Study On Charged Characteristics Of Diesel Particulate Matter With Organic Metal Additives

Modern diesel engines possess strong power, high efficiency and long durability. However, the emission of particulate matters(PM), especially micro-nano particles emitted from diesel engine would bring about serious environmental pollution and harm effects to human health. Thus, how to reduce exhaust emissions of diesel engine has been a challenging and urgent issue for human beings to solve. With the application of diesel engine after-treatment technology, the total mass of diesel particulate matters have greatly reduced, but the effect on the number of micro-nano particle emissions is not obvious, in the latest particulate emission standard, the reduction of particle number(PN)is one of the major tasks. Electric agglomeration technology is a effective way to promote the agglomeration of PM and reduce the PN, which has the important signification on agglomeration theory and engineering value in diesel engine after-treatment technology.A bipolar charged device was designed to apply to diesel engine. The characteristics of charged particles was measured by using the high precision digital charge and Faraday cup. The effect of parameters on the characteristics of charged particles is investigated, such as PM specific resistance、discharge voltage、exhaust temperature.Based on the principle of polarity compatibility, four test fuels have been prepared including a mass fraction of 10mg/L、15mg/L with ferrocene particles and a mass fraction of 50mg/L、100mg/L with nano-CeO2 particles in diesel, which have been labelled as Fe10、Fe15、50CeO2、100CeO2. The bench test has been conducted to investigate the effect of organic metal additives on the charge-mass ratio of charged particles. The results showed that the charge-mass ratio of PM increased linearly with the charge voltage while using organic metal additives fuel, which seems to be similar to diesel fuel. The charge-mass ratio of PM with Fe15 fuel and 50CeO2 fuel have increased by 15% and 8%, compared with diesel fuel.A micro-orifice uniform desposition impactor was used to study the size distribution characteristics of the exhaust particulates of diesel engine. The physical structure and the chemical composition of PM samples with different test fuels were investigated by SEM and EDS. Experimental investigation shows that the exhaust particulate size distribution generally shifted to the direction of small size while the diesel engine fuelled with organic metal additives diesel fuel. The sample morphology is irregular distribution of chain or clusters. Compared to the sample of diesel fuel, the chain accumulation of particles decreased, clusters of particles accumulation increased, leading to the effect of particle matters agglomeration increased significantly.