High-temperature and high-pressure temperature field measurement method based on low-resolution ultraviolet absorption chromatography

Abstract

The invention discloses a high-temperature and high-pressure temperature field measurement method based on low-resolution ultraviolet absorption chromatography, which comprises the following steps: selecting electron transition of an ultraviolet band NO or OH as an absorption spectrum measurement object according to the temperature of a temperature field to be measured, and selecting a vibration band of the measurement object according to the concentration and size conditions of the temperature field to be measured, determining a wavelength range to be measured; selecting a wide-spectrum light source and a low-resolution spectrometer as a light source and a detector required by absorption spectrum measurement respectively; an absorption chromatography light path network is established, each light path uses the selected wide-spectrum light source and the low-resolution spectrometer, absorption spectrum measurement of measurement objects is carried out on all the light paths, the temperature of each spatial position is obtained through calculation of absorption spectrum signals collected by all the light paths, and temperature field reconstruction is completed. Accurate absorption spectrum temperature measurement under high-temperature and high-pressure conditions can be realized, and accurate measurement of a high-temperature and high-pressure temperature field is realized by combining a chromatography reconstruction algorithm.

Description

Technical Field

[0001] The invention belongs to the field of spectrum measurement and temperature measurement, and in particular relates to a high-temperature and high-pressure temperature field measurement method based on low-resolution ultraviolet absorption chromatography. Background Art

[0002] Temperature is an important physical parameter related to combustion power. It is closely related to performance, efficiency, economy, safety, etc. in the fields of energy industry, aerospace, etc. Therefore, there is an urgent need for accurate temperature measurement. With the continuous advancement of related industrial technologies, the demand for temperature measurement has also expanded towards higher temperatures, higher pressures, faster response speeds, and overall temperature field measurement. For example, the development and optimization of engines for automobiles, ships, aerospace, etc., urgently requires accurate measurement of the high temperature (~2000K) and high pressure (>1MPa) temperature field of the combustion chamber, so as to accurately evaluate the efficiency, performance, heat resistance, safety, etc. of the engine and combustion chamber, and serve as a data reference for further optimization.

[0003] Since traditional contact measurement technology cannot meet the above temperature measurement requirements, temperature measurement technology based on optical means has been widely studied and rapidly developed. Common temperature field measurement technologies include absorption spectral tomography, PLIF (Planar Laser Induced Fluorescence), CARS (Coherent anti-Stokes Raman Scattering) and other technologies. Among them, the temperature measurement accuracy of PLIF technology is poor, and the collision quenching increases with the increase of pressure, which greatly reduces the signal strength; CARS technology has high temperature measurement accuracy, but can only achieve single-point temperature measurement each time, the temperature field measurement speed is slow, and the optical path accuracy requirements are high, which is difficult to apply to the actual complex dynamic temperature field. In contrast, absorption spectral tomography technology has the advantages of calibration-free measurement, high temperature measurement accuracy, high time resolution, and low optical condition requirements. In addition, the equipment is mature, low cost, small size, and easy to integrate. It has become an irreplaceable common technology for on-site in-situ measurement of actual temperature fields.

[0004] However, the commonly used high-wavelength resolution absorption spectral tomography technology is difficult to achieve the measurement of high-temperature and high-pressure temperature fields. At present, there has been no research on absorption spectral tomography measurement to achieve high-pressure temperature field measurement, not only limited to actual temperature fields, but also no research on high-pressure temperature fields under ideal laboratory conditions. The main problem is that the commonly used laser absorption spectrum or the absorption spectrum using high-resolution spectrometers such as medium-step are both high-wavelength resolution spectral measurement technologies, with resolution better than line broadening or at the same level. The temperature measurement principle is to extract the integral area characteristics of independent spectral lines to solve the temperature information. However, under high-pressure conditions, the spectral lines are broadened violently and the overlapping interference is serious, and it is impossible to identify independent spectral lines to complete effective temperature measurement. Some studies have tried to use wavelength modulation technology or supercontinuum spectroscopy technology in a high-temperature and high-pressure uniform environment to extract effective information from the seriously overlapping spectrum, but the accuracy is low and the effect is not ideal. It cannot be applied to the absorption tomography of non-uniform temperature fields. Therefore, in the fields of temperature measurement and combustion power, there is an urgent need to develop a high-temperature and high-pressure temperature field measurement method based on absorption spectroscopy technology, and low-resolution ultraviolet absorption spectral tomography is one of the feasible methods. Summary of the invention

[0005] The purpose of the present invention is to provide a high-temperature and high-pressure temperature field measurement method based on low-resolution ultraviolet absorption tomography, in order to address the problem that the current existing absorption spectral temperature measurement technology mainly adopts high-wavelength resolution spectral measurement, the spectral lines overlap seriously under high-pressure conditions, and the non-uniform temperature field measurement under high-temperature and high-pressure conditions cannot be realized. The method can be free from the influence of spectral line broadening under high-pressure conditions and realize high-temperature and high-pressure temperature field measurement.

[0006] One aspect of the present invention provides a high temperature and high pressure temperature field measurement method based on low resolution ultraviolet absorption chromatography, comprising:

[0007] Step S1: According to the temperature of the temperature field to be measured, the electronic transition of NO or OH in the ultraviolet band is selected as the absorption spectrum measurement object, and according to the concentration and size conditions of the temperature field to be measured, the vibration spectrum band of the measurement object is selected to determine the wavelength range to be measured;

[0008] Step S2: Selecting a wide-spectrum light source and a low-resolution spectrometer as the light source and detector required for absorption spectrum measurement, respectively;

[0009] Step S3: Establish an optical path network for absorption tomography. Each optical path uses the wide-spectrum light source and low-resolution spectrometer selected in step S2. The absorption spectrum of the measurement object selected in step S1 is measured on all optical paths. The temperature of each spatial position is calculated from the absorption spectrum signal collected by each optical path to complete the temperature field reconstruction.

[0010] Preferably, in a temperature field with a temperature higher than 1200° C., the OH spectrum is selected as the measurement object, and according to the size of the temperature field and the OH concentration conditions, a selection is made from five spectral bands with different absorption intensities in the range of 220 nm to 330 nm;

[0011] In the temperature field below 1200°C, the NO spectrum is selected as the measurement object, and two spectral bands in the range of 216nm to 240nm are selected.

[0012] Preferably, when the OH spectrum is selected as the measurement object, five vibration bands of Δv=0, 1, 2, 3, and 4 are selected; when the NO spectrum is selected as the measurement object, two vibration bands of Δv=0 and -1 are selected.

[0013] Preferably, when the OH spectrum is selected as the measurement object, an LED is selected as the broad-spectrum light source; when the NO spectrum is selected as the measurement object, a deuterium lamp, a xenon lamp or a laser-driven white light source is selected as the broad-spectrum light source.

[0014] Preferably, the low-resolution spectrometer includes a grating spectrometer and a Fourier transform spectrometer.

[0015] Preferably, when the OH spectrum is selected as the measurement object, a grating spectrometer with a resolution of 0.1 nm is selected; when the NO spectrum is selected as the measurement object, a grating spectrometer with a resolution of 0.5 nm is selected.

[0016] According to the high-temperature and high-pressure temperature field measurement method based on low-resolution ultraviolet absorption tomography of the above aspect of the present invention, by adopting OH or NO electron transition in the ultraviolet band as the absorption spectrum measurement object, and adopting a wide-spectrum light source and a low-resolution spectrometer as the measurement light source and detector, it is possible to achieve accurate temperature measurement of the absorption spectrum under high-temperature and high-pressure conditions, and combine the tomography reconstruction algorithm to achieve accurate measurement of the high-temperature and high-pressure temperature field. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0018] Figure 1 It is a flow chart of a high-temperature and high-pressure temperature field measurement method according to an embodiment of the present invention;

[0019] Figure 2 It is a comparison diagram of low-resolution ultraviolet absorption spectra of NO and OH in one embodiment of the present invention and high-resolution absorption spectra of commonly used H2O under high pressure conditions;

[0020] Figure 3 is a comparison chart of the ultraviolet absorption intensity of OH and NO and the infrared absorption intensity of H2O at 2000K according to an embodiment of the present invention;

[0021] Figure 4 is a comparison diagram of the UV absorption spectrum of NO at different temperatures according to an embodiment of the present invention;

[0022] Figure 5 is a schematic diagram of simulation steps of an embodiment of the present invention;

[0023] Figure 6 It is a schematic diagram of simulation results of an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The embodiment of the present invention provides a high temperature and high pressure temperature field measurement method based on low resolution ultraviolet absorption chromatography, such as Figure 1 As shown, the high-temperature and high-pressure temperature field measurement method according to the embodiment of the present invention includes steps S1 to S3.

[0026] In step S1, according to the temperature of the temperature field to be measured, the electronic transition of NO or OH in the ultraviolet band is selected as the absorption spectrum measurement object, and according to the concentration and size conditions of the temperature field to be measured, the vibration spectrum band of the measurement object is selected to determine the wavelength range to be measured.

[0027] The main effects of selecting NO or OH UV absorption spectra as the measurement object are described in detail as follows:

[0028] (1) The NO or OH spectra in the UV band are immune to the effects of high pressure at low resolution. Figure 2 As shown in the figure, the commonly used high-resolution absorption spectrum of H2O is compared with the low-resolution spectrum of NO or OH in the ultraviolet band: the OH spectrum resolution is 0.1nm, and the NO spectrum resolution is 0.5nm, which is far worse than the spectral line self-broadening of about 1pm. Figure 2 As shown, it can be seen that compared with the current high-resolution absorption spectrum of H2O, which has serious spectral overlap or even becomes one piece under high-pressure conditions and cannot effectively distinguish independent spectral lines to complete temperature measurement, the low-resolution spectrum of ultraviolet NO or OH has basically the same structure under high-pressure conditions and normal pressure conditions, and is basically not negatively affected by high-pressure conditions;

[0029] (2) NO or OH has stronger absorption in the ultraviolet band. Figure 3 As shown, the OH line intensity can reach up to 10 at 2000K. -17 cm / mole, much higher than the H2O infrared absorption spectrum commonly used for temperature measurement. -22 cm / mole (near infrared)~10 -20 Line intensity in cm / mole (mid-infrared).

[0030] In one embodiment of the present invention, in step S1, when determining the wavelength range to be measured, according to the actual conditions such as temperature, concentration, size, etc. of the temperature field to be measured, appropriate molecules to be measured and vibration bands are selected to determine the wavelength range to be measured:

[0031] (1) In a temperature field above 1200°C, the OH spectrum can be selected as the measurement object, which has strong absorption and high temperature measurement sensitivity; and according to the actual temperature field size and OH concentration conditions, the appropriate spectrum band can be selected from the five vibration spectrum bands of Δv=0, 1, 2, 3, and 4 with different absorption intensities in the range of 220nm to 330nm, such as Figure 3 As shown, the line intensities of the five vibrational bands cover 10 -20 cm / mole~10 -17 Multiple orders of magnitude of cm / mole can select spectral bands with moderate absorption intensity to avoid excessive absorption reaching saturation or too weak absorption affecting the signal-to-noise ratio;

[0032] (2) In a temperature field below 1200°C, the NO spectrum can be selected as the measurement object, and the Δv=0, -1 band in the range of 216nm to 240nm is selected for temperature measurement. The simulated NO low-resolution (0.5nm) spectra at different temperatures are as follows: Figure 4 As shown, the temperature measurement sensitivity can be improved by utilizing the sensitivity of the spectral band intensity ratio to temperature, based on the different changes in the overall intensity of the two spectral bands with temperature.

[0033] In step S2, a wide spectrum light source and a low-resolution spectrometer are selected as the light source and detector required for absorption spectrum measurement, respectively, and the spectrometer resolution required for temperature measurement is determined. A low-resolution spectrometer refers to a spectrometer whose resolution is several orders of magnitude (0.1nm to 1nm) lower than the line broadening (~1pm), including but not limited to a grating spectrometer, a Fourier transform spectrometer, and the like.

[0034] The wide-spectrum light source may be selected from but not limited to LED, deuterium lamp, xenon lamp, laser-driven white light source, etc., and the spectrometer may be selected from grating spectrometer, Fourier transform spectrometer, etc.

[0035] In one embodiment of the present invention, a broadband light source and a spectrometer may be selected as follows:

[0036] (1) Broad-spectrum light source: For OH spectral temperature measurement, LED is selected, which has low cost, high power, small size, good stability and safety. For NO spectral temperature measurement, since LED cannot provide the corresponding wavelength output, flash xenon lamp is selected as the light source, which has low cost and high power. Deuterium lamp, laser-driven white light source, etc., which have better stability but higher cost, can also be selected.

[0037] (2) Spectrometer: For OH spectral temperature measurement, a grating spectrometer with a resolution of 0.1 nm is selected. For NO spectral temperature measurement, a grating spectrometer with a resolution of 0.5 nm is selected. Due to the lower resolution, it can be achieved by a portable spectrometer, reducing the size and cost of the equipment.

[0038] In step S3, a commonly used absorption chromatography method is used to combine the ultraviolet absorption spectrum measurement method described in steps S1 and S2 with the tomography reconstruction method to perform high temperature and high pressure non-uniform temperature field measurement, specifically including steps S31 to S33:

[0039] Step S31: constructing an optical path network for absorption chromatography, each optical path uses the wide-spectrum light source and spectrometer selected in step S2;

[0040] Step S32: measuring the absorption spectrum of the measurement object selected in step S1 for all optical paths;

[0041] Step S33: using a tomographic measurement method, the temperature field is calculated from the absorption spectrum signals collected by each optical path.

[0042] In an embodiment of the present invention based on simulation, the schematic diagram of step S3 is as follows: Figure 5 As shown, the temperature field reconstruction results are as follows Figure 6 As shown. The simulated temperature field is a three-peak distribution of three Gaussian distributions superimposed, with a maximum temperature of 2500K and a pressure of 3MPa; the optical path network formed in step S31 is a four-way optical path with 12 equally spaced parallel optical paths at an interval of 45° in each direction, using the OH ultraviolet absorption spectrum Δv=0 vibration band of 305nm~321nm, and the spectrometer resolution is 0.1nm.

[0043] In step S33, different absorption spectrum tomography measurement methods can be selected, including various currently disclosed tomography algorithms, and the following tomography measurement method is preferably used:

[0044] (1) Experimental absorption spectra α obtained by measuring each optical path exp As well as the absorbance theoretical model α(T, X), the temperature T and concentration X, and the corresponding α(T, X) are obtained by least squares fitting:

[0045] (T, X) = arg min || α exp +ln{-exp[-α(T,X)]*Φ}|| 2

[0046] Among them, Φ is the instrument function of the spectrometer, which is a Gaussian function with resolution as the half-maximum full width, and α(T, X) is the absorbance theoretical model:

[0047] α(T, X)=PXLS p (T)·φ v

[0048] Where P is the pressure, L is the optical path, φ v is the spectral line shape function, S p (T) is the unit pressure line strength.

[0049] (2) For the absorbance α(T, X) obtained on each light path, the absorption coefficient κ(T, X) at each spatial position can be calculated by applying a tomography algorithm. This process is a common method in the field of absorption spectral tomography.

[0050] (3) For the absorption coefficient κ(T, X) at each spatial position, the temperature T and concentration X at each spatial position are obtained by least squares fitting:

[0051] (T,X)=arg min||κ(T,X)-PXS p (T)·φ v || 2

[0052] The temperature T at each spatial position constitutes the temperature field, thus completing the tomographic measurement of the temperature field.

[0053] In this simulation-based embodiment, the reconstruction results of the high temperature and high pressure temperature field at 3MPa and 2500K are as follows: Figure 6 As shown, the reconstructed temperature field is basically consistent with the original temperature field, and the average temperature deviation is 3.4%, which preliminarily verifies the effectiveness of the present invention.

[0054] The high-temperature and high-pressure temperature field measurement method based on low-resolution ultraviolet absorption tomography in the above-mentioned embodiment of the present invention adopts OH or NO electron transition in the ultraviolet band as the absorption spectrum measurement object, and adopts a wide-spectrum light source and a low-resolution spectrometer as the measurement light source and detector, so as to achieve accurate temperature measurement of the absorption spectrum under high-temperature and high-pressure conditions, and finally completes the accurate measurement of the high-temperature and high-pressure temperature field in combination with the tomography reconstruction algorithm.

[0055] The present invention utilizes the advantage that low-resolution spectra in the ultraviolet band are not affected by high pressure, as well as the ability of wide-spectrum light sources and spectrometers to simultaneously measure a large number of spectral lines, to realize absorption spectral tomography measurement of high-temperature and high-pressure temperature fields, which effectively solves the difficult problems of severe spectral line overlap, low broadening model accuracy, and difficulty in realizing high-temperature and high-pressure temperature field measurement under high-pressure conditions in current high-resolution absorption spectra such as laser absorption and medium-step spectrometers; it provides effective spectral measurement technology support for non-contact measurement of high-temperature and high-pressure temperature fields in the fields of combustion diagnosis, energy and power, aerospace, etc.

[0056] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A high-temperature and high-pressure temperature field measurement method based on low-resolution ultraviolet absorption chromatography, characterized in that: include: Step S1: According to the temperature of the temperature field to be measured, the electronic transition of NO or OH in the ultraviolet band is selected as the absorption spectrum measurement object, and according to the concentration and size conditions of the temperature field to be measured, the vibration spectrum band of the measurement object is selected to determine the wavelength range to be measured; Step S2: Selecting a wide-spectrum light source and a low-resolution spectrometer as the light source and detector required for absorption spectrum measurement, respectively; Step S3: Establish an optical path network for absorption tomography. Each optical path uses the wide-spectrum light source and low-resolution spectrometer selected in step S2. The absorption spectrum of the measurement object selected in step S1 is measured on all optical paths. The temperature of each spatial position is calculated from the absorption spectrum signal collected by each optical path to complete the temperature field reconstruction.

2. The method according to claim 1, characterized in that In the temperature field with a temperature higher than 1200°C, the OH spectrum is selected as the measurement object, and according to the size of the temperature field and the OH concentration conditions, five spectral bands with different absorption intensities in the range of 220nm to 330nm are selected; In the temperature field below 1200°C, the NO spectrum is selected as the measurement object, and two spectral bands in the range of 216nm to 240nm are selected.

3. The method according to claim 2, characterized in that When the OH spectrum is selected as the measurement object, five vibration bands of Δv=0, 1, 2, 3, and 4 are selected; when the NO spectrum is selected as the measurement object, two vibration bands of Δv=0 and -1 are selected.

4. The method according to any one of claims 1 to 3, characterized in that When the OH spectrum is selected as the measurement object, LED is selected as the broad-spectrum light source; when the NO spectrum is selected as the measurement object, deuterium lamp, xenon lamp or laser-driven white light source is selected as the broad-spectrum light source.

5. The method according to any one of claims 1 to 3, characterized in that: Low-resolution spectrometers include grating spectrometers and Fourier transform spectrometers.

6. The method according to claim 5, characterized in that When the OH spectrum is selected as the measurement object, a grating spectrometer with a resolution of 0.1 nm is selected; when the NO spectrum is selected as the measurement object, a grating spectrometer with a resolution of 0.5 nm is selected.

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