Effects Of Emission And Charge Characteristics Of Diesel Particulate Matter With Fe-based Fuel Borne Catalyst

Diesel engine produce a harmful effect to the environment and human health because of the high mass and number concentration of micro-nano particles in engine exhaust.The optimization of engine in-cylinder combustion and after-treatment devices can significantly reduce diesel particulate mass emissions,but trapping the number of nano-sized particles is a big problem with the diesel particulate filter.Based on the electrical charge agglomeration theory,this paper established a positive and negative discharge device with an external high-voltage power,which will improve the efficiency of collision and condensation of particles by discharge exhaust particles.Thus,the adhesion force between particles become lager with Electrical Charge Agglomeration(ECA)technology,and the micro-nano particles can agglomeration more easily,further improving the collection efficiency of particulate matter.The effect of Fe-based Fuel Borne Catalyst(Fe-FBC)content on the exhaust particle size,internal structure and functional groups of diesel particulates was studied by bench test.Fe-FBC was added to the China standard V diesel at a mass ratio of 100mg/kg,200 mg/kg and 300 mg/kg to prepare three mixed fuels which is named Fe100,Fe200 and Fe300.The effect of different Fe-FBC content on particle size was studied by EEPS analyzer.The results show that when the diesel engine is burned with Fe-FBC fuel,the particle diameter of peak number concentration shifts toward the small particle size,and the total particle number concentration increases.The particles were observed by scanning electron microscopy.It was found that the diesel particles showed a cluster structure,and the Fe300 fuel particles showed more chain structure.Based on the Fractal Theory,the box-counting dimension of the particles was calculated.It was found that the box-counting dimension of the Fe300 fuel particles was smaller,indicating the internal carbon particle polymerization effect and the agglomeration of particles were reduced by Fe element.A self-made bipolar electrical charged agglomeration test bench was built,selectthe diesel and three kinds of Fe-FBC fuels and the discharged voltages were adjusted to 5 kV,10 kV,15 kV and 20 kV respectively.The diesel engine exhaust particles were captured by aqueous ion solution and the surface zeta potential and charge of the particles were measured by Zeta potential analyzer.The results show that increasing the positive and negative discharged voltage can significantly increase the zeta potential and charge of the particles.With the discharged voltage increases from 0kV to 15 kV,the particle zeta potential and surface charge has an obvious increment,and the surface charge of the four kind particles reach the maximum value at the 15 kV discharged voltage.Compared with diesel,Fe-FBC can significantly increase the zeta potential and the charge of particles.When the negative discharged voltage is 15 kV,compared with diesel,the surface charge carried by fuel particles of Fe100,Fe200 and Fe300 increase by 323.2%,754.1% and 1166.5%,respectively.The effect of discharged voltage on the size distribution and coagulation efficiency of exhaust particles were studied by Engine Exhaust Particle Size analyzer(EEPS).It is found that with the discharged voltage increases,the diameter of particles exhaust by diesel engine shifts toward a bigger particle size.When the discharged voltage is 20 kV,the diesel particle diameter at the peak number concentration was increased from 60.4 to 69.8nm,and the Fe300 particle diameter at the peak number concentration was increased from 10.8 to 19.1nm.With 20 kV discharged voltage,the total number concentration of diesel particles decrease,and the coagulation efficiency of diesel emission particles is the biggest,which is 21.5%.In addition,Fe element in the particles can significantly increase the coagulation efficiency of the particles,and the total amount of Fe300 particles have a greater reduction than diesel particles at a same discharged voltage.When the discharged voltage is 20 kV,the coagulation efficiency of diesel and Fe300 nuclear mode particles is 29.2% and 35.4% respectively.The diesel particulate filter was installed in the bench and the particulate capture efficiency of DPF was studied in this paper.It is found that the ECA can improve thecapture efficiency of DPF for small particle size particles,at the particle size between6.04~12.4nm,the original capture efficiency of DPF for diesel and Fe300 fuel particles is 35.1% and 39.6%.When the discharged voltage is 20 kV,the DPF capture efficiency of diesel and Fe300 particles in the above size range increases by 12.2%and 23.8%,respectively.Both the discharged voltage and Fe-FBC can increase the DPF mass capture efficiency,and the two technology can significantly reduce the quantity and mass emission of exhaust particles.