Effect Of Toluene/Nitrogen Addition On Soot Formation Characteristics In N-heptane/Iso-octane Laminar Diffusion Flame

At present,while gasoline engines improve fuel efficiency,the number of soot particles in the exhaust gas has increased significantly.Soot is the product of incomplete combustion of hydrocarbon fuels,which pollutes the environment and endangers human health.In the past few decades,most soot research has been on small-molecule gaseous hydrocarbon fuels,and the formation of soot in laminar diffusion flames from n-heptane,iso-octane,and toluene in liquid hydrocarbon fuels has rarely been studied.In this paper,a liquid fuel laminar diffusion combustion system is used to study the effect of toluene/nitrogen blending on soot formation in n-heptane/iso-octane combustion flame.The shape and temperature distribution of the flame,as well as the deposition morphology,particle size distribution,nanostructure,graphitization degree,functional group composition and oxidation activity of soot were studied.The results of the study are as follows:In the n-heptane flame,with the toluene blending from 0 vol%to 10 vol%,the flame height increased from 54 mm to 61 mm,and the temperature decreased at the same position.In addition,at the height of 30 mm of the n-heptane flame,with the blending of toluene,the growth process of soot was advanced,the average inner circle area of the corrosion pit reduced from 40.32μm~2 to 22.78μm~2.And the number of particles increased,the average particle size increased from 18.93 nm to 33.21 nm,the average fringe length increased from 0.818 nm to 0.885 nm,the average fringe tortuosity decreased from 1.187 nm to 1.097 nm,the degree of graphitization increased,and the oxidation activity decreased.In the iso-octane flame,with the toluene blending from 0 vol%to 10 vol%,the flame height increased from 64 mm to 69 mm,and the temperature decreased at the same position.In addition,at the middle height of the iso-octane flame,with the blending of toluene,the average corrosion pit inner circle area of soot reduced from42.14μm~2 to 21.04μm~2,the number of particles increased,the average particle size increased from 23.64 nm to 40.62 nm,the average fringe length increased from 0.799nm to 0.902 nm.The average fringe tortuosity decreases from 1.199 nm to 1.130 nm,the degree of graphitization was increased,and the oxidation activity was decreased.In the iso-octane flame,with the flow rate of the carrier gas nitrogen changed from350 mL/min to 250 mL/min,the flame height decreased from 64 mm to 54 mm,and the temperature increased at the same position.In addition,at the middle height of the iso-octane flame,with the decrease of the flow rate of the carrier gas nitrogen,the average inner circle area of the soot corrosion pit decreased from 42.14μm~2 to 25.5μm~2,the number of particles increased,and the average particle size increased from23.64 nm to 34.36 nm.And the average fringe length increased from 0.799 nm to 0.873nm,the average fringe tortuosity decreased from 1.199 nm to 1.102 nm,the degree of graphitization increased,and the oxidation activity decreased.