氨/柴双燃料发动机排放碳烟氧化过程的理化特性研究

Revealing the changes in physiochemical characteristics of soot in oxidation process from ammonia/diesel dual fuel engines contributes to control particle emissions from ammonia/diesel engines. This article investigates the changes in graphitization，functional groups，nanostructure，and pores of soot in the oxidation process from ammonia/diesel engines at different oxidation stages. The results show that the content of amorphous carbon decreases in soot oxidation process，while that of graphite carbon increases，resulting in a decline of soot graphitization. The initial particle size of soot decreases due to the strong oxidation，and the length distribution of microcrystals shifts towards the region of large sizes. The proportion of microcrystals below 1nm significantly decreases，leading to an increase in the order of soot nanostructure. Regarding functional groups，both aliphatic C−H and aromatic C−H functional groups exhibit the reduction to varying extents，and C−N functional groups are formed on soot surface when the mass loss reaches 40%. In addition，the content of C−O functional groups rises from 11.09% to 15.26%，while the proportion of C=O functional groups drops from 13.00% to 7.14%. When the mass loss is 40%，the content of COOH functional groups also increases significantly. However，the proportion of nitrogen-containing functional groups significantly decreases. Nitrogen oxide（N-O_x）is the first to deplete，and the pyridine-structure compound（N-6）and pyrrole-structure compound（N-5）exhibit greater reductions compared to the quaternary nitrogen compound（N-Q）. When the mass loss is less than 60%，the change in mesoporous volume in soot from ammonia/diesel engines is limited. However，the mesoporous volume significantly increases when the mass loss reaches 60%，especially for the volume of 2~10 nm pores，accompanied by a rapid increase in specific surface area.