Development of a Technique to Determine the Effects of Temperature and Composition on the Refractive Indices of Soot

碳氢化合物火焰中形成的碳烟的大小和组成随化学计量比和停留时间的不同而不同。为了研究与碳烟形成和氧化相关的基本过程，使用激光探头对颗粒尺寸和数密度进行了原位测量。对激光散射和吸收的解释至关重要的是粒子折射率。这项拟议的研究将确定折射率作为碳烟C/H比、颗粒温度和添加到燃料中的羰基铁的量的函数。测量将限于碳氢化合物-空气预混平焰的较低区域，那里的烟尘颗粒比激光探头的波长小得多。还将对加热到1100K的提取样品进行反射率测量，火焰中的颗粒温度将通过与可见光激光探头同步的高功率脉冲红外激光照明来控制。如果研究成功，能够以较小的不确定性量化碳烟颗粒的数密度和尺寸分布，将加强对碳氢化合物火焰中碳烟形成的研究，并提高辐射换热计算的准确性。这项研究还将首次评估金属添加剂对亚100 nm碳烟颗粒光学性质的影响，并可能导致研究其他重金属和氯化添加剂的模型实验。

Soot formed in hydrocarbon flames varies in size and composition with stoichiometry and residence time. To study the fundamental processes associated with soot formation and oxidation, laser probes are used for in situ measurement of the particle size and number density. Critical to the interpretation of the scattered and absorbed laser light is the particle index of refraction. The proposed research will determine the index of refraction as a function of the soot C/H ratio, the particle temperature, and the amount of iron carbonyl added to the fuel. Measurements will be limited to the lower regions of premixed hydrocarbon-air flat flames where the soot particles are much smaller than the wavelength of the laser probe. Reflectivity measurements will also be made on extracted samples heated up to 1100 K. Particle temperature in the flame will be controlled through high power pulsed IR laser illumination synchronized with a visible laser probe. If the research is successful, the ability to quantify with less uncertainty the number density and size distribution of soot particles will enhance investigations into the formation of soot in hydrocarbon flames, and increase the accuracy of radiative heat transfer calculations. This study will also provide the first ever assessment of the effect of a metal additive on sub- 100 nm soot particle optical properties, and could lead to a model experiment for investigating other heavy metal and chlorinated additives.