DPF Operating Characteristics Under High Carbon Loading And Its Influence On Diesel Engine Performanc

With the promulgation of the sixth phase of automobile emission regulations,the new requirements for particle number(PN)emission limits have led to higher challenges for emission control of internal combustion engines in China.How to better control diesel vehicle emissions is the most urgent task we are currently facing.The diesel particulate filter(DPF)is one of the most important technical means to solve carbon smoke emissions,It can help diesel engines meet the PM/PN limit requirements in the national VI emission regulations,and is currently the mainstream technology in the development of post-treatment for national VI diesel engines.At the same time,in order to ensure the safe operation of diesel particulate filters,it is necessary to explore their ultimate performance.This article first constructs a one-dimensional post-processing system model for diesel engines to study the regeneration performance of DPF with different structural carriers and ash loading under high carbon loading.Then,by constructing a one-dimensional simulation thermodynamic whole machine model,the influence of DPF on diesel engine performance is studied and analyzed,including the ash distribution coefficient,carrier inlet and outlet pore size ratio,carrier ratio,and DPF regeneration characteristics at different altitudes under high carbon loading.Construct a quarter channel model of DPF using 3D CFD simulation software to explore the internal airflow movement and carbon smoke deposition and migration patterns of DPF from a microscopic perspective.According to one-dimensional simulation calculations,it was found that the optimal regenerative capture performance of asymmetric structured carriers is achieved when the inlet/outlet aperture ratio is 1.3.In order to maintain the stability of the carrier operation,the wall thickness of the carrier should be controlled at around 10mil;From the comparison of carrier ratios,it was found that selecting DPF carriers with a larger aspect ratio ensures their ash holding capacity and improves DPF capture efficiency.The DPF regeneration characteristics of ACT300 mesh carrier are better than those of SCT300 mesh high porosity,SCT300 mesh low porosity,and SCT200 mesh carrier under low speed conditions;The performance of diesel engines equipped with a high mesh number asymmetric DPF first increases and then decreases with the increase of the inlet and outlet aperture ratio;As the altitude increases,the oxygen content in the intake of diesel engines decreases,leading to an increase in DPF pressure drop and a decrease in capture efficiency;Under high speed operating conditions,a lower oxygen content in the cylinder will increase diesel engine soot emissions;As the ash content and engine speed increase,the ACT carrier is less affected,so it has more advantages under high carbon load conditions.Based on the three-dimensional CFD simulation calculation,it was found that under high carbon loading,the number of carbon smoke particles deposited in the inlet channel of the asymmetric structure carrier was more,but due to the high inlet velocity,the distribution of carbon smoke was uneven.The distribution of carbon smoke particles in symmetric structured carriers is more uniform than that in asymmetric structured carriers;Due to the high inlet velocity,carbon smoke particles will deposit at the end of the channel,resulting in less carbon smoke on the wall of the channel.The presence of ash plugs leads to a chaotic trajectory of particle movement at the back of the channel;As the ash distribution coefficient increases,the velocity of the inlet channel of the carrier gradually increases,while the airflow velocity of the outlet channel gradually decreases.The thickening of the ash layer leads to a significant increase in the concentration of carbon smoke particles inside the inlet channel and an increase in capture efficiency;As the increase in ash content leads to an increase in ash stratification and ash blockage,the decrease in airflow velocity in the inlet duct will also lead to an increase in pressure;With the increase of carrier length,the airflow distribution and particle concentration distribution in the axial direction of DPF are more uniform,and the exhaust velocity of outlet channel decreases when the carrier length is shorter.