Soot in diesel fuel jets: effects of ambient temperature, ambient density, and injection pressure
Soot in diesel fuel jets: effects of ambient temperature, ambient density, and injection pressure
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DOI：
10.1016/j.combustflame.2004.04.006
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发表时间：
2004-07
影响因子：
4.4
通讯作者：
L. Pickett;D. Siebers
中科院分区：
文献类型：
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作者：
L. Pickett;D. Siebers
在一个光学可达的定容燃烧容器中，对喷入高温高压柴油机工况的燃料射流中的碳烟分布进行了测量。一个激光消光技术被用来进行定量测量的路径长度平均烟尘体积分数。火焰光度和平面激光诱导白炽成像被用来可视化燃料射流的炭黑区域。火焰剥离长度也进行了测量，并用于解释和分析的烟尘测量。燃油由一个带有100 μ m直径喷孔的共轨柴油喷油器喷射。使用的燃料是#2柴油。实验条件的矩阵包括环境气体温度从850到1300 K，环境气体密度从7.3到30.0 kg/m3，和注射压力从43到184 MPa。结果表明，燃料射流中的碳烟峰值随环境气体温度的升高而增加，且碳烟峰值的增加与温度呈线性关系。然而，在火焰尖端附近，碳烟水平随着环境温度的升高而降低，表明在较高温度下火焰尖端区域的碳烟氧化速率显著较高。研究结果还表明，随着环境气体密度的增加和喷射压力的降低，燃料射流中的碳烟峰值水平增加。随着环境密度的增加，这种增加相对于密度是非线性的。随着喷射压力降低的增加与喷射速度（或喷射器孔上压降的平方根）的降低成线性关系。总的来说，在柴油燃料喷射烟灰中观察到的趋势与在提离长度处的横截面平均当量比密切相关，其中烟灰水平随着当量比减小而减小（即，因为更多的空气夹带和燃料与空气的混合发生在提升长度的上游）。
Measurements of soot distributions in fuel jets injected into high-temperature, high-pressure diesel-like operating conditions were made in an optically accessible constant-volume combustion vessel. A laser-extinction technique was used to make quantitative measurements of path-length-averaged soot volume fraction. Flame luminosity and planar laser-induced incandescence imaging were used to visualize the sooting region of the fuel jet. Flame lift-off lengths were also measured and used in the interpretation and analysis of the soot measurements. Fuel was injected with a common-rail diesel fuel injector equipped with a single 100-μm-diameter orifice. The fuel used was #2 diesel fuel. The matrix of experimental conditions included ambient gas temperatures from 850 to 1300 K, ambient gas densities from 7.3 to 30.0 kg/m3, and injection pressures from 43 to 184 MPa. The results show that peak soot level in a fuel jet increases with increasing ambient gas temperature, with the increase scaling linearly with temperature. However, near the tip of the flame, the soot levels decrease with increasing ambient temperature, indicating significantly higher soot oxidation rates in the flame-tip region at higher temperatures. The results also show that the peak soot level in a fuel jet increases with increasing ambient gas density and decreasing injection pressure. The increase with increasing ambient density is nonlinear with respect to density. The increase with decreasing injection pressure is linear with decreasing injection velocity (or the square root of the pressure drop across the injector orifice). Overall, the trends observed in diesel fuel jet soot closely correlate with the cross-sectional average equivalence ratio at the lift-off length, with soot levels decreasing as the equivalence ratio decreases (i.e., as more air entrainment and mixing of fuel and air occur upstream of the lift-off length).