The Investigation On The Oxidation Performance Of The Diesel Exhaust Particulates By DOC

The particle emission of diesel engine is one of the main source of fog and haze in atomesphere. The governance haze of developed countries(especially in Europe) is consulted and drawed lessons, Chinese enacted the relatively stringent vehicle emission regulations. In order to satisfy the standard of emission regulations, a series of diesel engine after-treatment technology emerges, Which diesel oxidation catalyst(DOC) can achieve binding emission reduction targets by oxidation of HC, CO and Soluable Organic Fraction(SOF) of PM in diesel exhaust. DOC is usually used with other aftertreatment technology. Based on engine bench testing, DOC based Pt is equipped to a diesel. The variation trend of the size distribution characteristics, the smoke, and the oxidation characteristics of particulate matter before and after DOC are experimentally investigated.Based on YN38CRD2 type diesel engine, a diesel oxidation catalyst device is added. To collect the temperature and pressure signal before and after DOC, NI data acquisition card is used; To measure exhaust smoke before and after DOC, AVL 415 Smoker is used. The change rule of exhaust temperature for diesel operating conditions is got, and the rule of influence on exhaust smoke oxidation by DOC is investigated. Test and analysis results indicate that under the same rotating speed, DOC inlet temperature increases with the increase of torque; exhaust smoke decreases when exhaust particulate passes by DOC.To measure PM size distribution before and after DOC, DMS500 Fast Particle Spectrum is used. The regularities of particalate size distribution before and after DOC,and the change regularities of total particalate number concentration before and after DOC is got. Results indicate that DOC can reduce the number concentration of nucleation mode particle, the peak number concentration of nucleation mode particle and the number peak particle size decrease with the increase of exhaust temperature. DOC can reduce the number concentration of accumulation mode particle,but but the number concentration of accumulation mode particle increases with the increase of torque. With the increase of torque, the number concentration of total number concentration firstly decreases and then increases by DOC,because the exhaust gas temperature,350 degrees Celsius,is critical temperature of Sulfate generated.To measure PM oxidation characteristics before and after DOC, STA 449F3 simultaneous thermal analyzer prpduced by Netzsch limited company is used. The change regularities of particalate matter during thermogravimetric experiment process before and after DOC is got, each component content of particulate before and after DOC is achieved, the influence disciplinarian of the particle SOF concentration, particle apparent activation energy,and initial combustion temperature of dry soot are analyzed. Results indicate: because eachpoint calibration of the engine combustion is different, SOF concentration of the original emissions particle is no specific change trend when rotational speed changes.Because DOC can improve exhaust temperature, SOF concentration of particle decreases, particle apparent activation energy increases, and initial combustion temperature of dry soot increases when particle pass by DOC. Furthermore,since there is synergistic oxidation effect between SOF and dry soot, apparent activation energy of exhaust particles oxidation shows a declining trend with the increase of the content of SOF as a whole.