A high-temperature high-speed airflow total temperature, static temperature, dynamic temperature and flow velocity synchronous measurement system

Abstract

This invention discloses a synchronous measurement system for total temperature, static temperature, dynamic temperature, and flow velocity of a high-temperature, high-speed airflow. The components include a type B thermocouple, a temperature transmitter, two tunable diode lasers, a signal generator, an optical fiber coupler, a collimating mirror, a parabolic reflector, a photodetector, a data acquisition card, a high-temperature alloy mounting base, thermocouple branches, optical detection branches, and cage-type mounting accessories. The measurement system uses thermocouples and laser absorption spectroscopy to measure the total temperature and static temperature of the high-temperature, high-speed airflow, respectively. Then, based on the relationship between the total temperature, static temperature, dynamic temperature, and flow velocity of the high-temperature, high-speed airflow, the dynamic temperature and flow velocity of the airflow at the measured point in the flow field are determined. This invention achieves synchronous measurement of the total temperature, static temperature, dynamic temperature, and flow velocity of a high-temperature, high-speed airflow, and has advantages such as low cost, small size, portability, and fast data processing. It can be widely used in fields such as gas turbines and aero-engines.

Description

(I) Technical Field

[0001] This invention proposes a system for synchronously measuring total temperature, static temperature, dynamic temperature, and flow velocity of high-temperature, high-speed airflow, belonging to the three technical fields of tunable diode laser absorption spectroscopy, velocity, and temperature measurement. (II) Background Technology

[0002] Hypersonic vehicle technology has garnered widespread attention and in-depth research from the world's leading aerospace powers due to its immense military and potential commercial value. The core of a hypersonic vehicle is its propulsion system, and its development level represents a nation's comprehensive scientific and technological strength and industrial prowess. The combustion chamber is the primary component providing thrust, and quantitative analysis of the flow field parameters within the engine combustion chamber has significant theoretical and practical value for engine development. Currently, engine combustion chambers can generate gases with a total temperature of 900-2100 K, which, through expansion via supersonic nozzles, can produce airflows with Mach numbers of 4-7. The high speed and high temperature characteristics of the flow field pose significant challenges to the accurate measurement of flow field parameters, thus urgently requiring technologies capable of multi-parameter flow field measurement.

[0003] In high-temperature, high-speed flow fields, the total air temperature, static temperature, dynamic temperature, and flow velocity are key parameters for evaluating flow field quality. After decades of development and upgrades, thermocouple temperature measurement technology will continue to play an irreplaceable role in temperature measurement within the high-temperature, high-speed flow fields of aero-engine combustion chambers. In their 1991 paper, "The Dependence of Thermocouple Probe Calibration on Stagnation Density Changes," P. Smout et al. detailed the influence of airflow density on thermocouple measurement accuracy in high-temperature, high-speed flow fields and established relevant analytical models. Furthermore, in a variable-density wind tunnel at the University of Cambridge, the recovery characteristics of thermocouple probes under different density conditions were calibrated to make the measured temperature closer to the true total temperature of the flow field. In their paper "Transient Measurements of Temperature and Radiation Intensity in Spherical Microgravity Diffusion Flames," presented at the 44th AIAA Aerospace Sciences Meeting and Exhibit in 2006, Melissa K. Chernovsky et al. detailed a pulsed thermocouple for measuring gas flow temperatures above the melting point of ordinary thermocouples. The pulsed thermocouple is installed in the flow field under test. Before measurement, a cooling gas is turned on to bring the thermocouple to a lower temperature. At the start of the measurement, the cooling gas is turned off, and the thermocouple's temperature rises rapidly upon contact with the flow field. When the temperature approaches the thermocouple's melting point, the cooling gas is turned on again to lower the thermocouple's temperature. Finally, a first-order exponential function is used to calculate the temperature measured by the thermocouple.In their 1996 paper, "Development of a Stagnation Temperature Probe for Air-hydrogen Supersonic Combustion Flows," O. Pin et al. combined a type-B thermocouple temperature sensor with finite element simulation to measure the temperature of a hydrogen-oxygen premixed flame in a ramjet engine. However, this method required the prior establishment of an accurate dynamic data model of the thermocouple. In their 2007 paper, "Surface and Gas Measurements Along a Film-Cooled Wall," published in the *Journal of Thermophilic and Heat Transfer*, Volume 21, Issue 1, pp. 181-189, Carlos A. Cruz et al. used a thin-wire thermocouple to measure the temperature of a premixed flame. By calibrating and compensating for the time constant of the thermocouple filament, they achieved temperature measurement of a high-temperature, high-speed flow field. Thin-wire thermocouples possess excellent spatial resolution and relatively small steady-state and dynamic errors, thus finding widespread application. Atsushi Ishihara et al., in their 2000 paper "Measurement of the Burning Surface Temperature in Ammonium Perchlorate" (Proceedings of the Combustion Institute, Vol. 28, No. 1, pp. 855-862), designed an inverted U-shaped thermocouple that significantly improved the accuracy of near-wall airflow temperature measurements in engines. Similarly, DA Alspach et al., in their 1991 paper "Temperature Profile Measurements in Solid Propellant Flames" (27th Joint Propulsion Conference), also employed embedded thin-wire thermocouples to measure the flame temperature of solid propellants. Driven by new materials, new processes, and new methods, thermocouple-based temperature measurement technology continues to thrive and plays an irreplaceable role in temperature measurement in high-temperature and high-speed flow fields.

[0004] Tunable Diode Laser Absorption Spectroscopy (TDLAS) is an optical non-contact temperature measurement technique. Due to its advantages of non-invasiveness, high selectivity, high precision, simple structure, and cost-effectiveness, it has been widely used in measuring the flow field temperature of engine combustion chambers. In their 2012 paper, "Two-line thermometry and H2O measurement for reactive mixtures in rapid compression machine near 7.6 μm, Combustion and Flame," published in Volume 159, pp. 3493-3501 of *Combustion and Flame*, Apurba Kumar Das et al. used quantum cascade laser absorption spectroscopy near 7.6 μm to measure the temperature of the reaction mixture in a rapid compressor. This method can measure high-temperature gas flows in a rapid compressor within a temperature range of 300 K–1200 K, with a temperature measurement uncertainty of less than 11%. In their 2017 paper, "Compactoptical probe for flame temperature and carbon dioxide using interbandcascade laser absorption near 4.2 μm," published in Volume 178, pp. 158-167 of *Combustion and Flame*, JJ Girard et al. used a compact optical probe composed of a sapphire rod to measure flame temperature at different heights near 4.2 μm based on laser absorption spectroscopy. Within the temperature range of 1200 K to 2000 K, the temperature measurement accuracy was less than 15 K, and the uncertainty was 20-50 K.In their 2020 paper "TDLAS-based in situ diagnostics for the combustion of preheated ultra-lean dimethyl ether / air mixtures" published in Fuel, Vol. 263, pp. 116652-116659, Václav Nevrly et al. used the absorption of H2O and hydroxyl radicals near 1572 nm to perform in-situ measurement of the flame temperature of a high-temperature laminar premixed ultra-lean dimethyl ether / air mixture and reconstructed the flame structure, achieving a temperature measurement error of less than 25 K in the temperature range of 600 K-1200 K. In their 2020 paper, "Ultraviolet absorption cross-section measurements of shock-heated O2 from 2000–8400 K using a tunable laser," published in the Journal of Quantitative Spectroscopy & Radiative Transfer, Volume 247, pp. 106959–106972, Ajay Krish et al. used a picosecond pulsed ultraviolet laser to measure the cross-sectional temperature of shock-heated oxygen. In the experiment, the shock temperature of the oxygen gas stream reached as high as 10700 K. The cross-sectional temperature of the oxygen gas stream was measured using two oxygen absorption lines at 211.2 nm and 236.9 nm, and the error between the measurement and the cross-sectional temperature calculated by the Stanford model was within 15%. In their 2020 paper, "Sensitive and interference-immuneformaldehyde diagnostic for high-temperature reacting gases using two-color laser absorption near 5.6μm," published in Volume 213, pp. 194-201 of the journal *Combustion and Flame*, Yiming Ding et al. used a two-color differential absorption diagnostic method based on laser absorption spectroscopy to measure the temperature of high-temperature, high-speed gas flow in a shock tube near 5.6μm. This method can achieve high-speed, high-sensitivity temperature measurement within the temperature range of 870K-1800K.In their paper "Gaussian process regression for direct laser absorption spectroscopy in complex combustion environments" published in *Optics Express*, Volume 29, Issue 12, pp. 17926-17939 in 2021, Weitian Wang et al. addressed the issues of slow processing speed and insufficient accuracy in post-processing of mixed spectral lines by proposing a Gaussian process regression method based on absorption spectroscopy. This method directly extracts multiple unknown thermodynamic parameters from absorption spectral profile data. It can accurately and efficiently infer gas temperatures within the range of 300K-2500K, with a relative error of less than 3% in temperature measurement. The entire solution process requires no iteration, cyclic simulation, or human intervention. In their paper "Noise Immune Absorption Profile Extraction for the TDLAS Thermometry Sensor by Using an FMCW Interferometer" published in IEEE Transactions on Instrumentation and Measurement, Volume 72, pp. 1-11, 2023, Wenbin Zhou et al. used laser absorption spectroscopy to measure the temperature of the exhaust flame at the engine combustion chamber outlet, employing H2O near-infrared at 7185.59 cm⁻¹. -1 and 7444.35cm -1 The spectral lines show a temperature measurement error of less than 10% for highly turbulent flames within the temperature range of 600K-1200K. Non-contact temperature measurement technology based on tunable diode laser absorption spectroscopy has the advantages of a high upper temperature limit and no interference with the measured flow field. However, this method measures the static temperature of the airflow, not the total airflow temperature. Therefore, current optical non-contact temperature measurement technology cannot replace thermocouples for measuring the total airflow temperature.

[0005] Based on the above background, this invention proposes a simultaneous measurement system for total temperature, static temperature, dynamic temperature, and velocity of high-temperature, high-speed airflow. This system can simultaneously extract the total temperature, static temperature, dynamic temperature, and velocity of the airflow at measurement points in a high-temperature, high-speed flow field, thus solving the problem that existing measurement systems can only measure a single parameter in the flow field. This invention combines thermocouple and laser absorption spectroscopy temperature measurement technologies. Thermocouples and laser absorption spectroscopy are used to measure the total temperature and static temperature of the airflow in the flow field, respectively. Then, based on the relationship between the total temperature, static temperature, dynamic temperature, and velocity of the airflow in the high-temperature, high-speed flow field, the dynamic temperature and velocity of the airflow are further calculated. In a high-temperature, high-speed flow field, the total temperature of the airflow is equal to the sum of the static temperature and dynamic temperature. Knowing the total temperature and static temperature, the dynamic temperature can be calculated. The velocity of the airflow in the flow field is related to the Mach number of the airflow and the local speed of sound. The Mach number can be obtained from the total temperature and static temperature of the airflow, and the local speed of sound can be obtained from the static temperature. Therefore, knowing the total temperature and static temperature, the velocity of the airflow in the flow field can also be calculated. This invention enables simultaneous measurement of multiple parameters in high-temperature, high-speed flow fields. It also features low cost, small size, portability, and fast data processing, and can be widely used in fields such as gas turbines and aero engines. (III) Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing combustion chamber parameter measurement technologies by providing a system for simultaneously measuring the total temperature, static temperature, dynamic temperature, and flow velocity of a high-temperature, high-speed airflow. This system falls under the technical fields of tunable diode laser absorption spectroscopy, velocity, and temperature measurement. The components of the measurement system include a type B thermocouple, a temperature transmitter, two tunable diode lasers, a signal generator, a fiber optic coupler, a collimating lens, a parabolic mirror, a photodetector, a data acquisition card, a high-temperature alloy mounting base, a thermocouple branch, an optical detection branch, and cage-type mounting accessories.

[0007] To achieve the above technical objectives, the technical solution adopted in this invention is as follows: The measurement system uses thermocouples and laser absorption spectroscopy to measure the total temperature and static temperature of the airflow at the test point in the flow field, respectively. Then, based on the relationship between the total temperature, static temperature, dynamic temperature, and flow velocity of the airflow in the flow field, the dynamic temperature and flow velocity of the airflow at the test point are calculated. When the measuring probe is inserted into the high-temperature, high-speed flow field, the airflow sequentially passes through an optical detection branch and a thermocouple branch mounted on a high-temperature alloy mounting base. The optical detection branch uses laser absorption spectroscopy to measure the static temperature of the airflow at the test point, while the thermocouple branch uses a type B thermocouple to measure the total temperature of the airflow at the test point. Both ends of the thermocouple branch are open, with one end having a threaded outer wall for easy installation on the high-temperature alloy mounting base. A type B thermocouple is inserted into the thermocouple branch, forming a measurement point at the unthreaded end of the branch. A temperature transmitter converts the temperature measured by the thermocouple into an electrical signal and transmits it to the data acquisition card. One end of the optical detection branch is closed, and the other end is open. A rectangular through hole is formed in the wall of the closed end of the optical detection branch to facilitate the passage of high-temperature, high-speed airflow. The outer wall of the open end of the optical detection branch is machined into a threaded structure for easy installation on the high-temperature alloy mounting base. The laser emitted by the tunable diode laser passes through the high-temperature target airflow in the optical detection branch and is received by the photodetector. The static temperature of the airflow at the measurement point is calculated using the dual-color thermometry method in laser absorption spectroscopy. There are two through threaded holes at the center of the high-temperature alloy mounting base for installing the optical detection branch and the thermocouple branch, respectively. A 6mm through hole is machined at each of the four corners of the high-temperature alloy mounting base for installing the cage-like support rod. Two 3mm threaded holes are machined on the side walls of the four through holes of the high-temperature alloy mounting base for fixing the cage-like support rod. The specific implementation process is as follows:

[0008] Step 1: A type B thermocouple is inserted into the thermocouple branch tube, forming a measurement point at the end of the branch tube. This measurement point is close to the rectangular through hole on the wall of the optical detection branch tube. It is approximately assumed that the thermocouple and laser absorption spectroscopy temperature measurement techniques are measuring the same point. The temperature measured by the type B thermocouple is the total temperature T of the high-temperature, high-speed flow field. * The temperature value is converted into an electrical signal by a temperature transmitter and transmitted to the data acquisition card.

[0009] Step Two: The signal generator produces a sawtooth wave signal to modulate two tunable diode lasers. The two tunable diode lasers alternately generate laser light using a time-division multiplexing strategy, with each sawtooth wave laser signal covering one absorption line of the target gas. The tunable lasers generated by the two tunable diode lasers are combined using a fiber optic coupler, and then... i This indicates the initial light intensity of the tunable diode laser.

[0010] Step 3: The combined laser beam is collimated using a fiber optic collimator. The collimated combined laser beam first passes through a parabolic mirror with a 3mm diameter central aperture, then enters the optical detection branch. After being reflected at the closed end of the optical detection branch, it is converged and reflected again by the parabolic mirror with the 3mm diameter central aperture onto the photosensitive surface of the photodetector. The detection signal can be represented as:

[0011] I t (t)=I i exp(-α(v(t))) (1)

[0012] Where α(v(t)) is the absorptivity of the target gas in the flow field, which can be expressed as:

[0013]

[0014] Where P is the gas pressure at the measurement point in the flow field, L is the absorption path length of the target gas in the flow field, X(l) is the mole volume fraction of the target gas in the flow field, T(l) is the temperature at the measurement point in the flow field, and S[T(l)] is the spectral intensity of the selected absorption line, which depends only on the temperature. It is the line shape function of the absorption spectral line, which satisfies the normalization condition, and l represents the position on the absorption path.

[0015] Step 4: Obtain the initial laser intensity I through data fitting. i By selecting the non-absorption regions q1 and q2 on both sides of the absorption peak of the spectral line, and fitting the light intensity data of the non-absorption regions q2 and q2, a baseline I without absorption terms is obtained. i ; after obtaining baseline I i Then, the absorption rate curve a(v) is calculated by formula (1) in step three.

[0016] Step 5: The tunable diode laser at the target gas absorption line α i The integral absorption area A at (v) is... i satisfy:

[0017]

[0018] Where i = 1 or 2 represents the laser's serial number. If the gas pressure, temperature, and target gas concentration are uniformly distributed along the path length, then the ratio of the integrated absorption areas of the two absorption lines is a single-valued function of temperature.

[0019]

[0020] After obtaining the integrated absorption areas of the two absorption lines, the gas temperature at the measurement point is calculated using colorimetry. This temperature represents the static temperature T of the gas flow in the flow field. sBased on the formula: Total temperature of airflow = Dynamic temperature + Static temperature, the dynamic temperature (T) of the airflow in the flow field can be calculated. d =T * -T s .

[0021] Step Six: In a high-temperature, high-speed flow field, the Mach number Ma of the airflow is related to the total temperature and static temperature of the airflow, and can be expressed as:

[0022]

[0023] Where k is the fluid parameter specific heat ratio, which is generally considered a constant. After calculating the Mach number of the airflow according to (5), the flow velocity V of the airflow at the measurement point is calculated according to the definition of the Mach number.

[0024] V = Ma·c (6)

[0025] Where c is the local speed of sound, its expression is:

[0026]

[0027] Where R is the gas constant, which is a known quantity.

[0028] The advantages of this invention are: by combining laser absorption spectroscopy temperature measurement technology and thermocouple temperature measurement technology, it is possible to simultaneously measure the total temperature, static temperature, dynamic temperature and flow velocity of high-temperature and high-speed airflow, which can be widely used in fields such as gas turbines and aero engines. (iv) Description of the attached drawings

[0029] Figure 1 This is a structural diagram of the device used for absorption spectroscopy and thermocouple measurements.

[0030] Figure 2 This is a view of the optical detection branch.

[0031] Figure 3 This is a view of the thermocouple branch pipe.

[0032] Figure 4 View of the high-temperature alloy mounting bracket. (V) Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings. The present invention provides a system for simultaneously measuring the total temperature, static temperature, dynamic temperature, and flow velocity of a high-temperature, high-speed airflow. The measuring device is as follows: Figure 1 As shown, the measuring device includes a signal generator 1, a tunable diode laser 2, a tunable diode laser 3, a fiber optic coupler 4, a collimating lens 5, a parabolic mirror 6, a temperature transmitter 7, a type B thermocouple 8, a high-temperature alloy mounting base 9, a thermocouple branch tube 10, an optical detection branch tube 11, a photodetector 12, and a data acquisition card 13, wherein:

[0034] The signal generator 1 is connected to the tunable diode laser 2 and the tunable diode laser 3. The signal generator 1 generates a sawtooth wave signal to modulate the tunable diode laser 2 and the tunable diode laser 3. The tunable diode laser 2 and the tunable diode laser 3 alternately generate lasers using a time-division multiplexing strategy. Each sawtooth wave laser signal covers one absorption line of the target gas.

[0035] The lasers generated by the tunable diode laser 2 and the tunable diode laser 3 are combined using a fiber optic coupler 4. After being collimated by a collimating lens 5, the combined laser first passes through a parabolic reflector 6 with a central aperture, and then enters the optical detection branch 11. After being reflected at the closed end of the optical detection branch 11, it is then converged and reflected again by the parabolic reflector 6 onto the photosensitive surface of the photodetector 12. The optical detection branch 11 is shown in the figure below. Figure 2 As shown.

[0036] The type B thermocouple 8 is inserted into the thermocouple branch tube 10, forming a measuring point at the end of the thermocouple branch tube 10. This measuring point is close to a rectangular through hole on the wall of the optical detection branch tube 11. The signal end of the type B thermocouple 8 is connected to the temperature transmitter 7. The thermocouple branch tube 10 is shown in the figure below. Figure 3 As shown.

[0037] The thermocouple branch 10 and the optical detection branch 11 are mounted on the high-temperature alloy mounting base 9, as shown in the view below. Figure 4 As shown.

[0038] The data acquisition card 13 acquires the laser absorption spectrum signal measured by the photodetector 12 and the temperature signal measured by the type B thermocouple 8 obtained by the temperature transmitter 7, which are used for the subsequent extraction of the total temperature, static temperature, dynamic temperature and flow velocity of the airflow in the high temperature and high speed flow field.

[0039] The center wavelengths of tunable diode laser 2 and tunable diode laser 3 are determined according to the type of gas molecules selected for the test, such as water vapor at 1342nm, 1392nm, etc.

[0040] A system for simultaneously measuring total temperature, static temperature, dynamic temperature, and flow velocity of a high-temperature, high-speed airflow, specifically implemented by the following steps:

[0041] Step 1: A type B thermocouple 8 is inserted into the thermocouple branch tube 10, forming a measurement point at the end of the thermocouple branch tube 10. This measurement point is close to the rectangular through hole on the wall of the optical detection branch tube 11. It is approximately assumed that the thermocouple and laser absorption spectroscopy temperature measurement technology are measuring the same point. The temperature measured by the type B thermocouple 8 is the total temperature T of the combustion flow field. * The temperature value is converted into an electrical signal by a temperature transmitter 7 and transmitted to the data acquisition card 13.

[0042] Step 2: Signal generator 1 generates a sawtooth wave signal to modulate tunable diode lasers 2 and 3. Tunable diode lasers 2 and 3 alternately generate lasers using a time-division multiplexing strategy, with each sawtooth wave laser signal covering one absorption line of the target gas. The tunable lasers generated by tunable diode lasers 2 and 3 are combined using an optical fiber coupler 4, and then... i This indicates the initial light intensity of the tunable diode laser.

[0043] Step 3: The combined laser beam is collimated using a fiber optic collimator 5. The collimated combined laser beam first passes through a parabolic reflector 6 with a central 3mm diameter aperture, then enters the optical detection branch 11. After being reflected at the closed end of the optical detection branch 11, it is then converged and reflected again by the parabolic reflector 6 onto the photosensitive surface of the photodetector 12. The detection signal can be expressed as:

[0044] I t (t)=I i exp(-α(v(t))) (1)

[0045] Where α(v(t)) is the absorptivity of the target gas in the flow field, which can be expressed as:

[0046]

[0047] Where P is the gas pressure at the measurement point in the flow field, L is the absorption path length of the target gas in the flow field, X(l) is the mole volume fraction of the target gas in the flow field, T(l) is the temperature at the measurement point in the flow field, and S[T(l)] is the spectral intensity of the selected absorption line, which depends only on the temperature. It is the line shape function of the absorption spectral line, which satisfies the normalization condition, and l represents the position on the absorption path.

[0048] Step 4: Obtain the initial laser intensity I through data fitting. i By selecting the non-absorption regions q1 and q2 on both sides of the absorption peak of the spectrum, and fitting the light intensity data of the non-absorption regions q1 and q2, a baseline I without absorption terms is obtained. i ; after obtaining baseline I i Then, the absorption rate curve a(v) is calculated by formula (1) in step three.

[0049] Step 5: The tunable diode laser at the target gas absorption line α i The integral absorption area A at (v) is... i satisfy:

[0050]

[0051] Where i = 1 or 2 represents the laser's serial number. If the gas pressure, temperature, and target gas concentration are uniformly distributed along the path length, then the ratio of the integrated absorption areas of the two absorption lines is a single-valued function of temperature.

[0052]

[0053] After obtaining the integrated absorption areas of the two absorption lines, the gas temperature at the measurement point is calculated using colorimetry. This temperature represents the static temperature T of the gas flow in the flow field. s The dynamic temperature T of the airflow in the flow field can be calculated based on the formula: total temperature of airflow = dynamic temperature + static temperature. d =T * -T s .

[0054] Step Six: In a high-temperature, high-speed flow field, the Mach number Ma of the airflow is related to the total temperature and static temperature of the airflow, and can be expressed as:

[0055]

[0056] Where k is the fluid parameter specific heat ratio, which is generally considered a constant. After calculating the Mach number of the airflow according to (5), the flow velocity V of the high-temperature airflow at the measurement point is calculated according to the definition of Mach number.

[0057] V = Ma·c (6)

[0058] Where c is the local speed of sound, its expression is:

[0059]

[0060] Where R is the gas constant, which is a known quantity.

[0061] The above description of the present invention and its embodiments is not limited thereto, and the accompanying drawings are merely one embodiment of the present invention. Any structure or embodiment similar to this technical solution designed without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A system for synchronously measuring total temperature, static temperature, dynamic temperature, and flow velocity of a high-temperature, high-speed airflow, the system comprising a type B thermocouple, a temperature transmitter, two tunable diode lasers, a signal generator, a fiber optic coupler, a collimating lens, a parabolic reflector, a photodetector, a data acquisition card, a high-temperature alloy mounting base, thermocouple branches, optical detection branches, and cage-type mounting accessories; wherein: The measurement system uses thermocouples and laser absorption spectroscopy to measure the total temperature and static temperature of the airflow at the test point in the flow field, respectively. Then, based on the relationship between the total temperature, static temperature, dynamic temperature, and velocity of the airflow in the flow field, the dynamic temperature and velocity of the airflow at the test point are calculated. When the measuring probe is inserted into the high-temperature, high-speed flow field, the airflow passes sequentially through an optical detection branch and a thermocouple branch mounted on a high-temperature alloy mounting base. The optical detection branch uses laser absorption spectroscopy to measure the static temperature of the airflow at the test point, while the thermocouple branch uses a type B thermocouple to measure the total temperature of the airflow at the test point. Both ends of the thermocouple branch are open, with one end having a threaded outer wall for easy installation on the high-temperature alloy mounting base. A type B thermocouple is inserted into the thermocouple branch, forming a measurement point at the unthreaded end of the branch. A temperature transmitter converts the temperature measured by the thermocouple into an electrical signal and transmits it to the data acquisition card. One end of the optical detection branch is sealed. The optical detection branch tube is closed at one end and open at the other. A rectangular through hole is formed on the wall of the closed end of the optical detection branch tube to facilitate the passage of high-temperature, high-speed airflow through the optical detection branch tube. The outer wall of the open end of the optical detection branch tube is machined into a threaded structure for easy installation on a high-temperature alloy mounting base. The laser emitted by the tunable diode laser passes through the high-temperature target airflow in the optical detection branch tube and is received by the photodetector. The static temperature of the airflow at the test point is calculated using the dual-color thermometry method in laser absorption spectroscopy. There are two through threaded holes at the center of the high-temperature alloy mounting base for installing the optical detection branch tube and the thermocouple branch tube, respectively. There is a 6mm through hole at each of the four corners of the high-temperature alloy mounting base for installing the support rod of the cage structure. There are two 3mm threaded holes on the side wall of the four through holes of the high-temperature alloy mounting base for fixing the support rod of the cage structure. The feature is that it includes the following steps: Step one: a B-type thermocouple is inserted into the thermocouple branch pipe, and a measuring point is formed at the end of the thermocouple branch pipe, which is close to the rectangular through hole on the wall of the optical detection branch pipe. It is approximately considered that the thermocouple and the laser absorption spectrum temperature measurement technology measure the same measured point; the temperature measured by the B-type thermocouple is the total temperature T of the high-temperature high-speed flow field * , which is converted into an electrical signal by a temperature transmitter and transmitted to a data acquisition card; Step two: the signal generator generates sawtooth wave signals to modulate the two tunable diode lasers, the two tunable diode lasers alternately generate laser light by using time division multiplexing strategy, each sawtooth wave laser signal covers an absorption spectral line of the target gas, the tunable lasers generated by the two tunable diode lasers are combined by using a fiber coupler, and the combined laser light is used as the excitation light source of the target gas i represents the initial light intensity of the tunable diode laser; Step 3: The combined laser beam is collimated using a fiber optic collimator. The collimated combined laser beam first passes through a parabolic mirror with a 3mm diameter central aperture, then enters the optical detection branch. After being reflected at the closed end of the optical detection branch, it is converged and reflected again by the parabolic mirror with the 3mm diameter central aperture onto the photosensitive surface of the photodetector. The detection signal can be represented as: l(t)=lexp(-α(v(t)))(1) Where α(v(t)) is the absorptivity of the target gas in the flow field, which can be expressed as: Where P is the gas pressure at the measurement point in the flow field, L is the absorption path length of the target gas in the flow field, X(l) is the mole volume fraction of the target gas in the flow field, T(l) is the temperature at the measurement point in the flow field, and S[T(l)] is the spectral intensity of the selected absorption line, which depends only on the temperature. It is the line shape function of the absorption spectral line, which satisfies the normalization condition, and l represents the position on the absorption path; Step 4: Obtain the initial laser intensity I through data fitting. i By selecting the non-absorption regions q1 and q2 on both sides of the absorption peak of the spectrum, and fitting the light intensity data of the non-absorption regions q1 and q2, a baseline I without absorption terms is obtained. i ; after obtaining baseline I i Then, the absorption rate curve a(v) is calculated using formula (1) in step three; Step 5: The tunable diode laser at the target gas absorption line α i The integral absorption area A at (v) is... i satisfy: Where i = 1 or 2 represents the laser's serial number. If the gas pressure, temperature, and target gas concentration are uniformly distributed along the path length, then the ratio of the integrated absorption areas of the two absorption lines is a single-valued function of temperature. After obtaining the integrated absorption areas of the two absorption lines, the gas temperature at the measurement point is calculated using colorimetry. This temperature represents the static temperature T of the gas flow in the flow field. s The dynamic temperature T of the airflow in the flow field can be calculated based on the formula: total temperature = dynamic temperature + static temperature. d =T * -T s ; Step Six: In a high-temperature, high-speed flow field, the Mach number Ma of the airflow is related to the total temperature and static temperature of the airflow, and can be expressed as: Where k is the fluid parameter specific heat ratio, which is generally considered a constant. After calculating the Mach number of the airflow according to (5), the flow velocity V of the airflow at the measurement point is calculated according to the definition of the Mach number. V = Ma·c (6) Where c is the local speed of sound, its expression is: Where R is the gas constant, which is a known quantity.

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