CN114518180A - Temperature and amplitude remote measuring system and method based on laser dispersion spectrum - Google Patents
Temperature and amplitude remote measuring system and method based on laser dispersion spectrum Download PDFInfo
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Abstract
The invention provides a temperature and amplitude remote measuring system and method based on laser dispersion spectrum, which comprises a laser emission module, an electro-optic modulator, a beam splitter, a collimating mirror, a transmission and reflection integrated optical module, a photoelectric detector, a data acquisition and processing module, a gas cell, a primary reflecting device and the like. When the temperature and the amplitude are remotely measured, light is modulated in intensity through the electro-optical modulator and then is divided into two paths through the beam splitter, and one path of light is directly input into the electro-optical detector to serve as a reference phase signal. The other path retroreflects the light beam passing through the gas cell in the original path through an original direction reflecting device, converges to the photoelectric detector through the transmission-reflection integrated optical module, and finally calculates the phase change caused by distance and the phase change caused by dispersion through the data acquisition processing module, and the phase changes are respectively used for calculating amplitude and temperature. The passive measurement device is simple in structure and easy to realize, can perform long-term stable passive measurement, can be used for testing the thermal vibration of the wall surface of a key part in the fields of aerospace and the like, and has wide application prospect.
Description
Technical Field
The invention provides a temperature and amplitude remote measuring system and method based on laser dispersion spectrum, belonging to the technical field of non-contact remote measurement.
Background
In the experimental verification of the development and design of main equipment such as aeroengines, super engines, heavy-duty gas turbines and the like. Some of the critical component walls involved are affected by high temperatures caused by combustion and high frequency vibrations caused by mechanical vibrations. These may lead to thermal vibration coupling phenomena which weaken the fatigue resistance of the outer wall structure of the device, reducing its fatigue life. Furthermore, high temperatures and vibrations are usually present at the same time, but at the present stage the measurements of these parameters are often separate. Therefore, joint measurement of the thermal shock parameters is a necessary trend. In past research, the temperature and vibration measurement is isolated, and the temperature and vibration measurement can be divided into contact type and non-contact type.
For vibration measurement, contact-type vibration measurement is mainly an accelerometer, for example, in 2017 Mahmood et al, sensor and actuator a: a flexible MEMS accelerometer working at a maximum temperature of 350 ℃ is introduced in a Design, preparation and characterization of a flexible MEMS accelerometer using multi-Level UV-LIGA based on multi-Level UV-LIGA in an article, namely, Design, characterization and characterization of flexible MEMS accelerometer based on multi-Level UV-LIGA, of volume 263 and 530 of physics, the sensor has a simpler structure, but can only realize measurement at lower temperature and lower frequency, and has a single measurement parameter. In 2021, Xiong et al, in the Journal of IEEE Sensors (IEEE Sensors Journal), Vol 21, p 5819, an article for improving the Sensitivity of MEMS Resonant Accelerometers by Using Electrostatic Spring Softening Effect (Using Electrostatic Spring Softening Effect) introduced a micromechanical Resonant accelerometer with wide application prospect in high-precision measurement, the sensor has the advantages of high Sensitivity, frequency output, large dynamic response range and the like, and the sensor can be designed with a multi-level micro-lever for increasing the Sensitivity, which also causes the problem of increased structural complexity, and the high-temperature environment can influence the stability of circuit equipment, thus the measurement under the high-temperature environment can not be carried out.
For non-contact vibration measurement, the laser vibration measurement technology is a widely researched and commonly applied method at present, and includes various technical means such as a holographic method, an interference method, a laser speckle method, a laser triangulation method, a laser doppler method and the like. The holographic method and the interference method mainly measure the fringe change caused by vibration through laser interference, and further measure the vibration parameters. For example, in an examination of system axial measurement error caused by spatial variance effect in digital holography (examination of spatial variance effect in digital holography), which is published by Hao et al in 2019 at volume 112, page 16 of Optics and laser Engineering (Optics and laser in Engineering), the influence of the spatial variance effect on the system axial measurement error (phase error) is studied by applying the digital holography technology to displacement measurement caused by spatial axial vibration. However, the system based on the holographic interference method has a complex optical system, is difficult to be used in engineering environment, and is only suitable for basic research in laboratory environment. The laser speckle method and the laser triangulation method are mainly used for measuring the micro displacement caused by vibration, and an application of High-precision frequency modulation continuous wave laser ranging in precision ranging (High-resolution frequency-modulated continuous wave laser ranging for precision distance measurement) in an article published by Shi et al in Optical Engineering (Optical Engineering) 53, 122402 in 2014 introduces a method for measuring the micro distance based on the laser triangulation method of continuous wave modulation, and verifies that the system has the ranging resolution of 50 μm under the distance of 8.7 m. In the paper "Absolute Distance Measurement by Frequency Scanning Interferometry Based on Hilbert Phase Subdivision" (Absolute Distance Measurement Using Frequency-Scanning interference Based on Hilbert Phase Subdivision), published by Jiang et al in 2019, volume 19, page 5132 of Sensors (Sensors), hubert transform is used to extract the Phase of an auxiliary interference signal, and the time point corresponding to the Phase interval is calculated, so that the Measurement of the vibration Absolute Distance is realized, and the vibration Measurement precision is improved to 4.64 μm. However, in coherent detection, optical frequency nonlinearity in the laser modulation process causes beat frequency signal spectrum broadening, which reduces spatial resolution, and the system also has the disadvantage of high complexity. Compared with the vibration measuring means, the laser Doppler vibration measuring technology obtains the vibration state of the object by analyzing the Doppler frequency shift generated by vibration, the laser Doppler method has the advantages of high measuring speed, high resolution, high integration level and the like, and the laser Doppler vibration measuring instrument is a commercial and mature vibration measuring instrument. Tian et al published a paper "Pulsed laser-scanning laser Doppler vibrometer (PL-SLDV) phased array for aluminum plate damage detection" (PL-SLDV) phased array for damp detection in aluminum plates "by Tian et al in 2019, in Mechanical Systems and Signal Processing, volume 121, page 158, and detected damage to the plane of the aluminum plate due to vibration using a non-contact scanning Doppler vibrometer array, and imaged the vibration cracks at a vibration frequency of 9kHz in combination with a new imaging algorithm. Liu et al, in 2020, published in Measurement Science and Technology, volume 31, page 25202, a paper "New Algorithm for determining the pose of a scanning laser Doppler vibrometer" (A novel algorithm for determining the position of the laser beam of a scanning laser Doppler vibrometer) in which a galvanometer system is used to direct the laser beam to scan an object, presents a novel and easily implemented algorithm for determining the pose, such as direction and position, of a scanning laser Doppler vibrometer. Taking the blade of an aeroengine as an example, the position of the controlled laser spot is accurate, and the maximum deviation from the actually arranged measuring point on the surface is less than 1 mm. However, due to the interference of the external environment, the laser interference signal collected by the laser doppler vibrometer not only carries the vibration signal of the object to be measured, but also carries more external environment noise, and even under most circumstances, the vibration signal can be completely covered by the noise. According to the vibration measurement methods reported in the literature at present, the influence of a high-temperature environment damages equipment, the signal to noise ratio of a measurement result is reduced, and the vibration measurement methods cannot realize temperature measurement.
For temperature measurement, contact temperature measurement means mainly include thermocouples, temperature indicating paints, temperature indicating crystals and the like, but the measurement mode has serious interference to a flow field, and measurement accuracy is sharply reduced in severe environments such as high temperature, high pressure and strong corrosivity, for example, in 2018, Khatri et al, sensor and actuator a: a paper based on thin film thermocouples and thermopile element mass production compatible multifunctional thermal Sensors (A batch fabrication-compatible multi-functional thermal sensor based on a thermocouple and a high temperature coating) in Physics and Actuators A: Physical, 280, pp 188, proposes a high temperature multifunctional thermal sensor combining a thermocouple and a high temperature coating, which can be mass produced using industry standard micro-fabrication techniques. The thin film thermocouple and thermopile functions are designed to provide both surface temperature and surface thermal flux data. The sensor has small volume, is convenient to install and use, and can measure the temperature to 800 ℃. The thin-film thermocouple has the advantages of thin structure size, high response speed and the like, but has the problems of difficult lead connection and poor thermoelectric property consistency. In 2021, Wang et al studied the Application of flexible thermocouple wires in the thermal processing of the domestic aviation industry in an Application of flexible thermocouple wires in aviation thermal processing, which was published in "Industrial Metrology" at 31, volume 31, phase 6, page 33 (Application of flexible thermal wire in thermal processing), and the flexible thermocouple wires were characterized by lightness, fast thermal response speed and low price. However, during the use process, the welding point can be broken due to problems such as installation or violent vibration, so that the measurement result is unstable and inaccurate. The flexible thermocouple wires need to be arranged on the surface or inside the part to be measured. When the thermocouple wire is arranged, reliable contact between a thermocouple measuring end and a measured part is ensured, an accurate correction rule needs to be obtained, a specific test piece and a test working condition need to be combined, various factors such as the shape, the installation position and the air flow condition of the thermocouple wire are designed, and errors are easily generated due to electrode short circuit caused by high temperature. The invention patent of 'turbine blade temperature measuring method based on flame spraying' (patent number: ZL 201510937517.8) applied by the national gas turbine institute in 2015 discloses a method for measuring the temperature of a turbine blade by fixing a fine thermocouple on a metal surface by using a high-temperature insulating coating, wherein the fine thermocouple is fixed in the insulating coating on the surface by spraying a high-temperature material on the surface of the high-temperature material, and the surface temperature of the turbine rotor blade is accurately measured by using the fine thermocouple. Other contact type temperature measuring technology is a disposable temperature measuring method in which temperature indicating paint and temperature indicating crystals are commonly used in the aerospace field. Wherein a temperature sensing instrument is required for analyzing the surface temperature distribution of the combustion chamber. The temperature indicating paint is a paint whose temperature distribution is measured by a color change of the paint. Analysis of such coatings can be accomplished by observing the color change due to temperature. A test of applying a Temperature indicating Paint to an industrial Gas turbine Combustor impingement cooling front panel is disclosed in a paper of Journal of Gas turbine and Power Engineering (Journal of Engineering for Gas Turbines and Power Print) 139, 041508, volume, Using a Novel Thermal History coating to verify Combustor Liner Surface Temperature Measurements Under Full Load Conditions (variation of Surface Temperature Measurements on a comburer line Under Fuel-Load Conditions), by Krewinlel et al 2017, wherein relative hot and cold spots caused by impingement cooling can be determined, and local and global Temperature variations of the entire Combustor assembly are shown. The crystal temperature measurement technology is derived from the crystal irradiation swelling effect generated by irradiation point defects. In 2018, Pornphatdaaudom et al, in Nuclear Materials and Energy, volume 16, page 24, paper "Physical Properties Change of neutron-irradiated aluminum nitride and its annealing recovery behavior" of Nuclear-irradiated aluminum nitride and the same recovery reactor by using a step-heating spectrometer ", measured different temperature points of aluminum nitride crystals in a Nuclear test reactor, with a maximum temperature of 1673K. However, the temperature indicating paint and the temperature indicating crystal are usually disposable for measuring the temperature, and only the highest point temperature can be measured, so that the limitation is large. The contact type thermal vibration measurement means is influenced by measurement errors such as radiation errors, heat conduction errors and speed errors during measurement, so that actually measured values are inaccurate or unstable, the requirements on various parameters, particularly temperature measurement accuracy, in the fields of aeroengines and the like are high, and various calibration and parameter correction are required to be performed on selected contact type equipment to ensure the measurement accuracy. Although the wireless transceiver can be used for remote telemetry by a contact type measurement mode, the measurement precision of the measurement equipment or the telemetry equipment can be influenced in a high-temperature environment due to the intrusion and contact type measurement modes, the interference to a temperature field can be caused, and the long-time online monitoring is not facilitated.
For non-contact temperature measurement, the laser spectroscopy has the advantages of small influence of a tested environment, high response speed and the like. The method is more suitable for temperature measurement under severe environment conditions, and comprises spectral radiation temperature measurement, anti-Stokes Raman scattering spectrum temperature measurement, excimer laser induced fragmentation fluorescence, laser fluorescence spectrum temperature measurement, laser absorption spectrum temperature measurement and the like. The technologies can be used for measuring various variables in a temperature field, but the detection of the temperature has great limitation due to the complex equipment, the detection is easily influenced by substances in the environment, and the like, and most of the technologies are difficult to be used for temperature detection in a large-scale range. For example, a Precise infrared radiation temperature measurement scheme is proposed in a paper for Precise infrared temperature measurement of reference background radiation in gas turbine air cooling application (precision induced Thermal with background radiation for gas turbine air cooling application) published by Dong et al in International Journal of Thermal Sciences (International Journal of Thermal Sciences) at 158, page 106534 in 2020, and the measurement accuracy is improved by considering the background radiation of high temperature environment and the spectral emissivity of the object, and the thermocouple measurement value is well matched within 5%. A paper by Zentgraf et al, vol.235, 111707, Combustion and Flame (Combustion and Flame), 2022, for simultaneous quantitative measurement of CO by using laser diagnostics2CO and temperature and Detailed evaluation of thermochemistry in sidewall quench burners (Detailed assessment of the thermochemistry in a side-wall quenching burner by chemical and qualitative assessment of thermal and qualitative measurement of CO2CO and temperature using laser diagnostics) the mole fraction of CO produced by combustion was diagnosed using coherent anti-stokes raman spectroscopy, and the wall temperature after high temperature exposure was additionally assessed by laser diagnostics, however this technique is limited by laser performance, which is a property of lasersThe repetition frequency is only about 10Hz, which is not suitable for rapid and dynamic temperature measurement, and simultaneously, the nanosecond coherent anti-Stokes Raman spectrum temperature measurement technology can be interfered by a non-resonance background, and signals are mixed with the non-resonance background signals, so that the accuracy of temperature measurement is influenced. In 2021, Rao et al, Applied Spectroscopy, Vol.42, p.349, Characterization of a Methane-Air Laminar Diffusion Flame by Laser-Induced Breakdown Spectroscopy (LIBS) for the Characterization of the propagation of Methane-Air Laminar Diffusion Flame, revealed the spatial distribution of its composition. The correlation of typical emissions with thermocouple measured flame temperature was estimated and the results indicated that the trend of temperature change can be characterized by the intensity of the emissions of the combustion products. The signal intensity of the laser-induced breakdown spectroscopy is influenced by many factors, such as laser energy, the wavelength range of a spectrometer, the sensitivity of a detector and the like, and the system is complex and is not suitable for field temperature detection in industrial scenes. The laser fluorescence spectrum temperature measurement can independently realize the detection of a temperature field, is a ratio measurement technology based on laser, detects the fluorescence of two lower electronic states of atoms through laser excitation, and generates the fluorescence ratio which is related to the temperature of gas. In the paper of the international society for Combustion (Proceedings of the public Institute) at 37, volume 1417, by Weng et al, 2020, "synchronous calibration of two-wire atomic fluorescence and its application in soot high-precision temperature imaging" (simultaneous atomic fluorescence spectroscopy for high-precision temperature imaging) a non-linear two-wire atomic fluorescence thermometry technique for turbulent, slow flames was developed to improve the accuracy of gas temperature plane measurements, temperature measurements were made in stationary and turbulent flames, the accuracy under temperature measurement conditions of 1610K and 1854K was ± 67K and ± 75K, respectively, and temperature field imaging with spatial resolution of 550 × 550 μm was achieved. However, similar to laser-induced breakdown spectroscopy, the system is complex and not suitable for remote temperature telemetry in industrial settings, because it requires the use of a good high-speed camera to ensure time resolution. The temperature measurement technology based on the laser spectrum can realize the temperature detection to a certain extent, but the detection system has high complexity, is difficult to stably measure for a long time, and is difficult to be used for remote measurement of a remote field temperature point.
Compared with the temperature measurement means, the laser absorption spectroscopy technology has the advantages of non-invasiveness, quick response, high sensitivity, strong anti-interference capability and the like, has great potential in the aspect of temperature measurement, and can not realize measurement of wall surface temperature by measuring the temperature mean value on a path in past research. In 2021, Yang et al published in "Fuel" (Fuel) 288, 119666 paper "Temperature and OH Concentration measurement method by Ultraviolet Broadband Absorption Spectrum in Methane/Air Laminar Premixed flame" (Temperature and OH Concentration Measurements by Ultraviolet Broadband Absorption and Absolution of OH (X) in amine Methane/Air Premixed Flames) and realized measurement of multiple spectral lines of Temperature and OH group Concentration with accuracy of Temperature measurement within 16K by using a broad-band Ultraviolet laser. However, the baseline and linear fitting in the weak-light-intensity direct absorption method are easily interfered by the external environment, the anti-noise capability is weak, the spectral measurement is inaccurate, and the method is difficult to be used for temperature early warning in the industrial environment. A Single-ended intermediate infrared laser absorption sensor used for time-resolved measurement of water concentration and temperature in the annular space of a rotary detonation engine (Single-ended mid-infrared laser-absorption sensor for time-resolved measurements of water concentration and temperature in the annular space of the rotary detonation engine) is disclosed in a paper of the International society of Combustion (Proceedings of the Combustion Institute) 37, 1435, of Peng et al, 2019, and a Single-ended dual-wavelength infrared sensor with a measurement rate of 20kHz is designed. The method involves directing a laser beam into the burner through a turning mirror and reflecting backscattered radiation from the mirror polished stainless steel burner inner surface back to the detection assembly to complete the temperature measurement. The method can realize the same-end receiving and transmitting of the laser and the detection signal, but in the method, when the inner surface of the combustor loses gloss after being fired for many times, the detection signal becomes weaker along with the increase of the measurement time, the service life is short, and the long-time stable detection cannot be realized. Of course, these methods only can measure the temperature and the temperature distribution, but do not have the function of vibration measurement.
Recently, laser dispersive spectroscopy has been proposed as a new test method, which has been used in thermometry and ranging. In the 2010 Wysocki et al, in the "optical quick report" (Optics Express) volume 18, 26123, the paper "Molecular dispersion spectroscopy for chemical sensing of chirped mid-infrared quantum cascade laser" for chemical sensing, a method of generating bicolor laser light by acousto-optic modulation, generating beat frequency on a photodetector, then obtaining dispersion frequency by frequency demodulation to perform concentration measurement is introduced, and named as chirped dispersion spectroscopy, which is not affected by saturated absorption at high concentration and still shows good linear response in high concentration measurement. Nikodem et al published in 2012 in Applied Physics B, volume 109, page 477 of paper Chirp dispersion Spectroscopy for molecular Spectroscopy harmonic detection (Chirp laser dispersion with harmonic detection of molecular spectra) proposed Chirp dispersion Spectroscopy based on chirp modulation and combined phase-sensitive detection, which has stronger anti-noise capability, can detect the strongest nitrous oxide at high concentration, and realizes accurate gas concentration measurement at high concentration. In 2014, Mateos et al published in "optical rapid report" (Optics Express) 22, volume 22, page 14143, and in "Heterodyne phase-sensitive detection without calibrated molecular dispersion spectroscopy" (Heterodyne phase-sensitive detection for calibration-free molecular dispersion spectroscopy) proposed that an electro-optical modulator generates three-color laser for recording dispersion spectroscopy to realize dispersion Heterodyne spectroscopy measurement, and then phase shift caused by dispersion is obtained through phase-sensitive detection to realize a measurement method of gas concentration parameters. The above methods of dispersive spectroscopy all focus on the measurement of concentration because dispersive spectroscopy is not affected by fluctuations in optical power and has the advantage of zero baseline measurement, which can be applied to high concentrations or long distancesAnd (4) detecting the concentration of the separated gas. For temperature measurement, the mid-IR heterodyne phase-sensitive dispersion spectroscopy on temperature and H in laminar flow was published by Ma et al in 2018 in Applied Physics B (Applied Physics B) volume 124, page 12Sensing of O (Temperature and H)2O sensing in a laminar premixed flame using mid-dispersed specific dispersion spectrum) the dispersion spectrum was used for temperature measurement of the premixed flame and the water concentration was obtained, two H + in the temperature range of 1000-2The peak-to-peak ratio of the O dispersion spectrum is in monotonic relation with the temperature, which shows the capability of double-line temperature measurement by using the laser dispersion spectrum. In 2021, Hangauer et al published in optical communications (Optics Letters) volume 46, page 198-201, volume 2, Chirped laser dispersion spectroscopy for simultaneous distance detection and chemical spectrum sensing (Chirped laser dispersion spectroscopy) used for simultaneous distance detection and chemical spectrum sensing to measure the distance and distance by using the characteristic of high frequency intensity modulation required in both laser absorption phase spectroscopy and continuous optical distance, and simultaneously to measure the concentration and distance, the measured distance can reach several kilometers, but the method has low distance measurement accuracy and does not obtain temperature information. At the present stage, a high-precision vibration and temperature measurement means is urgently needed for the remote measurement of the temperature and the amplitude of the wall surface of a key part in a major power device, and the dispersion spectrum has the potential of realizing the simultaneous measurement of the high-precision temperature and the amplitude.
Based on the technical background, the invention provides a temperature and amplitude remote measuring system and method based on laser dispersion spectrum, a gas pool and a primary reflection device are placed in a high-temperature vibration environment to be monitored, the temperature and distance change of a field to be measured can be rapidly sensed, the temperature and vibration frequency and amplitude of the surface to be measured are calculated through phase change caused by molecular transition and optical path change through phase sensitive detection, and the absolute distance of an object can be obtained through comparison with an original signal, so that the remote measuring function is realized.
Disclosure of Invention
The invention provides a temperature and amplitude remote measuring system and method based on laser dispersion spectrum, wherein the system comprises a laser emission module, an electro-optic modulator, a beam splitter, a data acquisition and processing module, a collimating mirror, a transmission and reflection integrated optical module, a gas cell and a primary reflecting device which are sequentially arranged according to paths of light beam propagation and electric signal generation, transmission and processing.
The laser emission module emits modulated laser, the modulated laser is subjected to high-frequency intensity modulation through the electro-optical modulator and then passes through the beam splitter, one beam of the modulated laser is directly input into the photoelectric detector 1 and then is input into the data acquisition processing module, the other beam of the modulated laser passes through the transmission-reflection integrated optical module after being collimated through the collimating mirror and then is input into the gas pool, the light passing through the gas pool is reflected to the transmission-reflection integrated optical module through the original path after passing through the original direction reflection device, and then the light is received by the photoelectric detector 2 and then is output to the data acquisition processing module to realize the calculation of thermal vibration parameters; the laser emission module, the electro-optical modulator, the beam splitter, the collimating mirror, the photoelectric detector 1, the transmission-reflection integrated optical module, the photoelectric detector 2 and the data acquisition processing module can be integrated into a set of monitoring instrument, and then the high-precision remote measurement of temperature and vibration parameters is carried out on a gas pool and a primary reflection device in any high-temperature vibration environment to be measured; the method for calculating the thermal vibration parameters comprises the following steps: obtaining an initial phase by performing phase-sensitive detection on light intensity signals obtained by the photodetector 1 and the photodetector 2
And detecting phase
Obtaining sums due to distance variations from non-absorbing partial fits of the detected phases
By phase change
And initial phase
Obtaining a distance phase, calculating a change in amplitude due to vibration, and detecting the phase
And phase change
The difference in absorption phase is obtained and the temperature of the gas cell is calculated by colorimetry.
The laser emission module comprises a tunable laser, the central wavelength and the light intensity output by the laser can be modulated through temperature and current, the laser outputs laser with continuous wavelength in a certain range, then the laser is input into an electro-optical modulator to realize high-frequency intensity modulation of light, so that incident laser generates two frequency spectrum bands on two sides of the central wavelength except the laser wavelength emitted by the tunable laser to generate three-color laser, the two frequency spectrum bands and the central wavelength are separated by an intensity modulation frequency, and the three-color laser is divided into two beams; one beam is received by the electro-optical detector 1 and used for calculating an initial phase, the other beam is received by the electro-optical detector 2 and used for calculating a detection phase after passing through an object to be detected, then phase change caused by gas absorption is used for calculating temperature information, and phase change caused by optical path change is used for calculating vibration information. The transmission-reflection integrated optical module can respectively realize the functions of transmission and reflection of laser beams from different directions, and realizes the integration of receiving and transmitting sensor signals.
Firstly, the output wavelength of the laser is controlled by modulating the injection current of the laser emission module, the laser emission module emits sweep-frequency laser after modulation, and at a certain moment, the laser emitted by the laser is regarded as the frequency omega0The laser is modulated in intensity by an electro-optical modulator with frequency of omega to generate three-color beams with known frequency interval omega, and then the modulated laser is divided into two beams by a beam splitter, and one beam is directly input as a reference signalPhotodetector 1 to obtain an initial phase; the other beam of light is used as a detection signal, is collimated by a collimating mirror and then reaches the light in the gas cell through a transmission-reflection integrated optical module, and as the molecular transition can be absorbed and dispersed simultaneously, three-color laser passing through a 107 gas cell can experience different phase shifts caused by different refractive indexes near the target absorption transition; then the original reflection device reversely propagates along the original light direction to reach the transmission-reflection integrated optical module and converge to the photoelectric detector 2, and the phase change caused by the displacement change caused by the temperature and vibration of the gas sample in the gas cell can be expressed as
Wherein the content of the first and second substances,
and
the respective tables are the phase changes, ω, caused by the optical path variations and the dispersion0Is the frequency of light, c is the speed of light, n is the refractive index, Δ L and LcIn formula (1), the former term is the phase change caused by a non-absorption optical path, the latter term is the relative phase change caused by absorption dispersion, firstly, the phase shift caused by distance change is obtained by fitting the non-absorption part of a detection signal, the frequency spectrum distribution of target vibration can be obtained by solving a reference phase spectrum, and the corresponding optical path length can be expressed as
Wherein the content of the first and second substances,
is the initial phase obtained by the photodetector 1, canThe influence of the group delay phase on the measurement result is eliminated, the absolute phase change caused by the direct distance change between the monitoring instrument and the primary reflection device caused by vibration can be obtained through the difference between the absolute phase and the initial phase, the absolute distance change can be further obtained, the average value of the distance change is the position information of the target, and finally the frequency distribution of the vibration can be obtained through carrying out frequency spectrum solution on the offset phase of the baseline; when the laser is swept through a molecular transition, absorption and dispersion occur simultaneously, and as can be seen from the Kramers-Kronig relationship, the refractive index is a function related to absorption and can be expressed as
Wherein, ω is the frequency of light, α (ω) is the absorption coefficient located at frequency ω, so the gas dispersion spectrum can obtain the same gas information as the absorption spectrum, the peak-to-peak values of the dispersion spectrum at two different molecular transitions reflect the line intensity at different spectral lines, and the position where the square sum of the deviation values corresponding to the phases is the minimum is determined by calculating the phase peak-to-peak values of the two spectral lines, utilizing the deviation between the measured value and the theoretical value, and looking up the table, thereby obtaining the measured value of the temperature. By the aid of the thermal vibration remote measurement system, multi-parameter measurement of the temperature and the amplitude of a high-temperature vibration target can be realized.
The invention has the beneficial effects that: the invention has simple structure and high integration degree. Temperature and vibration information in the thermal vibration coupling environment are sensed through a gas pool serving as a passive device, reflection-type detection equipment is designed by combining the characteristics of high sensitivity and accurate measurement of a laser dispersion spectrum technology, temperature field remote measurement with nonintrusive, quick response, high sensitivity, low cost and high precision can be realized, the flexibility of the system is high, the transmission-reflection integrated optical module and the primary reflection device have multiple groups of selection schemes and are adaptive to different application occasions, the application to various environments can be realized by changing the gas components of the gas pool in the induction module and the emergent light wavelength of the corresponding laser group, the application range is wide, and the practicability is high.
Drawings
Figure 1 is an exemplary block diagram of a temperature and amplitude telemetry system and method based on laser dispersion spectroscopy,
the system comprises a laser emitting module 101, an electro-optical modulator 102, a beam splitter 103, a collimating mirror 104, a photoelectric detector 105, a transmission-reflection integrated optical module 106, a gas cell 107, a forward reflecting device 108, a photoelectric detector 109 and a data acquisition and processing module 110.
Fig. 2 is a flowchart for calculating temperature and vibration information from the detection signal.
FIG. 3 is 6036cm-1Laser dispersion spectrum of (1).
FIG. 4 is 6046cm-1Laser dispersion spectrum of (1).
Detailed Description
The present invention is further illustrated by the following examples.
The typical structure is shown in figure 1, and the system comprises a laser emission module 101, an electro-optical modulator 102, a beam splitter 103, a collimating mirror 104, a photoelectric detector 105, a transmission-reflection integrated optical module 106, a gas cell 107, a forward reflecting device 108, a photoelectric detector 109, a data acquisition processing module 1110, and a temperature and amplitude remote measurement system and a temperature and amplitude remote measurement method based on laser dispersion spectrum, wherein the data acquisition processing module 107, the gas cell 108, the forward reflecting device 109, the photoelectric detector 2 and the data acquisition processing module 1110 are sequentially arranged according to paths of light beam propagation and electric signal generation, transmission and processing.
In this embodiment, the 101 laser emission module adopts two distributed feedback semiconductor lasers, the 106 transmission-reflection integrated optical module adopts an off-axis parabolic reflector with an aperture of 50.8mm, a reflection angle of 90 degrees and a reflection focal length of 152.4mm and a 3mm alignment through hole, the 108 forward reflecting device adopts a pyramid prism with an aperture of 25.4mm and a reflection precision of 5 ″, under the condition, the effective telemetering distance of the system can reach more than 1000m, the telemetering distance is mainly limited by the aperture of the off-axis parabolic reflector and the reflection precision of the pyramid prism, and the 107 gas pool and the 108 forward reflecting device are bonded by high-temperature epoxy resin with matched refractive index to form the induction module.
In this embodiment, the 107 gas pool contains methane and nitrogen, and the 101 laser emission moduleThe central beam is 6036cm-1And 6046cm-1The sensing module of the distributed bragg reflection type semiconductor laser is placed at a 357K temperature point, and a specific temperature parameter calculation process of a laser absorption spectrum is shown in fig. 3 and comprises the following steps:
firstly, the 101 laser emission module emits laser covering gas absorption wavelength through controlling current and temperature wavelength modulation, the modulated laser is subjected to high-frequency modulation with the frequency of 400MHz through a 102 electro-optic modulator to obtain three-color light with two side bands, the three-color light is divided into two beams through a 103 beam splitter, one beam is directly input to 105 electro-optic modulator 1 to be used as an original phase signal, the other beam is collimated through a 104 collimating mirror and then passes through a 106 transmission and reflection integrated optical module, the light passing through the 106 transmission and reflection integrated optical element is incident to a 107 gas pool, the light passing through the 107 gas pool is reflected to the 105 transmission and reflection integrated optical module through an 108 original direction reflecting device and then is converged to a 109 modulator 2 to be used as a detection phase signal, and finally the two beams are input to a 106 data acquisition and processing module.
Step two, obtaining an original phase through phase-sensitive detection in a 106 data acquisition processing module
And detecting phase
Then the phase change due to the distance change is obtained by fitting the non-absorbing part of the detected phase
And step three, calculating peak values of absorption phases of the two spectral lines, then calculating the temperature to be 600K by a colorimetric method, calculating the frequency spectrum distribution of the distance phase difference to obtain the frequency of vibration to be 150Hz, substituting the phase difference caused by the distance into a formula (3) to solve the distance change caused by the vibration, wherein the amplitude of the vibration is 0.00097m, obtaining the position of a vibration source to be a distance sensor 0.2578m by the average value of the distance change, and realizing high-precision measurement of the temperature and vibration information.
The 101 laser emission module, the 102 electro-optical modulator, the 103 beam splitter, the 104 collimating mirror, the 105 photoelectric detector 1, the 106 transmission-reflection integrated optical module, and the 109 photoelectric detector 2, the 110 data acquisition processing module can be integrated into a set of monitoring instrument, and high-precision telemetering of temperature and vibration is carried out by a 107 gas cell and a 108 forward reflection device in any applicable temperature field.
The above description of the invention and its embodiments is not intended to be limiting, and the illustrations in the drawings are intended to represent only one embodiment of the invention. Without departing from the spirit of the invention, it is within the scope of the invention to design structures or embodiments similar to the technical solution without creation.
Claims (3)
1. A temperature and amplitude remote measuring system and method based on laser dispersion spectrum comprises a 101 laser emission module, a 102 electro-optic modulator, a 103 beam splitter, a 104 collimating mirror, a 105 photoelectric detector 1, a 106 transmission and reflection integrated optical module, a 107 gas cell, a 108 forward reflecting device, a 109 photoelectric detector and a 110 data acquisition and processing module; the laser emission module 101 emits modulated laser, the modulated laser is subjected to high-frequency intensity modulation through an electro-optical modulator 102 and then is divided into two beams through a beam splitter 103, one beam is directly input into a photoelectric detector 105 and then input into a data acquisition processing module 110, the other beam is collimated through a collimating mirror 104 and then enters a gas cell 107 through a transmission and reflection integrated optical module 106, light passing through the gas cell 107 is reflected to the transmission and reflection integrated optical module 106 through a primary reflection device 108 and then is converged to a photoelectric detector 109 and then input into a data acquisition processing module 110 to realize calculation of thermal vibration parameters; initial phases are obtained by phase-sensitive detection by 105 photodetector 1 and 109 photodetector 2, respectively
And detecting phase
Then the non-absorption part of the detection phase is fitted to obtain the distanceCaused by variation of
By phase change
And initial phase
Obtaining a distance phase, calculating a change in amplitude due to vibration, and detecting the phase
And phase change
The difference in absorption phase is obtained and the gas temperature in the gas cell is calculated 107 by colorimetry.
2. The system and the method for telemetering temperature and amplitude based on laser dispersion spectrum according to claim 1, wherein the laser emitted from the laser emitting module 101 passes through an electro-optical modulator 102 to realize high-frequency intensity modulation of light, two spectral bands are generated on two sides of the central wavelength to generate three-color laser, in order to realize synchronous measurement of temperature and amplitude, the three-color laser is divided into two beams, one beam is received by an electro-optical detector 105 1 for calculating initial phase, and the other beam is received by an electro-optical detector 109 for calculating detection phase after passing through an object to be measured; the 106 transmission-reflection integrated optical module can respectively realize the functions of transmission and reflection on laser beams from different directions, a detection signal passes through the 106 transmission-reflection integrated optical module and then is reflected back to the original direction by the 108 original-direction reflecting device, and then the 106 transmission-reflection integrated optical module reflects the light beam to deviate from the original light path and converge to the 109 photoelectric detector 2, so that the integration of receiving and transmitting the sensor signal is realized.
3. Root of herbaceous plantThe system and method as claimed in claim 1, wherein the output wavelength and intensity of the laser are first controlled by modulating the injection current and temperature of the 101 laser emitting module, the 101 laser emitting module emits a frequency-swept laser by modulation, and at a certain time, the laser emitted from the laser is regarded as having a frequency ω0The laser is subjected to intensity modulation through a 102 electro-optical modulator with modulation frequency of omega to generate a three-color light beam with known frequency interval omega, then the modulated laser is divided into two beams through a 103 beam splitter, and one beam is directly input into a 105 photoelectric detector 1 as a reference signal to obtain an initial phase; the other beam of light is collimated by a 104 collimating mirror as a detection signal and then reaches a 107 gas cell through a 104 transmission and reflection integrated optical module; the light passing through the 107 gas cell can be absorbed and dispersed at the same time due to molecular transition, and three-color laser passing through the 107 gas cell can cause different phase shifts near the target absorption transition due to different refractive indexes; then reversely propagates along the direction of the original light through the 108 original reflection device to reach 106 the transmission reflection integrated optical module and converge to 109 the photoelectric detector 2, and the phase change caused by the displacement change caused by the temperature and vibration of the gas sample in the gas cell 107 can be expressed as the phase change caused by the temperature and vibration of the gas sample
Wherein the content of the first and second substances,
and
the respective tables are the phase changes, ω, caused by the optical path variations and the dispersion0Is the frequency of light, c is the speed of light, n is the refractive index, Δ L and LcTotal optical path and 107 gas cell length, omega is the modulation frequency of the electro-optical modulator, determines the capability of the system to measure the phase, and in formula (1), the former term is the phase change caused by the non-absorption optical pathThe latter term is the phase change caused by absorption dispersion, firstly, the phase shift caused by distance change is obtained by fitting the non-absorption part of the detection signal, the frequency spectrum distribution of the target vibration can be obtained by solving the reference phase spectrum, and the corresponding optical path length can be expressed as
Wherein the content of the first and second substances,
the initial phase is obtained by the 105 photoelectric detector 1, the influence of the group delay phase on the measurement result can be eliminated, the absolute phase change generated by the distance change between the monitoring instrument and the 107 gas pool caused by vibration can be obtained through the difference with the initial phase, the absolute distance change can be further obtained, the average value of the distance change is the position information of the target, and finally the frequency distribution of vibration can be obtained through carrying out frequency spectrum solution on the offset phase of the baseline; when the laser is swept through a molecular transition, absorption and dispersion occur simultaneously, and as can be seen from the Kramers-Kronig relationship, the refractive index is a function related to absorption and can be expressed as
Where ω is the frequency of the light and α (ω) is the absorption coefficient at frequency ω;
the gas information same as the absorption spectrum can be obtained by utilizing the dispersion spectrum of the gas, and the peak values of the dispersion spectrum at two different molecular transitions reflect the line intensities at different spectral lines; combining with a HITRAN database, calculating two spectral line phase peak values through simulation to prepare a lookup table of a ratio and temperature, then performing table lookup according to a measured value, calculating the deviation of the measured value and a theoretical lookup table value, and reducing the deviation through iteration to realize temperature measurement; by the thermal vibration remote measuring system, multi-parameter measurement of the temperature and the amplitude of a high-temperature vibration target can be realized.
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