CN108981953B - Laser absorption spectrum temperature measurement method and system based on interferometric modulation principle - Google Patents

Laser absorption spectrum temperature measurement method and system based on interferometric modulation principle Download PDF

Info

Publication number
CN108981953B
CN108981953B CN201811235909.XA CN201811235909A CN108981953B CN 108981953 B CN108981953 B CN 108981953B CN 201811235909 A CN201811235909 A CN 201811235909A CN 108981953 B CN108981953 B CN 108981953B
Authority
CN
China
Prior art keywords
data
absorption
absorption spectrum
laser
fitting
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201811235909.XA
Other languages
Chinese (zh)
Other versions
CN108981953A (en
Inventor
徐立军
曹章
李远青
邱爽
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Beihang University
Original Assignee
Beihang University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Beihang University filed Critical Beihang University
Priority to CN201811235909.XA priority Critical patent/CN108981953B/en
Publication of CN108981953A publication Critical patent/CN108981953A/en
Application granted granted Critical
Publication of CN108981953B publication Critical patent/CN108981953B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Spectrometry And Color Measurement (AREA)

Abstract

The invention provides a laser absorption spectrum temperature measurement method and system based on an interferometric modulation principle. After the laser signal is generated, the laser signal passes through the Mach-Zehnder interferometer, then passes through the gas to be detected, and data are collected by the photoelectric detector and uploaded to the data processing unit for processing. And extracting absorption light intensity data and mapping of the relative wave number and the absorption light intensity data from the measured data, fitting to obtain initial values of a baseline and absorption spectrum parameters, correcting the initial values through iteration, calculating integral absorption rate according to the corrected absorption spectrum parameters, and calculating the temperature of the gas to be measured through the integral absorption rate of a plurality of spectral lines. The optical system has the advantages of simple structure, no movable part, capability of inhibiting background radiation noise, outstanding overall effect, wide application range, high reliability and wide application prospect.

Description

Laser absorption spectrum temperature measurement method and system based on interferometric modulation principle
(I) technical field
The invention provides a laser absorption spectrum temperature measurement method and a laser absorption spectrum temperature measurement system based on an interferometric modulation principle, in particular to a Mach-Zehnder fiber interferometer multiplexed into an etalon and a light intensity modulator in a measurement system, and the laser modulation technology is applied to the field of temperature measurement.
(II) background of the invention
The gas parameter measuring method based on the laser absorption spectrum is developed rapidly as a rapid and high-sensitivity non-contact measuring method, is an effective method in the field of temperature and substance concentration measurement, is widely applied to the aspects of combustion diagnosis, combustion control and the like, and has great application potential and considerable prospect.
Typical single-path absorption Spectroscopy measurement methods are divided into Direct Absorption Spectroscopy (DAS) and Wavelength Modulation Spectroscopy (WMS), two absorption lines single-path laser absorption Spectroscopy techniques are used to obtain the average temperature and component concentration of the flow field along the laser path, as x. L iu and j.b. jeffries in 2006, "Applied Physics B" vol 82, No. 3 469, 478 entitled "Development of Tunable diode laser sensor for measuring gas turbine exhaust temperature" (Development of Tunable diode laser sensor for measuring gas turbine exhaust temperature), which is validated in large industrial gas turbines for power generators, the average temperature along the laser path is reached by near infrared water absorption Spectroscopy for gas turbine purposes of emission Spectroscopy, as a baseline, a high temperature spectrum (DAS) technique is developed for high temperature Spectroscopy, and the background spectrum reflectance of infrared Spectroscopy (DAS) is developed as a high temperature scattering technique that is not used in the field of high temperature Spectroscopy, high temperature Spectroscopy (DAS) and low temperature Spectroscopy technique for high temperature Spectroscopy (DAS) and high temperature Spectroscopy (spectral emission Spectroscopy) is used in the field of the background Spectroscopy technique for high temperature Spectroscopy.
In the WMS method, a high-frequency sinusoidal signal is superimposed on a slow ramp scanning waveform, the wavelength and intensity of a laser are modulated, AS indicated by the grid b.rieker and Jay b.jeffries in 2009, Applied Optics, volume 48, page 29, entitled "Calibration-free wavelength Modulation Absorption Spectroscopy technique for measuring gas temperature and concentration in harsh environment" (Calibration-wavelength Modulation in Noise Optics), while in contrast to the direct Absorption method, in carbon dioxide measurement in supersonic gas flow, the WMS-2f method is improved by 4 times in signal-to-Noise ratio, AS indicated by the algorithm of attenuation-wavelength Modulation in wo-10, the wavelength Modulation technique is achieved by the Tunable Absorption Spectroscopy, the wavelength Modulation method is achieved by the Diode, the wavelength Modulation and Amplitude Modulation method is achieved by the Diode, the fiber optic modulator, the fiber optic, the fiber.
As in Y Deguchi and M Noda, published in 2002 in Journal of Bacteriology (Journal of Bacteriology) 190, volume 7, 2637 and 2641, entitled "laser diagnostic techniques for temperature and species concentration monitoring for Industrial applications" (Industrial applications of temperature and species concentration monitoring), interferometers are used as etalons to ensure synchronization of optical frequencies in both DAS and WMS methods.
Based on the background, the invention provides a laser absorption spectrum temperature measurement method and system based on interferometric modulation, which measure uniform temperature through a single optical path dual-spectral line and simultaneously acquire etalon data and absorption spectrum information through one optical path. On the basis of relatively simplifying the system structure, the light intensity modulation is realized, the background noise is inhibited to a certain extent, and the temperature measurement is realized.
Disclosure of the invention
The core technology of a gas thermometer based on a laser absorption spectrum technology is how to accurately extract absorption spectrum information from a laser signal. In general gas temperature measurement systems based on laser absorption spectroscopy, a single optical path is used as an etalon to extract the change relation of relative wave numbers along with time, and the optical systems are complex.
The invention provides an absorption spectrum temperature measurement system based on interferometric modulation and a spectrum reconstruction method based on iteration, a Mach-Zehnder fiber interferometer is multiplexed into an etalon as a light intensity modulation device, a single light path is not required to be used as the etalon, an optical system is simplified, and background noise can be suppressed.
The elements used include: the device comprises a laser generating unit, a Mach-Zehnder optical fiber interferometer, a photoelectric detection unit, a data processing unit and the like.
The technical scheme adopted by the invention is as follows: after passing through the Mach-Zehnder fiber optic interferometer, the laser is converted into parallel space light through the collimating mirror, and the parallel space light passes through the measured gas and is collected by the photoelectric detector. The initial values of the parameters of the spectrum data and the baseline data are obtained by demodulating and fitting the acquired measurement signals, and then the initial values are corrected through an iterative process to obtain the final values of the spectrum fitting parameters. And (4) solving the integral absorption rate of the spectrum data through the fitting parameters of the spectrum data, and calculating to obtain the temperature value of the gas to be detected.
In the process of respectively resolving and outputting laser relative wave number data and absorption light intensity data by collecting data, the adopted resolving method comprises the following steps:
firstly, laser signals generated by a laser generation module pass through a Mach-Zehnder interferometer to obtain measurement signals scanned by light intensity modulation wavelength, then pass through a measured object and are finally collected by a photoelectric detector, the form of the collected signals is shown as formula (1) in principle,
Figure GDA0002406341760000021
wherein, IMZI(t) is the time-varying measurement data acquired by the photodetector, I0(t) is light intensity data of a laser signal generated by a laser before passing through a Mach-Zehnder interferometer and a measurement object, vFSRIs the Free Spectral Range (FSR), K of the interferometer1、K2、φ0The parameters are determined by the self structure of the Mach-Zehnder fiber interferometer, when the used interferometer is fixed, the parameters are constants, v (t) is output laser relative wave number data, and α (v (t)) is an absorption spectrum of a measured object;
resolving and outputting laser relative wave number data v (t) according to the acquired data, wherein laser signals passing through the Mach-Zehnder interferometer and the measured object are shown as a formula (1), the laser relative wave number data can be obtained by resolving light intensity data, and the wave number changes into a free spectral range between two extreme points of the laser signal intensity; in order to more accurately extract the position of the extreme point under the limited number of sampling points, the following method is adopted when extracting the relative wave number data, and the method is used for IMZI(t) high-pass filtering the signal, wherein the cut-off frequency is the scanning frequency of the laser signal; recording the zero crossing points of the filtered signals, wherein the midpoint position of every two adjacent zero crossing points is the position of an extreme point; the relative wavenumbers represented by the data points of the two extreme points are different by a free spectral range, so that the relative wavenumber data v (t) of the data laser can be obtained;
step three, demodulating the acquired data to obtain absorption light intensity data: substituting the relative wave number data v (t) of the laser into (1) to obtain the mapping relation between the relative wave number v and the measurement data, as shown in formula (2)
Figure GDA0002406341760000031
Free spectral range v from mach-zehnder interferometerFSRCan give a signal as described in the formula (3)
Figure GDA0002406341760000032
The (2) and (3) are combined and subjected to orthogonal demodulation to obtain absorption light intensity data I (t), as shown in the formula (4)
Figure GDA0002406341760000033
Wherein I0(t) is the light intensity signal of the laser signal generated by the laser before entering the Mach-Zehnder interferometer, Ibase(t) is with0(t) the proportional signal, which is the baseline data in the ideal case during data processing, α (v (t)) is the absorption spectrum of the measured object.
Obtaining a baseline parameter and an absorption spectrum parameter in a solving process in a fitting mode, and further solving the temperature value of the measured gas by iteratively correcting a fitting result, wherein the adopted solving method comprises the following steps:
step one, determining mathematical models used for fitting in different processes, estimating fitting parameters of a baseline in a least square fitting mode according to absorption light intensity data, fitting the baseline by using a cubic polynomial, and obtaining a fitting parameter group ParaBase of the baseline0The model used is shown in (5)
Figure GDA0002406341760000041
Wherein, the fitting parameter group ParaBase0The absorbance data α (t) is then obtained based on beer Lambert's law, as shown in (6)
Figure GDA0002406341760000042
Substituting the relative wave number data v (t) of the laser to obtain absorption spectrum data α (v), fitting on the basis of the absorption spectrum data, and adopting a model shown as (7),
Figure GDA0002406341760000043
wherein A is the integral absorption rate of the absorption spectrum, phiv(v) As a Voigt linear broadening function. Since the Voigt linear function calculation comprises the calculation of volume integral, the analytic solution can not be directly obtained, only the solution can be obtained through numerical calculation, in order to quickly obtain the absorption coefficient at the center of the spectral line and the half-height width of the Voigt linear, a simplified model as shown in (8) is adopted,
Figure GDA0002406341760000044
wherein v is0For the central wave number of the absorption spectrum,. DELTA.vCBroadening the half-width of the line, Δ v, for collisionsDFor Doppler broadening of the half width of the line, Δ vVThe half-width of the spectral line of the Voigt linear function can be obtained by empirical formula (9) Phiv(v0) The value of the Voigt linear function at the center frequency of the spectral line can be obtained from (10), (11) and (12).
Figure GDA0002406341760000045
Figure GDA0002406341760000046
Figure GDA0002406341760000047
Figure GDA0002406341760000051
Therefore, when fitting absorption spectrum data by using the simplified absorption spectrum model (7), the absorption spectrum parameter ParaSpec0Needs to include A, Δ vC、ΔvDAnd v0Four parameters.
α (v) is used as original data, an absorption spectrum fitting model (7) is adopted for fitting to obtain fitting parameters ParaSpec of the absorption spectrum0。
Step two, using the obtained fitting parameters of the baseline and the absorption spectrum as initial values, and according to the absorption light intensity data I (t) and the fitting parameters ParaBase using the baselinei-1Calculated baseline data Ibasefitting(i-1)(t) division and obtaining the absorption spectrum data α from (6)i(t)；
Step three, the absorption spectrum data αi(t) and the relative wavenumber data v (t) of the laser, resulting in a mapping α between the absorption spectrum and the relative wavenumber of the laseri(v) Fitting the absorption spectrum data by the absorption spectrum model (7) to obtain an absorption spectrum parameter ParaSpeci；
Step four, the absorption light intensity data is taken as a fitting target, and according to the absorption spectrum parameters ParaSpeciAnd mapping v (t) of the absorption light intensity data relative to wave number, and fitting a baseline to obtain a parameter ParaBaseiAnd fitted absorption intensity data Ii(t)；
Step five, judging the absorption light intensity data I (t) and the fitting data I thereofi(t) residual squared SiAnd the relative change of the sum of squares of the residual errors and the last time is calculated, when the change quantity is larger than 0.1%, the step II is returned, otherwise, the fitting parameter ParaSpec of the corrected absorption spectrum is outputiParabase as a parameter of fit to the baselinei；
And step six, obtaining integral absorption rate according to the absorption spectrum parameters, and calculating through the integral absorption rates of the plurality of absorption spectra to obtain the temperature of the gas to be measured.
The invention has the advantages that: according to the invention, the Mach-Zehnder interferometer is multiplexed as the etalon and the light intensity modulator, only one light path is needed in the measurement process, and the system structure for measuring temperature by adopting a direct absorption method based on the tunable absorption spectrum technology is simplified; according to the invention, the Mach-Zehnder interferometer is multiplexed to be used as an etalon and a light intensity modulator, light intensity modulation is carried out on the basis of temperature measurement by a direct absorption method, and background noise is inhibited to a certain extent; in the calculation algorithm, the spectral parameters and the baseline parameters obtained by adopting the baseline fitting method are used as initial values, and the fitting result is corrected in an iterative mode to obtain more accurate spectral parameters, so that the system error is reduced.
(IV) description of the drawings
FIG. 1 is a block diagram of a single path laser absorption spectroscopy temperature measurement system;
FIG. 2 is a graph of the absorption signal as a function of time after demodulation;
FIG. 3 is a graph of relative wavenumber versus time;
FIG. 4 relationship of simulation data and results before and after comparison iteration.
(V) detailed description of the preferred embodiments
In this example, the effectiveness of the method is demonstrated by numerical simulation given a uniform temperature of the gas being measured.
The invention is further described with reference to the accompanying drawings in which:
in fig. 1, a tunable semiconductor laser control module (1) and a tunable semiconductor laser (2) jointly form a laser generation unit, which is connected with a mach-zehnder optical fiber interferometer (3) through an optical fiber, transmission light in the optical fiber is converted into collimated light (parallel light) through a collimating mirror (4), the collimated light passes through a gas to be measured (5), and then the measured data is collected and uploaded by a data collection module (7) through a photoelectric detector (6), and subsequent data processing is performed through a data processing unit (8) to obtain a final resolving result.
In the simulation process, the simulated environment is set as follows, the absorption target is water molecules, the molar concentration is 0.5%, the temperature is 298K, the pressure is 1atm, and the absorption distance is 80 cm. Parameter K of the Mach-Zehnder fibre optic interferometer used1＝K2＝0.5,vFSR＝0.01cm-1The central wavenumbers of the selected absorption spectra were 7183.89cm-1、7185.59cm-1。
Step one, laser is emitted by a laser generation module, the laser is converted into space light through a collimating mirror after passing through a Mach-Zehnder optical fiber interferometer, the space light penetrates through a region to be detected and is received by a detector to obtain a path of absorption signal, the signal form is shown as (1), and the system structure is shown as figure 1;
Figure GDA0002406341760000061
step two, reconstructing the mapping relation between the relative wave number and the absorption light intensity data according to the acquired data, and firstly, carrying out comparison on the IMZI(t) high-pass filtering the signal, wherein the cut-off frequency is the scanning frequency of the laser signal; then, recording the zero crossing points, wherein the midpoint position of every two adjacent zero crossing points is the position of an extreme point; the relative wave numbers represented by the data points of the two extreme points are different by a Free Spectral Range (FSR), and therefore, a mapping relation v (t) between the relative wave numbers and the absorption intensity data can be obtained, and the result is shown in FIG. 2.
Step three, resolving the light intensity absorption data according to the detection signal, firstly, carrying out coordinate transformation according to the mapping relation v (t) between the relative wave number and the absorption light intensity data to obtain the data shown in (2)
Figure GDA0002406341760000062
Free spectral range v from mach-zehnder interferometerFSRThe form of the reference signal can be given as described in the formula (3)
Figure GDA0002406341760000063
After demodulation, the same absorption light intensity data as the traditional direct absorption method measurement signal can be obtained, as shown in formula (4)
I(t)＝I0(t)·α(v(t)) (4)
Wherein I0(t) is a light intensity signal of the laser signal generated by the laser before entering the mach-zehnder interferometer, and α (v (t)) is an absorption spectrum of the object to be measured, and the result is shown in fig. 3.
And step four, calculating and correcting the baseline parameters and the absorption spectrum parameters through an iterative process. First by baseline fittingObtaining estimated values of fitting parameters of the baseline and the absorption spectrum, and then taking the estimated fitting parameters of the baseline and the absorption spectrum as initial values. Wherein the central wave number is 7183.89cm-1The initial value of the spectrum fitting parameter of (A) ParaSpec7183-0Δ v of (a)C、ΔvDA and v00.1860, 0.1860, 0.0113, and 0.0838, respectively, the initial values of the baseline fitting parameters ParaBase7183-0＝[0,0,0.0003,3.9044](ii) a The central wave number is 7185.59cm-1The initial value of the spectrum fitting parameter of (A) ParaSpec7185-0Δ v of (a)C、ΔvDA and v00.5162, 0.5162, 0.0973 and 0.1952, respectively, the initial values of the baseline fitting parameters ParaBase7185-0＝[0,0,0.0003,3.8880]；
Step five, starting an iterative process, and fitting parameters ParaBase according to the absorption light intensity data and the used base lineiDividing the calculated baseline data and taking the negative logarithm to obtain absorption spectrum data; then, Voigt function fitting is carried out on the absorption spectrum data to obtain an absorption spectrum parameter ParaSpeci(ii) a Secondly, the absorption light intensity data is taken as a fitting target, and according to the absorption spectrum parameters ParaSpeciAnd mapping v (t) of the absorption light intensity data relative to wave number, and fitting a baseline to obtain a parameter ParaBaseiAnd fitted absorption intensity data Ii(t); finally, judging the absorption light intensity data I (t) and the fitting data I thereofi(t) residual squared SiAnd the relative change of the sum of squares of the residual errors and the last time is summed, when the variation is larger than 0.1%, the first step of the continuous iteration process is returned to continue fitting, otherwise, the process is considered to be converged, and the fitting parameter ParaSpec of the corrected absorption spectrum is outputiParabase as a parameter of fit to the baselinei. Wherein the central wave number is 7183.89cm-1The fitting parameters of the absorption spectrum are iterated for 186 times, and the fitting parameters of the spectrum are ParaSpec7183-186Δ v of (a)C、ΔvDA and v00.0117, 0.1055, 0.0047, and 0.0841, respectively, the baseline fitting parameter value ParaBase7183-186＝[-1.0848e-14,2.1269e-10,0.0003,3.8971]Center wave number of 7185.59cm-1Is iterated over 290 timesSpectral fitting parameter value ParaSpec7185-290Δ v of (a)C、ΔvDA and v00.0716, 0.1928, 0.0240, and 0.1980, respectively, the baseline fitting parameter value ParaBase7185-290＝[-6.10e-15,9.21e-11,2.95e-4,3.8837]；
The integral absorption rate is obtained according to the absorption spectrum parameters, the temperature of the gas to be measured is obtained by calculating the integral absorption rates of the plurality of absorption spectra, and the comparison between the initial value of the absorption spectrum obtained by calculating and the absorption spectrum after iterative correction is shown in fig. 4. The set temperature was 298K and the calculated temperature was 299.9K.
The above description of the invention and its embodiments is not intended to be limiting, and the illustrations in the drawings are intended to represent only one embodiment of the invention. Without departing from the spirit of the invention, it is within the scope of the invention to design structures or embodiments similar to the technical solution without creation.

Claims (4)

1. A laser absorption spectrum temperature measurement method based on an interference modulation principle comprises a laser generation unit, a Mach-Zehnder optical fiber interferometer, a collimating mirror, a photoelectric detector, a data acquisition module and a data processing unit, and is characterized in that laser signals are generated by the laser generation unit, then intensity modulation is completed through the Mach-Zehnder optical fiber interferometer, the laser signals penetrate through a measured object and are detected by the photoelectric detector, the data acquisition module acquires data and transmits the data to the data processing unit, in the data processing process, the mapping relation between absorption light intensity data and relative wave number and absorption light intensity data is respectively solved through the acquired data, then the estimated value of a baseline parameter is solved according to the part of the absorption light intensity data which is approximate to no absorption, the estimated value of the absorption spectrum parameter is solved according to the mapping relation between the relative wave number and the absorption light intensity data, and correcting the estimated values of the baseline and the absorption spectrum parameters in an iterative mode, obtaining the integral absorption rate of the corresponding spectral line in the measured target environment according to the corrected absorption spectrum parameters, and calculating the temperature value of the measured gas by combining a plurality of spectral line integral absorption rates.
2. The laser absorption spectrum temperature measurement method based on the interferometric modulation principle as claimed in claim 1, wherein: the method comprises respectively calculating the mapping relationship between the absorption intensity data and the relative wave number and absorption intensity data by collecting data,
firstly, laser signals generated by a laser generating unit pass through a Mach-Zehnder interferometer to obtain measurement signals scanned by light intensity modulation wavelength, then pass through a measured object and are finally collected by a photoelectric detector, the form of the collected signals is shown as formula (1) in principle,
Figure FDA0002406341750000011
wherein, IMZI(t) is the time-varying measurement data acquired by the photodetector, I0(t) is light intensity data of the laser signal generated by the laser generating unit before passing through the Mach-Zehnder interferometer and the measured object, vFSRIs the Free Spectral Range (FSR), K of the interferometer1、K2、φ0The parameters are determined by the self structure of the Mach-Zehnder fiber interferometer, when the used interferometer is fixed, the parameters are constants, v (t) is output laser relative wave number data, and α (v (t)) is an absorption spectrum of a measured object;
resolving and outputting laser relative wave number data v (t) according to the acquired data, wherein laser signals passing through the Mach-Zehnder interferometer and the measured object are shown as a formula (1), the laser relative wave number data can be obtained by resolving light intensity data, and the wave number changes into a free spectral range between two extreme points of the laser signal intensity; in order to more accurately extract the position of the extreme point under the limited number of sampling points, the following method is adopted when extracting the relative wave number data, and the method is used for IMZI(t) high-pass filtering the signal, wherein the cut-off frequency is the scanning frequency of the laser signal; recording the zero crossing points of the filtered signals, wherein the midpoint position of every two adjacent zero crossing points is the position of an extreme point; the relative wave numbers represented by the data points of the two extreme points are different by a free spectral range, so that the relative wave number of the data laser can be obtainedAccording to v (t);
step three, demodulating the acquired data to obtain absorption light intensity data: substituting the relative wave number data v (t) of the laser into (1) to obtain the mapping relation between the relative wave number v and the measurement data, as shown in formula (2)
Figure FDA0002406341750000012
In the formula I0(v) The laser light intensity which changes with the wave number and does not pass through the Mach-Zehnder interferometer and the measured object is substituted into the initial laser light intensity data I0(t) results;
free spectral range v from mach-zehnder interferometerFSRCan give a signal as described in the formula (3)
Figure FDA0002406341750000021
The (2) and (3) are combined and subjected to orthogonal demodulation to obtain absorption light intensity data I (t), as shown in the formula (4)
Figure FDA0002406341750000022
Wherein I0(t) is a light intensity signal of the laser signal generated by the laser generating unit before entering the Mach-Zehnder interferometer, Ibase(t) is with0(t) the proportional signal, which is the baseline data in the ideal case during data processing, α (v (t)) is the absorption spectrum of the measured object.
3. The laser absorption spectrum temperature measurement method based on the interferometric modulation principle as claimed in claim 1, wherein: the calculation process obtains the baseline parameters and the absorption spectrum parameters in a fitting mode, and further calculates the temperature value of the measured gas by iteratively correcting the fitting result, and comprises the following steps,
step one, estimating bases by a least square fitting mode according to absorption light intensity dataFitting the baseline by using a cubic polynomial to obtain a baseline fitting parameter set ParaBase0The model used is shown in (5)
Figure FDA0002406341750000023
Wherein t is time, and the parameter group ParaBase is fitted0For fitting polynomial parameters, ParaBase0(j) The jth element in the set of parameters is fit to the baseline, and then absorbance data α (t) is obtained based on beer's Lambert law, as shown in (6)
Figure FDA0002406341750000024
Substituting the relative wave number data v (t) of the laser to obtain absorption spectrum data α (v), fitting on the basis of the absorption spectrum data, and adopting a model shown as (7),
Figure FDA0002406341750000025
wherein A is the integral absorption rate of the absorption spectrum, phiv(v) For the Voigt linear function, because the calculation of the Voigt linear function comprises the calculation of volume integral, the analytic solution can not be directly obtained, and only can be solved through numerical calculation, in order to quickly obtain the absorption coefficient at the center of the spectral line and the half-height width of the Voigt linear function, a simplified model as shown in (8) is adopted,
Figure FDA0002406341750000031
wherein v is the absorption spectrum wave number point, v0For the central wave number of the absorption spectrum,. DELTA.vCBroadening the half-width of the line, Δ v, for collisionsDFor Doppler broadening of the half width of the line, Δ vVThe half-width of the spectral line of the Voigt linear function can be obtained by empirical formula (9) Phiv(v0) The value of the Voigt linear function at the center frequency of the spectral line can be obtained from (10), (11) and (12)：
Figure FDA0002406341750000032
Figure FDA0002406341750000033
Figure FDA0002406341750000034
Figure FDA0002406341750000035
Therefore, when fitting absorption spectrum data by using the simplified absorption spectrum model (7), the absorption spectrum parameter ParaSpec0Needs to include A, Δ vC、ΔvDAnd v0Four parameters;
α (v) is used as original data, an absorption spectrum fitting model (7) is adopted for fitting to obtain fitting parameters ParaSpec of the absorption spectrum0；
Step two, using the obtained fitting parameters of the baseline and the absorption spectrum as initial values, and according to the absorption light intensity data I (t) and the baseline data I obtained by calculation in the (I-1) th iterationbasefitting(i-1)(t) and (6) obtaining the absorption spectrum data α in the ith iterationi(t) wherein the baseline data I in the (I-1) th iterationbasefitting(i-1)(t) is the fitting parameter ParaBase of the baseline obtained using the (i-1) th iterationi-1Calculated according to formula (5);
step three, the absorption spectrum data αi(t) and the relative wavenumber data v (t) of the laser, resulting in a mapping α between the absorption spectrum and the relative wavenumber of the laseri(v) Fitting the absorption spectrum data by the absorption spectrum model (7) to obtain absorption spectrum parameters ParaSpec obtained by fitting in the ith iterationi；
Step four, the absorption light intensity data is taken as a fitting target, and the absorption spectrum obtained by fitting in the ith iteration is obtainedParameter ParaSpeciAnd mapping v (t) of the absorption light intensity data by relative wave number, fitting the baseline to obtain a baseline fitting parameter ParaBase obtained by the ith iteration fittingiAnd the absorption intensity data I fitted with the ith iterationi(t)；
Step five, judging the absorption light intensity data I (t) and the ith iteration fitting data I thereofi(t) residual squared SiAnd the relative change of the sum of squares of the residual errors and the last time is calculated, when the change quantity is larger than 0.1%, the step II is returned, otherwise, the fitting parameter ParaSpec of the corrected absorption spectrum is outputiParabase as a parameter of fit to the baselinei；
And step six, obtaining integral absorption rate according to the absorption spectrum parameters, and calculating through the integral absorption rates of the plurality of absorption spectra to obtain the temperature of the gas to be measured.
4. A laser absorption spectrum temperature measurement system based on an interference modulation principle comprises a laser generation unit, a Mach-Zehnder optical fiber interferometer, a collimating mirror, a photoelectric detector, a data acquisition module and a data processing unit, and is characterized in that laser signals are generated by the laser generation unit, then intensity modulation is completed through the Mach-Zehnder optical fiber interferometer, the laser signals penetrate through a measured object and are detected by the photoelectric detector, the data acquisition module acquires data and transmits the data to the data processing unit, in the data processing process, the mapping relation between absorption light intensity data and relative wave number and absorption light intensity data is respectively solved through the acquired data, then the estimated value of a baseline parameter is solved according to the part of the absorption light intensity data which is approximate to no absorption, the estimated value of the absorption spectrum parameter is solved according to the mapping relation between the relative wave number and the absorption light intensity data, and correcting the estimated values of the baseline and the absorption spectrum parameters in an iterative mode, obtaining the integral absorption rate of the corresponding spectral line in the measured target environment according to the corrected absorption spectrum parameters, and calculating the temperature value of the measured gas by combining a plurality of spectral line integral absorption rates.
CN201811235909.XA 2018-10-24 2018-10-24 Laser absorption spectrum temperature measurement method and system based on interferometric modulation principle Active CN108981953B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201811235909.XA CN108981953B (en) 2018-10-24 2018-10-24 Laser absorption spectrum temperature measurement method and system based on interferometric modulation principle

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201811235909.XA CN108981953B (en) 2018-10-24 2018-10-24 Laser absorption spectrum temperature measurement method and system based on interferometric modulation principle

Publications (2)

Publication Number Publication Date
CN108981953A CN108981953A (en) 2018-12-11
CN108981953B true CN108981953B (en) 2020-07-31

Family

ID=64543704

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201811235909.XA Active CN108981953B (en) 2018-10-24 2018-10-24 Laser absorption spectrum temperature measurement method and system based on interferometric modulation principle

Country Status (1)

Country Link
CN (1) CN108981953B (en)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110031198B (en) * 2019-04-25 2020-11-10 上海工程技术大学 Energy-considered strain load spectrum compiling method
CN111239072B (en) * 2019-11-25 2023-05-12 中国航空工业集团公司北京长城计量测试技术研究所 Method for accurately measuring temperature of combustion gas
CN113252204B (en) * 2021-04-01 2022-04-01 北京航空航天大学 Laser absorption spectrum temperature measurement method based on amplitude modulation
CN112798550B (en) * 2021-04-14 2021-07-13 四川大学 Wide-measurement-range laser absorption spectrum combustion diagnosis method
CN113390826B (en) * 2021-05-28 2022-11-01 中国科学院力学研究所 Integral absorbance measurement error estimation method for sight line non-uniform absorption spectrum measurement
CN113176222B (en) * 2021-06-09 2022-07-29 复旦大学 Gas concentration inversion method based on direct absorption spectrum
CN113358160B (en) * 2021-07-08 2022-05-17 天津大学 Atmospheric data measuring method and system
CN114993987B (en) * 2022-05-16 2024-04-30 北京航空航天大学 Temperature and gas concentration measuring method and system based on absorption spectrum amplitude modulation
CN117747008B (en) * 2024-02-07 2024-05-03 山东省科学院激光研究所 Baseline fitting and noise reduction method and system for gas laser absorption spectrum

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102680020A (en) * 2012-05-16 2012-09-19 清华大学 Gas parameter online measurement method based on wavelength modulation spectroscopy
CN103557886A (en) * 2013-10-29 2014-02-05 东南大学 Method for simultaneously measuring distribution of high-temperature gas two-dimensional transient temperature field and concentration field based on hyper spectrum
JP2014085301A (en) * 2012-10-26 2014-05-12 Nippon Telegr & Teleph Corp <Ntt> Light intensity measurement device for wavelength sweeping light source
CN107219190A (en) * 2017-05-05 2017-09-29 东南大学 A kind of non-calibrating gas parameter measuring method based on triangular modulation

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9766483B2 (en) * 2016-01-21 2017-09-19 Sumitomo Electric Industries, Ltd. Optical transceiver implementing erbium doped fiber amplifier

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102680020A (en) * 2012-05-16 2012-09-19 清华大学 Gas parameter online measurement method based on wavelength modulation spectroscopy
JP2014085301A (en) * 2012-10-26 2014-05-12 Nippon Telegr & Teleph Corp <Ntt> Light intensity measurement device for wavelength sweeping light source
CN103557886A (en) * 2013-10-29 2014-02-05 东南大学 Method for simultaneously measuring distribution of high-temperature gas two-dimensional transient temperature field and concentration field based on hyper spectrum
CN107219190A (en) * 2017-05-05 2017-09-29 东南大学 A kind of non-calibrating gas parameter measuring method based on triangular modulation

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
Rapid, Time-Division Multiplexed, Direct Absorption- and Wavelength Modulation-Spectroscopy;Alexander Klein 等;《Sensors》;20141114;第14卷(第11期);21497-21513 *
二极管激光吸收传感器测量超声速流场的温度和速度;王广宇 等;《光学学报》;20130930;第33卷(第9期);0912009-1至0912009-7 *
基于波长调制谐波信号主峰拟合的气体浓度测量方法;杨阳 等;《北京航空航天大学学报》;20171130;第43卷(第11期);2187-2192 *
多谱线 TDLAS 测温中谱线选择的实验研究;陈亚婧 等;《电子测量与仪器学报》;20171231;第31卷(第12期);1948-1952 *

Also Published As

Publication number Publication date
CN108981953A (en) 2018-12-11

Similar Documents

Publication Publication Date Title
CN108981953B (en) Laser absorption spectrum temperature measurement method and system based on interferometric modulation principle
CN111077109B (en) Temperature and concentration measuring system and method based on double-optical comb spectrum technology
CN111077110B (en) Temperature field and concentration field measuring system and method based on double-optical comb spectrum
Huang et al. Frequency-division multiplexing and main peak scanning WMS method for TDLAS tomography in flame monitoring
CN109100325B (en) Gas concentration measuring method based on spectral absorption rate second harmonic feature extraction
JP5983779B2 (en) Gas absorption spectroscopy apparatus and gas absorption spectroscopy method
CN108760681A (en) A kind of path averaged temperature measuring system and method decomposed based on waveform
CN109991189B (en) Fixed point wavelength modulation gas concentration measuring device based on wave number drift correction and measuring method thereof
CN113252204B (en) Laser absorption spectrum temperature measurement method based on amplitude modulation
CN112378616B (en) High-speed flow field multi-parameter measurement system and method based on wavelength modulation absorption spectrum
CN109696415B (en) Gas absorption rate online measurement method based on fast Fourier transform
CN109100044B (en) Single-light-path multispectral-based gas temperature probability density distribution fitting reconstruction method
CN111829982A (en) Multi-component gas concentration detection and temperature error correction method
CN108562237B (en) Device and method for performing spectrum calibration in optical frequency domain reflection sensing system by adopting HCN (hydrogen cyanide) air chamber
CN110514622B (en) Two-dimensional temperature and concentration reconstruction system and method based on histogram information
CN114993987B (en) Temperature and gas concentration measuring method and system based on absorption spectrum amplitude modulation
JP6863831B2 (en) Calculation method of calculation formula for output correction of photodetector and output correction method of photodetector
CN113447458A (en) Gas temperature and concentration parameter measuring method based on laser absorption impedance spectroscopy
CN111351770A (en) Wavelength modulation absorption spectrum absorption optical path and gas concentration synchronous inversion method
CN109270027A (en) A kind of gas absorptivity On-line Measuring Method based on the fitting of Sine Modulated time domain
CN111089661A (en) Temperature rapid extraction method based on laser absorption spectrum
CN114034653B (en) Wavelength modulation absorption spectrum chromatography reconstruction system based on deep learning
CN114544547A (en) Method and system for on-line recursive demodulation of wavelength modulation spectrum signals
Xu et al. FPGA-based real-time implementation of temperature measurement via tunable diode laser absorption spectroscopy
CN103411923B (en) A kind of normalization noise-reduction method adopting two-path tunable laser absorption spectrum technology

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant