Waste gas detection method and device for chimney pipeline

Abstract

The invention provides a waste gas detection method and device for a chimney pipeline, and relates to the field of tunable semiconductor laser absorption spectrum technology detection.The method comprises the steps that the ratio of second harmonic signal amplitudes of two adjacent absorption spectral lines of H2O and O2 is obtained, and the spectral line intensity ratio of the two adjacent absorption spectral lines of H2O and O2 is determined based on the ratio; fitting correlation coefficients of the spectral line intensity ratio of the two adjacent absorption spectral lines of O2 and H2O and the temperature are obtained, the gas corresponding to the maximum fitting correlation coefficient serves as reference gas, and the waste gas temperature value of the chimney pipeline is determined; and determining the concentration value of O2 and the humidity value of the waste gas based on the temperature value of the waste gas of the chimney pipeline and the pressure value of the waste gas of the chimney pipeline according to the temperature value of the waste gas and the second harmonic signals of the two adjacent absorption spectral lines of the reference gas. The detection method can improve the detection precision of the temperature, pressure, humidity and oxygen concentration value of the chimney pipeline waste gas.

Description

Technical Field

[0001] The invention relates to the field of tunable semiconductor laser absorption spectroscopy technology detection, and in particular to an exhaust gas detection method and device for chimney pipes. Background Art

[0002] In the field of waste gas emission monitoring of stationary pollution sources, in addition to the need to monitor conventional pollutant factors (SO 2 、NO x In addition to the concentration of NMHC, it is also necessary to monitor exhaust gas parameters such as temperature, pressure, flow rate, humidity, and oxygen concentration, which are important parameters for calculating exhaust gas emissions. Therefore, it is necessary to accurately monitor these parameters, which is of great significance for controlling the emission of pollutants in exhaust gas.

[0003] In the related technologies, tunable semiconductor laser absorption spectroscopy (TDLAS) is usually used in the process of exhaust gas detection. It has the characteristics of no need for pretreatment, strong selectivity, fast response speed, high accuracy and high precision. In recent years, it has been widely used in environmental and medical detection fields. TDLAS is mainly divided into direct absorption, frequency modulation and wavelength modulation technology based on signal detection methods. However, in the related technologies, when measuring exhaust gas parameters (temperature, pressure, humidity, oxygen concentration), absorption spectroscopy technology and hardware such as sensors are often used to determine the temperature, pressure, humidity and oxygen concentration of the exhaust gas. Once the hardware fails or the hardware detection accuracy is different under different environmental conditions, the accuracy of the detected temperature, pressure, humidity and oxygen concentration values ​​will be affected. Summary of the invention

[0004] Based on this, it is necessary to provide a method and device for detecting exhaust gas from chimney pipes in order to solve the above technical problems.

[0005] In a first aspect, the present application provides an exhaust gas detection method for a chimney pipe, the method comprising: Get H 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines of O and 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption spectral lines; wherein the first laser and the second laser are driven in time periods by a low-frequency triangular wave superimposed on a high-frequency sine wave, and the characteristic wavelength lasers emitted by the first laser and the second laser are both used to pass through the exhaust gas of the chimney pipe, and the characteristic wavelength laser emitted by one of the first laser and the second laser can cover H 2 O has two adjacent absorption lines, and the characteristic wavelength laser emitted by the other can cover O 2 Two adjacent absorption lines; Based on H 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines of O determines H 2 The intensity ratio of two adjacent absorption lines of O is based on O 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines determines O 2 The ratio of the intensity of two adjacent absorption lines; Get O 2 The fitting correlation coefficient between the intensity ratio of two adjacent absorption lines and temperature and H 2 The fitting correlation coefficient between the spectral line intensity ratio of two adjacent absorption lines of O and the temperature, the gas corresponding to the largest fitting correlation coefficient is used as the reference gas, and the exhaust gas temperature value of the chimney pipe is determined based on the spectral line intensity ratio of two adjacent absorption lines of the reference gas; According to the exhaust gas temperature value and the second harmonic signal of the two adjacent absorption lines of the reference gas, the exhaust gas pressure value of the chimney pipe is determined through the broadening mechanism of the gas line function, and the O 2 The concentration value and humidity value of the exhaust gas.

[0006] In one embodiment, obtaining O 2 The fitting correlation coefficient between the intensity ratio of two adjacent absorption lines and temperature and H 2 The fitting correlation coefficient between the intensity ratio of two adjacent absorption lines of O and the temperature, and the gas corresponding to the largest fitting correlation coefficient is used as the reference gas, including: According to O 2 The ratio of the intensity of two adjacent absorption lines and / or H 2 The ratio of the intensity of two adjacent absorption lines of O is used to determine the target temperature range; Get the target temperature range 2 The corresponding fitting correlation coefficient and H 2 The fitting correlation coefficient corresponding to O is calculated, and the gas corresponding to the largest fitting correlation coefficient is taken as the reference gas.

[0007] In one embodiment, according to 2 The ratio of the intensity of two adjacent absorption lines and / or H 2 The ratio of the intensity of two adjacent absorption lines of O determines the target temperature range, including: Obtaining a polynomial function; wherein the polynomial function is a monotonic function, and the temperature and the spectral line intensity ratio are a monotonic function relationship, and the polynomial coefficients of the polynomial function can be obtained by fitting through data points in a preset database, and the data points include different temperatures and the spectral line intensities or spectral line intensity ratios corresponding to different temperatures; Based on the monotonic function relationship between temperature and spectral line intensity ratio, a temperature range corresponding to O is selected from multiple candidate temperature ranges. 2 The ratio of the intensity of two adjacent absorption lines and / or H 2 The candidate temperature interval in which the line intensity ratio of two adjacent absorption lines of O matches is taken as the target temperature interval.

[0008] In one embodiment, determining the exhaust gas temperature value of the chimney pipe based on the spectral line intensity ratio of two adjacent absorption spectral lines of the reference gas includes: Substitute the intensity ratio of two adjacent absorption lines of the reference gas into a polynomial function with known polynomial coefficients to obtain the exhaust gas temperature value of the chimney duct; The polynomial function is: , a、b、c、d、e are the polynomial fitting coefficients; The calculation method for the intensity ratio of two adjacent absorption lines of the reference gas is: , r is the intensity ratio of two adjacent absorption lines of the reference gas, S(T) is the intensity of the absorption line, K 21 , K 22 are the harmonic signal calibration coefficients of the first and second absorption lines of the reference gas, It is the ratio of the second harmonic signal amplitudes of two adjacent absorption lines of the reference gas.

[0009] In one embodiment, the exhaust gas pressure value of the chimney pipe is determined according to the exhaust gas temperature value and the second harmonic signals of two adjacent absorption spectral lines of the reference gas through the broadening mechanism of the gas line function, including: Substitute the exhaust gas temperature value into the half-maximum full width calculation formula of Doppler broadening to obtain the half-maximum full width of Doppler broadening s g ; According to the second harmonic signals of two adjacent absorption lines of the reference gas, the half-height value Get the full width at half maximum of the comprehensive stretch s v ;in, is the left foot value of the second harmonic signal of one of the two adjacent absorption lines of the reference gas, The right foot value of the second harmonic signal of this absorption spectrum line, is the maximum value of the second harmonic signal of the absorption spectrum line; Full width at half maximum based on Doppler broadening s g and the full width at half maximum of the integrated broadening s v , determine the full width at half maximum of the collision broadening s l ; Full width at half maximum according to collision broadening s l The functional relationship between pressure and pressure is used to obtain the pressure value.

[0010] In one embodiment, the full width at half maximum based on Doppler broadening s g and the full width at half maximum of the integrated broadening s v Determine the full width at half maximum of collision broadening s l The calculation formula is as follows: ; Full width at half maximum according to collision broadening sl The calculation formula of the pressure value is as follows: ; in, P is the pressure value, T is the exhaust gas temperature, T 0 is the reference temperature, n 1 、n 2 、 1、 2 、 1、 2 They are the temperature correlation coefficient, air broadening coefficient and self-broadening coefficient corresponding to the second harmonic signals of two adjacent gas absorption lines of the reference gas.

[0011] In one embodiment, H is obtained respectively. 2 O and O 2 The second harmonic signals of two adjacent absorption lines include: The low-frequency triangular wave is superimposed on the high-frequency sine wave to form a triangular wave driving signal. The second harmonic signal is collected at the rising and falling edges of the triangular wave driving signal to obtain H 2 O and O 2 The second harmonic signals of two adjacent absorption spectral lines; wherein the driving signal in the form of a triangular wave drives the first laser or the second laser in each half cycle.

[0012] In one embodiment, the exhaust gas temperature value and the exhaust gas pressure value of the chimney duct are determined. 2 The concentration value and humidity value of the exhaust gas include: Substitute the exhaust gas temperature and exhaust gas pressure of the chimney pipe into the concentration calculation formula to obtain O 2 The concentration value and humidity value of the exhaust gas; the concentration calculation formula is: ; in, is the concentration value, y Representative gas type O 2 or H 2 Oh, O 2 or H 2 The left foot value of the second harmonic signal of one of the two adjacent absorption lines of O, is the right foot value of the second harmonic signal of the absorption spectrum line, , H 2 The concentration value of O is equal to the humidity value of the exhaust gas. L represents the optical path, b 0 、K y are the zero point absorption coefficient and the calibration coefficient, respectively. v c is the center frequency output by the first laser or the second laser, S(T) is the spectral line intensity of the gas, and S(T) Related to the exhaust gas temperature value of the chimney duct.

[0013] In one embodiment, determining H 2 The amplitude of the second harmonic signal of two adjacent absorption lines of O and 2 The amplitudes of the second harmonic signals of two adjacent absorption lines, and selecting the maximum value from the amplitudes of the four second harmonic signals; Get the frequency shift of the center frequency of the absorption line corresponding to the maximum value △υ , according to the frequency shift △υ Determine the exhaust gas velocity in the chimney duct V ; Exhaust gas flow rate V The calculation formula is: ; in, is the center frequency of the absorption line, f It is the incident angle of the laser beams with characteristic wavelengths emitted by the first laser and the second laser after being combined by the coupler and incident on the other side of the chimney pipe.

[0014] In a second aspect, the present application provides a device for exhaust gas detection of a chimney pipe, the device comprising: The signal generating circuit generates low-frequency triangle waves and high-frequency sine waves in different time periods; The laser comprises a first laser and a second laser. The first laser and the second laser are driven by a low-frequency triangular wave superimposed on a high-frequency sine wave in time periods. The characteristic wavelength lasers emitted by the first laser and the second laser are both used to pass through the exhaust gas of the chimney pipe. The characteristic wavelength laser emitted by one of the first laser and the second laser can cover H 2 O has two adjacent absorption lines, and the characteristic wavelength laser emitted by the other can cover O 2 Two adjacent absorption lines; a photodetector that receives laser light from exhaust gases passing through the chimney duct; The signal processing circuit performs the exhaust gas detection method in the above-mentioned embodiment based on the laser of the exhaust gas passing through the chimney duct.

[0015] The exhaust gas detection method and device for chimney pipes drive the first laser and the second laser in time periods by superimposing a low-frequency triangular wave with a high-frequency sine wave. The characteristic wavelength lasers emitted by the first laser and the second laser are both used for the exhaust gas passing through the chimney pipe. The characteristic wavelength laser emitted by one of the first laser and the second laser can cover H 2 O has two adjacent absorption lines, and the characteristic wavelength laser emitted by the other can cover O 2 Two adjacent absorption lines. First obtain H 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines of O and 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines is based on H 2 O, O 2 The corresponding ratio determines the corresponding spectral line intensity ratio; further, obtain the H 2 O, O 2The correlation coefficient of the polynomial fitting is performed on the corresponding spectral line intensity ratio, and the gas corresponding to the largest correlation coefficient is used as the reference gas. The exhaust gas temperature value of the chimney pipe is determined based on the spectral line intensity ratio of the two adjacent absorption spectral lines of the reference gas. Furthermore, the exhaust gas pressure value of the chimney pipe is determined through the broadening mechanism of the gas line function according to the exhaust gas temperature value and the second harmonic signal of the two adjacent absorption spectral lines of the reference gas. The exhaust gas temperature value and the exhaust gas pressure value of the chimney pipe are determined based on the exhaust gas temperature value and the exhaust gas pressure value of the chimney pipe. 2 The detection method and device are not affected by hardware failures and environmental conditions, and improve the detection accuracy of the temperature, pressure, humidity and oxygen concentration of the exhaust gas in the chimney pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a flow chart of an exhaust gas detection method for a chimney pipe in one embodiment; Figure 2 is a second harmonic signal diagram of two adjacent absorption spectral lines of one of the gases in one embodiment; Figure 3 A schematic flow chart of a method for determining polynomial coefficients and a reference gas in one embodiment; Figure 4 A schematic diagram of a process for determining polynomial coefficients and reference gas for each temperature interval in one embodiment; Figure 5 A schematic diagram of a process for determining the exhaust gas pressure of a pipeline through a widening mechanism in one embodiment; Figure 6 A schematic diagram of collecting second harmonic signals by two lasers in one embodiment; Figure 7 A diagram of a device for exhaust gas detection of a chimney pipe in one embodiment; Figure 8 The present invention is a specific process step diagram of a method and device for detecting exhaust gas from a chimney pipe in an embodiment. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0018] In one embodiment, Figure 1 As shown, a method for detecting exhaust gas from a chimney pipe is provided, comprising the following steps: Step 101: Get H 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines of O and 2The ratio of the second harmonic signal amplitudes of two adjacent absorption spectral lines; wherein the first laser and the second laser are driven in time periods by a low-frequency triangular wave superimposed on a high-frequency sine wave, and the characteristic wavelength lasers emitted by the first laser and the second laser are both used to pass through the exhaust gas of the chimney pipe, and the characteristic wavelength laser emitted by one of the first laser and the second laser can cover H 2 O has two adjacent absorption lines, and the characteristic wavelength laser emitted by the other can cover O 2 Two adjacent absorption lines.

[0019] Specifically, a low-frequency triangle wave (10Hz~100Hz) is superimposed on a high-frequency sine wave (10kHz~100kHz) to drive and modulate the two lasers in time periods (1~10s). This driving method enables the laser to emit light of a specific wavelength at different times and can cover H 2 O and O 2 The absorption spectrum of H 2 O has two adjacent absorption lines, and the light emitted by another laser covers O 2 The two lasers emit two absorption lines, and the wavelengths of laser light emitted by both lasers are used to pass through the exhaust gas of the chimney pipe. Although each laser is specialized for one gas (H 2 O or O 2 ), but has the ability to scan two different characteristic wavelengths of the gas. That is, the same laser can scan two adjacent characteristic wavelengths in the same gas, thereby obtaining two harmonic signals. 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines of O is calculated to obtain H 2 The ratio of the second harmonic signal amplitudes of the two absorption lines of O , by adding O 2 The ratio of the second harmonic signal amplitudes of the two absorption lines is calculated to obtain O 2 The ratio of the second harmonic signal amplitudes of the two absorption lines .

[0020] H 2 O as an example, H 2 The second harmonic signals of two adjacent absorption lines of O are as follows Figure 2 As shown, M 1 is the maximum value of the second harmonic signal of one of the absorption lines, M 2 It is the maximum value of the second harmonic signal of another absorption line. F 1 and F 3 are the left and right foot values ​​of the second harmonic signal of one of the absorption lines,F 2 and F 4 are the left and right foot values ​​of the second harmonic signal of another absorption line. Further, Figure 2 In the figure, the horizontal axis represents the wave number, which can be understood as the rate of change of wavelength with distance. It should be noted that two adjacent absorption lines can refer to two absorption lines with similar wave numbers and adjacent to each other. The vertical axis represents the second harmonic signal of two adjacent absorption lines. V 0 Represents the starting wave value during laser scanning, V 1 and V 2 are the left and right wave numbers corresponding to the half-height value of the second harmonic signal of one of the absorption lines; V c1 is the maximum value of the second harmonic signal of one of the absorption lines M 1 The corresponding wave number center point; V 3 and V 4 are the left and right wave numbers corresponding to the half-height value of the second harmonic signal of another absorption spectrum line; V c2 is the maximum value of the second harmonic signal of another absorption line M 2 The corresponding wave number center point. It should be noted that, based on H 2 O as an example, H 2 The amplitude of the second harmonic signal of one of the absorption lines of O is the difference between the highest value of the second harmonic signal of the absorption line and the average value of the left and right foot values ​​of the second harmonic signal of the coefficient line. Figure 2 In H 2 O as an example, H 2 The second harmonic signal amplitude of two adjacent absorption lines can be M 1 -( F 1 + F 3 ) / 2 and M 2 -( F 2 + F 4 ) / 2.

[0021] Step 102: Based on H 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines of O determines H 2 The intensity ratio of two adjacent absorption lines of O is based on O 2The ratio of the second harmonic signal amplitudes of two adjacent absorption lines determines O 2 The ratio of the spectral intensity of two adjacent absorption lines.

[0022] Specifically, for gas (H 2 O or O 2 ) The ratio of the intensity of two adjacent absorption lines can be determined by calibrating the ratio of the amplitudes of the second harmonic signals. The calibration process involves comparing the actual measured value with the theoretical value of a gas with a known concentration to establish a proportional relationship and obtain a calibration coefficient. Assume that for H 2 O During the calibration process, a calibration coefficient is obtained , then H 2 The spectral line intensity ratio of O can be expressed as Similarly for O 2 The spectral line intensity ratio can be expressed as It should be noted that the calibration factor needs to be determined experimentally, usually involving measuring H at a known concentration under controlled conditions. 2 O and O 2 The spectral line intensity ratio is compared with the corresponding second harmonic signal amplitude ratio. The calibration coefficient suitable for the measurement data can be found by the least square method or other statistical methods. .

[0023] Step 103: Get O 2 The fitting correlation coefficient between the intensity ratio of two adjacent absorption lines and temperature and H 2 The fitting correlation coefficient between the line intensity ratio of two adjacent absorption lines of O and the temperature, the gas corresponding to the largest fitting correlation coefficient is taken as the reference gas, and the exhaust gas temperature value of the chimney pipe is determined based on the line intensity ratio of two adjacent absorption lines of the reference gas.

[0024] Specifically, O can be directly obtained from the database 2 The fitting correlation coefficient between the intensity ratio of two adjacent absorption lines and temperature and H 2 The database can be a system that centrally stores and manages scientific data on gas absorption line characteristics, which can provide O 2 and H 2 The ratio of the spectral line intensity of gases such as O at different temperatures, 2 and H 2 The ratio of the spectral line intensities of gases such as O at different temperatures can be obtained through experimental measurement. That is, researchers use spectroscopic instruments to accurately record the absorption spectrum of the gas under controlled conditions and store the results in a database.

[0025] Compare2 and H 2 O, and select the gas corresponding to the maximum fitting correlation coefficient as the reference gas. 2 The fitting correlation coefficient is 0.88, H 2 The fitting correlation coefficient of O is 0.93. The fitting correlation coefficients of the two are compared and the gas with the largest fitting correlation coefficient is selected, that is, H 2 O as the reference gas. 2 The actual temperature value of the exhaust gas in the chimney duct is determined by the spectral line intensity ratio corresponding to O. Among them, linear or nonlinear regression analysis can be used to obtain a function of the spectral line intensity ratio changing with temperature, and the corresponding exhaust gas temperature can be calculated through this function.

[0026] Step 104: According to the exhaust gas temperature value and the second harmonic signals of two adjacent absorption lines of the reference gas, the exhaust gas pressure value of the chimney pipe is determined by the broadening mechanism of the gas line function, and the exhaust gas temperature value and the exhaust gas pressure value of the chimney pipe are determined. 2 The concentration value and humidity value of the exhaust gas.

[0027] Specifically, according to the obtained exhaust gas temperature value and the second harmonic signals of the two adjacent absorption lines of the reference gas, the exhaust gas pressure value is determined using the broadening mechanism of the gas function, which involves the calculation of Doppler broadening and collision broadening. The exhaust gas pressure value is determined by the broadening of the calculated second harmonic signal. The calculated exhaust gas temperature value and pressure value are substituted into the concentration calculation formula to obtain the exhaust gas humidity value and pressure value. 2 concentration value.

[0028] In this embodiment, the first laser and the second laser are driven in time periods by superimposing a low-frequency triangular wave with a high-frequency sine wave. The characteristic wavelength lasers emitted by the first laser and the second laser are both used to pass through the exhaust gas of the chimney pipe. The characteristic wavelength laser emitted by one of the first laser and the second laser can cover H 2 O has two adjacent absorption lines, and the characteristic wavelength laser emitted by the other can cover O 2 For two adjacent absorption lines, first obtain H 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines of O and 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines is based on H 2 O, O 2 The corresponding ratio determines the corresponding spectral line intensity ratio. This method can accurately determine the reference gas (H 2 O or O 2) and further, a polynomial fitting is performed based on the spectral line intensity ratio to determine the correlation coefficient, and the reference gas is selected by comparing the correlation coefficient. The temperature value of the exhaust gas is determined according to the spectral line intensity ratio of the reference gas, so that the most accurate temperature measurement results can be obtained under different working conditions, which is convenient for accurately calculating the temperature value of the exhaust gas from the chimney pipe. The pressure value of the exhaust gas from the chimney pipe is determined by using the broadening mechanism of the gas linear function and combining it with the determined exhaust gas temperature value. Based on the second harmonic signal of the reference gas and the pressure and temperature determined above, it is possible to further determine the O 2 The concentration value and humidity value of the exhaust gas, and thus the detection method of this embodiment is not affected by hardware failures and environmental conditions, and improves the detection accuracy of the temperature, pressure, humidity and oxygen concentration values ​​of the exhaust gas in the chimney pipe.

[0029] In one embodiment, Figure 3 As shown, get O 2 The fitting correlation coefficient between the intensity ratio of two adjacent absorption lines and temperature and H 2 The method comprises the following steps: Step 301: According to O 2 The ratio of the intensity of two adjacent absorption lines and / or H 2 The ratio of the intensity of two adjacent absorption lines of O is used to determine the target temperature range; Specifically, in an actual exhaust gas environment, laser absorption spectroscopy was used to measure O 2 and / or H 2 The intensity of two adjacent absorption lines of O is calculated. 2 and / or H 2 The intensity ratio of two adjacent absorption lines of O. Get O from the database 2 and / or H 2 The intensity ratio of two adjacent absorption lines in different temperature ranges, such as -100K~0K, 0K~100K, 100K~200K, etc. Then, the measured intensity ratio of the spectral line is compared with the database, and the spectral intensity ratio closest to the measured spectral intensity ratio in the database is found to determine the corresponding temperature range, so as to determine that the temperature of the exhaust gas environment is within a certain range, that is, to determine the target temperature range, such as 100K~200K.

[0030] Step 302: Obtain the target temperature range 2 The corresponding fitting correlation coefficient and H 2 The fitting correlation coefficient corresponding to O is calculated, and the gas corresponding to the largest fitting correlation coefficient is taken as the reference gas.

[0031] Specifically, in the target temperature range, using O 2 The line intensity ratio of O can be calculated by polynomial fitting with temperature. 2 The fitting correlation coefficient of 2 The line intensity ratio of O and temperature can be used to calculate the H 2 The fitted correlation coefficient of O. Comparison of O 2 and H 2 O can select the gas with the largest fitting correlation coefficient as the reference gas. 2 The fitting correlation coefficient is 0.91, H 2 The fitting correlation coefficient of O is 0.88, O 2 The fitting correlation coefficient is greater than H 2 O's fitting correlation coefficient, so choose O 2 as the reference gas.

[0032] In this embodiment, the gas with the largest fitting correlation coefficient is selected as the reference gas, which can effectively identify the gas that has the closest relationship with temperature in a specific temperature range, thereby improving the accuracy and reliability of temperature measurement.

[0033] In one embodiment, Figure 4 As shown, according to O 2 The ratio of the intensity of two adjacent absorption lines and / or H 2 The target temperature range is determined by calculating the intensity ratio of two adjacent absorption lines of O, including the following steps: Step 401: obtaining a polynomial function; wherein the polynomial function is a monotonic function, and the temperature and the spectral line intensity ratio are a monotonic function relationship, and the polynomial coefficients of the polynomial function can be obtained by fitting through data points in a preset database, and the data points include different temperatures and the spectral line intensities or spectral line intensity ratios corresponding to different temperatures; Specifically, the database may contain data points of different temperatures and the corresponding spectral line intensity ratios at different temperatures. The data points can reflect the effect of temperature changes on the spectral line intensity ratio. There is a monotonic function relationship between temperature and the spectral line intensity ratio, that is, as the temperature increases or decreases, the spectral line intensity ratio will increase or decrease monotonically accordingly. The data points can be fitted with a polynomial so that the fitted polynomial function can be as close to the actual data points as possible, thereby accurately describing the relationship between temperature and the spectral line intensity ratio. In the fitting process, the coefficients of the polynomial function can be calculated, and the polynomial coefficients can determine the specific characteristics of the polynomial function.

[0034] Step 402: Based on the monotonic function relationship between temperature and spectral line intensity ratio, select a temperature range that is consistent with 0 from multiple candidate temperature ranges. 2 The ratio of the intensity of two adjacent absorption lines and / or H 2 The candidate temperature interval in which the line intensity ratio of two adjacent absorption lines of O matches is taken as the target temperature interval.

[0035] Specifically, based on the polynomial function obtained in step 401, it is obtained that there is a monotonically increasing or decreasing relationship between the temperature and the spectral line intensity ratio. In actual measurement, it can be obtained that 2 and / or H 2 The ratio of the intensity of two adjacent absorption lines of O. 2 and / or H 2 The intensity ratio of two adjacent absorption lines is compared with the intensity ratio of the lines calculated by polynomial functions in multiple candidate temperature intervals. In a certain temperature interval, the theoretical ratio is closest to the measured ratio, and this interval can be determined as the target temperature interval.

[0036] In this embodiment, different temperatures and their corresponding spectral line intensities or ratio data points are obtained from a preset database, and these data points are used to fit a polynomial function to determine its fitting coefficient. Based on the monotonic function relationship, a temperature range corresponding to 0 is selected from multiple candidate temperature ranges. 2 and / or H 2 The interval with the best matching spectral line intensity ratio of O is taken as the target temperature interval. This method can effectively determine the temperature interval that is most consistent with the gas absorption characteristics, thereby improving the accuracy and reliability of temperature measurement. By selecting a suitable target temperature interval, the temperature changes in the exhaust gas can be monitored more accurately.

[0037] In one embodiment, determining the exhaust gas temperature value of the chimney pipe based on the spectral line intensity ratio of two adjacent absorption spectral lines of the reference gas includes: Substitute the intensity ratio of two adjacent absorption lines of the reference gas into a polynomial function with known polynomial coefficients to obtain the exhaust gas temperature value of the chimney duct; The polynomial function is: , where a 、b、c、d、e are the polynomial fitting coefficients; The calculation method for the intensity ratio of two adjacent absorption lines of the reference gas is: ; r is the intensity ratio of two adjacent absorption lines of the reference gas. S ( T ) is the intensity of the absorption line, K21 , K 22 are the harmonic signal calibration coefficients of the first and second absorption lines of the reference gas, It is the ratio of the second harmonic signal amplitudes of two adjacent absorption lines of the reference gas.

[0038] Specifically, for the reference gas H 2 O or O 2 The relationship between the spectral line intensity ratio and temperature is fitted by a polynomial to determine the polynomial fitting coefficients a , b , c , d , e , so that the function can best describe the relationship between the spectral line intensity ratio of the reference gas and the temperature. Substitute the measured spectral line intensity of the reference gas into the polynomial function to calculate the temperature value of the exhaust gas from the chimney pipe T , Assume H 2 O is the reference gas, H 2 The coefficients of the polynomial function of O are a=0.01, b=0.02, c=0.03, d=0.04, e=25, and H is measured by laser. 2 The ratio of the spectral intensity of O r =1.5. r =1.5 Substitute into the polynomial function to calculate the temperature and get the temperature T It is 25.2451K.

[0039] It should be noted that when measuring exhaust gas parameters, the temperature value is calculated through the second harmonic signal of the double spectrum. The specific process is: Get H 2 O, O 2 The ratio of the second harmonic signal amplitudes of two adjacent absorption lines of two gases ,calculate The formula is as follows: ; In the formula, y Representative gas type H 2 O or O 2 ; and It is the maximum value of the second harmonic signal of one absorption line of the reference gas and the maximum value of the second harmonic signal of another absorption line. and are the left and right foot values ​​of the second harmonic signal of one of the absorption lines of the reference gas, and is the left foot value and right foot value of the second harmonic signal of another absorption line of the reference gas. By calculation, the ratio of the amplitude of the second harmonic signal of two adjacent absorption lines of the reference gas is obtained. .

[0040] Furthermore, under the condition of weak absorption (absorbance ≤ 0.05), the line intensity of two adjacent absorption lines is approximately linearly related to the peak height of the second harmonic signal of the two adjacent absorption lines. At this time, it can be considered that the line intensity ratio of the two adjacent absorption lines is equal to the peak height ratio of the second harmonic signal of the two adjacent absorption lines. r It can be as follows: ; In the formula, K 21 、K 22 are the harmonic signal calibration coefficients of one and the other absorption lines of the reference gas, respectively. It should be noted that the peak height of the second harmonic signal of the absorption line can be calculated by subtracting the average of the left foot value and the right foot value from the highest value, that is, the peak height of the second harmonic signal of the absorption line can be expressed as .

[0041] By comparison with step 101, it can be obtained that the peak height value of the second harmonic signal of the absorption spectrum line and the amplitude of the second harmonic of the absorption spectrum line are named differently with the same definition. In the subsequent steps, the amplitude of the second harmonic signal of the absorption spectrum line and the peak height value of the second harmonic signal of the absorption spectrum line have the same meaning, that is, the maximum value of the second harmonic signal of the absorption spectrum line minus the average value of the left foot value and the right foot value. The formula can be expressed as .

[0042] For example, when a known standard gas concentration is introduced, the harmonic signal calibration coefficient can be obtained: K , the calculation formula is as follows: K= ; In the formula, V pp is the amplitude of the second harmonic signal when the standard gas is introduced, b 0 is the zero-point coefficient, which is the amplitude of the harmonic signal when no gas is introduced. is the concentration of the standard gas, is the pressure during calibration, To calibrate the optical path, is the spectral line intensity at the calibration temperature, g ( T , P, C) is the linear compensation parameter under the calibration environment. It should be noted that various parameters of the standard gas can be obtained by querying in the database.

[0043] In this embodiment, through the accurate measurement of polynomial fitting and spectral line intensity ratio, the method can provide more accurate exhaust gas temperature measurement results. The polynomial function is determined by polynomial fitting, and the measured reference gas spectral line intensity is substituted into the polynomial function to calculate the temperature value of the chimney pipe exhaust gas, which can reduce the influence of random errors and enhance the reliability of temperature data. This method can adapt to different working conditions because it is based on the actual measurement data for fitting and can adapt to changes in temperature, pressure and gas concentration. Compared with the contact temperature measurement method, the non-contact measurement method based on absorption spectroscopy technology reduces the physical wear of the sensor and reduces the maintenance cost.

[0044] In one embodiment, Figure 5 As shown, according to the exhaust gas temperature value and the second harmonic signals of two adjacent absorption spectral lines of the reference gas, the exhaust gas pressure value of the chimney pipe is determined through the broadening mechanism of the gas line function, including the following steps: Step 501: Substitute the exhaust gas temperature value into the half-maximum full width calculation formula of Doppler broadening to obtain the half-maximum full width of Doppler broadening s g ; Specifically, the exhaust gas temperature has been obtained through the above steps T , the full width at half maximum of the Doppler broadening formula can be calculated by the following formula: . is the laser wavelength, c is the speed of light, k is the Boltzmann constant, m is the molecular mass of the gas. T Substituting into the above formula, calculate the half-maximum width of Doppler broadening s g .

[0045] Step 502: Based on the second harmonic signals of two adjacent absorption lines of the reference gas, Get the full width at half maximum of the comprehensive stretch s v ;in, is the left foot value of the second harmonic signal of one of the two adjacent absorption lines of the reference gas, The right foot value of the second harmonic signal of this absorption spectrum line, is the maximum value of the second harmonic signal of the absorption spectrum line; For example, the reference gas is O 2 For example, O can be obtained through software 2The maximum value of the second harmonic signal of one of the absorption lines M 1 , left foot value F 1 and right foot value F 3 ; and the maximum value of the second harmonic signal of another absorption line M 2 , left foot value F 2 and right foot value F 4 By calculating the peak height of the second harmonic signal of one absorption line and the peak height of the second harmonic signal of the other absorption line, the peak heights of the second harmonic signals of the two absorption lines are compared. The maximum value and the bottom value of the second harmonic signal of the larger absorption line can be substituted into the formula to calculate the half-height full width of the comprehensive broadening. s v .

[0046] Furthermore, the peak height of the second harmonic signal of the absorption spectrum of the reference gas can be calculated by subtracting the average of the left foot value and the right foot value from the highest value. That is, the peak height of the second harmonic signal of one absorption spectrum of the reference gas is M 1 - (F 1 + F 3 ) / 2, the peak height of the second harmonic signal of the other absorption line is M 2 -( F 2 + F 4 ) / 2. Compare the peak heights of the second harmonic signals of the two absorption lines. The maximum value of the second harmonic signal of the larger absorption line and the left and right foot values ​​can be substituted into the formula to calculate the half-height full width of the comprehensive broadening. s v .

[0047] It should be noted that, according to the obtained second harmonic signals of two adjacent absorption lines of the reference gas, the half-height value Get the full width at half maximum of the comprehensive stretch s v .in y Representative gas type H 2 O or O 2 , is the maximum value of the second harmonic signal of one of the two adjacent absorption lines of the reference gas, is the left foot value of the second harmonic signal of one of the two adjacent absorption lines of the reference gas, The right foot value of the second harmonic signal of this absorption spectrum line.

[0048] Furthermore, i=1 or 2; the value of i can be determined by comparing the peak height values ​​of the second harmonic signals of the two absorption spectra; if the peak height value of the second harmonic signal of one absorption spectrum line is larger, then i=1; if the peak height value of the second harmonic signal of the other absorption spectrum line is larger, then i=2.

[0049] Step 503: Full width at half maximum based on Doppler broadening s g and the full width at half maximum of the integrated broadening s v , determine the full width at half maximum of the collision broadening s l ; Specifically, a specific formula can be used to determine the half-width at half maximum of the collision broadening σ l , which takes into account the full width at half maximum of the Doppler broadening σ g and the half-width of the comprehensive broadening σ v The formula is as follows: ; in, s v It is comprehensive broadening, which is caused by collision broadening s l and Doppler broadening s g The result of the joint action. s v and σ g Calculate s l . We need to rearrange this formula to get: ; The full width at half maximum of collision broadening can be obtained by solving this equation s l .

[0050] Step 504: Full width at half maximum according to collision broadening s l The functional relationship between pressure and pressure is used to obtain the pressure value.

[0051] Specifically, a specific formula can be used to calculate the collision broadening FWHM σ l Calculate the exhaust gas pressure value in the chimney pipe. The formula takes into account the gas pressure P, saturation pressure P S , air broadening coefficient γair , self-broadening coefficient γ self , and the temperature ratio T 0 / T The formula is as follows: ; In this formula, s l Represents the full width at half maximum of the collision broadening. c air is the broadening coefficient caused by collision with air molecules. c self is the broadening coefficient caused by the molecular self-collision. P is the currently measured pressure. P S is the saturation pressure, the pressure point at which the gas begins to condense. T 0 is the reference temperature, usually a standard temperature such as 273K, T is the currently measured temperature. m It is an index related to gas properties and measurement conditions. The value range and calculation formula can be changed according to actual conditions. It is a correction factor introduced to make more precise adjustments for different measurement environments.

[0052] For example, assuming , c air =0.01, c self =0.02, P S =1000Pa, T 0 =298K, T=320K, Substituting various parameters into the formula, we can calculate that the gas pressure P is 1227Pa.

[0053] In this embodiment, the method can provide more accurate exhaust pressure measurement results by using accurate calculation of Doppler broadening and collision broadening. By comprehensively considering Doppler broadening and collision broadening, the method can reduce the influence of random errors and enhance the reliability of pressure data. The non-contact measurement method based on absorption spectroscopy technology reduces physical wear on the sensor and reduces maintenance costs.

[0054] In one embodiment, the full width at half maximum based on Doppler broadening s g and the full width at half maximum of the integrated broadening s v Determine the full width at half maximum of collision broadening sl The calculation formula is as follows: ; Full width at half maximum according to collision broadening s l The calculation formula of the pressure value is as follows: ; in, P is the pressure value, T is the exhaust gas temperature, T 0 is the reference temperature, n 1 、n 2 , 1 , 2 , 1 , 2 They are the temperature correlation coefficient, air broadening coefficient and self-broadening coefficient corresponding to the second harmonic signals of two adjacent gas absorption lines of the reference gas.

[0055] Specifically, according to the broadening mechanism of the gas linear function, the Doppler broadening can be represented by a Gaussian linear function, and the half-maximum width of the Doppler broadening is: ; In the formula, m is the molecular mass; k is the Boltzmann constant; c is the speed of light, c =3×1010cm / s. The collision broadening is represented by the Lorentzian line function, and the half-height full width of the collision broadening is: ; In the formula, P is the sample gas pressure; P S is the partial pressure of the absorbed gas; T 0 is the reference temperature, which is 296K; n、 , They are the temperature correlation coefficient, air broadening coefficient and self-broadening coefficient, respectively, obtained through the Hitran database. The Hitran (High-resolution Transmission Molecular Absorption Database) database is a widely used molecular absorption spectral database that contains a large amount of molecular spectral data, which is essential for studying the molecular absorption characteristics in the atmosphere and astrophysics. The Hitran database provides the absorption spectral parameters of molecules at different temperatures and pressures, which can be used to simulate and interpret molecular spectra.

[0056] In actual detection applications, both the half-width of gas Doppler broadening and the half-width of collision broadening exist. The half-width of the comprehensive broadening of the two effects forms the gas spectral line broadening, which is expressed by the Voigt line function. The half-width of the comprehensive broadening is: ; Another calculation method can be used to obtain s g , s v as well as s l Value, the calculated temperature value T Substitute the full width at half maximum of the Doppler broadening into s g In the formula, we can get s g The full width at half maximum of Doppler broadening is: ; In the formula, c is the speed of light, m is the molecular mass; k is the Boltzmann constant; c is the speed of light, c =3×1010cm / s.

[0057] According to the collected second harmonic signal, the half-height value Get comprehensive width s v Value. s g , s v Value, can be obtained s l for: ; according to s l The functional relationship between the pressure P and the pressure P is further obtained: ; in, P is the pressure value, T is the exhaust gas temperature, T 0 is the reference temperature, n 1 、n 2 , , They are the temperature correlation coefficient, air broadening coefficient and self-broadening coefficient corresponding to the second harmonic signals of two adjacent gas absorption lines of the reference gas.

[0058] Will and Compare and select the gas signal with the larger value for the next step of pressure calculation. Select the second harmonic signals of two adjacent gas absorption lines to obtain the half-maximum full width of the comprehensive broadening. s v Full width at half maximum s g Value, get the pressure P , P s The system of linear equations in two variables: ; Further obtain the sample gas pressure P value: ; in, P is the pressure value, T is the exhaust gas temperature, T 0 is the reference temperature, n 1 、n 2 , 1 , 2 , 1 , 2 They are the temperature correlation coefficient, air broadening coefficient and self-broadening coefficient corresponding to the second harmonic signals of two adjacent gas absorption lines of the reference gas.

[0059] In this embodiment, the method accurately calculates the half-maximum width of the Doppler broadening. s g , the full width at half maximum of the comprehensive widening s v and the full width at half maximum of collision broadening s l, thus accurately calculating the pressure measurement results. By considering the temperature correlation coefficient, air broadening coefficient and self-broadening coefficient, this method can improve the accuracy of the measurement data. The non-contact measurement method reduces the reliance on physical sensors, thereby reducing maintenance costs and potential failure risks.

[0060] In one embodiment, H is obtained respectively 2 O and O 2 The second harmonic signals of two adjacent absorption spectral lines include: a triangular wave driving signal formed by superimposing a low-frequency triangular wave with a high-frequency sine wave, and collecting the second harmonic signals at both the rising and falling edges of the triangular wave driving signal to obtain H 2 O and O 2 The second harmonic signals of two adjacent absorption lines; wherein the driving signal in the form of a triangular wave drives the first laser or the second laser in each half cycle (the specific schematic diagram of the two lasers collecting the second harmonic signals is as shown in Figure 6 As shown, signal 1 is the second harmonic signal collected by one of the lasers, and signal 2 is the second harmonic signal collected by the other laser. The two lasers collect second harmonic signals in half a period T respectively).

[0061] Specifically, a low-frequency triangle wave (10Hz~100Hz) superimposed with a high-frequency sine wave (10kHz~100kHz) is used to drive and modulate two lasers in time periods (1s~10s). Considering H 2 O and O 2 It is widely present in most atmospheres and has a large absorption signal at high concentrations. The characteristic wavelengths emitted by the two lasers can cover H 2 O and O 2 For two adjacent absorption lines, only the first laser emits a characteristic wavelength laser or the second laser emits a characteristic wavelength laser in each half cycle. When emitting light, it is driven in a triangular wave mode. Second harmonic signal acquisition is performed on both the rising and falling edges of the triangular wave to increase the effective data duty cycle, reduce the time consumption of digital average filtering, eliminate white noise, and improve the signal-to-noise ratio. After superposition, the tuning current follows the following rules within the cycle: ; in ， ， Represent the two driving currents, frequencies and phases respectively. ， Represents the triangle wave modulation coefficient. f m Under the sinusoidal current modulation frequency, the laser output frequency and light intensity can be expressed as: , .

[0062] In the formula, v c is the center frequency of the laser output; a is the amplitude of sinusoidal modulation; I c is the light intensity at the laser center frequency; i 0 To modulate the amplitude of light intensity; g is the phase difference between frequency modulation and light intensity modulation. Following the Lambert-Beer law, under weak absorption conditions, the laser light intensity after passing through the absorption medium can be expressed by the Fourier series as follows: ; make ω=2πfmt , further, we get the nth harmonic signal Hn for: ; In the formula, Kn is the calibration coefficient of the nth harmonic signal; S ( T ) is the spectral line intensity; P is the gas pressure; L To measure the optical path; X is the gas concentration.

[0063] The present invention uses a second harmonic signal to measure exhaust gas parameters. The second harmonic signal is: ; In this embodiment, by collecting the second harmonic signal at both the rising and falling edges of the triangular wave drive signal, the signal collection efficiency and quality can be improved, thereby obtaining a more accurate H 2 O and O 2 This method can reduce the time consumption of digital average filtering, eliminate white noise, and thus improve the signal-to-noise ratio, making the detection of absorption spectra more sensitive and accurate. Driving only one laser in each half cycle can optimize the efficiency of the laser, reduce energy consumption, and extend the service life of the laser. By accurately collecting H 2 O and O 2 The absorption spectrum data can be used to more accurately perform polynomial fitting to determine the temperature and pressure values ​​of the exhaust gas. This method is suitable for harsh environments such as high temperature, high humidity, and high corrosion, and improves the applicability of the monitoring system.

[0064] In one embodiment, the exhaust gas temperature value of the chimney duct and the exhaust gas pressure value of the chimney duct are determined. 2 The concentration value and humidity value of the exhaust gas include: Substitute the exhaust gas temperature and exhaust gas pressure of the chimney pipe into the concentration calculation formula to obtain O 2 The concentration value and humidity value of the exhaust gas; the concentration calculation formula is: ; in, is the concentration value, y represents the gas type O 2 or H 2 Oh, O 2 or H 2 The left foot value of the second harmonic signal of one of the two adjacent absorption lines of O, is the right foot value of the second harmonic signal of the absorption spectrum line, , H 2 The concentration value of O is equal to the humidity value of the exhaust gas. L represents the optical path, b 0 、K y are the zero point absorption coefficient and the calibration coefficient, respectively. v c is the center frequency output by the first laser or the second laser, S ( T ) is the spectral line intensity of the gas, and S ( T ) is related to the exhaust gas temperature value of the chimney duct.

[0065] Specifically, when the exhaust gas temperature value T and the exhaust gas pressure value P of the chimney pipe are known, the exhaust gas temperature value and the exhaust gas pressure value in the chimney pipe are substituted into the concentration calculation formula to obtain 2 The concentration value and the humidity value of the exhaust gas, the concentration calculation formula is: ; in, is the concentration value, y Representative gas type O 2 or H 2 Oh, O 2 or H 2 The left foot value of the second harmonic signal of one of the two adjacent absorption lines of O, is the right foot value of the second harmonic signal of the absorption spectrum line, If the gas is H 2 O,H 2 The concentration of O is equal to the humidity of the exhaust gas; if the gas is O 2 , represents O 2 The concentration value of the gas.L represents the optical path, b 0 , K y They are the zero point absorption coefficient and the calibration coefficient respectively, which are obtained when the zero point standard gas and the range standard gas of known concentration are introduced, and the values ​​are stored in the hardware storage chip and automatically called when the concentration is calculated. v c is the center frequency output by the first laser or the second laser, S ( T ) is the spectral line intensity of the gas, and S ( T ) is related to the exhaust gas temperature value of the chimney pipe. S ( T ) parameters can be queried in the molecular spectroscopy database Hitran. S ( T ) can be calculated by the following formula: ; In the formula, Q ( T ) is the molecular internal partitioning function, is the reference temperature T 0 The molecular internal partitioning function under E is the molecular transition base energy, h is Planck's constant, k is the Boltzmann constant, c is the speed of light, S ( T 0 ) is the reference temperature T 0 The intensity of the spectral line.

[0066] It should be noted that the calculation of O 2 When the concentration value is 2 Compare the peak heights of the second harmonic signals of two adjacent absorption spectra to determine which absorption spectrum has the highest value of the second harmonic signal and the left and right foot values, and substitute them into the calculation formula to calculate the value. 2 Similarly, when calculating the humidity value of the exhaust gas, it is necessary to calculate the H 2 O compares the peak height values ​​of the second harmonic signals of two adjacent absorption spectra to determine which absorption spectrum line has the highest value of the second harmonic signal and the left and right foot values ​​that can be substituted into the calculation formula to calculate the humidity of the exhaust gas.

[0067] In this embodiment, the method can provide accurate O by calculating through precise mathematical formula. 2Concentration and exhaust gas humidity measurement results. Combining parameters such as temperature, pressure, optical path and spectral line intensity, this method reduces measurement errors and improves data reliability.

[0068] In one embodiment, H is determined 2 The amplitude of the second harmonic signal of two adjacent absorption lines of O and 2 The amplitudes of the second harmonic signals of two adjacent absorption lines, and selecting the maximum value from the amplitudes of the four second harmonic signals; Get the frequency shift of the center frequency of the absorption line corresponding to the maximum value △υ , according to the frequency shift △υ Determine the exhaust gas flow velocity V of the chimney duct; the calculation formula for the exhaust gas flow velocity V is:

[0069] in, is the center frequency of the absorption line, f It is the incident angle of the laser beams with characteristic wavelengths emitted by the first laser and the second laser after being combined by the coupler and incident on the other side of the chimney pipe.

[0070] Specifically, the flow velocity measurement is based on the Doppler effect. The lasers emitted by two lasers are collimated and then enter the coupler. After the two lasers are merged into one, they are then passed through a beam splitter to separate the light energy at a ratio of 1:1 and the light at an angle of f The light signal incident on the other side of the chimney pipe is absorbed and attenuated by the gas to be measured and received by the first photodetector 1 and the second photodetector 2 respectively, and processed by the signal processing circuit.

[0071] Furthermore, for H 2 O and O 2 The amplitudes of the second harmonic signals of the four corresponding absorption lines of the two gases are compared, and the absorption line with the largest second harmonic signal amplitude is selected for subsequent calculation, that is, flow rate calculation.

[0072] The second harmonic signals corresponding to the absorption of the two beams of light will shift, that is, the center frequency of the absorption spectrum will shift, and the frequency shift is △υ , calculated using the exhaust gas flow rate formula V :

[0073] Where c is the speed of light, c=3×1010cm / s, and the frequency shift is △υ , is the center frequency of the absorption line, f It is the incident angle of the laser beams with characteristic wavelengths emitted by the first laser and the second laser after being combined by the coupler and incident on the other side of the chimney pipe.

[0074] In this embodiment, the frequency shift of the absorption spectrum is used to determine the flow rate, providing a high-precision flow rate measurement method, which is particularly suitable for high-speed gas flow. This method does not require physical contact with the exhaust gas, reduces the wear and maintenance requirements of the measuring equipment, reduces maintenance costs, and reduces potential safety hazards during the measurement process. In addition, the method can provide real-time flow rate data, which helps to adjust relevant parameters in a timely manner and optimize combustion efficiency.

[0075] Based on the same inventive concept, the embodiment of the present application also provides a device for realizing the above-mentioned exhaust gas detection applied to a chimney pipe, such as Figure 7 As shown, an exhaust gas detection device applied to a chimney pipe comprises: The signal generating circuit generates low-frequency triangle waves and high-frequency sine waves in different time periods; The laser comprises a first laser and a second laser. The first laser and the second laser are driven by a low-frequency triangular wave superimposed on a high-frequency sine wave in time periods. The characteristic wavelength lasers emitted by the first laser and the second laser are both used to pass through the exhaust gas of the chimney pipe. The characteristic wavelength laser emitted by one of the first laser and the second laser can cover H 2 O has two adjacent absorption lines, and the characteristic wavelength laser emitted by the other can cover O 2 Two adjacent absorption lines; a photodetector that receives laser light from exhaust gases passing through the chimney duct; The signal processing circuit performs the above series of steps based on the laser light passing through the exhaust gas of the chimney pipe.

[0076] Specifically, the signal generating circuit 1 generates a driving signal for controlling the operation of the laser in time periods, and the driving signal is a signal generated by superimposing a low-frequency triangular wave with a high-frequency sine wave. The characteristic wavelength laser emitted by each of the lasers 2 and 5 is used to pass the exhaust gas through the chimney pipe. The characteristic wavelength laser emitted by one of the first laser and the second laser can cover H 2 O has two adjacent absorption lines, and the characteristic wavelength laser emitted by the other can cover O 2 Two adjacent absorption lines. The first temperature control circuit 3 and the second temperature control circuit 4 are used to control and maintain the operating temperature of the laser to ensure the stability of the laser and the accuracy of the measurement. The first collimator 6 and the second collimator 7 are used to adjust the direction and shape of the light beam to ensure that the laser can accurately pass through the exhaust gas in the chimney pipe. The coupler 8 is used to merge the two laser beams into one to measure H 2 O and O 2 The beam splitter 9 splits the combined beam into two paths again to measure H 2 O and O 2The chimney pipe 10 is a channel for exhaust gas emission. The laser beam passes through the exhaust gas in the pipe to measure the absorption spectrum of the exhaust gas. The first photodetector 11 and the second photodetector 12 are used to receive the laser after passing through the exhaust gas. The detector converts the optical signal into an electrical signal for subsequent processing. The signal processing circuit 13 receives the output signal of the photodetector and performs data processing. The display screen 14 is used to display the measurement results for the operator to monitor. The airflow is the exhaust gas flow of the chimney pipe.

[0077] In this embodiment, the exhaust gas parameter detection device based on absorption spectroscopy technology can accurately monitor the exhaust gas parameters in the chimney pipe in real time, including temperature, pressure, flow rate, humidity and oxygen concentration. This non-contact measurement reduces physical wear, extends the life of the equipment, and reduces the cost of maintaining the equipment.

[0078] It should be noted that if Figure 8 As shown, for a method and device for measuring exhaust gas parameters based on absorption spectroscopy technology provided by the present application, the method and device monitor the temperature, pressure, flow rate, humidity and oxygen concentration in the exhaust gas in the chimney, specifically including the following steps: Step 801: Low-frequency triangle wave superimposed sine wave drives and modulates two lasers in time periods. The characteristic wavelength lasers emitted by the two lasers can cover H 2 O and 2 absorption lines; Step 802: Get H 2 O, O 2 The second harmonic signal amplitudes of two adjacent absorption lines of the two gases are compared to obtain the line intensity ratio r, and the temperature value T is obtained by polynomial fitting; Step 803: Calculate the pressure through the broadening mechanism of the gas line function, from s g , s v Value, get the half-height full width of collision broadening s l Value, according to s l With pressure P The functional relationship between them gives the pressure value; Step 804: Calculate the sample gas velocity based on the Doppler effect V ; Step 805: Obtain the sample gas temperature according to the above calculation T and pressure P , substituted into the derived concentration calculation formula, the humidity and oxygen concentration values ​​are obtained respectively.

[0079] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for detecting exhaust gas from a chimney pipe, characterized in that: The method comprises: Obtaining a ratio of the second harmonic signal amplitudes of two adjacent absorption lines of H2O and a ratio of the second harmonic signal amplitudes of two adjacent absorption lines of O2; wherein the first laser and the second laser are driven in time periods by superimposing a low-frequency triangular wave with a high-frequency sine wave, the characteristic wavelength lasers emitted by the first laser and the second laser are both used for exhaust gas passing through the chimney pipe, and the characteristic wavelength laser emitted by one of the first laser and the second laser can cover the two adjacent absorption lines of H2O, and the characteristic wavelength laser emitted by the other laser can cover the two adjacent absorption lines of O2; Determine the line intensity ratio of the two adjacent absorption lines of H2O based on the ratio of the second harmonic signal amplitudes of the two adjacent absorption lines of H2O, and determine the line intensity ratio of the two adjacent absorption lines of O2 based on the ratio of the second harmonic signal amplitudes of the two adjacent absorption lines of O2; Obtaining the fitting correlation coefficient between the line intensity ratio of the two adjacent absorption lines of O2 and the temperature and the fitting correlation coefficient between the line intensity ratio of the two adjacent absorption lines of H2O and the temperature, taking the gas corresponding to the largest fitting correlation coefficient as the reference gas, and determining the exhaust gas temperature value of the chimney pipe based on the line intensity ratio of the two adjacent absorption lines of the reference gas; According to the exhaust gas temperature value and the second harmonic signals of two adjacent absorption spectral lines of the reference gas, the exhaust gas pressure value of the chimney pipe is determined through the broadening mechanism of the gas linear function, and the concentration value of O2 and the humidity value of the exhaust gas are determined based on the exhaust gas temperature value of the chimney pipe and the exhaust gas pressure value of the chimney pipe.

2. The exhaust gas detection method according to claim 1, characterized in that: Obtaining the fitting correlation coefficient between the ratio of the intensity of two adjacent absorption lines of O2 and the temperature and the fitting correlation coefficient between the intensity of two adjacent absorption lines of H2O and the temperature, and taking the gas corresponding to the largest fitting correlation coefficient as the reference gas, including: Determining a target temperature range according to a spectral line intensity ratio of two adjacent absorption lines of O2 and / or a spectral line intensity ratio of two adjacent absorption lines of H2O; The fitting correlation coefficient corresponding to the O2 and the fitting correlation coefficient corresponding to the H2O in the target temperature range are obtained, and the gas corresponding to the largest fitting correlation coefficient is used as the reference gas.

3. The exhaust gas detection method according to claim 2, characterized in that: Determining a target temperature range according to a spectral line intensity ratio of two adjacent absorption lines of O2 and / or a spectral line intensity ratio of two adjacent absorption lines of H2O includes: Obtaining a polynomial function; wherein the polynomial function is a monotonic function, and the temperature and the spectral line intensity ratio are a monotonic function relationship, and the polynomial coefficients of the polynomial function can be obtained by fitting through data points in a preset database, and the data points include different temperatures and the spectral line intensities or spectral line intensity ratios corresponding to different temperatures; Based on the monotonic function relationship between the temperature and the spectral line intensity ratio, a candidate temperature interval that matches the spectral line intensity ratio of the two adjacent absorption lines of O2 and / or the spectral line intensity ratio of the two adjacent absorption lines of H2O is selected from multiple candidate temperature intervals as the target temperature interval.

4. The exhaust gas detection method according to any one of claims 1 to 3, characterized in that: Determining the exhaust gas temperature value of the chimney pipe based on the spectral line intensity ratio of two adjacent absorption spectral lines of the reference gas includes: Substituting the spectral line intensity ratio of two adjacent absorption spectral lines of the reference gas into a polynomial function with known polynomial coefficients to obtain the exhaust gas temperature value of the chimney pipe; The polynomial function is: , a, b, c, d, e are the polynomial fitting coefficients; The calculation method for the intensity ratio of two adjacent absorption lines of the reference gas is: ； r is the intensity ratio of two adjacent absorption lines of the reference gas, S(T) is the intensity of the absorption line, K 21 , K 22 are the harmonic signal calibration coefficients of the first and second absorption lines of the reference gas, It is the ratio of the second harmonic signal amplitudes of two adjacent absorption lines of the reference gas.

5. The exhaust gas detection method according to claim 1, characterized in that: According to the exhaust gas temperature value and the second harmonic signals of two adjacent absorption spectral lines of the reference gas, the exhaust gas pressure value of the chimney pipe is determined through the broadening mechanism of the gas linear function, including: Substitute the exhaust gas temperature value into the half-maximum full width calculation formula of Doppler broadening to obtain the half-maximum full width of Doppler broadening σ g ; According to the second harmonic signals of two adjacent absorption lines of the reference gas, the half-height value Get the full width at half maximum of the comprehensive stretch σ v ;in, is the left foot value of the second harmonic signal of one of the two adjacent absorption lines of the reference gas, The right foot value of the second harmonic signal of this absorption spectrum line, is the maximum value of the second harmonic signal of the absorption spectrum line; Based on the full width at half maximum of the Doppler broadening σ g and the half-maximum width of the comprehensive broadening σ v , determine the full width at half maximum of the collision broadening σ l ; Full width at half maximum according to collision broadening σ l The functional relationship between pressure and pressure is used to obtain the pressure value.

6. The exhaust gas detection method according to claim 5, characterized in that: Based on the full width at half maximum of the Doppler broadening σ g and the half-maximum width of the comprehensive broadening σ v Determine the full width at half maximum of collision broadening σ l The calculation formula is as follows: ； Full width at half maximum according to collision broadening σ l The calculation formula of the pressure value is as follows: ； in, P is the pressure value, T is the exhaust gas temperature, T 0 is the reference temperature, n 1 、n 2.

1.

2.

1. 2 are the temperature correlation coefficient, air broadening coefficient and self-broadening coefficient corresponding to the second harmonic signals of two adjacent gas absorption lines of the reference gas.

7. The exhaust gas detection method according to claim 1, characterized in that: Obtain the second harmonic signals of two adjacent absorption lines of H2O and O2 respectively, including: A triangular wave driving signal is formed by superimposing a low-frequency triangular wave on a high-frequency sine wave. Second harmonic signal acquisition is performed at both the rising and falling edges of the triangular wave driving signal to obtain the second harmonic signals of two adjacent absorption lines of H2O and O2 respectively; wherein the triangular wave driving signal drives the first laser or the second laser in each half cycle.

8. The exhaust gas detection method according to claim 1, characterized in that: Determining the concentration value of O2 and the humidity value of the exhaust gas based on the exhaust gas temperature value of the chimney pipe and the exhaust gas pressure value of the chimney pipe includes: Substitute the exhaust gas temperature value of the chimney pipe and the exhaust gas pressure value of the chimney pipe into the concentration calculation formula to obtain the concentration value of O2 and the humidity value of the exhaust gas; wherein the concentration calculation formula is: ； in, is the concentration value, y Represents gas type O2 or H2O, It is the left foot value of the second harmonic signal of one of the two adjacent absorption lines of O2 or H2O. is the right foot value of the second harmonic signal of the absorption spectrum line, The concentration value of H2O is equal to the humidity value of the exhaust gas. L represents the optical path, b 0. K y are the zero point absorption coefficient and the calibration coefficient, respectively. v c The center frequency of the first laser or the second laser output ,S(T) is the spectral line intensity of the gas, and S(T) Related to the exhaust gas temperature value of the chimney duct.

9. The exhaust gas detection method according to claim 1, characterized in that: The method further comprises: Determine the amplitudes of the second harmonic signals of two adjacent absorption lines of H2O and the amplitudes of the second harmonic signals of two adjacent absorption lines of O2, and select the maximum value from the amplitudes of the four second harmonic signals; Obtain the frequency shift of the center frequency of the absorption spectrum line corresponding to the maximum value △υ , according to the frequency shift △υ Determine the exhaust gas flow rate of the chimney duct V ; Exhaust gas flow rate V The calculation formula is: ； in, is the center frequency of the absorption line, φ It is the incident angle of the laser beams with characteristic wavelengths emitted by the first laser and the second laser after being combined by the coupler and incident on the other side of the chimney pipe.

10. An exhaust gas detection device applied to a chimney pipe, characterized in that: The device comprises: The signal generating circuit generates low-frequency triangle waves and high-frequency sine waves in different time periods; The laser comprises a first laser and a second laser, wherein the low-frequency triangular wave superimposed on the high-frequency sine wave drives the first laser and the second laser in time periods, the characteristic wavelength lasers emitted by the first laser and the second laser are both used for exhaust gas passing through the chimney pipe, and the characteristic wavelength laser emitted by one of the first laser and the second laser can cover two adjacent absorption lines of H2O, and the characteristic wavelength laser emitted by the other laser can cover two adjacent absorption lines of O2; a photodetector to receive laser light from exhaust gas passing through the chimney duct; A signal processing circuit executes the exhaust gas detection method for a chimney pipe according to any one of claims 1 to 9 based on the laser of the exhaust gas passing through the chimney pipe.

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