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Gas concentration measuring method based on spectral absorptivity second harmonics feature extraction

A gas concentration measurement and second harmonic technology, applied in the field of laser absorption spectroscopy, can solve the problems of limited application range and low measurement signal-to-noise ratio

Active Publication Date: 2018-12-28
SOUTHEAST UNIV
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Problems solved by technology

However, the existing methods for extracting spectral absorptivity from waveform features are often only suitable for harmonic analysis under small modulation coefficients or Lorentzian line shapes, and the measurement signal-to-noise ratio is low and the application range is limited.

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  • Gas concentration measuring method based on spectral absorptivity second harmonics feature extraction
  • Gas concentration measuring method based on spectral absorptivity second harmonics feature extraction
  • Gas concentration measuring method based on spectral absorptivity second harmonics feature extraction

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Embodiment 1

[0107] The following is CH 4 Molecule 6046.95cm -4 CH 4 Measurement of volume concentration, CH 4 The gas distribution concentration is: 2.10×10 -2 , 1.57×10 -2 , 1.05×10 -2 , 5.28×10 -3 , 2.08×10 -3 , 1.10×10 -3 , 5.01×10 -4 , 2.54×10 -4 . The fitting result of WMS-2f / 1f waveform fitting method and the harmonic comparison result that measuring method of the present invention obtains are as follows figure 2 shown. Depend on figure 2 It can be seen that when CH 4 When the volume concentration is high (>1.10×10 -3 ), the WMS-2f / 1f waveform is complete and the fitting residual is small. But with CH 4 The reduction of volume concentration and the reduction of measurement signal-to-noise ratio lead to obvious distortion of WMS-2f / 1f waveform. At this time, the WMS-2f / 1f waveform fitting method is no longer suitable for calculating CH 4 volume concentration. Different from the WMS-2f / 1f waveform fitting method, the second harmonic feature extraction method based ...

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Abstract

The invention discloses a gas concentration measuring method based on spectral absorptivity second harmonics feature extraction. The method disclosed by the invention realizes calculation of integralabsorbance by virtue of harmonic characteristics by building a spectral absorptivity second harmonics peak height-peak width characteristic relation applicable to any modulation coefficient and considering a Voith line type, thus gas parameter information is obtained; meanwhile, in an implementation process of the method, a logarithm processing technology is adopted, influence of residual amplitude modulation on harmonic signal distortion is directly eliminated, and measurement accuracy is improved; the measuring method disclosed by the invention does not need to perform complex least-squaresiteration fitting calculation and only needs to perform filtering processing once, thus requirements on a hardware system are reduced; information of feature points of a waveform still can be relatively accurately extracted when a complete harmonic signal can not be obtained, and a lower measurement limit is lower; and excessive parameters such as a self-broadening coefficient, collision broadening coefficients of various other components and a temperature-dependent index in a database do not need to be utilized, dependence on database parameters is reduced, and application range is wider.

Description

technical field [0001] The invention relates to a gas concentration measurement method based on the second harmonic feature extraction of spectral absorptivity, and belongs to the technical field of laser absorption spectroscopy. Background technique [0002] Tunable diode laser absorption spectroscopy (TDLAS) can achieve online measurement of multiple parameters such as component concentration, temperature, pressure, and velocity, and has the characteristics of high sensitivity, fast time response, and non-contact. It has broad application prospects in the field of gas detection and combustion diagnosis. [0003] In order to reduce the influence of noise on the measurement results and improve the signal-to-noise ratio, the wavelength modulation spectroscopy (WMS) method is often used in the signal detection method, and the second harmonic detection is the most commonly used. In the actual quantitative measurement of wavelength modulation spectroscopy, the measurement resul...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/39
CPCG01N21/39G01N2021/399
Inventor 周宾王一红
Owner SOUTHEAST UNIV
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