| With the increase of smog weather and the decline of air quality in recent years,people are paying more and more attention to the living environment.In terms of particulate matter emissions from motor vehicles,the government has enacted more stringent regulations,and the ultra-fine particulate emissions from gasoline direct-injection?GDI?engines have attracted attention.This paper focuses on the field of soot measurement.Firstly,the optical diagnostic method related to soot measurement is compared and studied,the technical development process,measurement principle and application effect are compared and analyzed in detail,give full consideration to the advantages and disadvantages,finally decided to use the two-color laser induced incandescence method?2C-LII?as the measurement method in this paper.In this paper,a laminar ethylene-air diffusion flame LII test system and a GDI optical engine LII test system are established.The light intensity response coefficient of the ICCD camera is calibrated,the light intensity response coefficient corresponding to 400 nm is2.08×10-7,and the light intensity response coefficient corresponding to 600 nm is 7.8×10-9.The soot distribution of a laminar ethylene-air diffusion flame having a height of 64 mm was measured by the 2C-LII test method.The soot of ethylene-air flame first increases and then decreases in the direction of fuel diffusion until it completely disappears.When the flame height is lower than 28mm,the distribution of soot is bimodal.When the flame height exceeds 28mm,the distribution of the bimodal state begins to weaken,the soot in the center of the flame begins to increase;the most concentrated area of the soot is outside the ethylene-air flame,where the maximum soot volume fraction is about 8.2×10-6.The test results are in good agreement with the reference data,verifying the accuracy of the test method.The soot volume fraction in the GDI optical engine cylinder was measured using the 2C-LII test method.The soot volume fraction at the three injection widths of 6000?s,7000?s and8000?s from the top of the cylinder liner at 5mm,10mm and 15mm were measured.At the same time,the volume fraction of soot at three planes under the pulse width of 8000?s is studied with the crank angle.The experimental result show that:1)When the piston just passes through the selected plane,the corresponding crank angle is the most concentrated moment of the plane;the 10mm plane is the thickest area,the 5mm plane is the second,the 15mm plane is the thinnest area,and the 15mm plane is located at the edge of the soot thick zone.2)The most concentrated time of 5mm and 10mm planes:the overall level of soot concentration under the 6000?s injection pulse width is relatively low,and the soot volume fraction corresponding to the 7000?s and 8000?s injection pulse width is relatively large,the soot volume fraction of the 7000?s fuel injection pulse width is slightly larger,but the distribution is not uniform.The volume fraction of soot near the side of the intake valve is relatively large,relatively small near the side of the exhaust valve;the most concentrated time of 15mm plane:the soot concentration distribution characteristics corresponding to the 7000?s and 8000?s injection pulse widths have changed.The most concentrated part of soot is mainly distributed in the upper part of the middle,which is shifted downward compared to the other two planes.3)Under the 8000?s injection pulse width,each plane starts from its most concentrated time,as the piston gradually descends,the soot concentration gradually decreases.At the end of the expansion stroke,the obvious concentrated area of the soot gradually disappears and the distribution is more uniform.The DMS500 fast particle analyzer was used to measure the quantitative concentration and particle size distribution of the particles under the three injection widths of 6000?s,7000?s and8000?s.The particle size distribution of the particles corresponding to the three injection pulse widths is bimodal,one peak is in the nuclear state and the other is in the accumulation state.The total number of 8000?s injection pulse width is the largest,most of which are nuclear particles,and the accumulation of particles are relatively small;The total number of particles corresponding to the 7000?s injection pulse width is slightly smaller,most of which are accumulated particles,and nuclear particles are relatively few;6000?s injection pulse width corresponds to the smallest number of total particles,most of which are nuclear particles,and the accumulation particles are relatively few. |
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