Laser-induced incandescent-based particulate matter temperature field measurement method and device

Abstract

The invention discloses a particulate matter temperature field measurement method and device based on laser-induced incandescent, and belongs to the technical field of laser application and temperature field diagnosis. The device comprises a pulse laser module, a beam expanding module, a sheet light heating module, an image acquisition module and a synchronous control module, and the working process is as follows: laser is subjected to beam splitting and beam expanding to form sheet light heating particles, double cameras are matched with different band-pass optical filters to synchronously acquire double-color incandescent signals, and multi-energy density signal acquisition is completed under sequential control. The initial temperature of the particles is solved by combining the double-color temperature measurement principle and the separation double-pulse principle; the method has the beneficial effects that high temporal-spatial resolution measurement of the two-dimensional temperature field of the particulate matter is realized, measurement errors caused by particle sublimation are effectively avoided, and the method is adaptive to various to-be-measured objects such as soot particles and metal particles, can be widely applied to industrial scenes such as laboratory basic research and combustion diagnosis, metal cutting and nano material synthesis, and has wide application prospects. And the method has important engineering application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser application and temperature field diagnosis, in particular to a particle temperature field measurement method and device based on laser-induced incandescence. BACKGROUND

[0002] Temperature, as a core physical parameter representing the energy state of matter and the progress of reaction, plays a key role in the field of material processing, energy power, chemical synthesis and environmental monitoring, directly affecting the success of process optimization, safety control and mechanism research. For example, the temperature distribution of metal powder in laser additive manufacturing determines the stability of the molten pool and the mechanical properties of the product, and the temperature of carbon soot particles in the engine combustion process is related to energy utilization efficiency and pollutant emission. Therefore, it is of great significance to realize accurate measurement of particle temperature field for technical breakthrough in related fields.

[0003] Current particle temperature field measurement methods mainly include contact and non-contact methods: contact measurement: represented by thermocouple temperature measurement, although it has the advantages of simple structure and low cost, it needs to be in direct contact with the measured object, which easily disturbs the original field distribution, and is affected by the thermal inertia of the probe, with slow response speed, unable to capture the transient temperature change of the particle, low spatial resolution, and difficult to meet the fine diagnosis needs of complex flow field or non-uniform system; non-contact measurement: relying on optical diagnosis technology, the main methods include infrared radiation temperature measurement, laser-induced fluorescence (LIF) and laser-induced incandescence (LII) technology. Among them, infrared radiation temperature measurement realizes non-invasive remote measurement, but the measurement accuracy depends on the emissivity of the particle (which is difficult to accurately obtain), and is easily disturbed by the environmental background radiation, with significant error in non-uniform particle system; laser-induced fluorescence method has high sensitivity, but the signal is easily affected by quenching effect and background scattering, and needs complex calibration process, with limited applicability.

[0004] Laser-induced incandescence (LII) technology has become a key research direction for temperature measurement of complex particle systems due to its high signal strength and time resolution. This technology uses high-energy pulsed laser to heat the particle to incandescence state instantaneously, and uses the temperature-dependent time decay signal emitted during the cooling process to retrieve the temperature. However, traditional LII technology usually uses photomultiplier tubes (PMT) for signal acquisition, which is usually used for single-point or one-dimensional line measurement, making it difficult to obtain spatial two-dimensional temperature field, and it is difficult to ensure the accuracy of temperature measurement without sublimation of the particle. Therefore, how to invent a particle temperature field measurement method and device based on laser-induced incandescence to solve these problems has become a problem that needs to be solved by technical personnel in the field. SUMMARY

[0005] In order to make up for the above shortcomings, the present application provides a kind of laser-induced incandescent particle temperature field measurement method and device, to solve the problem that traditional LII technology usually realizes single point or one-dimensional line measurement by using photomultiplier (PMT) for signal acquisition, which is inconvenient for obtaining two-dimensional temperature field in space, and it is difficult to ensure the accuracy of temperature measurement under the premise of avoiding particle sublimation.

[0006] The present application is implemented as follows:

[0007] The present application provides a kind of laser-induced incandescent particle temperature field measurement device, comprising pulse laser module, beam expansion module, sheet light heating test particle module, image data acquisition module and synchronous control module.

[0008] The pulse laser module comprises a pulse laser, a half-wave plate, a polarization beam splitter and a first optical garbage can, the half-wave plate is arranged on the optical path between the pulse laser and the polarization beam splitter, and the first optical garbage can is arranged corresponding to the transmission light exit direction of the polarization beam splitter.

[0009] The beam expansion module comprises a first lens and a second lens, the first lens and the second lens are arranged in sequence along the reflection light exit direction of the polarization beam splitter, forming a coaxial beam expansion system.

[0010] The sheet light heating test particle module comprises a cylindrical lens, a test particle sample and a second optical garbage can, the cylindrical lens is arranged on the exit light path of the beam expansion module, the test particle sample is located in the sheet light convergence area of the cylindrical lens, and the second optical garbage can is arranged corresponding to the exit direction of the sheet light after transmitting through the test particle sample.

[0011] The image data acquisition module comprises a first band-pass filter, a first camera, a second band-pass filter and a second camera, the first band-pass filter is installed in front of the lens of the first camera, the second band-pass filter is installed in front of the lens of the second camera, and the first camera and the second camera are respectively located on both sides of the test particle sample, and the imaging optical axis is perpendicular to the sheet light propagation direction.

[0012] The synchronous control module comprises a digital delay generator, the trigger signal input end of the digital delay generator is electrically connected with the Q signal output end of the pulse laser, and the two signal output ends of the digital delay generator are respectively electrically connected with the external trigger input end of the first camera and the second camera.

[0013] Preferably, the pulse laser is a pulse output type laser, and the wavelength and pulse width are selected according to the absorption characteristics and physical properties of the test particle sample, preferably a Q-switched nanosecond laser with a wavelength of 1064 nm and a pulse width of 20 ns.

[0014] Preferably, the sample of particles to be measured is a particle that can absorb a specific wavelength of laser output from a pulsed laser.

[0015] Preferably, the digital delay generator has at least two adjustable output ports, and the delay time and trigger level of each output port can be independently set.

[0016] The laser-induced incandescence-based particle temperature field measurement method of the measurement device described above comprises the following steps:

[0017] Step 1: Obtain the laser output from the pulsed laser, which is a nanosecond pulsed laser with a wavelength of 1064±50 nm and a pulse width of 10-50 ns. After adjusting the polarization state of the laser using a half-wave plate, the laser is split into two beams by a polarizing beam splitter.

[0018] Step 2: The laser transmitted by the polarizing beam splitter in Step 1 is collected by a first optical garbage can, and the laser reflected by the polarizing beam splitter is expanded by a first lens and a second lens.

[0019] Step 3: The laser expanded by the first lens and the second lens in Step 2 is converged in one direction by a cylindrical lens to form a sheet of light.

[0020] Step 4: The sheet of light formed by the cylindrical lens in Step 3 heats the sample of particles to be measured, and the light transmitted through the particles is collected by a second garbage can.

[0021] Step 5: The incandescence signal emitted by the sample particles to be measured in Step 4 is collected by the first camera and the second camera using a first band-pass filter and a second band-pass filter.

[0022] Step 6: The first camera and the second camera in Step 5 are both in external trigger mode and are triggered by the same signal output from the digital delay generator, which is triggered by the Q signal output from the laser.

[0023] Step 7: Adjust the energy density of the laser that heats the particles by rotating the half-wave plate, and simultaneously use the image data acquisition module to collect the dual-color time decay signal images under different energy densities.

[0024] Step 8: Solve the maximum temperature T M from the image gray values of the dual-color signals collected in Step 7 under different energy densities. The calculation is based on the dual-color temperature measurement principle formula, and the gray value S of the dual-color incandescence intensity at the beginning of the temperature drop t=0 ns is substituted into the formula to calculate T M .

[0025] Step 9: According to the maximum temperature T M, draw the maximum temperature T M The relationship diagram with the energy density F, the energy density range for calculating the initial temperature T0 of the particles is obtained, which refers to the linear region of the curve, and the particles will sublimate beyond the linear region and cannot be calculated using the model of the principle;

[0026] Step 10, selecting two suitable energy densities F1 and F2 and two corresponding maximum temperatures T M1 and T M2 of the two-dimensional distribution value, the initial temperature T0 of the particles is calculated according to the formula, the initial temperature T0 is calculated according to the formula of the principle of separating double pulses, and the formula is:

[0027]

[0028] Wherein, the F1, F2 are two different values in the effective energy density range, the T M1 , T M2 are the maximum temperatures corresponding to F1 and F2, the two energy densities F1 and F2 cannot exceed the highest threshold value of the sublimation of the particles and are not equal.

[0029] Preferably, the sample of the particles to be measured in step 4 emits a time decay signal closely related to temperature after absorbing the energy of the light.

[0030] Preferably, the center wavelengths of the first band-pass filter and the second band-pass filter in step 5 are different, the quantum efficiency curves, gate widths, gains, exposure times and other parameters of the first camera and the second camera are consistent, and the system response is calibrated.

[0031] Preferably, the same trigger signal output by the digital delay generator in step 6 refers to consistent parameter values of delay time and trigger level.

[0032] The beneficial effects of the present application are:

[0033] 1, the present application innovatively adopts the signal acquisition architecture of "double camera + double color band-pass filter", through arranging the cameras with consistent parameters on both sides of the sample of the particles to be measured, and matching the band-pass filters with different center wavelengths, the double-color time decay images of the incandescent signals of the particles can be synchronously collected; this design not only can obtain the temperature data of each pixel point in space, form a complete two-dimensional temperature distribution map, but also can realize nanosecond-level time resolution by controlling the exposure gate width and collection interval of the camera, accurately capture the transient temperature change in the heating-cooling process of the particles, compared with the traditional method, the measurement dimension is upgraded from "point / line" to "plane", the time and space resolution is significantly improved, and key technical support is provided for studying the generation, evolution and energy transfer law of the particles in a non-uniform system.

[0034] 2, On the one hand, the application utilizes the cooperation of half-wave plate and polarization beam splitter to flexibly adjust the energy density of heating laser, realizes signal acquisition under multiple energy densities; on the other hand, the linear region of the screening curve is selected as the effective energy density range, to ensure that the particles in the range are only heated to incandescent state without sublimation, and on this basis, combined with the principle of separated double pulses, two different energy densities and corresponding maximum temperatures in the effective range are selected, the initial temperature of the particles is accurately calculated through the formula, and the measurement error caused by sublimation is completely avoided.

[0035] 3, The method and device of the application have good universality, in terms of particle type adaptation, the core requirement of the device for particulate matter is only "absorbing pulsed laser of specific wavelength", without relying on the specific form or composition of the particles, the absorption characteristics and incandescent signal characteristics of different particles can be matched by flexibly adjusting the key parameters (such as wavelength, pulse width) of the pulsed laser and the center wavelength of the double-color band-pass filter, to realize accurate temperature field measurement; in terms of application scenario coverage, the device can meet the needs of laboratory basic research, and can also be applied to core engineering scenarios of industrial production, including combustion diagnosis field, metal cutting field, nanometer material synthesis field, realizing full-scene coverage from basic research to industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation to the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0037] Figure 1 is a flowchart of a particle temperature field measurement method and device based on laser-induced incandescence provided by the embodiments of the application;

[0038] Figure 2 is a schematic diagram of the overall structure of a particle temperature field measurement method and device based on laser-induced incandescence provided by the embodiments of the application;

[0039] Figure 3 is a two-dimensional distribution diagram of the initial temperature of soot particles of a particle temperature field measurement method and device based on laser-induced incandescence provided by the embodiments of the application.

[0040] In the figure: 1, pulse laser module; 11, pulse laser; 12, half-wave plate; 13, polarization beam splitter; 14, first optical garbage can; 2, beam expansion module; 21, first lens; 22, second lens; 3, sheet light heating test particle module; 31, cylindrical lens; 32, test particle sample; 33, second optical garbage can; 4, image data acquisition module; 41, first band-pass filter; 42, first camera; 43, second band-pass filter; 44, second camera; 5, synchronous control module; 51, digital delay generator. DETAILED DESCRIPTION

[0041] To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0042] Embodiment one

[0043] Reference Figures 1-3 A particle temperature field measuring device based on laser-induced incandescence, comprising a pulse laser module 1, a beam expansion module 2, a sheet light heating test particle module 3, an image data acquisition module 4 and a synchronous control module 5.

[0044] The pulse laser module 1 comprises a pulse laser 11, a half-wave plate 12, a polarization beam splitter 13 and a first optical garbage can 14. The half-wave plate 12 is arranged on the light path between the pulse laser 11 and the polarization beam splitter 13. The first optical garbage can 14 is arranged corresponding to the transmission light exit direction of the polarization beam splitter 13.

[0045] The beam expansion module 2 comprises a first lens 21 and a second lens 22. The first lens 21 and the second lens 22 are arranged in sequence along the reflection light exit direction of the polarization beam splitter 13, constituting a coaxial beam expansion system.

[0046] The sheet light heating test particle module 3 comprises a cylindrical lens 31, a test particle sample 32 and a second optical garbage can 33. The cylindrical lens 31 is arranged on the exit light path of the beam expansion module 2. The test particle sample 32 is located in the sheet light convergence area of the cylindrical lens 31. The second optical garbage can 33 is arranged corresponding to the exit direction of the sheet light after transmitting through the test particle sample 32.

[0047] The image data acquisition module 4 includes a first bandpass filter 41, a first camera 42, a second bandpass filter 43, and a second camera 44. The first bandpass filter 41 is mounted on the front end of the lens of the first camera 42, and the second bandpass filter 43 is mounted on the front end of the lens of the second camera 44. The first camera 42 and the second camera 44 are located on both sides of the particle sample 32 to be tested, and the imaging optical axis is perpendicular to the direction of sheet light propagation.

[0048] The synchronization control module 5 includes a digital delay generator 51. The trigger signal input terminal of the digital delay generator 51 is electrically connected to the Q signal output terminal of the pulsed laser 11. The two signal output terminals of the digital delay generator 51 are electrically connected to the external trigger input terminals of the first camera 42 and the second camera 44, respectively.

[0049] Furthermore, the pulsed laser 11 is a pulsed output laser, and its wavelength and pulse width are adapted and selected according to the absorption characteristics and physical properties of the particle sample 32 to be tested. Preferably, it is a Q-switched nanosecond laser with a wavelength of 1064nm and a pulse width of 20ns. The particle sample 32 to be tested is a particulate matter that can absorb the laser of a specific wavelength output by the pulsed laser 11. The digital delay generator 51 has at least two adjustable output ports, and the delay time and trigger level of each output port can be set independently.

[0050] It should be noted that:

[0051] In the pulsed laser module 1, the laser output from the laser 11 is split into two beams by a half-wave plate 12 and a polarization beam splitter 13. One of the transmitted laser beams is collected by the first optical bin 14, and the other reflected laser beam is expanded by the first lens 21 and the second lens 22 and then incident on the cylindrical lens 31. The beams converge in a single direction to form sheet light, which heats the particle sample 32 to be tested. The light transmitted through the particles is collected by the second optical bin 33. The particle sample 32 to be tested includes, but is not limited to, carbon soot particles and metal particles.

[0052] In the image data acquisition module 4, the particle sample 32 under test absorbs laser energy and emits an incandescent signal. The signal is acquired by the first camera 42 and the second camera 44 after passing through the first bandpass filter 41 and the second bandpass filter 43, respectively. The center wavelengths of the first bandpass filter 41 and the second bandpass filter 43 are 495nm and 650nm, respectively, and the half-width at half-maximum (WHM) are 25nm and 20nm, respectively. They are installed corresponding to the two gated ICCD cameras. The first camera 42 and the second camera 44 are placed facing each other, and their imaging optical axes are perpendicular to the direction of light propagation. The gate width, gain, delay and other parameters are kept consistent to ensure the accuracy of dual-color temperature measurement.

[0053] In the synchronization control module 5, both the first camera 42 and the second camera 44 adopt an external triggering method. They use a DG645 model digital delay generator 51 to output the same trigger signal, with the trigger delay set to 191ns and the output level being 5V. The external trigger signal of the digital delay generator 51 is provided by the Q-switching signal of the laser.

[0054] During the experiment, the laser energy density of the incoming light was adjusted by rotating the half-wave plate 12. The energy density adjustment range was 90-445 mJ / cm², and image acquisition was completed under different energy densities. The grayscale value of the obtained two-color incandescent signal at the start of cooling (t = 0 ns) was processed, and the highest temperature T was calculated according to the two-color thermometry formula. M Plot the relationship between the highest temperature and energy density; when the energy density exceeds 225 mJ / cm², the carbon soot particles undergo sublimation, so the energy used must be lower than this threshold.

[0055] Two energy densities within the linear range were further selected: F1 was 90 mJ / cm² (corresponding to a laser energy of 10 mJ / pulse), and F2 was 135 mJ / cm² (corresponding to a laser energy of 15 mJ / pulse). The highest temperature T was calculated for each. M1 and T M2 Then, the two-dimensional distribution of the initial temperature T0 of the soot particles is obtained using the formula for calculating the separation of two pulses, such as... Figure 3 As shown.

[0056] Implementation results:

[0057] In this embodiment, carbon soot particles generated by the combustion of kerosene lamp flames were selected as the test sample. These particles are characterized by their single composition, stable formation environment, and typical temperature distribution, making them a commonly used standard sample for verifying the reliability of particulate matter temperature field measurement methods. Using the measurement method and device proposed in this invention, a two-dimensional distribution spectrum of the initial temperature of carbon soot particles was successfully obtained (as shown in Figure 3). It can be clearly observed from the spectrum that the temperature field of carbon soot particles exhibits a significant spatial gradient distribution: the temperature of carbon soot particles in the core region of the flame is concentrated at 2200-2400K, which is in the high-temperature peak range; as it diffuses towards the edge of the flame, the particle temperature gradually decreases, and the temperature in the edge region drops to 1700-1900K. The overall temperature distribution pattern is highly consistent with the generation and evolution mechanism of carbon soot particles during combustion. The core region has more complete combustion and higher reaction intensity, resulting in a particle temperature that is significantly higher than that in the edge region.

[0058] To further verify the accuracy of the measurement results, the experimental data were compared with the research conclusions on the temperature distribution of soot particles in several published authoritative literatures. It was found that the temperature gradient range, peak temperature range, and spatial distribution trend of the two were highly consistent, with the deviation controlled within ±5%, which fully demonstrates the reliability of the quantitative accuracy of this measurement method. At the same time, the temperature data of each spatial pixel in the two-dimensional spectrum is clearly distinguishable without obvious noise interference, indicating that the image acquisition system and data processing algorithm of the device can effectively ensure the spatial resolution of the measurement and accurately capture the local temperature differences of non-uniform particle systems.

[0059] Furthermore, by adjusting the laser energy density to 90-135 mJ / cm² (all below the sublimation threshold of 225 mJ / cm² for soot particles) during the experiment, interference from particle sublimation on the measurement results was successfully avoided, further verifying the scientific validity and practicality of the "effective energy density range screening" mechanism in this invention. In summary, the results of this implementation fully demonstrate that the measurement method and device based on laser-induced incandescence proposed in this invention not only overcomes the limitations of traditional methods and achieves accurate measurement of the two-dimensional temperature field of particulate matter, but also possesses good stability and repeatability. It can provide reliable technical support for the study of particulate matter temperature characteristics in fields such as combustion diagnostics and environmental monitoring, and has significant engineering application value and promotion prospects.

[0060] The working principle is as follows:

[0061] When a laser pulse irradiates a particle, the particle is rapidly heated during the pulse duration and then begins to cool after the laser pulse ends. The heated particle emits an incandescent signal (LII signal) similar to that of a blackbody, the intensity of which is related to the particle temperature and can be described by Planck's law.

[0062] ,

[0063] Where λ is the wavelength, h is Planck's constant, and c is the speed of light. is the absorption coefficient of the particle, and D is the particle size. It is Boltzmann's constant. It is the temperature of the particles.

[0064] During the heating process of the particles, since the radiation and conduction of the particles are very small compared to absorption, they can be ignored. Furthermore, since the energy density of the laser is less than the energy threshold that causes particle sublimation, sublimation is also ignored. In this case, the change in the internal energy of the particles is only caused by absorption, and the energy conservation expression for the particles is:

[0065] ,

[0066] in The instantaneous power of the laser pulse on the particle satisfies Let F be the laser energy density and τ be the laser pulse duration. Integrating both sides of the above equation yields:

[0067] ,

[0068] The above equation can be further simplified to obtain:

[0069] .

[0070] The maximum temperature T of the particles can be determined using a two-color thermometry method. M The following can be obtained from the LII signal intensity at two wavelengths:

[0071] ,

[0072] in and It uses the center wavelength of two bandpass filters. and It is the bandwidth of two bandpass filters. It is the camera's calibration coefficient.

[0073] Furthermore, by utilizing the principle of split dual pulses, the particle temperature T0 can be calculated. Two laser energy densities, F1≠F2, and their corresponding two maximum temperatures T can be selected. M1 and T M2 According to the formula:

[0074] ,

[0075] The temperature of the particles can then be determined.

[0076] Example 2

[0077] Reference Figure 1 For example, a particle temperature field measurement method based on laser-induced incandescence using a measuring device includes the following steps:

[0078] Step 1: Obtain the laser output from the pulsed laser 11. The laser is a nanosecond-level pulsed laser with a wavelength of 1064±50nm and a pulse width of 10-50ns. After adjusting the polarization state of the laser using a half-wave plate 12, the laser is split into two beams by a polarization beam splitter 13.

[0079] Specifically, the laser is an Nd:YAG Q-switched nanosecond pulsed laser with a wavelength of 1064 nm and a pulse width of 20 nm.

[0080] Step 2: The laser transmitted by the polarization beam splitter 13 in step 1 is collected by the first optical trash can 14, and the laser reflected by the polarization beam splitter 13 is expanded by the first lens 21 and the second lens 22.

[0081] Specifically, the focal length of the first lens 21 is -100mm, and the focal length of the second lens 22 is 200mm.

[0082] Step 3: The laser beam expanded by the first lens 21 and the second lens 22 in step 2 is focused in one direction by the cylindrical lens 31 to form a sheet beam.

[0083] Step 4: In step 3, the cylindrical lens 31 forms a sheet light to heat the particle sample 32 to be tested. The light transmitted through the particles is collected by the second optical trash can 33. In step 4, the particle sample 32 to be tested emits a time decay signal closely related to temperature after absorbing the energy of the sheet light.

[0084] Specifically, the focal length of the cylindrical lens 31 is 500mm, and the sheet light converges in the x-direction. The particle sample 32 to be tested is carbon soot particles produced by the combustion of kerosene lamps. The thickness of the sheet light is greater than the carbon soot particle producing area (the Rayleigh distance of the light after passing through the cylindrical lens 31 is 369.2mm, which is 10mm greater than the flame particle area).

[0085] Step 5: The incandescent signal emitted by the particle sample 32 in Step 4 is acquired by the first bandpass filter 41 and the first camera 42, the second bandpass filter 43 and the second camera 44 as a dual-color signal. In Step 5, the center wavelengths of the first bandpass filter 41 and the second bandpass filter 43 are different, and the quantum efficiency curves, gate width, gain, exposure time and other parameters of the first camera 42 and the second camera 44 are consistent, and their system response has been calibrated. Before acquiring the signal, the laser is turned off, and the ambient background light signal is acquired synchronously by the two cameras. The background light gray value is subtracted in the subsequent calculation.

[0086] Specifically, the first camera 42 and the second camera 44 are placed opposite each other, with their imaging optical axes perpendicular to the direction of sheet light propagation, and the first bandpass filter 41 is located in front of the first camera 42, and the second bandpass filter 43 is located in front of the second camera 44.

[0087] Specifically, the first bandpass filter 41 has a center wavelength of 495nm and a half-width at half-maximum (WHM) of 25nm, and the second bandpass filter 43 has a center wavelength of 650nm and a WHM of 20nm; both the first camera 42 and the second camera 44 are gated ICCD cameras.

[0088] Specifically, the first camera 42 and the second camera 44 both have a gate width of 10ns, a gain of 1200, and an internal delay of 70ns. They are both sampled every 10ns for a total of 250 times (i.e., time t = 0-2500ns) to obtain the signal attenuation process of soot particles.

[0089] In step 6, both the first camera 42 and the second camera 44 in step 5 use external trigger mode and are triggered by the same signal output by the digital delay generator 51. The digital delay generator 51 uses external trigger mode and is triggered by the Q signal output by the laser. The same trigger signal output by the digital delay generator 51 in step 6 means that the delay time and trigger level parameters are set to be consistent.

[0090] Specifically, the digital delay generator 51 uses a DG645, and the delay of both output signals is set to 191ns (the time when the light pulse appears relative to the Q signal), and the trigger level is 5V.

[0091] Step 7: Adjust the energy density of the laser for heating particles by rotating the half-wave plate 12, and at the same time use the image data acquisition module 4 to acquire two-color time decay signal images under different energy densities.

[0092] Specifically, the laser energy density can be adjusted from 90 to 445 mJ / cm² (energy range 10 to 50 mJ / pulse).

[0093] Step 8: Calculate the maximum temperature T for the image grayscale values ​​of the two-color signals with different energy densities acquired in Step 7. M The solution involves calculating T based on the dual-color thermometry principle formula. The grayscale value S of the dual-color incandescent intensity at the moment t=0ns when cooling begins is substituted into the formula to obtain T. M ;

[0094] Specifically, the calculation is performed based on the dual-color temperature measurement principle formula. The gray value of the dual-color incandescence intensity of the carbon soot particles at the moment when the cooling begins (t=0ns) is substituted into the formula to calculate the maximum temperature distribution of the carbon soot particles under different energy densities.

[0095] Step 9, based on the maximum temperature T obtained in Step 8 M Plot the maximum temperature T M The relationship between energy density F and the energy density F is used to calculate the energy density range of the initial temperature T0 of the particles. The energy density range refers to the linear region of the curve. Beyond the linear region, the particles will sublimate and cannot be calculated using this principle model.

[0096] Specifically, the sublimation threshold energy density of the carbon soot particles in this example is 225 mJ / cm² (energy is 25 mJ / pulse).

[0097] Step 10: Select two suitable energy density intensities F1 and F2 from Step 9, and two corresponding maximum temperatures T. M1 and T M2 The two-dimensional distribution value is used to calculate the initial temperature T0 of the particles according to the formula. The initial temperature T0 is also calculated based on the separation double-pulse principle formula, which is:

[0098]

[0099] Where F1 and F2 are two different values ​​within the effective energy density range, and T M1 T M2 To correspond to the maximum temperatures of F1 and F2, both energy densities F1 and F2 must not exceed the highest threshold for particulate matter to sublimate and the two must not be equal.

[0100] Specifically, in this example, we choose F1 = 90 mJ / cm² and F2 = 135 mJ / cm² (corresponding to energies of 10 and 15 mJ / pulse).

[0101] It should be noted that the specific model and specifications need to be selected and determined based on the actual specifications of the device. The specific selection and calculation method adopts the existing technology in this field, so it will not be described in detail here.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A laser-induced incandescence-based particulate temperature field measurement device, comprising: It comprises a pulse laser module (1), a beam expansion module (2), a sheet light heating sample module (3), an image data acquisition module (4) and a synchronous control module (5). The pulse laser module (1) comprises a pulse laser (11), a half-wave plate (12), a polarization beam splitter (13) and a first optical garbage can (14), the half-wave plate (12) is arranged on the light path between the pulse laser (11) and the polarization beam splitter (13), and the first optical garbage can (14) is arranged corresponding to the transmission light exit direction of the polarization beam splitter (13). The beam expansion module (2) comprises a first lens (21) and a second lens (22), the first lens (21) and the second lens (22) are arranged in sequence along the reflection light exit direction of the polarization beam splitter (13) to form a coaxial beam expansion system. The sheet light heating sample module (3) comprises a cylindrical lens (31), a sample (32) and a second optical garbage can (33), the cylindrical lens (31) is arranged on the exit light path of the beam expansion module (2), the sample (32) is located in the sheet light convergence area of the cylindrical lens (31), and the second optical garbage can (33) is arranged corresponding to the exit direction of the sheet light after the sheet light transmits through the sample (32). The image data acquisition module (4) comprises a first band-pass filter (41), a first camera (42), a second band-pass filter (43) and a second camera (44), the first band-pass filter (41) is installed at the front end of the lens of the first camera (42), the second band-pass filter (43) is installed at the front end of the lens of the second camera (44), and the first camera (42) and the second camera (44) are respectively located on the two sides of the sample (32), and the imaging optical axes are perpendicular to the sheet light propagation direction. The synchronous control module (5) comprises a digital delay generator (51), the trigger signal input end of the digital delay generator (51) is electrically connected with the Q signal output end of the pulse laser (11), and the two signal output ends of the digital delay generator (51) are respectively electrically connected with the external trigger input ends of the first camera (42) and the second camera (44).

2. The apparatus according to claim 1, wherein The pulse laser (11) is a pulse output type laser, the wavelength and pulse width of which are selected according to the absorption characteristics and physical properties of the sample (32), preferably a wavelength of 1064 nm and a pulse width of 20 ns.

3. The apparatus according to claim 1, wherein The sample (32) is a particle that can absorb laser of a specific wavelength output by the pulse laser (11).

4. The apparatus according to claim 1, wherein The digital delay generator (51) has at least two adjustable output ports, and the delay time and trigger level of each output port can be independently set.

5. The method of claim 1-4, wherein the laser-induced incandescence based particle temperature field measurement method is performed by the measurement device. The method comprises the following steps: Step 1: obtaining the laser output by the pulse laser (11), the laser is a nanosecond pulse laser with a wavelength of 1064±50 nm and a pulse width of 10-50 ns, adjusting the polarization state of the laser by the half-wave plate (12), and then dividing the laser into two beams by the polarization beam splitter (13). Step 2, the laser transmitted by the polarization beam splitter (13) in step 1 is collected by the first optical garbage can (14), and the laser reflected by the polarization beam splitter (13) is expanded by the first lens (21) and the second lens (22); Step 3, the laser expanded by the first lens (21) and the second lens (22) in step 2 is converged in one direction by the cylindrical lens (31) to form a sheet of light; Step 4, the sheet of light formed by the cylindrical lens (31) in step 3 heats the sample (32) of particles to be measured, and the light transmitted through the particles is collected by the second optical garbage can (33); Step 5, the incandescent signal emitted by the sample (32) of particles to be measured in step 4 is collected by the first band-pass filter (41) and the first camera (42), and the second band-pass filter (43) and the second camera (44) to collect the dual-color signal; Step 6, the first camera (42) and the second camera (44) in step 5 are both in external trigger mode, triggered by the same signal output by the digital delay generator (51), and the digital delay generator (51) is triggered by the Q signal output by the laser in external trigger mode; Step 7, the energy density of the laser for heating particles is adjusted by rotating the half-wave plate (12), and the dual-color time decay signal image is collected under different energy densities using the image data acquisition module (4). Step 8. The maximum temperature T of the image gray value of the two-color signal of different energy density collected in the step 7 is solved M ; The calculation is performed according to the formula of the two-color temperature measurement principle. The gray value S of the two-color incandescent intensity at the start of the temperature reduction t=0 ns is brought into the formula to obtain T M ; Step 9, plot the maximum temperature T M vs. the fluence F to obtain the fluence range for calculating the initial particle temperature T0, which is the linear region of the curve beyond which sublimation of the particles occurs and the model cannot be used. M Step 9, plot the maximum temperature T M vs. the fluence F to obtain the fluence range for calculating the initial particle temperature T0, which is the linear region of the curve beyond which sublimation of the particles occurs and the model cannot be used. M Step 9, plot the maximum temperature T M vs. the fluence F to obtain the fluence range for calculating the initial particle temperature T0, which is the linear region of the curve beyond which sublimation of the particles occurs and the model cannot be used. M Step 9, plot Step 10: Select two suitable energy densities F1 and F2 and two corresponding maximum temperatures T from step 9. M1 and T M2 The two-dimensional distribution value is used to calculate the initial temperature T0 of the particles according to the formula. The initial temperature T0 is also calculated based on the separation double-pulse principle formula, which is: ； wherein F1, F2 are two different values in the range of effective energy density, T M1 , T M2 are the maximum temperatures corresponding to F1, F2, both energy densities F1 and F2 cannot exceed the highest threshold value at which the particles sublimate and are not equal.

6. The method according to claim 5, wherein The sample (32) of particles to be measured in step 4 emits a time decay signal closely related to temperature after absorbing the energy of the sheet of light.

7. The method according to claim 5, wherein the laser-induced incandescence is based on a temperature field of the particles. The center wavelengths of the first band-pass filter (41) and the second band-pass filter (43) in step 5 are different, the quantum efficiency curves, gate widths, gains, exposure times and other parameters of the first camera (42) and the second camera (44) are consistent, and the system responses are calibrated.

8. The method according to claim 5, wherein, The same trigger signal output by the digital delay generator (51) in step 6 refers to consistent parameter values of delay time and trigger level.

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