Acousto-optic coupling three-dimensional flame area temperature field monitoring system

Abstract

The utility model discloses an acousto-optic coupling three-dimensional flame area temperature field monitoring system, which comprises a computer, a power amplifier, a relay, a loudspeaker, a microphone and a signal analyzer which are sequentially connected, and further comprises a three-dimensional rack, a light field camera and a blackbody furnace, a plurality of groups of loudspeakers and microphones are arranged, and each group of loudspeakers and microphones are located at the same position on the three-dimensional rack; the signal input end of the light field camera is respectively connected with the three-dimensional flame and the blackbody furnace in the three-dimensional rack, and the signal output end of the light field camera is connected with the signal input end of the computer; the blackbody furnace is used for the light field camera to calibrate the relationship between the gray level of the two-dimensional layered flame original brightness image and the radiation intensity; measurement targets of the system are gas temperature and three-dimensional flame temperature in a three-dimensional to-be-measured area which is surrounded by a three-dimensional rack and contains three-dimensional flame, the overall temperature of a gas medium in a three-dimensional space is measured by using a non-contact sound velocity method temperature measurement principle, and a more comprehensive contribution is made to temperature monitoring of a key area of a hearth.

Description

Technical Field

[0001] The utility model belongs to the technical field of non-contact measurement, and in particular relates to an acoustic-optical coupling three-dimensional flame area temperature field monitoring system which utilizes a sound signal received by a microphone to perform cross-correlation analysis to obtain the sound wave flight time. Background Art

[0002] According to the temperature measurement principle of the sound velocity method and the dependence of sound velocity on temperature, the acoustic wave flight time (TOF) between the microphone pairs 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 multiple sound paths and gridded areas 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 It is the inverse of the speed of sound of the jth grid in ROI. i is the TOF of the ith sound path. M is the number of sound paths, N is the number of ROI grids. A is the coefficient matrix, b is the TOF matrix, and x is the inverse sound velocity matrix.

[0012] The coefficient matrix A can be calculated based on the specific size 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 sound wave signal and the microphone. Then, the linear equations are solved using the temperature field reconstruction algorithm to obtain the inverse sound speed matrix x. Finally, the relationship between the sound speed and the gas temperature is substituted to reconstruct the grid average temperature of the area to be measured.

[0013] The two-color method uses a CCD camera to capture the radiation brightness information of the flame, selects the ratio of any two primary colors from the three primary colors of red (R), green (G), and blue (B) in the obtained image, and combines the CCD camera with the calibration results of the blackbody furnace to calculate the temperature and realize the measurement of the flame temperature field. The two-color method has a measurement accuracy of 95-98% and is easy to use, but general CCD cameras can only capture two-dimensional flame images, making it difficult to implement high-precision and high-speed measurements of three-dimensional actual flames.

[0014] The existing technology used in furnace temperature measurement is usually to use the contact temperature measurement method to measure the temperature of key points, as well as the optimization algorithm and application scenario expansion of the two-dimensional acoustic wave temperature measurement technology.

[0015] The existing contact temperature measurement method, 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. The contact temperature measuring element that relies on the principle of thermal balance has poor measurement immediacy in complex and changing environments;

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

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

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

[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 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. It is costly, complex to implement, time-consuming to measure, and requires high assembly precision. It is not suitable for industrial combustion equipment monitoring in high temperature, vibration, and fly ash environments.

[0023] In summary, there is an urgent need for a new acoustic-optical 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 utility model is to provide an acoustic-optical coupled three-dimensional flame area temperature field monitoring system to solve one or more of the technical problems that the existing contact temperature measurement method affects the heat and mass exchange process in the furnace, the contact temperature measurement elements based on the principle of thermal balance have poor measurement immediacy in complex and changing environments, the service life and reliability of contact temperature measurement elements 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 utility model uses the non-contact sound velocity method temperature measurement principle to measure the overall temperature of the gas medium in three-dimensional space, improves the reconstruction data volume and resolution, and makes more comprehensive monitoring of the temperature in the three-dimensional area to be measured. The utility model 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, and improves the efficiency of three-dimensional flame temperature measurement.

[0026] In order to achieve the above purpose, the technical solution of the utility model is:

[0027] An acoustic-optical coupling three-dimensional flame area temperature field monitoring system comprises 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 black body 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 the microphones 6 are multiple groups, and each group of speakers 5 and microphones 6 is located at the same position on the three-dimensional stand 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 stand 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 the 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 acoustic-optical 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 stand 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 a sound wave signal for output; the microphone 6 receives the sound wave 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 sound wave flight time required for the sound wave to reach the microphone 6 from the designated speaker 5 is obtained through cross-correlation analysis; after completing multiple rounds of sound wave flight time measurement, the sound wave flight time is known, and the positional relationship between the three-dimensional stand 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 stand 4, and the three-dimensional temperature field is reconstructed.

[0030] In the optical method part, the light field camera 8 shoots the three-dimensional flame in the three-dimensional stand 4 to obtain the original light field image of the three-dimensional flame, and then transmits the captured data to the computer 1. The computer 1 uses light field layered imaging 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 temperature fields for the multiple two-dimensional layered flame original brightness images obtained by light field layered imaging, and then interpolation is performed to obtain the overall temperature field of the three-dimensional flame.

[0031] Acoustic-optical 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 of the overall temperature of the gas medium in the three-dimensional space obtained by the sound velocity method temperature measurement. The temperature measurement result of the sound velocity method is 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 the microphone 6 as non-contact measuring devices 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 measuring 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.

[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 sound 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 multi-channel 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 stand 4 through a single shot, including 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.

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

[0040] Compared with the conventional two-dimensional furnace acoustic temperature measurement system, the acoustic-optic coupling three-dimensional flame area temperature field monitoring system in the utility model only needs to change the position of the two-dimensional microphone and the loudspeaker on the basis of the original two-dimensional furnace acoustic temperature measurement system, add several microphones and loudspeakers, replace the CCD camera with a light field camera, and add calibration equipment such as a black body furnace. These devices themselves have simple structures, low prices, and stable performance. Therefore, the acoustic-optic coupling three-dimensional flame area temperature field monitoring system is expected to achieve significant energy saving and economic benefits, and can achieve the following beneficial effects:

[0041] (1) The utility model uses the non-contact sound velocity method to measure the overall temperature of the gas medium in three-dimensional space, thereby improving the amount and resolution of reconstructed data and making more comprehensive monitoring of the temperature of key areas of the furnace.

[0042] (2) The utility model 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.

[0043] (3) The utility model 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.

[0044] (4) The utility model takes into account the influence of factors such as measurement background noise, sound wave attenuation, and reverberation, and selects electric sound source and linear sweep frequency 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) as temperature field reconstruction algorithm. These existing methods in the prior art are used to improve the overall sound wave flight time measurement accuracy and the final three-dimensional temperature field reconstruction accuracy.

[0045] (5) The utility model 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 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 accuracy 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.

[0046] (6) The utility model uses optical methods to correct the problems of the sound velocity method, such as small amount of reconstruction data, low image resolution, and reconstruction accuracy that needs to be improved; 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.

[0047] (7) The acoustic-optic coupled three-dimensional flame area temperature field monitoring method of the utility model 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 stand, the number and arrangement of microphones and loudspeakers on the three-dimensional test stand, and the position and distance of the light field camera relative to the flame in the three-dimensional test stand. It has good applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a structural schematic diagram of the utility model system. DETAILED DESCRIPTION

[0049] In order to more clearly understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0050] like Figure 1 As shown, the utility model is an acoustic-optical coupling 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 loudspeaker 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 loudspeaker 5, the output end of the loudspeaker 5 is connected to the signal receiving end of the microphone 6, the signal output end of the microphone 6 is connected to the signal analyzer 7 The input end of the signal analyzer 7 is connected to the USB port of the computer 1; the loudspeaker 5 and the microphone 6 are multiple groups, and each group of the loudspeaker 5 and the microphone 6 is located at the same position on the three-dimensional stand 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 stand 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 the acoustic-optical 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 stand 4 and containing the three-dimensional flame.

[0051] The sound card of the computer 1 converts the audio file of the preset sweep 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 a sound wave signal for output; the microphone 6 receives the sound wave 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 sound wave flight time required for the sound wave to reach the microphone 6 from the designated speaker 5 is obtained through cross-correlation analysis; after completing multiple rounds of sound wave flight time measurement, the sound 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.

[0052] In the system of the utility model, the loudspeaker 5 and the microphone 6 as non-contact measuring devices are located on the three-dimensional platform 4 outside the three-dimensional measured area, and the light field camera 8 as a non-contact measuring device is located outside the three-dimensional platform 4, and does not interfere with the heat and mass exchange in the three-dimensional measured area.

[0053] As a preferred embodiment of the utility model, installation sites are set at the endpoints and midpoints of each side of the three-dimensional platform 4, and a total of 20 installation sites are set for installing 20 speakers 5 and 20 microphones 6. The more sensor installation sites there are, the more sufficient the measurement data is, and the better the reconstruction performance of the sound velocity method is. However, in actual engineering applications, in order to ensure structural strength and reliability, it is not advisable to modify too many installation sites on industrial combustion equipment. In order to balance the reconstruction performance of the sound velocity method and actual engineering needs, the endpoints and midpoints of each side of the three-dimensional platform 4 are set as installation sites, so that the temperature measurement data of the sound velocity method in 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 installation site 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.

[0054] The computer 1 is a core component of the acoustic-optic coupling three-dimensional flame area temperature field monitoring system. The system uses the audio file of the preset sweep frequency signal stored in the computer 1 as the sound source signal for the temperature measurement by the sound velocity method; at the same time, the computer 1 receives and stores all the data from the signal analyzer 7, and obtains the acoustic wave flight time by cross-correlation analysis; according to the acoustic wave flight time, the positional relationship between the three-dimensional stand 4 and 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 stand 4 is reconstructed by the least squares QR decomposition (LSQR) method; in addition, the computer 1 receives and stores all the data from the light field camera 8, firstly performs light field layered imaging on the three-dimensional flame in the three-dimensional stand 4 photographed by the light field camera 8, and obtains the original brightness images of the three layers of the three-dimensional luminous body of the flame; secondly, the light field image of the black body furnace 9 photographed by the light field camera 8 is processed, and the black body furnace is calibrated; according to the calibration result, the two-color method is used to measure the temperature of multiple two-dimensional layered flame original brightness images obtained by the light field layered imaging, and multiple two-dimensional layered flame temperature fields are obtained, and then interpolation is performed to obtain the overall temperature field of the three-dimensional flame.

[0055] 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 sweep frequency sound wave signals in sequence; the measurement sequence is controlled by the relay 3, which improves the speed and efficiency of the measurement;

[0056] As a preferred embodiment of the utility model, 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, can emit various types of sound wave signals, and is suitable for sound source selection for temperature measurement using the sound velocity method.

[0057] The microphone 6 is a non-directional measurement microphone, suitable for measuring in a free field or semi-free field without reflection. It adopts a pre-polarization method without the need for an external polarization voltage, and is suitable for microphone selection for temperature measurement by the sound velocity method. Multiple microphones 6 remain turned on during the measurement process and convert the received sound signals into electrical signals, which are then transmitted to the signal analyzer 7 for adjustment and collection; the signal analyzer 7 integrates signal conditioning and signal collection functions, and its multi-channel sampling channels realize multi-channel continuous signal collection of digital 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.

[0058] 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, breaking through the limitation that the traditional CCD camera can only obtain a two-dimensional image with a fixed depth of field. All data collected by the light field camera 8 are finally transmitted to the computer 1 for storage, calculation and analysis.

[0059] 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. 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.

[0060] As a preferred embodiment of the utility model, the three-dimensional platform 4 is a cube platform with a side length of 1 meter. The cube frame can match the appearance of a large number of industrial equipment and is suitable for the sonic velocity 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.

[0061] like Figure 1 As shown, the three-dimensional temperature field measurement method of the acoustic-optically coupled three-dimensional flame area temperature field monitoring system of the utility model, according to the temperature measurement principle of the sound velocity method, based on the dependence of the sound velocity on the 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 connection line between 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.

[0062] The acoustic-optic coupled three-dimensional flame area temperature field monitoring system generates an analog signal of a linear frequency sweep signal with a sweep frequency range of 1-3kHz and a sweep frequency period of 0.1s through a signal generation program and a sound card of a computer 1; after being amplified by a power amplifier 2 with a single-channel rated power of 50W, 20 4Ω / 5W small electric speakers 5 are controlled by a 32-way serial port relay 3 to convert the analog signal output by the computer 1 into a sound wave signal for transmission in turn.

[0063] After the relay 3 controls a single speaker 5 to transmit a sound wave signal, 20 prepolarized electret non-directional measurement microphones 6 with an open circuit sensitivity of 50±2mV / Pa and a frequency response range of 20kHz work throughout the process, and convert the received 20-channel sound signals into electrical signals and transmit them to the signal analyzer 7 for adjustment, collection, and finally transmit them to the 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, the signal received by the microphone 6 adjacent to the designated speaker 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 from the microphone 6 adjacent to the designated speaker 5 to the other microphones 6 (specifically, the peak location, signal interception, and PHAT weighted cross-correlation delay estimation are performed in sequence for the 20-channel signals received by all the microphones 6, and the sound wave flight time of the sound signal between each microphone pair 6 can be obtained). Therefore, after the relay 3 controls the different loudspeakers 5 to work in sequence, the computer 1 finally obtains the required multiple sound wave flight times.

[0064] Based on the measured multiple sound wave flight times and the positional relationship between the three-dimensional platform 4, the speaker 5 and the 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 by the least squares QR decomposition (LSQR) method, and then the three-dimensional temperature field of the flame location in the three-dimensional space is obtained.

[0065] A Lytro Illum light field camera 8 is used to shoot the three-dimensional butane flame in the three-dimensional stand 4 to obtain the original light field image of the three-dimensional butane flame, and then the data obtained from the shooting is transmitted to the computer 1 for light field layered imaging: Assuming that the shot butane flame is a three-dimensional semi-transparent luminous body with a thickness of δ, three layered positions are preset inside the flame according to the layered imaging theory, and the layer interval is 5mm. Since the flame is semi-transparent, the flame image of each layer is the superposition image of the original brightness distribution of each layer and the defocus information of other layers;

[0066] The digital refocusing function of the light field camera 8 reproduces the two-dimensional flame images of different fault planes, and then the computer 1 processes and calculates the image plane brightness distribution of the superimposed image of the focused image at the three preset layered positions inside the flame and the defocused images on other planes. Combined with the Van Citter iterative deconvolution, the original brightness images of the three preset layered positions inside the flame can be obtained to complete the light field layered imaging.

[0067] 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. The 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 was less than 1373K, so the calibration temperature changed from 1123K to 1373K, and the temperature was changed every 50K. Each time the temperature of the blackbody furnace 9 was changed, data was collected once after the temperature of the blackbody furnace 9 was stabilized. The light field image of the blackbody furnace 9 taken by the light field camera 8 was transmitted to the computer 1, and the grayscale data of the three channels of R, G, and B were extracted respectively, and the average grayscale value of each channel was calculated. According to the set temperature value of the blackbody furnace, the relationship between the radiation intensity and the grayscale average value was 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 were 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.

[0068] 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 method temperature measurement. The sound velocity method temperature measurement result is continuously iterated until convergence to obtain a new three-dimensional gas temperature field in the overall three-dimensional space containing the three-dimensional flame.

[0069] The utility model uses the non-contact sound velocity method to measure the overall temperature of the gas medium in three-dimensional space, making a more comprehensive contribution to the temperature monitoring of key areas of the furnace; the utility model uses mature microphones and speakers and other equipment to control the measurement sequence through relays, thereby improving the speed and efficiency of measurement; considering the influence of measurement background noise, sound wave attenuation, reverberation and other factors, the sound source signal and time delay estimation method are selected according to the actual situation, thereby improving the measurement accuracy of the sound wave flight time and the reconstruction accuracy of the three-dimensional temperature field; the utility model uses a light field camera, combining the advantages of light field layered imaging and two-color temperature measurement technology Point, successfully realized 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; the utility model uses optical methods to correct the problems of small amount of reconstruction data, low image resolution and need to improve reconstruction accuracy of the sound velocity method; at the same time, the sound velocity method is used to break through the limitation that the two-color method and light field layered imaging cannot measure transparent gas media; and the interference of the measurement process on the measured area is minimized, thereby improving the measurement accuracy; the acoustic-optical coupling three-dimensional flame area temperature field monitoring method can be extended to the measurement of three-dimensional measured areas of other shapes other than cubes, and has good applicability.

[0070] 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 principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An acoustic-optical coupling three-dimensional flame area temperature field monitoring system, characterized in that: It includes 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 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) are 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 the radiation intensity of the original brightness image of the two-dimensional layered flame; the measurement target of the acoustic-optical 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.

2. The acoustic-optic coupled three-dimensional flame area temperature field monitoring system according to claim 1, characterized in that: A loudspeaker (5) and a microphone (6) as non-contact measurement equipment are located on a three-dimensional platform (4) outside the three-dimensional area to be measured, and a 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 acoustic-optic coupled three-dimensional flame area 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 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 acoustic-optic coupled three-dimensional flame area 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 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).

5. The acoustic-optic coupled three-dimensional flame area 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 signal.

6. The acoustic-optic coupled three-dimensional flame area 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 coupling three-dimensional flame area temperature field monitoring system according to claim 1, characterized in that: The signal analyzer (7) integrates a signal conditioning function and a signal collection function, and its multi-channel sampling channels realize multi-channel continuous signal collection of digitized sound waves and support subsequent channel expansion.

8. The acoustic-optic coupled three-dimensional flame area temperature field monitoring system according to claim 1, characterized in that: The light field camera (8) obtains an original flame light field image of a three-dimensional flame in the three-dimensional stand (4) through a single shot, which contains all four-dimensional light field information of the flame.

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

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