Exploiting line-mixing effects for laser absorption spectroscopy at extreme combustion pressures
Exploiting line-mixing effects for laser absorption spectroscopy at extreme combustion pressures
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在极端燃烧压力下利用激光吸收光谱的线混合效应
DOI：
10.1016/j.proci.2020.08.037
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发表时间：
2021
影响因子：
3.4
通讯作者：
Spearrin, R. Mitchell
中科院分区：
文献类型：
--
作者：
Lee, Daniel D.;Bendana, Fabio A.;Nair, Anil P.;Danczyk, Stephen A.;Hargus, William A.;Spearrin, R. Mitchell
一种独特的光谱策略已经被开发用于在与现代燃烧装置相关的极端压力（P > 50 atm）下的一氧化碳（CO）和二氧化碳（CO2）的激光吸收传感。该策略利用谱线混合的谱带变窄效应，其严重影响谱线间距小的谱线密集区域，例如带头。线混合被证明是为了对抗碰撞线加宽效应，这种效应会降低在高压下的差分吸收，并且通常会限制激光吸收方法的压力范围。在这项工作中，仅在与燃烧相关的高温下观察到的CO和CO2的R分支带头分别位于2.3 µm和4.2 µm附近。光谱线混合模型开发的每个带头区域占碰撞引起的人口转移率之间的旋转能态在很宽的范围内的升高的温度和压力。使用松弛矩阵形式主义的修改指数间隙模型被证明捕捉到的人口转移率和启用缩放的热力学依赖。由于线混合效应，在高气体密度下，观察到带头处的差分吸收增加了十倍，从而能够使用相对窄带的可调谐半导体激光器进行检测。利用改进的光谱模型，在煤油和超临界甲烷的亚尺度火箭燃烧室中，在高压（高达104 atm）范围内对温度、CO和CO2进行了激光吸收测量。
A unique spectroscopic strategy has been developed for laser absorption sensing of carbon monoxide (CO) and carbon dioxide (CO2) at extreme pressures (P > 50 atm) relevant to modern combustion devices. The strategy exploits the band narrowing effects of line mixing, which acutely impact spectrally dense regions, such as bandheads, where line spacing is small. Line mixing is shown to counter collisional line-broadening effects that reduce differential absorption at elevated pressures and often limit the pressure range of laser absorption methods. In this work, the R-branch bandheads of CO and CO2, which are only observed at high temperatures relevant to combustion, are targeted near 2.3 µm and 4.2 µm, respectively. Spectral line-mixing models were developed for each bandhead region to account for the collision-induced population transfer rates between rotational energy states over a wide range of elevated temperatures and pressures. Modified-exponential-gap models using the relaxation matrix formalism were shown to capture the thermodynamic dependence of the population transfer rates and enabled scaling. Differential absorption at the bandheads was observed to increase by up to a factor of ten at high gas densities, due to line-mixing effects, enabling detection with relatively narrow-band tunable semi-conductor lasers. With refined spectroscopic models, laser absorption measurements of temperature, CO, and CO2were demonstrated over a range of high pressures (up to 104 atm) in a sub-scale rocket combustor operated with kerosene and supercritical methane.
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DOI：
--
发表时间：
1966
期刊：
影响因子：
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DOI：
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发表时间：
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期刊：
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影响因子：
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影响因子：
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