An acoustic-optical coupled three-dimensional flame area temperature field monitoring system and operation method

Abstract

The present invention discloses an acousto-optic coupled three-dimensional flame area temperature field monitoring system and an operating method. The system includes a computer, a power amplifier, a relay, a three-dimensional test bench, a loudspeaker, a microphone, a signal analyzer, a light field camera and a blackbody furnace. The present invention uses a non-contact sound velocity method to measure the overall temperature of a gas medium in a three-dimensional space, making a more comprehensive contribution to the temperature monitoring of key areas of a furnace. The present invention uses mature equipment such as microphones and loudspeakers, and controls the measurement sequence through relays, thereby improving the speed and efficiency of measurement. Considering the influence of factors such as measurement background noise, sound wave attenuation, and reverberation, the sound source signal and time delay estimation method are selected according to actual conditions, thereby improving the measurement accuracy of the sound wave flight time and the reconstruction accuracy of the three-dimensional temperature field. The three-dimensional sound velocity method temperature measurement can be extended to the measurement of three-dimensional test areas of other shapes besides cubes, and has good applicability. The present invention uses a light field camera, which can simultaneously record all the information of the entire four-dimensional light field in a single exposure. It combines the advantages of light field layered imaging, which can restore multiple two-dimensional layered flame original brightness images from a single light field image, and the advantages of two-color temperature measurement technology, which is simple to use, high precision and high reliability. It successfully realizes the measurement of the three-dimensional flame overall temperature field using a single light field camera, thereby improving the efficiency of three-dimensional flame temperature measurement.

Description

Technical Field

[0001] The present invention belongs to the field of non-contact measurement technology, and in particular relates to an acousto-optic coupling three-dimensional flame area temperature field monitoring system and an operating method thereof, which utilizes cross-correlation analysis of acoustic signals received by a microphone to obtain acoustic wave transit time. Background Art

[0002] According to the principle of temperature measurement using the velocity of sound method, based on the dependence of the velocity of sound on temperature, the time of flight (TOF) of the acoustic wave between the microphone pair can be obtained in the target region (ROI), and then the temperature distribution within the ROI can be obtained by the reconstruction algorithm.

[0003] In theory, the speed of sound depends on the gas temperature:

[0004]

[0005] Where: c is the speed of sound (m / s), γ is the adiabatic gas constant, R is the molar gas constant, R = 8.314 J / (mol·K), M is the average molecular weight of the gas (g / mol), T is the absolute temperature (K), and Z is the gas constant determined by the composition and properties of the gas.

[0006] The TOF is obtained by integrating along a single acoustic path l:

[0007]

[0008] Where f is the reciprocal of the speed of sound at a specific point in the ROI, s / m.

[0009] Similarly, in the case of multiple sound paths and a gridded area to be measured, there are:

[0010]

[0011] Where l ij is the length of the i-th sound path in the j-th grid. j is the inverse of the speed of sound of the jth grid in ROI. i is the TOF of the i-th acoustic path. M is the number of acoustic paths, N is the number of ROI grids. A is the coefficient matrix, b is the TOF matrix, and x is the inverse speed of sound matrix.

[0012] The coefficient matrix A can be calculated based on the specific dimensions of the area to be measured and the specific arrangement of the loudspeaker and microphone. The TOF matrix b can be obtained by estimating the time delay between the time difference between the acoustic wave signal and the arrival of the microphone. The linear equations are then solved using the temperature field reconstruction algorithm to obtain the inverse sound velocity matrix x. Finally, the relationship between sound velocity and gas temperature is substituted into the equation to reconstruct the grid average temperature of the area to be measured.

[0013] The two-color method uses a CCD camera to capture the flame's radiant brightness. The ratio of any two primary colors (red (R), green (G), and blue (B)) is then selected from the image. The temperature is then calculated by combining the CCD camera with the calibration results of a blackbody furnace to measure the flame's temperature field. The two-color method offers an accuracy of 95-98% and is simple to use. However, typical CCD cameras can only capture two-dimensional flame images, making it difficult to perform high-precision and high-speed measurements of actual three-dimensional flames.

[0014] For existing furnace temperature measurement, the commonly used technical routes are contact temperature measurement method to measure the temperature of key points, as well as the optimization algorithm and application scenario expansion of two-dimensional acoustic wave temperature measurement technology.

[0015] Existing contact temperature measurement methods, two-dimensional sound velocity temperature measurement technology, and two-color temperature measurement technology still have certain defects, including:

[0016] 1. The contact temperature measurement method affects and participates in the heat and mass exchange process in the furnace, interferes with the normal operation of the furnace, and reduces the measurement accuracy;

[0017] 2. Contact temperature measuring elements that rely on the principle of thermal balance have poor measurement immediacy in complex and changing environments;

[0018] 3. The service life of contact temperature measuring elements is shortened and the reliability is reduced in harsh environments;

[0019] 4. The current two-dimensional acoustic temperature measurement system still faces problems in practical applications, such as small amount of reconstruction data, low image resolution, and the need to improve reconstruction accuracy;

[0020] 5. The current two-dimensional acoustic temperature measurement system generally uses a pneumatic sound source with sharp autocorrelation characteristics and easy to detect. However, this source has the same probability distribution as the furnace background noise, which causes the background noise to affect the acoustic wave flight time measurement process, resulting in inaccurate temperature measurement of the measured area.

[0021] 6. The current two-dimensional sound velocity method temperature measurement technology can only measure the two-dimensional cross-sectional temperature field, and cannot accurately measure the three-dimensional spatial temperature field;

[0022] 7. The two-color temperature measurement method generally uses a CCD camera, which can only capture two-dimensional flame images. High-precision and high-speed measurement of the actual three-dimensional flame requires a multi-CCD camera system or a single CCD camera timing control. This is costly, complex to implement, time-consuming to measure, and requires high assembly precision. It is not suitable for monitoring industrial combustion equipment in high temperature, vibration, and fly ash environments.

[0023] In summary, there is an urgent need for a new acousto-optic coupled three-dimensional flame area temperature field monitoring system and operation method. Summary of the Invention

[0024] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an acoustic-optical coupled three-dimensional flame area temperature field monitoring system and operation method to solve one or more of the following technical problems: the existing contact temperature measurement method affects the heat and mass exchange process in the furnace, the contact temperature measurement element based on the thermal balance principle has poor measurement immediacy in complex and changing environments, the service life and reliability of the contact temperature measurement element decrease in harsh environments, the two-dimensional acoustic temperature measurement reconstruction data volume is small and the resolution is low, background noise, sound wave attenuation, spatial reverberation and other factors reduce the temperature measurement accuracy of the sound velocity method, a single CCD camera is difficult to complete three-dimensional actual flame high-precision and high-speed measurement, and there is insufficient research on high-precision real-time monitoring of the three-dimensional temperature field of the furnace.

[0025] The present invention utilizes the non-contact sound velocity method temperature measurement principle to measure the overall temperature of the gas medium in three-dimensional space, thereby improving the amount of reconstructed data and the resolution, and making more comprehensive monitoring of the temperature in the three-dimensional area to be measured. The present invention uses a light field camera, and a single exposure can simultaneously record all the information of the entire four-dimensional light field. It combines the advantages of light field layered imaging that can restore multiple two-dimensional layered flame original brightness images from a single light field image and the advantages of two-color temperature measurement technology that is simple to use, high in precision, and high in reliability. It successfully realizes the measurement of the overall temperature field of the three-dimensional flame using a single light field camera, thereby improving the efficiency of three-dimensional flame temperature measurement. The present invention couples the sound velocity method, light field layered imaging, and two-color method, and uses the sound velocity method to break through the limitation of the two-color method and light field layered imaging that cannot measure transparent gas media; and minimizes the interference of the measurement process on the area to be measured, thereby improving the measurement accuracy.

[0026] In order to achieve the above object, the technical solution of the present invention is:

[0027] An acousto-optic coupled three-dimensional flame area temperature field monitoring system includes a computer 1, a power amplifier 2, a relay 3, a three-dimensional stand 4, a loudspeaker 5, a microphone 6, a signal analyzer 7, a light field camera 8 and a blackbody furnace 9;

[0028] The analog signal output end of the computer 1 is connected to the signal input end of the power amplifier 2, the signal output end of the power amplifier 2 is connected to the signal input end of the relay 3, the signal output end of the relay 3 is connected to the input end of the speaker 5, the output end of the speaker 5 is connected to the signal receiving end of the microphone 6, the signal output end of the microphone 6 is connected to the input end of the signal analyzer 7, and the signal output end of the signal analyzer 7 is connected to the USB port of the computer 1; the speakers 5 and microphones 6 are multiple groups, and each group of speakers 5 and microphones 6 is located at the same position on the three-dimensional platform 4; the signal input end of the light field camera 8 is respectively connected to the three-dimensional flame and the blackbody furnace 9 within the three-dimensional platform 4, and the signal output end of the light field camera 8 is connected to the signal input end of the computer 1; the blackbody furnace 9 is used by the light field camera 8 to calibrate the relationship between the grayscale and radiation intensity of the original brightness image of the two-dimensional layered flame. All blackbody furnace 9 data collected by the light field camera 8 is ultimately transmitted to the computer 1 for storage, calculation and analysis; the measurement target of the acousto-optic coupled three-dimensional flame area temperature field monitoring system is the gas temperature and the three-dimensional flame temperature within the three-dimensional test area surrounded by the three-dimensional platform 4 and containing the three-dimensional flame.

[0029] In the acoustic method part, the sound card of the computer 1 converts the audio file of the preset sweep frequency signal into an analog signal; the analog signal is first amplified by the power amplifier 2, and then reaches the designated speaker 5 through the relay 3 to be converted into an acoustic signal for output; the microphone 6 receives the acoustic signal and converts it into an electrical signal and transmits it to the signal analyzer 7 for adjustment and acquisition, and then the acquired data is sent to the computer 1 for processing: the acoustic wave flight time required for the acoustic wave to reach the microphone 6 from the designated speaker 5 is obtained through cross-correlation analysis; after completing multiple rounds of acoustic wave flight time measurements, the acoustic wave flight time is known, and the positional relationship between the three-dimensional platform 4 and the speaker 5 and the microphone 6 is known. The least squares QR decomposition (LSQR) method is used to calculate the temperature value of the flame position of the overall temperature of the gas medium in the three-dimensional space surrounded by the three-dimensional platform 4, and the three-dimensional temperature field is reconstructed.

[0030] In the optical method part, the light field camera 8 captures the three-dimensional flame in the three-dimensional platform 4 to obtain the original light field image of the three-dimensional flame, and then transmits the captured data to the computer 1. Using light field layered imaging, multiple two-dimensional layered flame original brightness images are restored from the light field image; the multiple two-dimensional layered flame original brightness images obtained by the light field layered imaging are used using a two-color method to obtain multiple two-dimensional layered flame temperature fields, and then interpolation is performed to obtain the overall temperature field of the three-dimensional flame.

[0031] Acousto-optic coupling part: In computer 1, the three-dimensional flame overall temperature field obtained by combining light field layered imaging with two-color temperature measurement is used as the true value, replacing the temperature value of the flame location at the overall temperature of the gas medium in the three-dimensional space obtained by the sound velocity method temperature measurement. The sound velocity method temperature measurement results are continuously iterated until convergence, and a new three-dimensional gas temperature field in the overall three-dimensional space containing the three-dimensional flame is obtained.

[0032] The loudspeaker 5 and microphone 6 as non-contact measurement equipment are located on the three-dimensional platform 4 outside the three-dimensional area to be measured. The light field camera 8 as a non-contact measurement equipment is located outside the three-dimensional platform 4 and does not interfere with the heat and mass exchange in the three-dimensional area to be measured.

[0033] Preferably, installation sites are set at the end points and midpoints of each side of the three-dimensional platform 4, with a total of 20 installation sites for installing 20 speakers 5 and 20 microphones 6; on the installation sites of the three-dimensional platform 4, a single speaker 5 and microphone 6 are installed adjacent to each other at the same position, and it is approximately considered that the two are in the same position.

[0034] Preferably, the relay 3 is a multi-channel serial port relay, which controls the on and off of the circuit in the temperature measurement system to control multiple speakers 5 to emit corresponding swept frequency sound wave signals in sequence; the measurement sequence is controlled by the relay 3, which improves the speed and efficiency of the measurement.

[0035] Preferably, the speaker 5 is an electrodynamic sound source, which converts the input analog signal into a sound wave signal and outputs it.

[0036] Preferably, the microphone 6 is a non-directional measurement microphone. During the measurement process, the multiple microphones 6 remain turned on and convert the received acoustic signals into electrical signals, which are then transmitted to the signal analyzer 7 for adjustment and collection.

[0037] Preferably, the signal analyzer 7 integrates signal conditioning and signal collection functions, and its multiple sampling channels realize multi-channel continuous signal acquisition of digitized sound waves and support subsequent channel expansion. All data collected by the signal analyzer 7 are finally transmitted to the computer 1 for storage, calculation and analysis.

[0038] Preferably, the light field camera 8 obtains the original light field image of the three-dimensional flame in the three-dimensional platform 4 through a single shot, which contains all the four-dimensional light field information of the flame. All data collected by the light field camera 8 is ultimately transmitted to the computer 1 for storage, calculation and analysis.

[0039] Preferably, the three-dimensional platform 4 is a cube platform.

[0040] The three-dimensional temperature field measurement method of the acousto-optic coupled three-dimensional flame area temperature field monitoring system is based on the temperature measurement principle of the sound velocity method and the dependence of the sound velocity on temperature. The acoustic wave transit time of the sound wave propagating within the three-dimensional test area is obtained in the target area. Specifically, the three-dimensional platform 4 has multiple speaker 5 and microphone 6 installation points. When the line connecting two installation points is located within the three-dimensional test area rather than on the surface of the three-dimensional platform, the acoustic wave transit time between the two installation points is measured. Thus, multiple acoustic wave transit times need to be measured.

[0041] This acoustic-optic coupled three-dimensional flame area temperature field monitoring system converts a preset frequency sweep signal audio file into an analog signal through the sound card of a computer 1. Due to the attenuation of sound waves, to ensure the intensity of the sound signal when it reaches the microphone 6, the analog signal is amplified by a power amplifier 2. Then, a relay 3 sequentially controls multiple speakers 5 to convert the analog signal output by the computer 1 into a sound wave signal for transmission.

[0042] After relay 3 controls a single speaker 5 to transmit a sound wave signal, multiple microphones 6 operate throughout the entire process and convert the received multi-channel sound signals into electrical signals, which are then transmitted to signal analyzer 7 for adjustment, collection, and finally to computer 1 for storage and cross-correlation analysis. Specifically, the microphone 6 installed adjacent to the designated speaker 5 on the three-dimensional platform 4 first receives the sound signal emitted by the designated speaker 5, and then the other microphones 6 away from the designated speaker 5 successively receive the sound signal emitted by the designated speaker 5. At this time, a cross-correlation analysis is performed on the signal received by the microphone 6 adjacent to the designated speaker 5 and the signal received by the other microphones 6 to obtain the sound wave transit time of the sound signal propagating from the microphone 6 adjacent to the designated speaker 5 to the other microphones 6. Therefore, after relay 3 controls the operation of different speakers 5 in sequence, the computer 1 ultimately obtains the required multiple sound wave transit times.

[0043] Based on the measured multiple sound wave flight times and the positional relationship between the three-dimensional platform 4 and the speaker 5 and microphone 6, the temperature value of the flame location of the overall temperature of the gas medium in the three-dimensional space surrounded by the three-dimensional platform 4 is calculated using the least squares QR decomposition (LSQR) method, and then the three-dimensional temperature field at the flame location in the three-dimensional space is obtained.

[0044] Light field camera 8 captures the three-dimensional flame within 3D gantry 4, obtaining the original light field image of the three-dimensional flame. The captured data is then transmitted to computer 1 for light field layered imaging. Assuming the flame being captured is a three-dimensional, semi-transparent luminous body with a thickness of δ, N layered positions are preset within the flame according to layered imaging theory. Because the flame is semi-transparent, the image of each layer is a superposition of the original brightness distribution of each layer and the defocus information of other layers. According to Fourier optics theory, in a linear shift-invariant optical imaging system, the brightness function of each layer on the image plane is the convolution of the actual light intensity function on the corresponding object plane and the point spread function of the optical imaging system:

[0045]

[0046] Where h z'-z(x, y) is the point spread function (PSF) of the optical imaging system when focusing on the z' plane, obtained through parameter calibration of light field camera 8. f(x, y, z) is the brightness distribution along the z-axis, which is parallel to the optical axis. g(x, y, z') is the image plane brightness distribution, the superposition of the focused image of a specific plane z' on the z-axis and the defocused images of other planes. This is obtained by processing and calculating the two-dimensional flame images at different cross-sections using the digital refocusing function of light field camera 8 and then by computer 1.

[0047] Keeping the spatial position of the optical imaging system and the object constant, N layered focused images are acquired in sequence along the optical axis z direction, and the discretized sequence image of the three-dimensional luminous body is obtained as follows:

[0048]

[0049] The above formula has N equations with N unknown quantities f(x, y, iΔz). The equation group can be solved by combining the deconvolution algorithm. The solution f(x, y, iΔz) is the original brightness image of the i-th layer of the three-dimensional light source, completing the light field layered imaging.

[0050] After restoring multiple two-dimensional layered flame original brightness images from the light field image, the light field image of the blackbody furnace 9 is captured by the light field camera 8 and transmitted to the computer 1. The computer 1 extracts the grayscale data of the three channels R, G, and B respectively, calculates the average grayscale value of each channel, and calibrates the relationship between the radiation intensity and the grayscale average value according to the set temperature value of the blackbody furnace in combination with Planck's law. Based on the calibration results, the multiple two-dimensional layered flame original brightness images obtained by light field layered imaging are measured using the two-color method to obtain multiple two-dimensional layered flame temperature fields, and then interpolated to obtain the three-dimensional flame overall temperature field.

[0051] In computer 1, the three-dimensional flame overall temperature field obtained by combining light field layered imaging with two-color temperature measurement is used as the true value, replacing the temperature value of the flame location of the overall temperature of the gas medium in the three-dimensional space obtained by the sound velocity temperature measurement. The sound velocity temperature measurement results are continuously iterated until convergence, and a new three-dimensional gas temperature field in the overall three-dimensional space containing the three-dimensional flame is obtained.

[0052] Compared to conventional two-dimensional in-furnace acoustic temperature measurement systems, the acousto-optic coupled three-dimensional flame region temperature field monitoring system of the present invention only requires changing the positions of the two-dimensional microphone and loudspeaker on the basis of the original two-dimensional in-furnace acoustic temperature measurement system, adding several microphones and loudspeakers, replacing the CCD camera with a light field camera, and adding calibration equipment such as a blackbody furnace. These devices themselves are simple in structure, low in price, and have stable performance. Therefore, the acousto-optic coupled three-dimensional flame region temperature field monitoring system is expected to achieve significant energy conservation and economic benefits, and can achieve the following beneficial effects:

[0053] (1) The present invention uses the non-contact sound velocity method to measure the overall temperature of the gas medium in three-dimensional space, which improves the amount and resolution of reconstructed data and enables more comprehensive monitoring of the temperature of key areas in the furnace.

[0054] (2) The present invention utilizes mature equipment and processes such as microphones and loudspeakers, and measures the acoustic wave transit time on multiple acoustic paths in the area to be measured in sequence through relay control, thereby improving the speed and efficiency of measurement.

[0055] (3) The present invention only builds a stand outside the three-dimensional area to be measured to install a microphone and a loudspeaker, and sets a light field camera outside the three-dimensional area to be measured. The measuring element does not contact the flow field in the three-dimensional area to be measured, which minimizes the interference of the measurement process on the area to be measured and improves the measurement accuracy.

[0056] (4) The present invention takes into account the influence of factors such as measurement background noise, sound wave attenuation, and reverberation, selects electric sound source and linear sweep signal as sound source signal according to actual conditions, selects cross-correlation analysis as time delay estimation method, and selects least squares QR decomposition (LSQR) method as temperature field reconstruction algorithm, thereby improving the overall sound wave flight time measurement accuracy and the final three-dimensional temperature field reconstruction accuracy.

[0057] (5) The present invention uses a light field camera, which can simultaneously record all the information of the entire four-dimensional light field in one exposure. It combines the advantages of light field layered imaging, which can restore multiple two-dimensional layered flame original brightness images from a single light field image, and the advantages of two-color temperature measurement technology, which is simple to use, high precision and high reliability. It successfully realizes the measurement of the three-dimensional flame overall temperature field using a single light field camera, thereby improving the efficiency of three-dimensional flame temperature measurement.

[0058] (6) The present invention uses optical methods to correct the problems of the sound velocity method, such as small amount of reconstruction data, low image resolution, and need to improve reconstruction accuracy; at the same time, the sound velocity method is used to break through the limitations of the two-color method and light field layered imaging that cannot measure transparent gas media.

[0059] (7) The acousto-optic coupling three-dimensional flame area temperature field monitoring method of the present invention can be extended to the measurement and analysis of gas temperature in three-dimensional test areas of other shapes other than cubes. It only needs to change the shape and size of the three-dimensional test platform, the number and arrangement of microphones and speakers on the three-dimensional test platform, and the position and distance of the light field camera relative to the flame in the three-dimensional test platform, and has good applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0061] In order to more clearly understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0062] like Figure 1 As shown, the present invention is an acoustic-optical coupled three-dimensional flame area temperature field monitoring system, comprising a computer 1, a power amplifier 2, a relay 3, a three-dimensional stand 4, a speaker 5, a microphone 6, a signal analyzer 7, a light field camera 8 and a blackbody furnace 9; the analog signal output end of the computer 1 is connected to the signal input end of the power amplifier 2, the signal output end of the power amplifier 2 is connected to the signal input end of the relay 3, the signal output end of the relay 3 is connected to the input end of the speaker 5, the output end of the speaker 5 is connected to the signal receiving end of the microphone 6, and the signal output end of the microphone 6 is connected to the signal analyzer 7. The input end is connected, and the signal output end of the signal analyzer 7 is connected to the USB port of the computer 1; there are multiple groups of speakers 5 and microphones 6, and each group of speakers 5 and microphones 6 is located at the same position on the three-dimensional platform 4; the signal input end of the light field camera 8 is respectively connected to the three-dimensional flame and the blackbody furnace 9 in the three-dimensional platform 4, and the signal output end of the light field camera 8 is connected to the signal input end of the computer 1; the measurement target of this acousto-optic coupling three-dimensional flame area temperature field monitoring system is the gas temperature and the three-dimensional flame temperature in the three-dimensional test area surrounded by the three-dimensional platform 4 and containing the three-dimensional flame.

[0063] The sound card of the computer 1 converts the audio file of the preset sweep frequency signal into an analog signal; the analog signal is first amplified by the power amplifier 2, and then reaches the designated speaker 5 through the relay 3 to be converted into an acoustic signal for output; the microphone 6 receives the acoustic signal and converts it into an electrical signal and transmits it to the signal analyzer 7 for adjustment and acquisition, and then the acquired data is sent to the computer 1 for processing: the acoustic wave flight time required for the acoustic wave to reach the microphone 6 from the designated speaker 5 is obtained through cross-correlation analysis; after completing multiple rounds of acoustic wave flight time measurements, the acoustic wave flight time is known, and the positional relationship between the three-dimensional platform 4 and the speaker 5 and the microphone 6 is known. The least squares QR decomposition (LSQR) method is used to calculate the temperature value of the flame position of the overall temperature of the gas medium in the three-dimensional space surrounded by the three-dimensional platform 4, and the three-dimensional temperature field is reconstructed.

[0064] In the system of the present invention, the loudspeaker 5 and the microphone 6 as non-contact measurement devices are located on the three-dimensional platform 4 outside the three-dimensional area to be measured, and the light field camera 8 as a non-contact measurement device is located outside the three-dimensional platform 4 and does not interfere with the heat and mass exchange in the three-dimensional area to be measured.

[0065] As a preferred embodiment of the present invention, mounting sites are set at the endpoints and midpoints of each side of the three-dimensional platform 4, for a total of 20 mounting sites, for mounting 20 speakers 5 and 20 microphones 6. The greater the number of sensor mounting sites, the more sufficient the measurement data volume and the better the reconstruction performance of the sound velocity method. However, in actual engineering applications, to ensure structural strength and reliability, it is not advisable to modify too many mounting sites on industrial combustion equipment. To balance the reconstruction performance of the sound velocity method with actual engineering needs, 20 points, namely the endpoints and midpoints of each side of the three-dimensional platform 4, are set as mounting sites. This ensures that the temperature measurement data of the sound velocity method within the three-dimensional test area is evenly distributed, while avoiding the problem of missing measurement data at the corners and edges of the three-dimensional test area. At the mounting sites of the three-dimensional platform 4, a single speaker 5 and microphone 6 are installed adjacent to each other in the same position, and are approximately considered to be in the same position.

[0066] The computer 1 is a core component of the acousto-optic coupled three-dimensional flame area temperature field monitoring system. The system uses an audio file of a preset sweep frequency signal stored in the computer 1 as the sound source signal for temperature measurement using the sound velocity method. At the same time, the computer 1 receives and stores all data from the signal analyzer 7 and obtains the acoustic wave transit time by cross-correlation analysis. Based on the acoustic wave transit time and the positional relationship between the three-dimensional platform 4, the speaker 5, and the microphone 6, the three-dimensional temperature field of the gas in the three-dimensional space surrounded by the three-dimensional platform 4 is reconstructed using the least squares QR decomposition (LSQR) method. In addition, the computer 1 receives and stores all data from the light field camera 8. First, the three-dimensional flame within the three-dimensional platform 4 captured by the light field camera 8 is subjected to light field layered imaging to obtain original brightness images of the three layers of the three-dimensional flame luminous body. Secondly, the light field image of the blackbody furnace 9 captured by the light field camera 8 is processed and the blackbody furnace is calibrated. Based on the calibration results, the multiple two-dimensional layered flame original brightness images obtained by the light field layered imaging are subjected to two-color temperature measurement to obtain multiple two-dimensional layered flame temperature fields, which are then interpolated to obtain the overall three-dimensional flame temperature field.

[0067] The relay 3 is a multi-channel serial port relay, which controls the on and off of the circuit in the temperature measurement system to control multiple speakers 5 to transmit corresponding sweep frequency sound wave signals in sequence; controlling the measurement sequence by the relay 3 improves the speed and efficiency of the measurement;

[0068] As a preferred embodiment of the present invention, the speaker 5 is an electric sound source, which converts the input analog signal into a sound wave signal and outputs it. It has a simple structure, is safe and stable, has mature technology, and can emit various types of sound wave signals. It is suitable for sound source selection for temperature measurement using the speed of sound method.

[0069] Microphone 6 is a non-directional measurement microphone suitable for measurements in non-reflective free and semi-free fields. It utilizes prepolarization, eliminating the need for an external polarization voltage, making it a suitable microphone for temperature measurement using the velocity of sound method. Multiple microphones 6 remain active during the measurement process and convert received acoustic signals into electrical signals, which are then transmitted to a signal analyzer 7 for conditioning and acquisition. This signal analyzer 7 integrates signal conditioning and signal collection functions. Its multiple sampling channels enable multi-channel continuous signal acquisition of digitized acoustic waves and support subsequent channel expansion. All data collected by the signal analyzer 7 is ultimately transmitted to the computer 1 for storage, calculation, and analysis.

[0070] The light field camera 8 captures a single shot of the three-dimensional flame within the three-dimensional gantry 4, capturing the original light field image of the flame. This image contains all four-dimensional light field information of the flame, surpassing the limitation of traditional CCD cameras, which can only capture two-dimensional images with a fixed depth of field. All data collected by the light field camera 8 is ultimately transmitted to the computer 1 for storage, calculation, and analysis.

[0071] The blackbody furnace 9 is used by the light field camera 8 to calibrate the relationship between the grayscale and radiation intensity of the original brightness image of the two-dimensional layered flame. All the blackbody furnace 9 data collected by the light field camera 8 are finally transmitted to the computer 1 for storage, calculation and analysis.

[0072] As a preferred embodiment of the present invention, the three-dimensional platform 4 is a cube platform with a side length of 1 meter. The cube frame can match the shape of a large number of industrial equipment and is suitable for sonic temperature measurement of industrial combustion equipment. A total of 20 sensor installation sites are set at the end points and midpoints of each side of the three-dimensional platform 4, such as Figure 1 As shown by the five-pointed star on the central cube stand.

[0073] like Figure 1 As shown, the three-dimensional temperature field measurement method of the acousto-optic coupled three-dimensional flame area temperature field monitoring system of the present invention, based on the temperature measurement principle of the sound velocity method and the dependence of the sound velocity on temperature, can obtain the sound wave flight time of the sound wave propagating inside the three-dimensional test area in the target area; specifically, there are 20 loudspeaker 5 and microphone 6 installation points on the three-dimensional platform 4. When the line connecting two installation points is located inside the three-dimensional test area rather than on the surface of its three-dimensional platform, the sound wave flight time between the two installation points is measured, thus a total of 58 sound wave flight times need to be measured.

[0074] The acousto-optic coupled three-dimensional flame area temperature field monitoring system uses a computer 1 signal generation program and a sound card to generate an analog signal of a linear sweep frequency signal with a sweep frequency range of 1-3kHz and a sweep frequency period of 0.1s. After being amplified by a single-channel power amplifier 2 with a rated power of 50W, 20 4Ω / 5W small electric speakers 5 are controlled by a 32-channel serial port relay 3 to sequentially convert the analog signal output by the computer 1 into an acoustic wave signal for transmission.

[0075] After a single speaker 5 transmits an acoustic signal, relay 3 controls 20 prepolarized electret non-directional measurement microphones 6 with an open-circuit sensitivity of 50±2 mV / Pa and a frequency response range of 20 kHz. These 20 received acoustic signals are converted into electrical signals and transmitted to signal analyzer 7 for conditioning, acquisition, and ultimately to computer 1 for storage and cross-correlation analysis. Specifically, the microphone 6 mounted adjacent to a designated speaker 5 on the three-dimensional gantry 4 first receives the acoustic signal emitted by the designated speaker 5. Then, the other microphones 6 located further away from the designated speaker 5 successively receive the acoustic signal emitted by the designated speaker 5. At this point, cross-correlation analysis is performed on the signal received by the microphone 6 adjacent to the designated speaker 5 and the signals received by the other microphones 6 to determine the acoustic transit time of the acoustic signal from the microphone 6 adjacent to the designated speaker 5 to the other microphones 6. (Specifically, peak location, signal interception, and PHAT-weighted cross-correlation delay estimation are sequentially performed on the 20 signals received by all microphones 6 to determine the acoustic transit time of the acoustic signal between each pair of microphones 6.) Therefore, after the relay 3 controls the different speakers 5 to work in sequence, the computer 1 finally obtains the required multiple sound wave flight times.

[0076] Based on the measured multiple sound wave flight times and the positional relationship between the three-dimensional platform 4 and the speaker 5 and microphone 6, the temperature value of the flame location of the overall temperature of the gas medium in the three-dimensional space surrounded by the three-dimensional platform 4 is calculated using the least squares QR decomposition (LSQR) method, and then the three-dimensional temperature field at the flame location in the three-dimensional space is obtained.

[0077] A Lytro II-type light field camera 8 is used to capture the three-dimensional butane flame within the three-dimensional gantry 4, obtaining a raw light field image of the three-dimensional butane flame. The captured data is then transmitted to a computer 1 for light field layered imaging. Assuming the captured butane flame is a three-dimensional, semi-transparent luminous body with a thickness of δ, three layer positions are preset within the flame, with a layer spacing of 5 mm, according to layered imaging theory. Because the flame is semi-transparent, the image of each layer is a superposition of the original brightness distribution of each layer and the defocus information of other layers. According to Fourier optics theory, in a linear shift-invariant optical imaging system, the brightness function of each layer on the image plane is the convolution of the actual light intensity function on the corresponding object plane and the point spread function of the optical imaging system:

[0078]

[0079] Where h z'-z (x, y) is the point spread function (PSF) of the optical imaging system when focusing on the z' plane, obtained through parameter calibration of light field camera 8. f(x, y, z) is the brightness distribution along the z-axis, which is parallel to the optical axis. g(x, y, z') is the image plane brightness distribution, the superposition of the focused image of a specific plane z' on the z-axis and the defocused images of other planes. This is obtained by processing and calculating the two-dimensional flame images at different cross-sections using the digital refocusing function of light field camera 8 and then by computer 1.

[0080] Keeping the spatial position of the optical imaging system and the object constant, three layered focused images are acquired in sequence along the optical axis z direction, and the discretized sequence images of the three-dimensional luminous body are obtained as follows:

[0081]

[0082] The three equations above have three unknown quantities f(x, y, iΔz). Combined with the Van Citter iterative deconvolution algorithm, the equation system can be solved. The solution f(x, y, iΔz) is the original brightness image of the i-th layer of the three-dimensional light source, completing the light field layered imaging.

[0083] After restoring multiple two-dimensional layered flame original brightness images from the light field image, the German optris BR1450 blackbody furnace was used for calibration. Its temperature range is 100-1450℃, the accuracy is ±0.4%, and the effective emissivity is 0.99, which meets the calibration requirements. To prevent overexposure of the image, an exposure time of 0.8ms was used during shooting. The butane flame was selected as the research object. For the stainless steel burner, the maximum temperature is less than 1373K, so the calibration temperature changes from 1123K to 1373K, and the temperature is changed every 50K. Each time the temperature of the blackbody furnace 9 is changed, data is collected once after the temperature of the blackbody furnace 9 stabilizes. The light field image of the blackbody furnace 9 taken by the light field camera 8 is transmitted to the computer 1 and the grayscale data of the three channels R, G, and B are extracted respectively. The average value of the grayscale value in each channel is calculated. According to the set temperature value of the blackbody furnace, the relationship between the radiation intensity and the grayscale average value is calibrated in combination with Planck's law. According to the calibration results, the three two-dimensional layered flame original brightness images obtained by light field layered imaging are measured using the two-color method to obtain the three two-dimensional layered flame temperature fields, and then interpolated to obtain the three-dimensional flame overall temperature field.

[0084] In computer 1, the three-dimensional flame overall temperature field obtained by combining light field layered imaging with two-color temperature measurement is used as the true value, replacing the temperature value of the flame location of the overall temperature of the gas medium in the three-dimensional space obtained by the sound velocity temperature measurement. The sound velocity temperature measurement results are continuously iterated until convergence, and a new three-dimensional gas temperature field in the overall three-dimensional space containing the three-dimensional flame is obtained.

[0085] The present invention utilizes the non-contact sound velocity temperature measurement principle to measure the overall temperature of a gas medium in three-dimensional space, making a more comprehensive contribution to temperature monitoring in key furnace areas. The present invention utilizes established devices such as microphones and speakers, controlling the measurement sequence through relays, thereby improving measurement speed and efficiency. Taking into account the influence of factors such as measurement background noise, sound wave attenuation, and reverberation, the present invention selects the sound source signal and delay estimation method based on actual conditions, thereby improving the accuracy of sound wave transit time measurement and three-dimensional temperature field reconstruction. The present invention utilizes a light field camera, combining the advantages of light field layered imaging and two-color temperature measurement technology to successfully measure the overall three-dimensional flame temperature field using a single light field camera, thereby improving the efficiency of three-dimensional flame temperature measurement. The present invention uses optical methods to correct the problems of the sound velocity method, such as the small amount of reconstruction data, low image resolution, and poor reconstruction accuracy. The sound velocity method also overcomes the limitations of the two-color method and light field layered imaging, which cannot measure transparent gas media. Furthermore, the present invention minimizes interference with the measured area during the measurement process, thereby improving measurement accuracy. The acousto-optic coupling three-dimensional flame region temperature field monitoring method can be extended to measure three-dimensional measured areas of shapes other than cubes, demonstrating good applicability.

[0086] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An acoustic-optic coupled three-dimensional flame area temperature field monitoring system, characterized by: It includes a computer (1), a power amplifier (2), a relay (3), a three-dimensional platform (4), a speaker (5), a microphone (6), a signal analyzer (7), a light field camera (8) and a black body furnace (9); The analog signal output end of the computer (1) is connected to the signal input end of the power amplifier (2), the signal output end of the power amplifier (2) is connected to the signal input end of the relay (3), the signal output end of the relay (3) is connected to the input end of the speaker (5), the output end of the speaker (5) is connected to the signal receiving end of the microphone (6), the signal output end of the microphone (6) is connected to the input end of the signal analyzer (7), and the signal output end of the signal analyzer (7) is connected to the USB port of the computer (1); the speakers (5) and microphones (6) are multiple groups, and each group of speakers (5) and microphones (6) is located at the same position on the three-dimensional platform (4); The signal input end of the light field camera (8) is respectively connected to the three-dimensional flame and the black body furnace (9) in the three-dimensional platform (4), and the signal output end of the light field camera (8) is connected to the signal input end of the computer (1); the black body furnace (9) is used for the light field camera (8) to calibrate the relationship between the grayscale and radiation intensity of the original brightness image of the two-dimensional layered flame, and all the black body furnace (9) data collected by the light field camera (8) are finally transmitted to the computer (1) for storage, calculation and analysis; the measurement target of the acousto-optic coupling three-dimensional flame area temperature field monitoring system is the gas temperature and the three-dimensional flame temperature in the three-dimensional test area surrounded by the three-dimensional platform (4) and containing the three-dimensional flame; In the acoustic method part, the sound card of the computer (1) converts the audio file of the preset sweep frequency signal into an analog signal; the analog signal is first amplified by the power amplifier (2), and then reaches the designated speaker (5) through the relay (3) to be converted into an acoustic signal for output; the microphone (6) receives the acoustic signal and converts it into an electrical signal and transmits it to the signal analyzer (7) for adjustment and collection, and then the collected data is sent to the computer (1) for processing: the acoustic wave flight time required for the acoustic wave to reach the microphone (6) from the designated speaker (5) is obtained through cross-correlation analysis; after completing multiple rounds of acoustic wave flight time measurement, the acoustic wave flight time is known, and the positional relationship between the three-dimensional platform (4) and the speaker (5) and the microphone (6) is known, and the temperature value of the flame position of the overall temperature of the gas medium in the three-dimensional space surrounded by the three-dimensional platform (4) is calculated by the least squares QR decomposition method, and the three-dimensional temperature field is reconstructed; In the optical method, the light field camera (8) captures the three-dimensional flame in the three-dimensional platform (4) to obtain the original light field image of the three-dimensional flame, and then transmits the captured data to the computer (1). The light field layered imaging is used to restore multiple two-dimensional layered flame original brightness images from the light field image; the two-color method is used to obtain multiple two-dimensional layered flame original brightness images obtained by the light field layered imaging to obtain multiple two-dimensional layered flame temperature fields, and then interpolation is performed to obtain the three-dimensional flame overall temperature field; Acousto-optic coupling part: In the computer (1), the three-dimensional flame overall temperature field obtained by combining light field layered imaging with two-color temperature measurement is used as the true value, replacing the temperature value of the flame position at the overall temperature of the gas medium in the three-dimensional space obtained by the speed of sound temperature measurement. The speed of sound temperature measurement results are continuously iterated until convergence, and a new three-dimensional gas temperature field in the overall three-dimensional space containing the three-dimensional flame is obtained.

2. The acousto-optic coupled three-dimensional flame region temperature field monitoring system according to claim 1, characterized in that: The loudspeaker (5) and microphone (6) as non-contact measurement equipment are located on a three-dimensional platform (4) outside the three-dimensional area to be measured, and the light field camera (8) as a non-contact measurement equipment is located outside the three-dimensional platform (4) and does not interfere with heat and mass exchange in the three-dimensional area to be measured.

3. The acousto-optic coupled three-dimensional flame region temperature field monitoring system according to claim 1, characterized in that: Installation sites are set at the end points and midpoints of each side of the three-dimensional platform (4), with a total of 20 installation sites being set for installing 20 loudspeakers (5) and 20 microphones (6); at the installation sites of the three-dimensional platform (4), a single loudspeaker (5) and microphone (6) are installed adjacent to each other at the same position, and it is approximately considered that the two are in the same position.

4. The acousto-optic coupled three-dimensional flame region temperature field monitoring system according to claim 1, characterized in that: The relay (3) is a multi-channel serial port relay, which controls the on / off of circuits in the temperature measurement system to control multiple speakers (5) to sequentially transmit corresponding sweep frequency sound wave signals; the measurement sequence is controlled by the relay (3), thereby improving the speed and efficiency of the measurement.

5. The acousto-optic coupled three-dimensional flame region temperature field monitoring system according to claim 1, characterized in that: The loudspeaker (5) is an electrodynamic sound source, which converts an input analog signal into a sound wave signal and outputs the sound wave signal.

6. The acousto-optic coupled three-dimensional flame region temperature field monitoring system according to claim 1, characterized in that: The microphone (6) is a non-directional measurement microphone. During the measurement process, the multiple microphones (6) remain turned on and convert the received sound signals into electrical signals, which are then transmitted to the signal analyzer (7) for adjustment and collection.

7. The acousto-optic coupled three-dimensional flame region temperature field monitoring system according to claim 1, characterized in that: The signal analyzer (7) integrates signal conditioning functions and signal collection functions. Its multiple sampling channels realize multi-channel continuous signal acquisition of digitized sound waves and support subsequent channel expansion. All data collected by the signal analyzer (7) are finally transmitted to the computer (1) for storage, calculation and analysis.

8. The acousto-optic coupled three-dimensional flame region temperature field monitoring system according to claim 1, characterized in that: The light field camera (8) obtains the original light field image of the three-dimensional flame in the three-dimensional platform (4) through a single shot, which contains all four-dimensional light field information of the flame; all data collected by the light field camera (8) are finally transmitted to the computer (1) for storage, calculation and analysis.

9. The acousto-optic coupled three-dimensional flame region temperature field monitoring system according to claim 1, characterized in that: The three-dimensional platform (4) is a cube platform.

10. The measurement method of the acousto-optic coupled three-dimensional flame area temperature field monitoring system according to any one of claims 1 to 9, characterized in that: According to the temperature measurement principle of the sound velocity method, based on the dependence of the sound velocity on the temperature, the acoustic wave transit time of the sound wave propagating inside the three-dimensional test area is obtained in the target area; specifically, there are multiple speaker (5) and microphone (6) installation points on the three-dimensional platform (4), and when the line connecting two installation points is located inside the three-dimensional test area rather than on the surface of the three-dimensional platform, the acoustic wave transit time between the two installation points is measured, thereby having multiple acoustic wave transit times to be measured; The acousto-optic coupled three-dimensional flame area temperature field monitoring system converts an audio file of a preset frequency sweep signal into an analog signal through the sound card of a computer (1); due to the attenuation of sound waves, in order to ensure the intensity of the sound signal when it reaches a microphone (6), the analog signal is amplified by a power amplifier (2), and then a relay (3) sequentially controls multiple speakers (5) to convert the analog signal output by the computer (1) into a sound wave signal for transmission; After the relay (3) controls a single loudspeaker (5) to transmit a sound wave signal, the multiple microphones (6) work in full operation, and convert the received multi-channel sound signals into electrical signals and transmit them to the signal analyzer (7) for adjustment and collection, and finally transmit them to the computer (1) for storage and cross-correlation analysis; specifically, the microphone (6) installed adjacent to the designated loudspeaker (5) on the three-dimensional platform (4) first receives the sound signal emitted by the designated loudspeaker (5), and then the other microphones (6) away from the designated loudspeaker (5) successively receive the sound signals emitted by the designated loudspeaker (5). At this time, the signal received by the microphone (6) adjacent to the designated loudspeaker (5) and the signal received by the other microphones (6) are cross-correlatedly analyzed to obtain the sound wave flight time of the sound signal propagating from the microphone (6) adjacent to the designated loudspeaker (5) to the other microphones (6); therefore, after the relay (3) controls the operation of different loudspeakers (5) in sequence, the computer (1) finally obtains the required multiple sound wave flight times; Based on the measured multiple sound wave flight times and the positional relationship between the three-dimensional platform (4), the loudspeaker (5) and the microphone (6), the temperature value of the flame position of the overall temperature of the gas medium in the three-dimensional space surrounded by the three-dimensional platform (4) is calculated by the least squares QR decomposition method, thereby obtaining a three-dimensional temperature field at the flame position in the three-dimensional space; A light field camera (8) captures a three-dimensional flame within a three-dimensional platform (4) to obtain an original light field image of the three-dimensional flame, and then transmits the captured data to a computer (1) for light field layered imaging: assuming that the captured flame is a three-dimensional semi-transparent luminous body with a thickness of δ, N layered positions are preset within the flame according to the layered imaging theory; since the flame is semi-transparent, the flame image of each layer is a superposition of the original brightness distribution of each layer and the defocus information of other layers; according to Fourier optics theory, in a linear shift-invariant optical imaging system, the brightness function of each layer on the image plane is the convolution of the actual light intensity function on the corresponding object plane and the point spread function of the optical imaging system: Where h z'-z (x, y) is the point spread function PSF when the optical imaging system focuses on the z' plane for imaging, which is obtained by parameter calibration of the light field camera (8); f(x, y, z) is the brightness distribution on the z axis parallel to the optical axis; g(x, y, z') is the brightness distribution on the image plane of the superimposed image of the focused image of a certain plane z' on the z axis and the defocused images of other planes, which is obtained by the digital refocusing function of the light field camera (8) to reproduce the two-dimensional image of the flame at different fault planes and then process and calculate it with the computer (1); Keeping the spatial position of the optical imaging system and the object constant, N layered focused images are acquired in sequence along the optical axis z direction, and the discretized sequence image of the three-dimensional luminous body is obtained as follows: The above formula has N equations with N unknown quantities f(x, y, iΔz). The equations can be solved by combining the deconvolution algorithm. The solution f(x, y, iΔz) is the original brightness image of the i-th layer of the three-dimensional luminous body, completing the light field layered imaging. After restoring a plurality of two-dimensional layered flame original brightness images from the light field image, a light field image of the black body furnace (9) is photographed by a light field camera (8) and transmitted to a computer (1). The computer (1) extracts the grayscale data of the three channels R, G, and B respectively, calculates the average value of the grayscale value under each channel, and completes the calibration of the relationship between the radiation intensity and the grayscale average value according to the set temperature value of the black body furnace and the Planck law; Based on the calibration results, the two-dimensional layered flame original brightness images obtained by light field layered imaging are used to measure temperature using the two-color method to obtain multiple two-dimensional layered flame temperature fields, and then interpolated to obtain the three-dimensional flame overall temperature field; In a computer (1), the three-dimensional flame overall temperature field obtained by combining light field layered imaging with two-color temperature measurement is used as the true value, replacing the flame position temperature value of the overall temperature of the gas medium in the three-dimensional space obtained by the sound velocity temperature measurement. The sound velocity temperature measurement results are continuously iterated until convergence, and a new three-dimensional gas temperature field in the overall three-dimensional space containing the three-dimensional flame is obtained.

Images