Laser Spectroscopy of Early Soot Formation Process in a Transient Spray Flame : Imaging and Spectral Measurements of Laser-induced Emission at Two Different Excitation Wavelengthes
Laser Spectroscopy of Early Soot Formation Process in a Transient Spray Flame : Imaging and Spectral Measurements of Laser-induced Emission at Two Different Excitation Wavelengthes
复制标题
瞬态喷雾火焰中早期烟灰形成过程的激光光谱：两种不同激发波长下激光诱导发射的成像和光谱测量
DOI：
10.1299/kikaib.71.1708
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
H. Kosaka
中科院分区：
文献类型：
--
作者：
T. Aizawa;H. Kosaka
为了研究柴油喷射火焰中早期烟尘的形成过程，在快速压缩机（2.8 MPa, 710 K）中对瞬态喷射火焰中烟尘前体和烟尘颗粒的激光诱导发射进行了二维成像和光谱测量。采用三次谐波（355nm）和四次谐波（266nm） Nd: YAG激光脉冲作为光源，对烟尘前驱体的激光诱导荧光（LIF）和喷雾火焰中烟尘颗粒的激光诱导白炽化（LII）进行了研究。二维成像覆盖了喷嘴孔下游30 mm至55 mm之间的区域。二维成像结果表明，266 nm激发的强激光诱导发射只出现在喷射火焰的激光入射侧，而355nm激发的强激光诱导发射则是整个截面分布，表明266 nm激发的强激光诱导发射体比355 mil激发的强激光诱导发射体在喷射火焰中更强、更丰富。光谱测量是在喷嘴孔下游35、45和55毫米的三个不同位置进行的，沿着喷雾的中轴线，在之前的二维成像研究中观察到煤烟前体的LIF。在上游位置测量的光谱显示，在400 ~ 500 nm处有宽发射峰，这可归因于多环芳烃（PAHs）的LIF。在下游位置测量的光谱与烟尘颗粒的灰体辐射非常相似。
In order to investigate early soot formation process in a diesel spray flame, 2 D imaging and spectral measurements of laser-induced emission from soot precursors and soot particles in a transient spray flame achieved in a rapid compression machine (2.8 MPa, 710 K) were conducted. 3rd harmonic (355 nm) and 4th harmonic (266 nm) Nd : YAG laser pulses were used as the light source for laser-induced fluorescence (LIF) from soot precursors and laser induced incandescence (LII) from soot particles in the spray flame. The 2-D imaging covered an area between 30 mm and 55 mm downstream from the nozzle orifice. The results of 2-D imaging showed that strong laser induced emission excited at 266 nm appears only on the laser incident side of the spray flame, in contrast to an entire cross-sectional distribution of the emission excited at 355 nm, indicating that 266 nm-excited emitters are stronger absorbers and more abundant than 355 mil excited emitters in the spray flame. The spectral measurments were conducted at three different positions, 35, 45 and 55 mm downstream from the nozzle orifice, along the central axis of the spray, where LIF from soot precursors was observed in a previous 2-D imaging study. The spectra measured in upstream positions showed broad emission peaked around 400 to 500 nm, which is attributable to LIF from polycyclic aromatic hydrocarbons (PAHs). The spectra measured in downstream positions appeared very much like grey-body emission from soot particles.