Aero-engine combustion flow field measuring instrument based on static snapshot spectral imaging

Abstract

The invention relates to the field of combustion flow field measurement, in particular to an aero-engine combustion flow field multi-parameter measuring instrument which comprises an optical fiber image transmission bundle array, a front optical system and a rear static snapshot interference spectral imaging system, and the front optical system and the rear static snapshot interference spectral imaging system are respectively coupled with the optical fiber image transmission bundle array. The front optical system is fixedly mounted on the casing wall of the aero-engine; the rear static snapshot interference spectrum imaging system comprises a micro lens array, a beam splitter, a high-order reflection type step mirror, a low-order reflection type step mirror, a collimating mirror and an area array detector, and the micro lens array is arranged at the incident end of the beam splitter; the high-order reflection-type step mirror and the low-order reflection-type step mirror are arranged at the reflection end and the transmission end of the beam splitter and are orthogonal in the step direction; and the collimating mirror and the area array detector are sequentially arranged at the beam combining end of the beam splitter. According to the invention, the influence of factors such as aero-engine vibration, operation noise and environment on the measurement process is eliminated, and the stability of the measuring instrument is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of combustion flow field measurement, and particularly relates to a multi-parameter measuring instrument for the combustion flow field of an aero-engine. Background Art

[0002] Measuring the distribution of the combustion temperature field inside an aero-engine is the most direct and effective way to evaluate the thermal load distribution and analyze thermal faults in the combustion chamber. At the same time, it can also provide an important basis for the design and research and development of the aero-engine combustion chamber and the optimization of the aerodynamic layout of turbine blades. With the development of the aviation industry, higher and higher requirements have been put forward for the combustion efficiency and pollutant emissions of aero-engines. The concentration distribution of the combustion products of an aero-engine can directly reflect parameters such as the combustion efficiency of aviation kerosene and the thrust level. By monitoring the concentration field of the combustion products, the combustion efficiency of the engine and the combustion characteristics of the fuel can be evaluated, and flight parameters such as the engine fuel injection volume and the intake compression ratio can be adjusted in real time to achieve fuel savings, improve the engine efficiency, and reduce pollutant emissions, etc.

[0003] The measurement of the combustion flow field of an aero-engine is mainly divided into the following three major types of technologies: The first type is the contact probe sampling technology. The contact probe sampling technology needs to sample the exhaust gas emitted by the aero-engine, and it requires a series of processes such as extraction and cooling, which is very time-consuming. As a result, the time cost of obtaining the combustion flow field data set of the aero-engine at each time point is extremely high, and it is impossible to measure parameters such as the composition, temperature, and concentration of high-temperature gas in real time in-situ. The possible continuous chemical reactions of high-temperature gas may cause changes in the composition or concentration of high-temperature gas, bringing more uncertainties to the measurement results. At the same time, the volume of the instrument and equipment is relatively large, and the daily maintenance cost is relatively high.

[0004] The second type is the optical telemetry technology, which is mainly used for telemetry of the gas discharged from the tail nozzle of the aero-engine and cannot measure the combustion flow field inside the aero-engine combustion chamber.

[0005] The third type is the active measurement technology based on tunable laser absorption spectroscopy. This technology is realized based on a tunable laser. Due to the narrow tunable range of the tunable laser, it is usually necessary to install multiple laser emission devices and laser receiving devices on the casing wall of the aero-engine to measure the concentration field distribution of multiple gases in the combustion flow field inside the aero-engine combustion chamber. Since multiple holes need to be reserved on the casing wall of the aero-engine, the modification difficulty of the aero-engine is relatively large. Summary of the Invention

[0006] In view of this, the present invention aims to provide a multi-parameter measuring instrument for the combustion flow field of an aero-engine, so as to solve the technical problem that it is difficult to simply, quickly, accurately and at low cost measure the combustion flow field inside the combustion chamber of an aero-engine by existing measurement methods.

[0007] To achieve the above object, the technical solution of the present invention is realized as follows: An aero-engine combustion flow field measuring instrument based on static snapshot spectral imaging, comprising a front optical system, a fiber optic image bundle array and a rear static snapshot interference spectral imaging system. The front optical system is fixedly installed on the casing wall of the aero-engine and is used to collect the radiation light field of the combustion flow field inside the combustion chamber of the aero-engine and collimate it; the fiber optic image bundle array is used to receive the collimated radiation light field and transmit it to the rear static snapshot interference spectral imaging system; the rear static snapshot interference spectral imaging system is used to perform multiple interference imaging on the collimated radiation light field to obtain an interference image array, perform spectral reconstruction on the interference image array to obtain an interference three-dimensional data cube of the radiation light field, perform spectral demodulation on the interference three-dimensional data cube to obtain a spectral data cube of the radiation light field, and use the spectral data cube to perform inverse reconstruction on the temperature field and concentration field of each combustion product; the rear static snapshot interference spectral imaging system includes a microlens array, a beam splitter, a high-order reflective echelle mirror, a low-order reflective echelle mirror, a collimating mirror and a area array detector. The microlens array is arranged at the incident end of the beam splitter, the high-order reflective echelle mirror and the low-order reflective echelle mirror are respectively arranged at the reflection end and the transmission end of the beam splitter, and the step directions of the high-order reflective echelle mirror and the low-order reflective echelle mirror are orthogonal; the collimating mirror and the area array detector are sequentially arranged at the beam combining end of the beam splitter.

[0008] Further, the high-order reflective echelle mirror and the low-order reflective echelle mirror perform mirror transformation and phase modulation on the incident array image field on the surface, and return to the beam splitter, and interfere on the image plane of the area array detector to form an interference image array.

[0009] Further, the number of steps of both the high-order reflective echelle mirror and the low-order reflective echelle mirror is N, the step height of the high-order reflective echelle mirror is h1, and the step height of the low-order reflective echelle mirror is h2. h1 and h2 satisfy the following relationship: ; The optical path difference formed by the orthogonality of the m-th step of the high-order reflective echelle mirror and the n-th step of the low-order reflective echelle mirror is: ; Then the phase change amount corresponding to the optical path difference is: ; Wherein, is the wave number.

[0010] Furthermore, the interference channels formed by the high-order reflective stepped mirror and the low-order reflective stepped mirror correspond one-to-one with the imaging channels formed by the microlens units in the microlens array.

[0011] Furthermore, by using a planar array detector to inversely reconstruct the multi-parameter physical quantities of the combustion flow field, the multi-parameter physical quantities including the temperature field and concentration field of various combustion products, the inverse reconstruction process of the multi-parameter physical quantities of the combustion flow field is specifically as follows: S1: Perform spectral reconstruction on the interference image array to obtain the interference three-dimensional data cube of the radiation light field; S2: Perform spectral demodulation on the interference three-dimensional data cube to obtain the spectral data cube of the radiation light field; S3: Use the spectral data cube to inversely reconstruct the temperature field and concentration field of each combustion product.

[0012] Furthermore, the specific process of step S1 is as follows: S11: According to the distribution difference of the characteristic information between the interference orders, perform edge detection on the interference image array, and then perform image segmentation on the interference image array based on the detected edges to form different interference units; S12: Analyze the image gray contrast of each interference unit to match the optical path difference; S13: Detect the same feature points for each interference unit, perform image registration on each interference unit based on the detected same feature points, and obtain the interference three-dimensional data cube.

[0013] Furthermore, in step S2, the interference three-dimensional data cube is spectrally demodulated by using the discrete Fourier transform method to obtain the spectral data cube ; ; wherein, is the wave number, is the interference three-dimensional data cube, is the imaginary unit.

[0014] Furthermore, the specific process of step S3 is as follows: S31: Establish a thermal radiation transfer model for the combustion flow field; wherein, the expression of the thermal radiation transfer model for the combustion flow field is: ; wherein, is the total radiation energy of each combustion product, is the transmittance of each combustion product, is the emissivity of each combustion product, is the background radiation energy inside the aero-engine combustion chamber, is the background temperature of the aero-engine combustion flow field, is the wavelength of the characteristic absorption peak of each combustion product received by the area array detector within the response band range, is the radiation energy of each combustion product at different wavelengths, is the temperature of each combustion product, is the response coefficient of the aero-engine combustion flow field measuring instrument; S32: Invert the spectral data cube according to the combustion flow field thermal radiation transfer model to obtain the multi-parameter physical quantities corresponding to different spectral distributions. The multi-parameter physical quantities include the temperature field and concentration field of each combustion product; S33: Perform spectral coordinate mapping on the multi-parameter physical quantities corresponding to different spectral distributions and the interference image array to realize the reconstruction of the temperature field and concentration field of each combustion product.

[0015] Further, in step S32, the specific process of obtaining the concentration field of each combustion product by performing spectral calculation on the spectral data cube according to the combustion flow field thermal radiation transfer model is as follows: S321a: Calculate the background radiation energy inside the aero-engine combustion chamber according to the combustion flow field thermal radiation transfer model. The calculation formula is as follows: ; S322a: Calculate the transmittance of each combustion product according to the background radiation energy inside the aero-engine combustion chamber. The calculation formula is as follows: ; S323a: Invert the concentration of each combustion product according to the relationship between the transmittance and concentration of each combustion product. Among them, the relationship between the transmittance and concentration of each combustion product is: ; Among them, is the concentration of each combustion product, is the optical path during measurement, is the absorption coefficient of each combustion product at different wavelengths; In step S32, the specific process of obtaining the temperature field of each combustion product by performing spectral calculation on the spectral data cube according to the combustion flow field thermal radiation transfer model is as follows: S321b: Select the wavelengths and adjacent to two characteristic absorption peaks within the gas characteristic band range. According to the combustion flow field thermal radiation transfer model, we get:

[0016] Simplify the above formula to:

[0017] Among them, is the ratio of the dual-band gas absorption coefficients of two characteristic absorption peaks; S322b: Calibrate the relationship between and at different temperatures. Utilize the absorption coefficients of each combustion product at different wavelengths and the temperature of each combustion product to invert the temperature of each combustion product .

[0018] Furthermore, the front optical system includes a housing, a reflector, and a collimating lens group. Among them, the housing is fixedly installed on the casing wall of the aeroengine; the reflector is installed inside the housing and is used to reflect the radiation light field of the combustion flow field to the collimating lens group; the collimating lens group is installed inside the housing and is used to collimate the radiation light field.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. The present invention uses a fiber optic image bundle array, a microlens array, and a high-low order reflective stepped mirror for multiple coupled imaging and organic integration. The front optical system and the rear static snapshot interferometric spectroscopic imaging system are coupled and connected to each other through the fiber optic image bundle array, and a static, miniaturized, and lightweight measuring instrument is constructed to eliminate the influence of factors such as the vibration, operating noise, and environment of the aeroengine during the measurement process, and improve the stability of the measuring instrument.

[0020] 2. The present invention can obtain multi-parameter information such as the temperature and concentration of each combustion product through one imaging, realize the function of transient measurement of the combustion flow field map inside the aeroengine, and provide more comprehensive data support for evaluating the combustion efficiency of the aeroengine.

[0021] 3. Only a hole needs to be reserved on the casing wall of the aeroengine to install the front optical system, and the modification difficulty of the aeroengine is small and it is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a schematic structural diagram of an aeroengine combustion flow field measuring instrument based on static snapshot spectroscopy imaging according to an embodiment of the present invention; Figure 2 is a schematic diagram of the multi-parameter inversion and reconstruction process of the combustion flow field according to an embodiment of the present invention.

[0023] The reference numerals therein include: a front optical system 1, a housing 11, a reflecting mirror 12, a collimating lens group 13, an optical fiber image transmission bundle array 2, an input end 21, an output end 22, a rear static snapshot interference spectral imaging system 3, a microlens array 31, a beam splitter 32, a high-order reflective echelette 33, a low-order reflective echelette 34, a collimating mirror 35, a planar array detector 36, a casing wall 4, and a combustion flow field 5. Specific embodiments

[0024] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present 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 only used to explain the present invention and do not constitute a limitation to the present invention.

[0025] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0026] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "mounted", "connected" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0028] The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0029] As Figure 1As shown in the figure, the embodiment of the present invention provides an aeroengine combustion flow field measuring instrument based on static snapshot spectral imaging, which includes a front optical system 1, an optical fiber image bundle array 2, and a rear static snapshot interference spectral imaging system 3. The front optical system 1 is fixedly installed on the casing wall 4 of the aeroengine and is used to collect the radiation light field of the combustion flow field 5 inside the aeroengine combustion chamber and collimate it; the optical fiber image bundle array 2 is used to receive the collimated radiation light field and transmit it to the rear static snapshot interference spectral imaging system 3; the rear static snapshot interference spectral imaging system 3 is used to perform multiple interference imaging on the collimated radiation light field to obtain an interference image array. The obtained interference image array is the scene interference image after multiple interference imaging of the scene image of the combustion flow field 5 inside the aeroengine combustion chamber, and perform spectral reconstruction on the interference image array to obtain the spectral interference three-dimensional data cube of the radiation light field, perform spectral demodulation on the spectral interference three-dimensional data cube to obtain the spectral distribution of the radiation light field, and use the spectral distribution of the radiation light field to inversely reconstruct the temperature field and concentration field of each combustion product.

[0030] The front optical system 1 includes a housing 11, a reflecting mirror 12, and a collimating lens group 13. The housing 11 is fixedly installed on the casing wall 4 of the aeroengine. The reflecting mirror 12 is installed inside the housing 1 and is used to reflect the radiation light field of the combustion flow field to the collimating lens group 13. The collimating lens group 13 is installed inside the housing 11 and is used to collimate the radiation light field.

[0031] The present invention only needs to reserve a hole position on the casing wall 4 of the aeroengine to complete the installation of the front optical system 1, so the modification difficulty of the aeroengine is reduced and it is easy to implement.

[0032] The rear static snapshot interference spectral imaging system 3 includes a microlens array 31, a beam splitter 32, a high-order reflective stepped mirror 33, a low-order reflective stepped mirror 34, a collimating mirror 35, and a area array detector 36. The microlens array 31 is arranged at the incident end of the beam splitter 32. The high-order reflective stepped mirror 33 and the low-order reflective stepped mirror 34 are respectively arranged at the reflective end and the transmissive end of the beam splitter 32, and the stepped directions of the high-order reflective stepped mirror 33 and the low-order reflective stepped mirror 34 are orthogonal. The collimating mirror 35 and the area array detector 36 are sequentially arranged at the beam combining end of the beam splitter 32.

[0033] The input end 21 of the fiber optic image bundle array 2 is coupled with the collimating lens group 13 for receiving the collimated radiation light field. The output end 22 of the fiber optic image bundle array 2 is coupled with the microlens array 31 for transmitting the collimated radiation light field to the microlens array 31. The scene image of the internal combustion flow field 5 of the aero-engine combustion chamber is collected by the front optical system 1 and the fiber optic image bundle array 2 and transmitted to the rear static snapshot interferometric spectroscopy imaging system 3, realizing the snapshot spectroscopy imaging of the internal combustion flow field 5 of the aero-engine combustion chamber. The scene image of the internal combustion flow field 5 of the aero-engine combustion chamber is respectively subjected to optical field coupling modulation with the fiber optic image bundle array 2 and the microlens array 31, performing multiple interference imaging on the scene image, and performing mirror transformation and phase modulation on the multiple interference imaging through the image field modulation of the high-order reflective echelle mirror 33 and the low-order reflective echelle mirror 34.

[0034] The aero-engine combustion flow field measuring instrument proposed by the present invention uses the front optical system 1 to image the engine combustion flow field and then obtains the spectral map information of the combustion flow field through the fiber optic image bundle array 2 and the rear static snapshot interferometric spectroscopy imaging system 3, and can perform measurements during the operation of the engine, that is, on-line measurement. The front optical system 1 can be integrated with the engine to achieve in-situ measurement.

[0035] Since the aero-engine combustion flow field measuring instrument of the present invention adopts a static structure, that is, there are no movable parts inside the aero-engine combustion flow field measuring instrument, and all optical structures are static structural components, it has high stability and strong adaptability. The aero-engine combustion flow field measuring instrument will not cause performance degradation or failure due to factors such as mechanical wear and vibration during the working process, and can operate stably for a long time.

[0036] Strong spectral noise is caused by the interference of complex environments such as vibration and high-temperature fluctuations during the operation of the engine in the measurement process. There are problems such as jitter and baseline drift in the measured spectrum, which affect the subsequent spectral inversion and the calculation of multi-parameter physical quantities. The present invention uses a flexible fiber optic array to isolate most of the environmental interferences such as vibration and high-temperature fluctuations, greatly reducing the interference of the engine operation during measurement on the spectral map measurement.

[0037] The radiation light field of the combustion flow field 5 inside the aero-engine combustion chamber is reflected by the mirror 12 to the collimating lens group 13, and after being collimated by the collimating lens group 13, it is coupled into the fiber optic image bundle array 2. It is transmitted through the fiber optic image bundle array 2 to the microlens array 31, and becomes a multiple imaging light field through the microlens array 31. The multiple imaging light field is divided into a reflected imaging light field and a transmitted imaging light field by the beam splitter 32. The reflected imaging light field is reflected by the beam splitter 32 to the high-order reflective stepped mirror 33. The high-order reflective stepped mirror 33 uses its stepped structure to perform mirror transformation and phase modulation on the reflected imaging light field. The transmitted imaging light field is transmitted through the beam splitter 32 to the low-order reflective stepped mirror 34. The low-order reflective stepped mirror 34 uses its stepped structure to perform mirror transformation and phase modulation on the transmitted imaging light field. The modulated reflected imaging light field and transmitted imaging light field return along the original path to the beam splitter 32, and after being collimated by the collimating mirror 35, they are received by the area array detector 36. The modulated reflected imaging light field and transmitted imaging light field are superimposed and interfered on the image plane of the area array detector 36 to form an interference image array.

[0038] Each step of the high-order reflective stepped mirror 33 corresponds to a row of microlens units of the microlens array 31, and each step of the low-order reflective stepped mirror 34 corresponds to a column of microlens units of the microlens array 31, so as to perform aperture segmentation on the multiple imaging light field, form multiple interference channels, each interference channel corresponds to a specific optical path difference, and each microlens unit constitutes an imaging channel, and the imaging channels and the interference channels correspond one by one.

[0039] The number of steps of both the high-order reflective stepped mirror and the low-order reflective stepped mirror is N. The step height of the high-order reflective stepped mirror is h1, and the step height of the low-order reflective stepped mirror is h2.

[0040] To ensure the coherence of the optical path difference sampling and the complementarity between the optical path differences, h1 and h2 satisfy the following relationship: ; The optical path difference formed by the orthogonality of the m-th step of the high-order reflective stepped mirror and the n-th step of the low-order reflective stepped mirror is: ; Then the phase change amount corresponding to the optical path difference is: ; where is the wave number.

[0041] The present invention realizes the inversion and reconstruction of multi-parameter physical quantities of the combustion flow field through the area array detector 36. The multi-parameter physical quantities include the temperature field and concentration field of various combustion products.

[0042] The specific process of the inversion and reconstruction of multi-parameter physical quantities of the combustion flow field by the area array detector 36 is as follows Figure 2 shown, including the following steps: S1: Perform spectral reconstruction on the interference image array to obtain the interference three-dimensional data cube of the radiation light field.

[0043] The specific process of step S1 is as follows: S11: According to the distribution difference of characteristic information between interference orders, perform edge detection on the interference image array, and then perform image segmentation on the interference image array based on the detected edges to form different interference units.

[0044] In the interference image array measured by the area array detector, the boundaries between the interference units are step-like vertical and horizontal stripes with alternating light and dark. There is regional discontinuity in the interference unit area. Based on this image area discontinuity, the edges of the interference units are identified. Based on morphological edge information enhancement and edge information extraction, the extraction of each interference unit in the interference image array is completed.

[0045] S12: Analyze the image gray contrast of each interference unit to match the optical path difference.

[0046] According to the interference principle, the optical path difference is related to the gray change of the interference fringes. The change of the optical path difference will cause the movement of the interference fringes, thus causing the change of the image gray distribution. By analyzing the change of the gray contrast, the change of the optical path difference can be inferred. Count the number of pixels of each gray value in the image to obtain the gray histogram, which reflects the gray distribution of the image. According to the gray histogram, calculate the gray difference between adjacent pixels to measure the local contrast.

[0047] S13: Detect the same feature points for each interference unit, perform image registration on each interference unit based on the detected same feature points, and obtain the interference three-dimensional data cube.

[0048] Match and stack the obtained interference units. Image registration is mainly divided into two steps. The first step is feature extraction. According to the deformation and rotation (optical system alignment error) between the units of the scene image obtained from the combustion flow field of the aero-engine, select a suitable feature detection and extraction algorithm to detect the feature points with unique properties, such as corner points and edge points, from the scene image of the combustion flow field. The second step is feature matching. Compare the feature descriptors of one interference unit with all the feature descriptors of another interference unit one by one, so as to find the matching feature points, estimate the geometric transformation model between the reference image and the image to be registered, and transform the image to be registered according to the estimated geometric transformation model to align it with the reference image to complete the registration.

[0049] S2: Perform spectral demodulation on the interference three-dimensional data cube to obtain the spectral data cube of the radiation light field.

[0050] The spectral demodulation of the interference three-dimensional data cube is carried out by means of discrete Fourier transform to obtain the spectral data cube : ; wherein, is the wave number, is the interference three-dimensional data cube, is the imaginary unit

[0051] S3: The temperature field and concentration field of each combustion product are inversely reconstructed by using the spectral data cube

[0052] The specific process of step S3 is as follows S31: Establish a thermal radiation transfer model for the combustion flow field; wherein, the expression of the thermal radiation transfer model for the combustion flow field is ; wherein, is the total radiation energy of each combustion product, is the transmittance of each combustion product, is the emissivity of each combustion product, is the background radiation energy inside the aero-engine combustion chamber, is the background temperature of the aero-engine combustion flow field, is the wavelength of the characteristic absorption peak of each combustion product received by the area array detector within the response wavelength range, is the radiation energy of each combustion product at different wavelengths, is the temperature of each combustion product, is the response coefficient of the aero-engine combustion flow field measuring instrument

[0053] S32: Invert the spectral data cube according to the thermal radiation transfer model of the combustion flow field to obtain multi-parameter physical quantities corresponding to different spectral distributions, and the multi-parameter physical quantities include the temperature field and concentration field of each combustion product

[0054] In step S32, the specific process of obtaining the concentration field of each combustion product by performing spectral calculation on the spectral data cube according to the thermal radiation transfer model of the combustion flow field is S321a: Calculate the background radiation energy inside the aero-engine combustion chamber according to the thermal radiation transfer model of the combustion flow field, and the calculation formula is as follows .

[0055] Due to its selective permeability, that is, the characteristic of partial absorption, the high-temperature gas has a transmittance close to 1 in certain wavelength bands. The radiation energy received within this wavelength band range is basically all from the background radiation energy. Therefore, it can be used to determine the equivalent radiation temperature spectrum from the background.

[0056] S322a: Calculate the transmittance of each combustion product according to the background radiation energy inside the aero-engine combustion chamber. The calculation formula is as follows: ; S323a: Invert the concentration of each combustion product according to the relationship between the transmittance and concentration of each combustion product. Among them, the relationship between the transmittance and concentration of each combustion product is: ; Among them, is the concentration of each combustion product, is the optical path during measurement, is the absorption coefficient of each combustion product at different wavelengths.

[0057] For example, the formulas for inverting the concentrations of water vapor and carbon dioxide in high-temperature gas: ; Among them, is the absorption coefficient of water vapor at different wavelengths, is the absorption coefficient of carbon dioxide at different wavelengths, is the concentration of water vapor, is the concentration of carbon dioxide.

[0058] In step S32, the specific process of obtaining the temperature field of each combustion product by performing spectral calculation on the spectral data cube according to the combustion flow field thermal radiation transport model is as follows: S321b: Select the wavelengths and adjacent to two characteristic absorption peaks within the gas characteristic wavelength band range. According to the combustion flow field thermal radiation transport model, we get:

[0059] Simplify the above formula to:

[0060] Among them, is the ratio of the two-band gas absorption coefficients of the two characteristic absorption peaks; S322b: Calibrate the relationship between and at different temperatures, and use the absorption coefficient of each combustion product at different wavelengths and the temperature The relationship between them is used to invert the temperatures of the combustion products .

[0061] S33: Perform spectral coordinate mapping on the multi-parameter physical quantities corresponding to different spectral distributions and the interference image array to reconstruct the temperature field and concentration field of each combustion product.

[0062] The coordinates of each pixel point in the interference image array and the gray value corresponding to the pixel point are in one-to-one correspondence with the spatial coordinates or spectral information of the scene image in the combustion flow field. By calculating the gray value and spectral distribution of each pixel point, the physical parameters corresponding to the pixel point coordinates (including the concentrations and temperatures of the combustion products) can be obtained. One-to-one correspondence between the physical parameters and the pixel point coordinates completes the spectral coordinate mapping.

[0063] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps recited in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is made herein.

[0064] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An aero-engine combustion flow field measuring instrument based on static snapshot spectral imaging, characterized in that: It comprises a front optical system, an optical fiber image transmission bundle array and a rear static snapshot interference spectrum imaging system. The front optical system is fixedly mounted on the casing wall of the aircraft engine and is used to collect the radiation light field of the combustion flow field inside the aircraft engine combustion chamber and to collimate it; the optical fiber image transmission bundle array is used to receive the collimated radiation light field and transmit it to the rear static snapshot interference spectrum imaging system; the rear static snapshot interference spectrum imaging system is used to perform multiple interference imaging on the collimated radiation light field to obtain an interference image array, and to perform spectrum reconstruction on the interference image array to obtain an interference three-dimensional data cube of the radiation light field, to perform spectrum demodulation on the interference three-dimensional data cube to obtain a spectrum data cube of the radiation light field, and to use the spectrum data cube to invert and reconstruct the temperature field and concentration field of each combustion product; The post-static snapshot interferometric spectral imaging system comprises a microlens array, a beam splitter, a high-order reflective step mirror, a low-order reflective step mirror, a collimator mirror and a planar array detector. The microlens array is arranged at the incident end of the beam splitter, the high-order reflective step mirror and the low-order reflective step mirror are arranged at the reflection end and the transmission end of the beam splitter respectively, and the step directions of the high-order reflective step mirror and the low-order reflective step mirror are orthogonal; the collimator mirror and the planar array detector are arranged in sequence at the beam combining end of the beam splitter.

2. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 1 is characterized in that: The high-order reflective step mirror and the low-order reflective step mirror perform mirror transformation and phase modulation on the array image field incident on the surface, and return to the beam splitter, superimposing interference on the image plane of the area array detector to form an interference image array.

3. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 1 or 2, characterized in that: The number of steps of the high-order reflective step mirror and the low-order reflective step mirror is N, the step height of the high-order reflective step mirror is h1, and the step height of the low-order reflective step mirror is h2. h1 and h2 satisfy the following relationship: ； The optical path difference formed by the orthogonal intersection of the mth step of the high-order reflective step mirror and the nth step of the low-order reflective step mirror for: ； The optical path difference The corresponding phase change for: ； in, is the wave number.

4. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 3 is characterized in that: The interference channel formed by the high-order reflective step mirror and the low-order reflective step mirror corresponds one-to-one to the imaging channel formed by the microlens units in the microlens array.

5. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 1, characterized in that: The multi-parameter physical quantities of the combustion flow field are inverted and reconstructed by using the array detector. The multi-parameter physical quantities include the temperature field and concentration field of various combustion products. The inversion and reconstruction process of the multi-parameter physical quantities of the combustion flow field is as follows: S1: reconstruct the interference image array to obtain the interference three-dimensional data cube of the radiation light field; S2: spectrally demodulate the interference three-dimensional data cube to obtain the spectrum data cube of the radiation light field; S3: Use the atlas data cube to invert and reconstruct the temperature field and concentration field of each combustion product.

6. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 5, characterized in that: The specific process of step S1 is: S11: performing edge detection on the interference image array according to the distribution difference of feature information between interference orders, and then performing image segmentation on the interference image array based on the detected edges to form different interference units; S12: performing image grayscale contrast analysis on each interference unit to match the optical path difference; S13: performing common feature point detection on each interference unit, and performing image registration on each interference unit based on the detected common feature points to obtain an interference three-dimensional data cube.

7. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 5, characterized in that: In step S2, the interference three-dimensional data cube is spectrally demodulated by discrete Fourier transform to obtain a spectrum data cube ; ； in, is the wave number, To interferometrically represent a 3D data cube, Is an imaginary unit.

8. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 5, characterized in that: The specific process of step S3 is: S31: Establish a combustion flow field thermal radiation transmission model; wherein the expression of the combustion flow field thermal radiation transmission model is: ； in, is the total radiation energy of each combustion product, is the transmittance of each combustion product, is the emissivity of each combustion product, is the background radiation energy inside the combustion chamber of an aircraft engine. is the background temperature of the aircraft engine combustion flow field, is the wavelength of the characteristic absorption peak of each combustion product received by the array detector within the response band, is the radiation energy of each combustion product at different wavelengths, is the temperature of each combustion product, is the response coefficient of the aircraft engine combustion flow field measuring instrument; S32: inverting the spectrum data cube according to the combustion flow field thermal radiation transmission model to obtain multi-parameter physical quantities corresponding to different spectral distributions, the multi-parameter physical quantities including the temperature field and concentration field of each combustion product; S33: Spectral coordinate mapping is performed on the multi-parameter physical quantities corresponding to different spectral distributions and the interference image array to achieve reconstruction of the temperature field and concentration field of each combustion product.

9. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 8, characterized in that: In step S32, the specific process of performing spectral calculation on the atlas data cube according to the combustion flow field thermal radiation transmission model to obtain the concentration field of each combustion product is as follows: S321a: The background radiation energy inside the combustion chamber of an aircraft engine is calculated based on the thermal radiation transfer model of the combustion flow field. The calculation formula is as follows: ； S322a: Calculate the transmittance of each combustion product based on the background radiation energy inside the combustion chamber of the aircraft engine. The calculation formula is as follows: ； S323a: Invert the concentration of each combustion product according to the relationship between the transmittance and concentration of each combustion product; wherein the relationship between the transmittance and concentration of each combustion product is: ； in, is the concentration of each combustion product, is the optical path length during measurement, is the absorption coefficient of each combustion product at different wavelengths; In step S32, the specific process of performing spectral calculation on the atlas data cube according to the combustion flow field thermal radiation transmission model to obtain the temperature field of each combustion product is as follows: S321b: Select the wavelengths of two adjacent characteristic absorption peaks within the characteristic band of the gas and , according to the thermal radiation transfer model of the combustion flow field: Simplify the above formula to: in, is the dual-band gas absorption coefficient ratio of the two characteristic absorption peaks; S322b: Calibrate at different temperatures and The relationship between the absorption coefficients of various combustion products at different wavelengths is used. The temperature of each combustion product The relationship between the temperature of each combustion product is inverted .

10. The aircraft engine combustion flow field measuring instrument based on static snapshot spectral imaging according to claim 1, characterized in that: The front optical system includes a shell, a reflector, and a collimator lens group; wherein the shell is fixedly mounted on the casing wall of the aircraft engine; the reflector is mounted in the shell to reflect the radiation light field of the combustion flow field to the collimator lens group; the collimator lens group is mounted in the shell to collimate the radiation light field.

Images