Kempema Nathan J, Long Marshall B
Opt Lett. 2018 Mar 1;43(5):1103-1106. doi: 10.1364/OL.43.001103.
This Letter reports on the effect of self-absorption on measured temperature for color-ratio soot pyrometry with a color camera. A series of increasingly nitrogen diluted atmospheric pressure ethylene/air laminar coflow diffusion flames are studied, providing flames with different optical path lengths, soot loading, and soot optical properties. Numerical calculations are used to simulate the change in collected flame emission signal with and without light attenuation using experimentally measured maps of the soot absorption coefficient. This parameter implicitly contains information about soot volume fraction and soot optical properties. The ratio of these calculations is used to correct the raw color-channel signals, resulting in temperature maps with improved accuracy. The change in calculated temperature varies spatially within each flame, with the maximum correction quantified to be 22 K for a flame with a maximum optical depth of 0.31. This correction is as much as 42 and 75 K for simulated flames with the same optical properties, structure, and a factor of two and five increase in soot volume fraction, respectively.
本信函报道了自吸收对采用彩色相机的比色烟尘高温测定法中测量温度的影响。研究了一系列氮气稀释程度不断增加的大气压乙烯/空气层流共流扩散火焰，这些火焰具有不同的光程长度、烟尘负载和烟尘光学特性。利用烟尘吸收系数的实验测量图谱，通过数值计算来模拟有无光衰减情况下收集到的火焰发射信号的变化。该参数隐含了有关烟尘体积分数和烟尘光学特性的信息。这些计算结果的比值用于校正原始颜色通道信号，从而得到精度更高的温度图谱。计算得到的温度变化在每个火焰内部随空间位置而异，对于最大光学深度为0.31的火焰，最大校正量为22K。对于具有相同光学特性、结构且烟尘体积分数分别增大两倍和五倍的模拟火焰，该校正量分别高达42K和75K。
