Soot Properties in Steady and Unsteady Non-Premixed Counterflow Flames

摘要：本文研究了层流火焰在受控时变流场作用下烟灰的形成。一个逆流燃烧器被使用，每侧都有一个扬声器来施加不稳定的应变率在火焰上。对稳定和非稳定火焰进行测量，包括半透明和成熟烟灰颗粒的体积分数，颗粒/聚集体大小，烟灰形态，颗粒速度，火焰温度，分子荧光和辐射损失。实验技术包括激光散射和消光、通过透射电子显微镜进行热电泳取样、可见吸收光谱、激光多普勒测速、双波长热分析法、热电偶测量、激光诱导荧光和总辐射热流。使用的燃料包括甲烷、丙烷、丙烯和乙炔；应变速率在20-200 SEC -1范围内变化。对烟尘和火焰的性质进行了计算预测，并与实验观测结果进行了比较。这是一种试图弥合层流（很容易研究）和湍流（反映实际系统）非预混燃烧碳氢化合物燃料之间差距的尝试。长期目标是在包括内燃机、燃气轮机和工业炉在内的一系列应用中完善控制烟灰形成的方法。

ABSTRACT - Koylu This is a study of soot formation in laminar flames that are forced by a controlled time-varying flow field. A counterflow burner is used with a loudspeaker on each side to impose unsteady strain rates on the flames. Measurements are made on steady and unsteady flames including volume fraction of translucent and mature soot particles, particle/aggregate sizes, soot morphology, particle velocity, flame temperature, molecular fluorescence, and radiative losses. Experimental techniques include laser scattering and extinction, thermophoretic sampling with examination by transmission electron microscopy, visible absorption spectroscopy, laser Doppler velocimetry, two-wavelength pyrometry, thermocouple measurements, laser-induced fluorescence, and total radiation heat flux. Fuels used include methane, propane, propylene, and acetylene; strain rates are varied in the range of 20-200 sec -1. Computational predictions of soot and flame properties are made and compared to the experimental observations. This is an attempt to bridge the gap between laminar (which is easily studied) and turbulent (reflecting practical systems) nonpremixed combustion of hydrocarbon fuels. The long-term goal is perfection of methods to control soot formation in a range of applications including internal combustion engines, gas turbines, and industrial furnaces.