中国物理B ›› 2020, Vol. 29 ›› Issue (9): 93301-093301.doi: 10.1088/1674-1056/aba5ff

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Effects of temperature and pressure on OH laser-induced fluorescence exciting A-X (1,0) transition at high pressures

Xiaobo Tu(涂晓波), Linsen Wang(王林森), Xinhua Qi(齐新华), Bo Yan(闫博), Jinhe Mu(母金河), Shuang Chen(陈爽)   

  1. 1 Science and Technology on Scramjet Laboratory, Hypervelocity Aerodynamics Institute, China Aerodynamics Research and Development Center, Mianyang 621000, China;
    2 China Aerodynamics Research and Development Center, Mianyang 621000, China
  • 收稿日期:2020-04-23 修回日期:2020-07-11 接受日期:2020-07-15 出版日期:2020-09-05 发布日期:2020-09-05
  • 通讯作者: Shuang Chen E-mail:chenshuang827@gamil.com
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 51976233 and 91641118).

Effects of temperature and pressure on OH laser-induced fluorescence exciting A-X (1,0) transition at high pressures

Xiaobo Tu(涂晓波)1,2, Linsen Wang(王林森)2, Xinhua Qi(齐新华)2, Bo Yan(闫博)2, Jinhe Mu(母金河)2, Shuang Chen(陈爽)2   

  1. 1 Science and Technology on Scramjet Laboratory, Hypervelocity Aerodynamics Institute, China Aerodynamics Research and Development Center, Mianyang 621000, China;
    2 China Aerodynamics Research and Development Center, Mianyang 621000, China
  • Received:2020-04-23 Revised:2020-07-11 Accepted:2020-07-15 Online:2020-09-05 Published:2020-09-05
  • Contact: Shuang Chen E-mail:chenshuang827@gamil.com
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 51976233 and 91641118).

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摘要： The effects of temperature and pressure on laser-induced fluorescence (LIF) of OH are numerically studied under the excitation of A-X (1,0) transition at high pressures. A detailed theoretical analysis is carried out to reveal the physical processes of LIF. It is shown that high pressure LIF measurements get greatly complicated by the variations of pressure- and temperature-dependent parameters, such as Boltzmann fraction, absorption lineshape broadening, central-frequency shifting, and collisional quenching. Operations at high pressures require a careful choice of an excitation line, and the Q1(8) line in the A-X (1,0) band of OH is selected due to its minimum temperature dependence through the calculation of Boltzmann fraction. The absorption spectra of OH become much broader as pressure increases, leading to a smaller overlap integral and thus smaller excitation efficiency. The central-frequency shifting cannot be omitted at high pressures, and should be taken into account when setting the excitation frequency. The fluorescence yield is estimated based on the LASKIN calculation. Finally, OH-LIF measurements were conducted on flat stoichiometric CH4/air flames at high pressures. And both the numerical and experimental results illustrate that the pressure dependence of fluorescence yield is dominated, and the fluorescence yield is approximately inversely proportional to pressure. These results illustrate the physical processes of OH-LIF and provide useful guidelines for high-pressure application of OH-LIF.

关键词: laser-induced fluorescence, OH, high pressure, numerical analysis

Abstract: The effects of temperature and pressure on laser-induced fluorescence (LIF) of OH are numerically studied under the excitation of A-X (1,0) transition at high pressures. A detailed theoretical analysis is carried out to reveal the physical processes of LIF. It is shown that high pressure LIF measurements get greatly complicated by the variations of pressure- and temperature-dependent parameters, such as Boltzmann fraction, absorption lineshape broadening, central-frequency shifting, and collisional quenching. Operations at high pressures require a careful choice of an excitation line, and the Q1(8) line in the A-X (1,0) band of OH is selected due to its minimum temperature dependence through the calculation of Boltzmann fraction. The absorption spectra of OH become much broader as pressure increases, leading to a smaller overlap integral and thus smaller excitation efficiency. The central-frequency shifting cannot be omitted at high pressures, and should be taken into account when setting the excitation frequency. The fluorescence yield is estimated based on the LASKIN calculation. Finally, OH-LIF measurements were conducted on flat stoichiometric CH4/air flames at high pressures. And both the numerical and experimental results illustrate that the pressure dependence of fluorescence yield is dominated, and the fluorescence yield is approximately inversely proportional to pressure. These results illustrate the physical processes of OH-LIF and provide useful guidelines for high-pressure application of OH-LIF.

Key words: laser-induced fluorescence, OH, high pressure, numerical analysis

中图分类号:  (Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion))

  • 33.50.-j
33.50.Dq (Fluorescence and phosphorescence spectra) 47.70.Pq (Flames; combustion)