Study Of CDPF On Physical And Chemical Characteristics Of PM In Diesel Vehicles

The contribution of diesel vehicles to the emission of motor vehicle pollutants is particularly outstanding.Attention should be paid to the reduction of particulate matter.CDPF?Catalyst Diesel Particulate Filter,CDPF?is the most effective method to control particulate emissions from diesel vehicles.The physical and chemical properties of particles determine the degree of impact on atmospheric visibility and human health.From a physical point of view,nuclear modal particles can not only reach the lungs and deposit through the human breath,they can even enter the blood circulation and flow to the brain and heart.Harm to the human body's breathing and immune system.Aggregate particulate matter is an important factor that causes atmospheric visibility to decline.From a chemical point of view,organic carbon?OC?and elemental carbon?EC?in the particles are the main components of the particles.There are also differences in the harm of the organic components to the environment and the human body.EC is a soot particle,which has a strong adsorption capacity,easy to adsorb toxic substances and provide a place for its chemical reactions;the organic carbon in the particulate matter discharged by diesel vehicles is more harmful to the human body are linear alkanes and polycyclic aromatic hydrocarbons,and more types of emissions,linear Alkanes are highly biologically toxic and can cause harm to the human nervous system,respiratory system,and skin and mucous membranes.PAHs are extremely carcinogenic to living organisms.Twelve heavy-duty diesel vehicles and nine types of in-use CDPF are selected using a laboratory chassis dynamometer and a full-flow dilution constant volume sampling system?CVS?to conduct an experiment on the effects of CDPF on the physical and chemical characteristics of diesel vehicles.The influence of physical characteristics and chemical properties of particulate matter.The relationship between driving conditions and the emission reduction effects of conventional pollutants and physical properties of particulate matter was analyzed.The influence of CDPF design parameters on the physical properties of particles was further explored from the perspective of physical properties of particles.CDPF for heavy diesel vehicles in China.the result shows:After loading CDPF,the average emission factors of conventional gaseous pollutants HC,CO and NOx are?0.2±0.1?,?1.2±1.5?and?17.5±7.8?g km^-1,The quantity and mass of particles loaded with CDPF are?3.1±2.1?×10¹⁴ km^-1 and?12.8±5.7?mg km^-1,respectively,and the emission reduction efficiency are 85.5%and 96.4%.With the increase of particle size,the emission reduction effect of particle quantity and quality is getting better and better.The smaller the particle size is,the worse the emission reduction effect is.This phenomenon is more obvious under high-speed conditions.There is no significant change in the proportion of carbon components in particulate matter before and after loading CDPF,accounting for about 64%.The emission factors of OC and EC are 6.8 mg km^-1,1.4 mg km^-1,and the emission reduction rates are 94.0%and98.8%.The measured linear alkanes are distributed between C12 and C36,and before and after loading CDPF,the linear alkanes are mainly divided between C16 and C26,with less distribution on both sides,and the emission reduction rate reach 67.2%.Among the 8polycyclic aromatic hydrocarbons measure,most of them are three-ring and four-ring.After loading CDPF,the emission factor of PAHs is 11.6 g km^-1,reducing the emission rate by90.2%and the toxicity by 91.6%.The larger the volume of CDPF,the higher the quantity and quality emission reduction ability of nuclear film particles,and the lower the quantity and quality of aggregates particles.The reduction effect of OC slightly improve with the increase of volume,but different volumes have no significant effect on EC,linear alkanes and PAHs.The higher the load of CDPF precious metal,the higher the emission reduction capacity of particles above 30 nm,but the lower the emission reduction capacity of particles below30 nm.The larger the load of precious metals,the higher the emission reduction capacity of EC,but no significant effect on OC,alkanes and PAHs.Increasing the proportion of Pd will improve the emission reduction ability of CDPF for particles of various particle size segments and particles of various modes,but the emission reduction ability decreases after adding Rh.The correlation between OC emission reduction effect and noble metal ratio is weak.The emission reduction effect of EC increase with the increase of Pd proportion in noble metal,but decrease after adding Rh.The noble metal ratio has little effect on the overall emission reduction of linear alkanes,and the increase of the proportion of Pd can increase the emission reduction effect of linear alkanes less,but the emission reduction ability decreases after adding Rh,which has no significant effect on the emission factors and toxicity of PAHs.After considering the cost,the quantity of particles in nuclear film state,the quantity of particles in aggregate state,the emission reduction effect of organic carbon and elemental carbon,the optimal CDPF design parameter volume is 5 dm³,the noble metal load is 0.3 g L^-1,and the noble metal ratio Pt:Pd:Rh is 5:1:0.