Measurement System and Method for High-Temperature Gas Concentration in Aero-Engine

Abstract

This invention relates to the field of spectroscopic measurement technology, and particularly to a measurement system and method for measuring the concentration of high-temperature combustion gases in aero-engines. The measurement system includes a supercontinuum laser source, a first collimating mirror, a second collimating mirror, a spectrometer, and a computer. The measurement method includes acquiring the actual transmittance spectrum of the high-temperature combustion gases; calculating the theoretical transmittance spectrum of the high-temperature combustion gases; constructing constraints; fitting the actual transmittance spectrum and the theoretical transmittance spectrum into the constraints; and calculating the concentration of the high-temperature combustion gases. The measurement system has a lightweight structure, requiring only holes for mounting the laser emission and absorption devices on the inner wall of the aero-engine casing. The measurement method uses a supercontinuum laser source, which, compared to ordinary lasers used in active gas detection, offers better spatial coherence, a wider spectral adjustment range, and higher intensity, enabling the detection of more types of gases. The method uses a multi-band combustion gas absorption model to solve for the temperature of the high-temperature combustion gases, improving the accuracy of the concentration calculation.

Description

Technical Field

[0001] This invention relates to the field of spectroscopic measurement technology, and in particular to a measurement system and method for high-temperature gas concentration in aero-engines. Background Technology

[0002] As a core component of an aircraft, the aircraft engine provides power for flight and is an extremely important part of the aircraft. Ensuring the stable operation of aircraft engines is crucial to reducing aircraft malfunctions and avoiding major flight accidents. Therefore, strengthening the monitoring of aircraft engine operating status, especially real-time online monitoring during flight, plays a vital role in ensuring the safety of aircraft transportation, and can predict potential safety hazards in advance, providing early warning information of malfunctions and reducing engine maintenance costs.

[0003] Real-time monitoring of the high-temperature exhaust gases produced by aero-engines is one of the effective methods for monitoring the condition of aero-engines. The formation of high-temperature exhaust gases is closely related to the degree of fuel combustion. By analyzing the components and measuring the concentration of high-temperature exhaust gases: firstly, it is possible to know the engine's fuel combustion efficiency, and thus adjust the engine's performance parameters such as fuel injection quantity and intake compression ratio in a timely manner; secondly, it can reflect the engine's operating condition and aging degree to a certain extent, which helps in the early warning of engine failures; and thirdly, it can control the emission of pollutants and greenhouse gases, providing the most direct data for the improvement and optimization of aviation fuel. Therefore, analyzing and measuring the high-temperature exhaust gases produced by aero-engines during operation is of great significance for improving the fuel combustion efficiency of aero-engines, monitoring the operating condition of aero-engines in real time, and analyzing and improving the emission of pollutants and greenhouse gases.

[0004] Currently, the technologies for measuring high-temperature gas emissions during aero-engine operation are mainly divided into traditional gas sampling and detection technologies and modern optical detection technologies. Traditional sampling technologies primarily involve two methods: manual sampling and pretreatment sampling. Manual sampling mainly includes chemical analysis and chromatography, both of which require manual sampling of the sample gas before separation and analysis. Pretreatment sampling involves processing the gas to be tested through a pretreatment system before inputting it into the measurement pipeline. Because the gas to be tested has different absorption capacities for specific frequencies of light emitted by infrared or ultraviolet light sources installed on both sides of the measurement pipeline, the concentration of the gas to be tested can be obtained by observing the degree of light intensity attenuation.

[0005] The traditional gas detection methods mentioned above all require sampling of the gas to be tested before further processing to obtain the composition and concentration of the gas to be tested. They cannot achieve real-time online and in-situ monitoring of the gas to be tested. Some continuous chemical reactions that may exist in high-temperature gas combustion may also affect the concentration of the target gas to be tested, bringing a lot of uncertainty to the concentration measurement results.

[0006] Modern optical detection technologies mainly include active tunable diode laser absorption spectroscopy (TDLAS) and passive Fourier transform infrared spectroscopy (FTIR) and spectral imaging techniques. TDLAS utilizes the selective absorption characteristics of the analyte gas to quantitatively analyze the attenuation of laser energy, thereby obtaining the components and concentrations of the analyte gas. It primarily involves adjusting the laser's current and operating temperature to change the laser's spectral linewidth and wavelength, achieving a narrower spectral resolution compared to the Doppler linewidth to scan an independent gas absorption line. This allows for the measurement of absorption lines that are extremely difficult to distinguish for gas molecules. The composition or concentration of the analyte gas is ultimately obtained by fitting the resulting spectral line using the least squares method. However, when using TDLAS technology, the relatively small wavelength range of the laser limits the types of gases that can be detected.

[0007] Passive detection methods like FTIR and spectral imaging, which do not require an external light source, have certain advantages in measuring high-temperature exhaust gases within the confined space of an aero-engine. This is because the combustion products of an aero-engine are in a high-temperature, high-pressure state, meeting the requirements for passive gas detection, i.e., there is a temperature difference between the background temperature and the gas being measured. However, the biggest limitation of FTIR technology is that the complex Fourier transform calculation process is very time-consuming, resulting in a slow system response and a relative lag in measuring high-speed engine exhaust gases. Furthermore, the spectrometer system for FTIR technology is expensive and quite bulky. Spectral imaging technology, due to its high spatial and spectral resolution, combined with advanced back-end imaging processing technology, can achieve even higher gas concentration detection resolution and is more suitable for remote sensing monitoring of atmospheric gases. However, due to its complex system structure, it is not well-suited for monitoring aero-engine exhaust gases. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a measurement system and method for high-temperature gas concentration in aero-engines, which can expand the types of detectable gases, improve the system's detection sensitivity, and simplify the system structure.

[0009] To achieve the above objectives, the present invention adopts the following specific technical solution:

[0010] The present invention provides a system for measuring the concentration of high-temperature combustion gases in an aero-engine. The aero-engine includes an air inlet, a compressor, a combustion chamber, turbine blades, and an exhaust port. The measurement system includes a supercontinuum laser source, a first collimating lens, a second collimating lens, a spectrometer, and a computer. The supercontinuum laser source and the first collimating lens are connected via optical fiber. The first collimating lens is installed on one side of the engine's inner wall at the exhaust port, and the second collimating lens is installed on the other side of the engine's inner wall at the exhaust port. The spectrometer is connected to the second collimating lens via optical fiber. The laser emitted by the supercontinuum laser source is collimated by the first collimating lens through the optical fiber and then incident on the high-temperature combustion gases at the exhaust port. After being absorbed by the high-temperature combustion gases, the laser is incident on the second collimating lens and transmitted to the spectrometer via optical fiber. The spectrometer receives the spectral information and transmits it to the computer. The computer processes the spectral information transmitted by the spectrometer to obtain the concentration of the high-temperature combustion gases in the aero-engine.

[0011] Furthermore, the computer includes an actual transmittance spectrum calculation module, a theoretical transmittance spectrum calculation module, and a constraint condition construction module. The actual transmittance spectrum calculation module is used to process spectral information based on Lambert-Beer's law and the main components of high-temperature gas to obtain the actual transmittance spectrum of high-temperature gas. The theoretical transmittance spectrum calculation module is used to construct a multi-band gas absorption model to solve for the temperature of high-temperature gas, calculate the gas absorption coefficient based on the temperature of high-temperature gas, and obtain the theoretical transmittance spectrum of high-temperature gas. The constraint condition construction module is used to construct constraint conditions using a nonlinear least squares fitting method, substitute the actual transmittance spectrum and the theoretical transmittance spectrum into the constraint conditions for fitting, and solve for the concentration of high-temperature gas.

[0012] Furthermore, the constraints of the constraint construction module are as follows:

[0013] min{τ-exp[-α(λ,T)·c·L]}=0;

[0014] Where τ is the actual transmittance spectrum of the high-temperature gas, α(λ,T) is the gas absorption coefficient, c is the concentration of the high-temperature gas, and L is the optical path length of the laser through the high-temperature gas.

[0015] The concentration corresponding to the point where the difference in the constraints is minimized is the concentration of the high-temperature gas required.

[0016] Furthermore, the calculation process of the actual transmittance spectrum calculation module is as follows:

[0017] The intensity of the laser emitted from the supercontinuum laser source after passing through a high-temperature combustion gas is received by a spectrometer. The laser energy received by the spectrometer is:

[0018] I = τ·I0 + (1-τ)·I gas ;

[0019] In the formula, I is the energy received by the spectrometer, I0 is the energy of the incident laser, and I gas It is the radiant energy of high-temperature gas;

[0020] Based on the main components of the high-temperature gas, select the gas characteristic absorption peak positions with high intensity in the existing absorption spectrum. At the high-intensity gas characteristic absorption peak positions, the transmittance spectrum τ of the high-temperature gas is 0. At this time, the energy received by the spectrometer only includes the energy radiated by the high temperature of the high-temperature gas itself. The energy emitted by the supercontinuum laser source has been completely absorbed by the high-temperature gas, so I = I gas Then, the actual transmittance spectrum τ of the high-temperature gas was calculated:

[0021]

[0022] Furthermore, the calculation process of the theoretical transmittance spectrum calculation module is as follows:

[0023] At the position of the high-intensity gas characteristic absorption peak, the transmittance spectrum of the high-temperature gas is τ = 0, at which point I = I gas That is, at the wavelength corresponding to the characteristic absorption peak of this gas, the high-temperature gas radiates energy outward in the form of a blackbody at the same temperature:

[0024]

[0025] To eliminate the fluctuations and uniqueness of single-point values ​​caused by spectral noise during the measurement process, several characteristic absorption bands of high-temperature gas were selected, and they were integrated using a narrower band integration mode.

[0026]

[0027] In the formula, the value of n is determined by the characteristic absorption peaks in the obtained transmittance spectrum, λ1, λ2, ..., λ n Δλ1, Δλ2, ..., Δλ are the wavelengths corresponding to the characteristic absorption peaks in the obtained high-temperature gas transmittance spectrum of the aero-engine; Δλ1, Δλ2, ..., Δλ2 are the wavelengths corresponding to the characteristic absorption peaks in the obtained high-temperature gas transmittance spectrum of the aero-engine. n These are the narrow bands extended by the wavelengths corresponding to the characteristic absorption peaks; C1 = 3.7418 × 10 -16 W·m 2 The first radiation constant is C2 = 1.4388 × 10⁻⁶. -2 m·K is the second radiation constant;

[0028] In the above formula, all temperatures are values ​​at the same moment. Therefore, the temperature deviation values ​​of the measured gas in multiple bands should approach zero, that is:

[0029]

[0030] The temperature that satisfies the above constraint is the temperature of the high-temperature gas. By substituting the obtained high-temperature gas temperature into the HITEMP database, the gas absorption coefficient α(λ, T) is obtained, and the theoretical transmittance spectrum of the high-temperature gas is obtained.

[0031] Furthermore, the supercontinuum laser source is selected from random fiber lasers or pulsed fiber lasers.

[0032] The method for measuring the high-temperature gas concentration in an aero-engine provided by this invention includes the following steps:

[0033] S1. Use the above measurement system to obtain the spectral information of the laser after absorption by the high-temperature gas;

[0034] S2. Based on Lambert-Beer's law and the existing absorption spectra of the main components of high-temperature gas, the acquired spectral information is processed to obtain the actual transmittance spectrum of the high-temperature gas.

[0035] S3. Construct a multi-band gas absorption model to solve for the temperature of the high-temperature gas, calculate the gas absorption coefficient, and obtain the theoretical transmittance spectrum of the high-temperature gas.

[0036] S4. The nonlinear least squares fitting method is used to construct the constraint conditions. The actual transmittance spectrum and the theoretical transmittance spectrum are substituted into the constraint conditions for fitting, and the concentration of high temperature gas is calculated.

[0037] Furthermore, the constraints for calculating the concentration of high-temperature fuel gas are as follows:

[0038] min{τ-exp[-α(λ,T)·c·L]}=0;

[0039] Where τ is the actual transmittance spectrum of the high-temperature gas, α(λ,T) is the gas absorption coefficient, c is the concentration of the high-temperature gas, and L is the optical path length of the laser through the high-temperature gas.

[0040] The concentration corresponding to the point where the difference in the constraints is minimized is the concentration of the high-temperature gas required.

[0041] Furthermore, in step S2, the specific process of processing the acquired spectral information based on Lambert-Beer's law and the existing absorption spectra of the main components of the high-temperature gas to obtain the actual transmittance spectrum of the high-temperature gas is as follows:

[0042] The intensity of the laser emitted from the supercontinuum laser source after passing through a high-temperature combustion gas is received by a spectrometer. The laser energy received by the spectrometer is:

[0043] I = τ·I0 + (1-τ)·I gas ;

[0044] In the formula, I is the energy received by the spectrometer, I0 is the energy of the incident laser, and I gas It is the radiant energy of high-temperature gas;

[0045] Based on the main components of the high-temperature gas, select the gas characteristic absorption peak positions with high intensity in the existing absorption spectrum. At the high-intensity gas characteristic absorption peak positions, the transmittance spectrum τ of the high-temperature gas is 0. At this time, the energy received by the spectrometer only includes the energy radiated by the high temperature of the high-temperature gas itself. The energy emitted by the supercontinuum laser source has been completely absorbed by the high-temperature gas, so I = I gas Then, the actual transmittance spectrum τ of the high-temperature gas was calculated:

[0046]

[0047] Furthermore, in step S3, the specific process of constructing a multi-band gas absorption model to solve for the temperature of the high-temperature gas, calculating the gas absorption coefficient, and obtaining the theoretical transmittance spectrum of the high-temperature gas is as follows:

[0048] At the position of the high-intensity gas characteristic absorption peak, the transmittance spectrum of the high-temperature gas is τ = 0, at which point I = I gas That is, at the wavelength corresponding to the characteristic absorption peak of this gas, the high-temperature gas radiates energy outward in the form of a blackbody at the same temperature:

[0049]

[0050] To eliminate the fluctuations and uniqueness of single-point values ​​caused by spectral noise during the measurement process, several characteristic absorption bands of high-temperature gas were selected, and they were integrated using a narrower band integration mode.

[0051]

[0052] In the formula, the value of n is determined by the characteristic absorption peaks in the obtained transmittance spectrum, λ1, λ2, ..., λ n Δλ1, Δλ2, ..., Δλ are the wavelengths corresponding to the characteristic absorption peaks in the obtained high-temperature gas transmittance spectrum of the aero-engine; Δλ1, Δλ2, ..., Δλ2 are the wavelengths corresponding to the characteristic absorption peaks in the obtained high-temperature gas transmittance spectrum of the aero-engine. n These are the narrow bands extended by the wavelengths corresponding to the characteristic absorption peaks; C1 = 3.7418 × 10 -16 W·m 2 The first radiation constant is C2 = 1.4388 × 10⁻⁶. -2 m·K is the second radiation constant;

[0053] In the above formula, all temperatures are values ​​at the same moment. Therefore, the temperature deviation values ​​of the measured gas in multiple bands should approach zero, that is:

[0054]

[0055] The temperature that satisfies the above constraint is the temperature of the high-temperature gas. The gas absorption coefficient α(λ, T) is obtained by substituting the obtained high-temperature gas temperature into the HITEMP database.

[0056] The present invention can achieve the following technical effects:

[0057] 1. The measurement system for high-temperature gas concentration in aero-engines provided by this invention uses a supercontinuum laser source, which has better spatial coherence, wider spectral adjustment range, and higher intensity than ordinary lasers used in active gas detection, and can detect more types of gases.

[0058] 2. The method for measuring the high-temperature gas concentration in aero-engines provided by this invention uses a multi-band gas absorption model to solve for the high-temperature gas temperature, which improves the accuracy of the concentration calculation.

[0059] 3. The measurement system directly receives signals from the spectrometer, and then processes the obtained spectral data. This simplifies the complex device, expands the types of gases that can be detected, and improves the system's detection sensitivity.

[0060] 4. The measurement system has a relatively lightweight structure, and only holes for installing laser emission and absorption devices need to be set on the inner wall of the aircraft engine casing. Attached Figure Description

[0061] Figure 1 This is a structural schematic diagram of an aero-engine provided according to an embodiment of the present invention.

[0062] Figure 2 This is a schematic diagram of the structure of a high-temperature gas concentration measurement system for an aero-engine provided according to an embodiment of the present invention.

[0063] Figure 3 This is a schematic diagram of the connection method of the measurement system for high-temperature gas concentration in an aero-engine provided according to an embodiment of the present invention.

[0064] Figure 4 This is a schematic diagram of the light intensity absorbed by the gas under test according to an embodiment of the present invention.

[0065] Figure 5 This is a schematic flowchart of a method for processing high-temperature gas concentration in an aero-engine according to an embodiment of the present invention.

[0066] The reference numerals in the figures include:

[0067] 1. Inlet, 2. Compressor, 3. Combustion chamber, 4. Turbine blades, 5. Exhaust port, 6. Cold end low temperature zone, 7. Hot end high temperature zone, 8. Supercontinuum laser source, 9. Spectrometer, 10. Fiber optic cable, 11. First collimating lens, 12. Second collimating lens, 13. High temperature combustion gas. Detailed Implementation

[0068] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0069] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0070] This invention provides a system for measuring the high-temperature gas concentration in an aero-engine. Figure 1 The structure of an aircraft engine is shown, such as Figure 1 As shown, the aero-engine includes a cold-end cryogenic zone 6 and a hot-end high-temperature zone 7. The cold-end cryogenic zone 6 includes an air inlet 1 and a compressor 2, while the hot-end high-temperature zone 7 includes a combustion chamber 3, turbine blades 4, and an exhaust port 5. The compressor 2 increases the pressure of the air entering the engine, providing high-pressure air to the combustion chamber to improve the efficiency of the engine's thermodynamic cycle. The combustion chamber 3 contains an ignition device that ignites and combusts the air compressed by the compressor 2. The air is then injected and combusted to release heat, increasing its temperature. This heat is then directed to the turbine for expansion and work, thus releasing the chemical energy of the fuel and converting it into heat energy. This increases the total gas volume, enhancing the ability of the gas to expand and perform work in the turbine and exhaust nozzle. The turbine blades 4 regulate the airflow speed and velocity entering the engine, preventing fuel waste caused by excessively fast airflow impact.

[0071] Figure 2 The structure of a system for measuring the high-temperature gas concentration in an aircraft engine is shown. Figure 3 The connection method of the measurement system is shown, such as... Figure 2 and Figure 3 As shown, the measurement system includes a supercontinuum laser source 8, a first collimating mirror 11, a second collimating mirror 12, and a spectrometer 9. The supercontinuum laser source 8 is connected to the first collimating mirror 11 via an optical fiber 10. The first collimating mirror 11 is installed on one side of the engine inner wall at the exhaust port 5, and the second collimating mirror 12 is installed on the other side of the engine inner wall at the exhaust port 5. The spectrometer 9 is connected to the second collimating mirror 12 via an optical fiber 10. The laser emitted by the supercontinuum laser source 8 is collimated by the first collimating mirror 11 through the optical fiber 10 and then incident on the high-temperature gas 13 at the exhaust port 5. After being absorbed by the high-temperature gas 13, the laser is incident on the second collimating mirror 12 and transmitted to the spectrometer 9 through the optical fiber 10. The spectrometer 9 receives the spectral information and transmits it to a computer for data processing to obtain the concentration of the high-temperature gas 13 in the aero-engine.

[0072] Currently, there are two main methods for generating supercontinuum laser sources: one is to use a pulsed fiber laser to pump a PCF (Polyfiber Fiber Amplifier) ​​to generate a near-infrared supercontinuum; the other is to directly generate a near-infrared supercontinuum in a pulsed fiber amplifier; and the third is to use a random fiber laser to generate a near-infrared supercontinuum. The random fiber laser utilizes Rayleigh scattering in the fiber to provide randomly distributed feedback, thus replacing the resonant cavity structure of a traditional laser. It can also utilize stimulated Raman scattering in a passive fiber to provide gain, offering advantages such as simple structure, time-domain stability, and high robustness. Therefore, when measuring high-temperature gases such as the concentration of high-temperature exhaust gas in aero-engines, a random fiber laser can be selected as the supercontinuum laser source. After emitting a supercontinuum laser beam, the light passes through a first collimating lens 11 and is incident on the high-temperature exhaust gas 13. The high-temperature exhaust gas 13 absorbs the characteristic bands of the supercontinuum laser beam. The absorbed laser light exits through a second collimating lens 12 and is transmitted through an optical fiber 10 to a spectrometer 9. The spectrometer 9 receives the relevant signals and then performs subsequent data processing on them using a computer.

[0073] This invention provides a method for measuring the high-temperature gas concentration in an aero-engine, comprising the following steps:

[0074] S 1. Use the above measurement system to obtain the spectral information of the laser after absorption by high-temperature gas.

[0075] S2. Based on Lambert-Beer's law and the existing absorption spectra of the main components of high-temperature gas, the acquired spectral information is processed to obtain the actual transmittance spectrum of the high-temperature gas.

[0076] The principle for measuring the high-temperature gas concentration in aero-engines is based on the Lambert-Beer law: that is, the degree to which the original light intensity of a beam of light is absorbed by a medium of a certain thickness after passing through it. The degree of light absorption by a substance is related to the thickness and concentration of the absorbing medium, hence the Lambert-Beer law.

[0077] The Lambert-Beer law is expressed as follows:

[0078] A = ln(I0 / I) t )=α(λ,T)·c·L; (1)

[0079] In the formula, A is the absorbance; I0 is the incident light radiation intensity, i.e., the intensity of the light before it passes through the high-temperature combustion gas; I t λ is the intensity of transmitted light radiation, i.e., the intensity of light after passing through the high-temperature gas; α(λ, T) is the absorption coefficient of light by the high-temperature gas, the value of which is related to wavelength and temperature; c is the concentration of the high-temperature gas; L is the optical path length of light passing through the high-temperature gas. Figure 4 This is a schematic diagram for measuring the intensity of light absorbed by a gas.

[0080] like Figure 4 As shown, when a laser beam of intensity I0 passes through a gas medium of length L, the laser intensity will attenuate due to the absorption of specific wavelengths of the laser by the gas medium. This attenuation contains information about the concentration of the gas being measured. According to the Lambert-Beer law, the change in intensity after attenuation can be expressed by the following formula:

[0081] I t =I0·exp[-α(λ,T)·c·L]; (2)

[0082] After formula transformation, we can obtain:

[0083] I t / I0=τ=exp[-α(λ,T)·c·L]; (3)

[0084] In the formula, τ is the transmittance spectrum of the high-temperature gas. As can be seen from formula (3), to solve for the concentration of the high-temperature gas, the transmittance of the laser after passing through the high-temperature gas must be known.

[0085] In the measurement system structure provided by this invention, the intensity of the laser emitted from the supercontinuum laser source after passing through the high-temperature gas is received by the spectrometer, and its energy is:

[0086] I = τ·I0 + (1-τ)·I gas (4)

[0087] In the formula, I is the total system energy received by the spectrometer, I0 is the incident laser energy, and I gas This refers to the radiant energy of the high-temperature gas. Specifically, the high-temperature gas transmittance τ and the radiant energy I of the high-temperature gas are... gas All of these are unknown quantities, and the high-temperature gas radiation energy I needs to be further calculated. gas Then, the high-temperature gas transmission rate is obtained through the above formula (4).

[0088] Based on the high-temperature exhaust gases produced by the aero-engine, the main components are determined to be H2O and CO2. Using existing absorption spectra in the HITEMP database, suitable and high-intensity characteristic absorption peaks of the high-temperature gas are selected. At these high-intensity characteristic absorption peaks, the transmittance of the high-temperature gas τ = 0. At this point, the energy received by the spectrometer only includes the energy radiated by the gas's own high temperature; the energy emitted by the supercontinuum laser has been completely absorbed by the high-temperature exhaust gases. Therefore, I = I0 gas This allows us to determine the radiation intensity of the high-temperature gas and then calculate the actual transmittance spectrum τ of the high-temperature gas.

[0089]

[0090] S3. Construct a multi-band gas absorption model to solve for the temperature of the high-temperature gas, calculate the gas absorption coefficient, and obtain the theoretical transmittance spectrum of the high-temperature gas.

[0091] At the position of the high-intensity gas characteristic absorption peak, the transmittance spectrum of the high-temperature gas is τ = 0, at which point I = I gas That is, at the wavelength corresponding to the characteristic absorption peak of this gas, the high-temperature gas radiates energy outward in the form of a blackbody at the same temperature:

[0092]

[0093] To eliminate the fluctuations and uniqueness of single-point values ​​caused by spectral noise during the measurement process, several characteristic absorption bands of high-temperature gas were selected, and they were integrated using a narrower band integration mode.

[0094]

[0095] In the above formula, the value of n can be determined by the characteristic absorption peaks in the obtained transmittance spectrum, λ1, λ2, ..., λ. n Δλ1, Δλ2, ..., Δλ are the wavelengths corresponding to the characteristic absorption peaks in the obtained high-temperature gas transmittance spectrum of the aero-engine; Δλ1, Δλ2, ..., Δλ2 are the wavelengths corresponding to the characteristic absorption peaks in the obtained high-temperature gas transmittance spectrum of the aero-engine. n These are the narrow bands extended by the wavelengths corresponding to the characteristic absorption peaks; C1 = 3.7418 × 10 -16 W·m 2 The first radiation constant is C2 = 1.4388 × 10⁻⁶. -2 m·K is the second radiation constant.

[0096] In the above formula, all temperatures are values ​​at the same moment. Therefore, the temperature deviation values ​​of the measured gas in multiple bands should be extremely small or even approach zero, that is:

[0097]

[0098] The temperature value corresponding to the above constraint condition is the temperature of the high-temperature gas. The gas absorption coefficient α(λ, T) is calculated from the obtained high-temperature gas temperature.

[0099] S4. The nonlinear least squares fitting method is used to construct the constraint conditions. The actual transmittance spectrum and the theoretical transmittance spectrum are substituted into the constraint conditions for fitting, and the concentration of high temperature gas is calculated.

[0100] A nonlinear least squares fitting method was used to construct the constraints, and the obtained transmittance spectrum of the high-temperature gas and the theoretical transmittance spectrum were substituted into the constraints for fitting.

[0101] min{τ-exp[-α(λ,T)·c·L]}=0; (9)

[0102] The concentration that satisfies the above constraint is the concentration of the high-temperature gas, that is, the concentration corresponding to the minimum difference is the concentration of the high-temperature gas.

[0103] Figure 5 The flowchart illustrates a method for treating high-temperature exhaust gas concentrations in aircraft engines, such as... Figure 5 As shown, the spectrometer 9 acquires the spectral information of the laser emitted from the supercontinuum laser source 8 after passing through the measured high-temperature gas 13. The spectral characteristics of the acquired high-temperature gas 13 are then analyzed and processed accordingly, such as spectral baseline correction and spectral line drift. Given the original laser emission intensity, the transmittance spectrum of the high-temperature gas obtained experimentally can be obtained. This spectrum is then fitted with the theoretical transmittance spectrum using nonlinear least squares fitting; the concentration corresponding to the point of minimum difference is the desired concentration of the measured gas. However, the absorption coefficient in the theoretical transmittance spectrum is an unknown variable, and its value is mainly affected by the temperature of the medium, i.e., the temperature of the measured gas. Therefore, a multi-band gas absorption model is constructed to solve for the temperature of the high-temperature gas, thereby determining the absorption coefficient and obtaining the theoretical transmittance spectrum. Finally, the concentration of the high-temperature gas in the aero-engine is calculated by fitting the experimentally obtained transmittance spectrum with the theoretical transmittance spectrum.

[0104] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0105] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

[0106] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A measurement system for the high-temperature gas concentration of an aero-engine, the aero-engine comprising an air inlet, a compressor, a combustion chamber, turbine blades and an exhaust port, characterized in that, The measurement system includes a supercontinuum laser source, a first collimating lens, a second collimating lens, a spectrometer, and a computer. The supercontinuum laser source is connected to the first collimating lens via optical fiber. The first collimating lens is installed on one side of the engine inner wall at the exhaust port, and the second collimating lens is installed on the other side of the engine inner wall at the exhaust port. The spectrometer is connected to the second collimating lens via optical fiber. The laser emitted by the supercontinuum laser source is collimated by the first collimating lens through the optical fiber and then incident on the high-temperature gas at the exhaust port. After being absorbed by the high-temperature gas, the laser is incident on the second collimating lens and transmitted to the spectrometer via optical fiber. The spectrometer receives the spectral information and transmits it to the computer. The computer processes the spectral information transmitted by the spectrometer to obtain the concentration of the high-temperature gas in the aero-engine. The computer includes an actual transmittance spectrum calculation module, a theoretical transmittance spectrum calculation module, and a constraint condition construction module. The actual transmittance spectrum calculation module is used to process spectral information according to Lambert-Beer the law and the main components of high-temperature gas to obtain the actual transmittance spectrum of high-temperature gas; the theoretical transmittance spectrum calculation module is used to construct a multi-band gas absorption model to solve the temperature of high-temperature gas, calculate the gas absorption coefficient based on the temperature of high-temperature gas, and obtain the theoretical transmittance spectrum of high-temperature gas; the constraint condition construction module is used to construct constraint conditions by using the nonlinear least squares fitting method, substitute the actual transmittance spectrum and the theoretical transmittance spectrum into the constraint conditions for fitting, and calculate the concentration of high-temperature gas. The constraints of the constraint construction module are as follows: ； Among them, is the actual transmittance spectrum of high-temperature gas, is the gas absorption coefficient, c is the concentration of high-temperature gas, and L is the optical path of the laser passing through the high-temperature gas; The concentration corresponding to the minimum difference in the constraints is the concentration of the high-temperature gas required. The calculation process of the actual transmittance spectrum calculation module is as follows: The intensity of the laser emitted from the supercontinuum laser source after passing through a high-temperature combustion gas is received by a spectrometer. The laser energy received by the spectrometer is: ； In the formula, is the energy received by the spectrometer, is the energy of the incident laser, is the radiation energy of the high-temperature gas; Select the gas characteristic absorption peak positions with high intensity in the existing absorption spectrum according to the main components of the high-temperature gas. At the gas characteristic absorption peak positions with high intensity, the transmittance spectrum of the high-temperature gas , at this time, the energy received by the spectrometer only contains the energy radiated by the high-temperature gas itself due to its high temperature, and the energy emitted by the supercontinuum laser source has been completely absorbed by the high-temperature gas, and it can be obtained , and then the actual transmittance spectrum of the high-temperature gas is calculated : ； The calculation process of the theoretical transmittance spectrum calculation module is as follows: Transmittance spectrum of high-temperature fuel gas at the position of the characteristic absorption peak of high-intensity gas At this time That is, at the wavelength corresponding to this characteristic absorption peak of the gas, the high-temperature fuel gas radiates energy outward in the form of a blackbody at the same temperature: ； To eliminate the fluctuations and uniqueness of single-point values ​​caused by spectral noise during the measurement process, several characteristic absorption bands of high-temperature gas were selected, and they were integrated using a narrower band integration mode. ； In the formula, the value of n is determined by the characteristic absorption peaks in the specifically obtained transmittance spectrum. , …… are respectively the wavelengths corresponding to the characteristic absorption peaks in the obtained high-temperature gas transmittance spectrum of the aero-engine. , …… are respectively the narrow bands expanded from the wavelengths corresponding to the characteristic absorption peaks. is the first radiation constant; is the second radiation constant; In the above formula, all temperatures are values ​​at the same moment. Therefore, the temperature deviation values ​​of the measured gas in multiple bands should approach zero, that is: ； The temperature corresponding to the satisfaction of the above formula constraints is the temperature of the high-temperature gas to be sought. The gas absorption coefficient is obtained by substituting the obtained high-temperature gas temperature into the HITEMP database , and the theoretical transmittance spectrum of the high-temperature gas is obtained.

2. The measurement system for the high-temperature gas concentration of an aeroengine according to claim 1, wherein The supercontinuum laser source is selected from random fiber lasers or pulsed fiber lasers.

3. A method for measuring the high-temperature gas concentration of an aero-engine, characterized in that, Includes the following steps: S1. Obtain the spectral information of the laser after absorption by high-temperature gas using the measurement system described in claim 1; S2. Based on Lambert-Beer the law and the existing absorption spectra of the main components of the high-temperature gas, data processing is performed on the obtained spectral information to obtain the actual transmittance spectrum of the high-temperature gas; S3. Construct a multi-band gas absorption model to solve for the temperature of the high-temperature gas, calculate the gas absorption coefficient, and obtain the theoretical transmittance spectrum of the high-temperature gas. S4. The nonlinear least squares fitting method is used to construct the constraint conditions. The actual transmittance spectrum and the theoretical transmittance spectrum are substituted into the constraint conditions for fitting, and the concentration of high temperature gas is calculated.

4. The method for measuring the high-temperature gas concentration of an aeroengine according to claim 3, wherein The constraints for calculating the concentration of high-temperature fuel gas are as follows: ； Among them, is the actual transmittance spectrum of high-temperature gas, is the gas absorption coefficient, c is the concentration of high-temperature gas, and L is the optical path of the laser passing through the high-temperature gas; The concentration corresponding to the point where the difference in the constraints is minimized is the concentration of the high-temperature gas required.

5. The method for measuring the high-temperature gas concentration in an aero-engine according to claim 3, characterized in that, In step S2, based on Lambert-Beer the law and the existing absorption spectra of the main components of the high-temperature gas, the specific process of processing the acquired spectral information to obtain the actual transmittance spectrum of the high-temperature gas is as follows: The intensity of the laser emitted from the supercontinuum laser source after passing through a high-temperature combustion gas is received by a spectrometer. The laser energy received by the spectrometer is: ； In the formula, is the energy received by the spectrometer, is the energy of the incident laser, is the radiant energy of the high-temperature gas; Select the gas characteristic absorption peak positions with high intensity in the existing absorption spectrum according to the main components of high-temperature gas. At the gas characteristic absorption peak positions with high intensity, the transmittance spectrum of high-temperature gas , at this time, the energy received by the spectrometer only contains the energy radiated by the high-temperature of the high-temperature gas itself, and the energy emitted by the supercontinuum laser source has been completely absorbed by the high-temperature gas, and it can be obtained , and then calculate the actual transmittance spectrum of the high-temperature gas : 。 6. The method for measuring the high-temperature gas concentration in an aero-engine according to claim 3, characterized in that, In step S3, the specific process of constructing a multi-band gas absorption model to solve for the temperature of the high-temperature gas, calculating the gas absorption coefficient, and obtaining the theoretical transmittance spectrum of the high-temperature gas is as follows: Transmittance spectrum of high-temperature gas at the position of high-intensity gas characteristic absorption peaks. ,at this time That is, at the wavelength corresponding to the characteristic absorption peak of this gas, the high-temperature gas radiates energy outward in the form of a blackbody at the same temperature: ； To eliminate the fluctuations and uniqueness of single-point values ​​caused by spectral noise during the measurement process, several characteristic absorption bands of high-temperature gas were selected, and they were integrated using a narrower band integration mode. ； In the formula, the value of n is determined by the characteristic absorption peaks in the obtained transmittance spectrum. , ... These are the wavelengths corresponding to the characteristic absorption peaks in the obtained high-temperature gas transmittance spectrum of the aero-engine. , ... These are the narrow bands extended by the wavelengths corresponding to the characteristic absorption peaks; It is the first radiation constant; It is the second radiation constant; In the above formula, all temperatures are values ​​at the same moment. Therefore, the temperature deviation values ​​of the measured gas in multiple bands should approach zero, that is: ； The temperature that satisfies the above constraint is the temperature of the high-temperature gas. The gas absorption coefficient is obtained by substituting the obtained high-temperature gas temperature into the HITEMP database. .

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