Study On Particle Movement And Settling Characteristics In Cold EGR System Under Pulsating Exhaust

As an important part of production and life,diesel engine has brought us a lot of convenience.EGR technology,as a key technology,can effectively control NOx emissions.The traditional EGR system directly directs the high-temperature exhaust gas into the combustion chamber,which increases the temperature and pressure of the combustion chamber and is more likely to cause damage to engine parts.Meanwhile,the effect of reducing NOx emissions is not significant.With the further stringent emission regulations,cold EGR technology has further development.Based on improving the inlet air temperature and NOx emission control,the particle deposition condition of the system wall has deterioration.In addition,the diesel engine has exhaust pulsation in the real situation,which has certain influence on the particle movement and settlement in the cold EGR system,thus affecting the normal operation of the cold EGR system.Therefore,it is of great significance to study the particle movement and settling rules in the cold EGR system under the action of pulsating exhaust to improve the working efficiency of the cold EGR system.The physical model of the cold EGR system was chosen and the corresponding geometric model was established.The velocity field,temperature field and turbulent kinetic energy field of the spiral tube and EGR valve were calculated and analyzed respectively.On this basis,the flow field under the pulsating condition was calculated and analyzed.The influence law of inlet velocity,structure parameters and pulsation conditions on the flow field in cold EGR system was obtained.The force model and motion model of particles in the cold EGR system was established.The force and motion of particles in the spiral groove pipe and EGR valve was studied respectively.The comparison between the order of magnitude and the size of the force exerted on the particles with different particle sizes and release positions under the action of pulsating exhaust was obtained,and the influence of pulsating on the trajectory of particles with different particle sizes and release positions was obtained.Based on the above,the settlement model of particles in the cold EGR system was established.The particle settlement in the spiral flute pipe and EGR valve was studied respectively.The particle settlement in different particle sizes and release positions under pulsating conditions was calculated and analyzed based on the force and movement characteristics of particles.The effects of particle size and release position on particle sedimentation rate and distribution in spiral slot pipe and EGR valve under pulsating exhaust was obtained.