Research Of The Microstructure And Oxidation Characteristics On Biodiesel Combustion Particulate Matter

Increasingly strict emission regulations,the use of biodiesel in diesel engines can effectively reduce particulate emissions,but the use of biodiesel with different chemical components and molecular structures can affect the environment in which particles are generated,changing the microstructure and oxidation characteristics of the burning particles.In this paper,a high-pressure common-rail diesel engine was used as the research object to carry out bench tests of four different fuels with diesel fuel,palm oil methyl ester,soybean oil methyl ester and gutter oil methyl ester respectively,analyze the influence of different loads and fuel types on combustion characteristics,microstructure and oxidation characteristics of combustion particulate matter.The main research contents and results are as follows:?1?Measuring the components of palm oil methyl ester,soybean oil methyl ester and gutter Oil methyl ester,calculating the physical and chemical characteristics parameters such as cetane number,iodine value and oxygen content.The test conditions are the maximum torque speed of diesel engine:1800r/min,50%load and 100%load.Under the same load,the maximum break pressure of biodiesel is higher,the ignition delay is shorter,and the combustion duration is longer.Among the three kinds of biodiesel,palm oil methyl ester has the largest maximum break pressure,the longest ignition delay,and the shortest burning duration;gutter oil methyl ester has the largest maximum break pressure,the shortest ignition delay,and the longest burning duration.As the load increases,the maximum break pressure of the four types of fuel combustion increases and the combustion duration extends.?2?In analysis of the morphology of agglomerates of different fuel combustion particles,use box counting dimension calculate the average diameter of their primary particles.The diesel particles are mainly agglomerated,and the biodiesel particles are mainly chain-shaped.The box counting dimension D of the four fuel particle is between 1.64-1.97,which increases with the load.The box counting dimension D of the biodiesel particle meter box under the same load is smaller than that of diesel particles,from large to small:diesel particles?29?palm oil methyl ester particles?29?soybean oil methyl ester particles?29?gutter oil methyl ester particles.The average diameter of the primary particles of the four fuel particles is between 23.07-46.34nm.The average diameter of the primary particles generated at 50%load is smaller,and multiple 4-8nm carbon cores can be seen inside;as the load increases,the average diameter of primary particles increases,and the"core-shell"structure is more obvious.Under the same load,the average diameter of the primary particles of diesel is the largest,and the average diameters of the primary particles of the three biodiesel particles from large to small are as follows:palm oil methyl ester particles?29?soybean oil methyl ester particles?29?gutter oil methyl ester particles.?3?Calculating the crystallite structure parameters of primary particles with different fuel.The average fringe length of the primary particles of the four fuel combustion particles is between0.9-1.4nm,the average tortuosity is between 1.1-1.4,and the average graphene layer distance is between 0.354-0.362nm.Under the same load,the fringe length of the diesel particles is the largest,the tortuosity is the smallest,and the graphene layer distance is the smallest.Among the three types of biodiesel,the gutter oil methyl ester particles have the smallest fringe length,the largest tortuosity,and the smallest graphene layer distance;The palm oil methyl ester particles have the longest fringe length,the smallest tortuosity,and the largest graphene layer distance.As the load increases,the average fringe length of the basic carbon particles of the particles increases,the average tortuosity decreases,and the average graphene layer distance decreases.?4?In analysis of the graphite structure parameters of different fuel combustion particles are analyzed.The I_D1/I_G value of different fuel combustion particles is between 1.05-1.7,and the I_D3/I_G value is between 0.21-0.57.As the load increases,the particle I_D1/I_G value decreases,the degree of graphitization increases,the I_D3/I_G value decreases,and the amorphous carbon content decreases.Under the same load,the I_D1/I_G value of diesel particles is the lowest,and the I_D3/I_G value is also the lowest,that is,the diesel particles have the highest graphitization degree and the least amorphous carbon content;among the three types of biodiesel,the graphitization degree from large to small is:Palm oil methyl ester particles?29?soybean oil methyl ester particles?29?gutter oil methyl ester particles,the amorphous carbon content in descending order is:the gutter oil methyl ester particles?29?soybean oil methyl ester particles?29?palm oil methyl ester particles.?5?The oxidation parameters of different fuel combustion particles are analyzed and the apparent oxidation activation energy required for their oxidation is calculated.The oxidation range of different fuel combustion particles is between 450-700?,and the apparent oxidation activation energy required for oxidation is between 90.2-132.6kJ·mol^-1.As the load increases,the ignition temperature of particles are higher and more difficult to oxidize.The apparent oxidation activation energy required for oxidation increases,and the oxidation activity decreases.Under the same load,the apparent oxidation activation energy required for the oxidation of diesel particles is the highest,and the oxidation activity is the lowest.Among the three kinds of biodiesel,the apparent oxidation activation energy required for the oxidation of gutter oil methyl ester particle is the smallest and the easiest to oxidize;the apparent oxidation activation energy required for the oxidation of palm oil methyl ester particles is the highest and the most difficult to oxidize.