,so that a reliable simulation model is built.The temperature field of DPF active regeneration is simulated with the 3D simulation model.The DPF wall temperature peak,the temperature gradient,the regeneration time and the soot regeneration energy consumption are used to evaluate the regeneration.By optimizing the exhaust parameters such as flow rate,temperature and O₂ volume fraction and on the basis of ensuring the safety of regeneration,regenerative energy consumption and regeneration time are reduced while high regeneration efficiency is ensured.Because of the accumulated ash in the DPF,the regeneration frequency is accelerated,but the safety of regeneration is improved at the same time.The internal flow field characteristics of the DPF are simulated by numerical simulation.According to the different pore structure and ash deposition of DPF,the regenerative flow and back pressure characteristics of DPF are analyzed,and the influence of ash characteristics on DPF back pressure of different pores is simulated.