Simulation Of Operating Characteristics Of DPF From Diesel Engine And Optimization Of Structural Parameters

Diesel Particulate Filter(DPF)can effectively reduce diesel particulate matter emissions and is one of the key technologies for future emission regulations.The rise of back pressure during DPF filtration process and the increase of wall temperature and thermal stress during regeneration will affect the overall performance of the aftertreatment system and engine system.Therefore,while discussing the operating characteristics of DPF,it is of great theoretical significance and application value to formulate appropriate DPF regeneration control methods and structural design optimization schemes.In this paper,the cordierite DPF used in small non-road diesel engines was studied.The experimental research and numerical simulation methods were combined to explore the characteristics of DPF filtration and regeneration.According to the working principle of DPF offline regeneration system,appropriate regeneration control methods were established.In addition,in order to effectively control the wall temperature during regeneration and improve the regeneration efficiency,the optimization of DPF structural parameters was carried out.Diesel engine test bench was used to conduct original emission test and pressure drop characteristic test on 186 FA diesel engine.The simulation software GT-POWER was used to establish the soot filtration model of DPF;and the filter parameters of the model were calibrated in combination with test data.Simulation calculation was carried out on the soot filtration process of DPF on the basis of the verified model.The results showed that the mass of the soot collected at deep bed filtration stage accounted for less than 4% of the total mass of soot,but deep bed pressure drop had significant impacts on the overall pressure drop;in the filtration process,the soot in the filter wall was not uniformly distributed at each individual slab,the closer to the wall,the higher the soot density;the difference in collection efficiency of each individual slab affected the distribution of soot at different locations within the wall.DPF offline regeneration system was established to conduct electric heating regeneration test assisted by oxygen supply device,and the impacts of the oxygen flow and inflow temperature on the wall temperature and regeneration efficiency were analyzed.The soot combustion model of DPF was established for the analysis of the temperature and flow rate distribution characteristics upon regeneration.Besides,the regeneration control system model of DPF was established to realize the control of regeneration opportunity and heating power.The results showed that the improvement of the oxygen concentration and temperature of inflow could help improve the regeneration rate,but it might intensify the temperature rise of DPF;in the regeneration process,the wall peak temperature of DPF appeared at the rear part of the filter where the soot burned the most rapidly;upon regeneration,the flow rate was high at the radial center of DPF and low at edges;the inlet flow rate gradually decreased and the outlet flow rate increased in the axial direction;DPF could be continuously and effectively regenerated without too high wall temperature under different inflow conditions by means of the established regeneration control system.Control variate method was used to analyze the impacts of structural parameters on DPF regeneration process.The results showed that the wall peak temperature upon regeneration and the regeneration rate decreased with the increase of wall thickness,and thicker filter wall tended to generate high pressure drop during regeneration;the higher the cell density of DPF,the lower initial pressure drop and wall temperature generated,and the longer time the regeneration took;the longer the filter,the lower the wall temperature upon regeneration,and the longer time the regeneration took;long filter helped to increase the available soot conversion time,but increased regeneration energy consumption.Design of experiment calculation and optimization of structural parameters were conducted on the regeneration process to lower the wall temperature and improve the regeneration efficiency.The results showed that there existed optimal structural parameter combination enabling DPF to decrease the risk of thermal failure on the premise of guaranteeing the regeneration efficiency.The optimized filter wall thickness,cell density,filter length and filter diameter were substituted into the original model and the simulation results were obtained.The wall peak temperature decreased by 5.3%~13.7% and the maximum temperature gradient decreased by 10.5%~18.1%.The regeneration duration was shortened by 0.6%~5.6%.The optimized DPF structure helped improve the regeneration process without imposing significant adverse effects on the filtration performance of the filter.