Gasoline addition in diesel fuel could not only improve the overall energy efficiency, but also could reduce the soot emission on diesel engine. However, the influence of gasoline on the soot forming characteristics has not been revealed fundamentally. A liquid burner system, modified from a Gülder burner, was applied to create strict laminar diffusion flame to carry out the related study. Also, optical diagnostics technologies including digital camera imaging and high speed two-dimension line-of-sight attenuation (2D-LOSA) were used to record the natural luminosity flame structure, smoke point, and soot volume fraction. During the experiments, the diesel ratio was varied as 0%, 20%, and 40% by volume, while the fuel flow rate was varied from 6 to 9 g/h. The results show that diffusion flames of blends can be distributed into three typical parts, soot free region, soot growth region, and soot oxidation region. With the fuel flow rate increasing, more soot was generated and the flame height was lifted. With the diesel ratio increasing in gasoline/diesel blends, the visible flame height decreased, the flame luminosity intensity decreased, the smoke point increased, and the 2D soot volume fraction value reduced, which indicates that diesel is less likely to produce soot than is gasoline in the laminar diffusion flame. The soot reducing effect of diesel is regarded because diesel can enhance the cool flame combustion in the free soot region due to its more obvious NTC (negative temperature coefficient) effect. It is also reasonable to expound that the soot emission reduces with addition of gasoline in diesel on engines mostly because of its volatility rather than its chemical characteristics.

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层流共流扩散火焰中汽油/柴油混合物的烟灰特性研究

在柴油中添加汽油不仅可以提高整体能效，而且可以减少柴油机上的烟尘排放。但是，从根本上没有揭示出汽油对烟灰形成特性的影响。应用了从Gülder燃烧器改造而来的液体燃烧器系统，以产生严格的层流扩散火焰来进行相关研究。此外，光学诊断技术（包括数码相机成像和高速二维视线衰减（2D-LOSA））用于记录自然光度火焰结构，烟点和烟灰体积分数。在实验过程中，柴油比例以体积计分别为0％，20％和40％，而燃料流速从6到9 g / h不等。结果表明，共混物的扩散火焰可分为三个典型部分：不含烟尘的区域，烟尘的生长区域和烟尘的氧化区域。随着燃料流量的增加，产生了更多的烟灰，并提高了火焰高度。随着汽油/柴油混合物中柴油比例的增加，可见火焰高度降低，火焰光度强度降低，烟点增加，二维烟灰体积分数值降低，这表明柴油比汽油更不可能产生烟灰。在层流扩散火焰中。之所以认为柴油具有减少烟灰的作用，是因为柴油由于其更明显的NTC（负温度系数）效应而可以增强自由烟灰区域的冷焰燃烧。有道理的是，烟灰的排放量随发动机柴油中汽油的添加而减少，这主要是由于其挥发性而不是其化学特性。