Luers Andrew, Salhlberg Anna-Lena, Hochgreb Simone, Ewart Paul
1Department of Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford, OX1 3PU UK.
2Department of Mechanical Engineering, Cambridge University, Trumpington Street, Cambridge, CB2 1PZ UK.
Appl Phys B. 2018;124(3):43. doi: 10.1007/s00340-018-6912-2. Epub 2018 Feb 13.
A systematic study of laser-induced thermal-grating scattering (LITGS) using nitric oxide as an absorbing species is presented as a means of thermometry in air-fed combustion. The relative contributions to the scattered signal from degenerate four-wave mixing, DFWM, and from laser-induced thermal-grating scattering, LITGS, are studied in the time domain for NO in N buffer gas up to 4 bar, using a pulsed laser system to excite the (0,0) γ-bands of NO at 226.21 nm. LITGS signals from combustion-generated NO in a laminar, pre-mixed CH/O/N flame on an in-house constructed slot burner were used to derive temperature values as a function of O concentration and position in the flame at 1 and 2.5 bar total pressure. Temperature values consistent with the calculated adiabatic flame temperature were derived from averaged LITGS signals over 50-100 single shots at 10 Hz repetition rate in the range 1600-2400 K with a pressure-dependent uncertainty of ± 1.8% at 1 bar to ± 1.4% at 2.5 bar. Based on observed signal-to-noise ratios, the minimum detectable concentration of NO in the flame is estimated to be 80 ppm for a 5 s measurement time at 10 Hz repetition rate.
本文介绍了一项以一氧化氮作为吸收物质的激光诱导热光栅散射（LITGS）的系统研究，作为空气喷射燃烧中温度测量的一种方法。在高达4巴的氮气缓冲气体中，使用脉冲激光系统在226.21nm激发一氧化氮的（0,0）γ带，在时域中研究了简并四波混频（DFWM）和激光诱导热光栅散射（LITGS）对散射信号的相对贡献。在内部构建的缝隙燃烧器上的层流预混CH/O/N火焰中，燃烧产生的一氧化氮的LITGS信号被用于在1和2.5巴总压下，得出作为火焰中氧气浓度和位置函数的温度值。在1600 - 2400K范围内，以10Hz重复频率在50 - 100次单次测量上对LITGS信号进行平均，得出与计算的绝热火焰温度一致的温度值，在1巴时压力相关的不确定度为±1.8%，在2.5巴时为±1.4%。基于观察到的信噪比，在10Hz重复频率下5秒测量时间内，火焰中一氧化氮的最低可检测浓度估计为80ppm。
