Research On The Soot Formation Characteristics Of N-decane/Butanol Blended Fuel In Coaxial Laminar Flow Diffusion Combustion

N-decane is an important diesel fuel,n-butanol is a very promising biofuel,and the research on the soot formation characteristics of n-decane blended with n-butanol can provide important research reference for the clean combustion of diesel blended biofuel.In the current research field of gasoline and diesel alternative fuel combustion,the main research problem on soot formation characteristics is that the measurement methods of the soot formation process are not rich enough,and the process of the growth of the soot precursor PAHs to primary soot particles is unknown.Therefore,in this paper,in the coaxial laminar diffusion flame,the soot formation and PAHs behavior during the combustion of n-decane blended with n-butanol fuel was experimentally measured and simulated,and the main research contents and results are as follows:This paper built an experimental platform for laser diagnosis and used three laser diagnosis methods for measuring the distribution of soot in flames,the distribution of soot precursors polycyclic aromatic hydrocarbons(PAHs)and hydroxyl(OH): The two-color laser-induced incandescence method(TC-LII)was used to quantitatively measure the carbon smoke volume fraction distribution in the coaxial diffusion flame;the planar laser-induced fluorescence legality(PLIF)was used to measure the flames in categories A1,A2,A3,A4 The distribution of PAHs;the OH distribution in the flame was qualitatively measured using planar laser-induced fluorescence.A simplified kinetic mechanism of 73 components and 275 reactions was developed to simulate the combustion characteristics of n-decane blended with n-butanol.The oxidative cracking reaction of n-decane was obtained by simplifying the detailed kinetic mechanism,the chemical kinetic mechanism was constructed in combination with the existing chemical reaction mechanism of oxidative cracking of n-butanol.First,the chemical workbench software was used to verify the ignition delay verification and the premixed flame verification.The results show that the simplified kinetic mechanism of n-decane blended with n-butanol in this paper can well predict the ignition delay and the volume fraction of various products in the premixed flame,proving that it can be used to predict the burning process of n-decane and n-butanol.Furthermore,the Coflame code was coupled to the above mechanism to calculate the combustion characteristics of n-decane.It was found that the soot distribution,OH distribution,and PAHs distribution obtained by the simulation calculation were similar to the experimental measurement results.Four different blending ratios of n-decane and n-butanol(D100,D80B20,D20B80,B100)were used to investigate the soot formation characteristics of n-decane blended with n-butanol in the coaxial laminar diffusion combustion flame.Combined with thermophoretic sampling and transmission electron microscopy analysis methods,soot particles of different heights in the axial direction of the coaxial diffusion flame were analyzed.The results of the study found that with the increase of the butanol blending ratio,the soot particle size and distribution range decreased accordingly.The primary particle size dp,the number of primary particles contained in accumulated particles Np,and the fractal dimension of different axial heights of n-decane coaxial laminar flow diffusion flame were analyzed.It is found that as the height increases,dp gradually decreases,and Np increases first and then decreases.The fractal dimension is always around 1.6.As the height increases,it first increases and then decreases.Six different blending ratios of n-decane and n-butanol(D100,D80B20,D60B40,D40B60,D20B80,B100)were used.Combined with the developed laser diagnostic method,quantitatively measured the soot volume fraction in six different laminar diffusion flames;Qualitatively measured the distribution of four PAHs(A1,A2,A3,A4)and OH in six different coaxial laminar diffusion flames.Experimental results show that as the proportion of n-butanol increases,the flame height decreases.At the same time,the soot volume fraction and the relative concentration of PAHs have decreased,and the relative concentration of OH has increased.Analyzing the relationship between OH and soot distribution,it was found that OH plays a key role in the oxidation of soot.