CN110095248B - High-frequency induction wind tunnel flow field imbalance diagnosis system and method - Google Patents

High-frequency induction wind tunnel flow field imbalance diagnosis system and method Download PDF

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CN110095248B
CN110095248B CN201910349198.7A CN201910349198A CN110095248B CN 110095248 B CN110095248 B CN 110095248B CN 201910349198 A CN201910349198 A CN 201910349198A CN 110095248 B CN110095248 B CN 110095248B
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signal
flow field
optical fiber
laser signal
laser
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CN110095248A (en
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林鑫
李飞
余西龙
欧东斌
曾徽
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Guangdong Aerospace Science And Technology Research Institute Nansha
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Institute of Mechanics of CAS
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01MTESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M9/00Aerodynamic testing; Arrangements in or on wind tunnels
    • G01M9/02Wind tunnels
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01MTESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M9/00Aerodynamic testing; Arrangements in or on wind tunnels
    • G01M9/06Measuring arrangements specially adapted for aerodynamic testing
    • G01M9/062Wind tunnel balances; Holding devices combined with measuring arrangements
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01MTESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M9/00Aerodynamic testing; Arrangements in or on wind tunnels
    • G01M9/06Measuring arrangements specially adapted for aerodynamic testing
    • G01M9/065Measuring arrangements specially adapted for aerodynamic testing dealing with flow
    • G01M9/067Measuring arrangements specially adapted for aerodynamic testing dealing with flow visualisation

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Abstract

The embodiment of the invention relates to a high-frequency induction wind tunnel flow field unbalance diagnosis system, which comprises: a test device, a first diagnostic unit and a second diagnostic unit; the collimator of the first diagnostic unit emits a laser signal, the laser signal is transmitted by the testing device after passing through a flow field of the testing device, and the transmitted laser signal is received by the receiver of the first diagnostic unit so as to acquire the translation temperature in the flow field; the second diagnostic unit collects the radiance in the flow field to obtain the electron temperature in the flow field in the test device. The system further comprises: and the signal trigger unit is used for controlling the first diagnosis unit and the second diagnosis unit. Therefore, the synchronous measurement of the electronic temperature and the translation temperature of the high-temperature flow field in the high-frequency induction plasma heater and after passing through the spray pipe can be realized, and further the quantitative evaluation of the unbalanced characteristic of the flow field of the high-frequency induction plasma heating wind tunnel can be realized.

Description

High-frequency induction wind tunnel flow field imbalance diagnosis system and method
Technical Field
The embodiment of the invention relates to the field of research on ground aerodynamic thermal tests of aircrafts, in particular to a high-frequency induction wind tunnel flow field imbalance diagnosis system and method.
Background
The high-frequency induction plasma heater does not have the inherent electrode ablation phenomenon of the traditional electric arc heater, can provide a chemically pure high-temperature flow field, and is an important test platform in the research fields of the surface catalytic property of a heat-proof material with strict requirements on the hot environment atmosphere, the real gas effect, the aerodynamic thermal assessment of the heat-proof material for deep space exploration (Mars, Venus, Titan and the like), and the like. The high-frequency induction plasma heater transmits energy to gas in a high-frequency induction-coupling mode to ionize the gas and generate high-temperature plasma, the unique heating mode enables the flow field of the high-frequency induction plasma heating wind tunnel to be greatly different from the flow field of the traditional electric arc wind tunnel, and the electron temperature in the flow field of the high-frequency induction plasma heating wind tunnel is obviously higher than the translation temperature, namely the high-frequency induction plasma heater has a typical unbalanced characteristic. Therefore, the traditional diagnosis methods for measuring macroscopic parameters of the electric arc wind tunnel flow field, such as total temperature, heat flow, pressure and the like, cannot meet the research requirements in the fields, research on the unbalanced phenomenon in the physical and chemical processes needs to be developed, a reliable and effective novel measurement technology needs to be developed, quantitative diagnosis of parameters such as electronic temperature, translation temperature and the like of the respective temperature ranges is deeply achieved, and effective evaluation of the unbalanced characteristic of the high-frequency induction plasma heating wind tunnel flow field is further achieved.
Disclosure of Invention
The invention provides a high-frequency induction wind tunnel flow field unbalance diagnosis system and method, which can realize effective evaluation of high-frequency induction plasma heating wind tunnel flow field unbalance characteristics through quantitative measurement of high-temperature airflow electronic temperature and translation temperature.
In a first aspect, a high-frequency induction wind tunnel flow field imbalance diagnosis system is provided, which includes: a test device, a first diagnostic unit and a second diagnostic unit;
the collimator of the first diagnostic unit emits a laser signal, the laser signal is transmitted by the testing device after passing through a flow field of the testing device, and the transmitted laser signal is received by the receiver of the first diagnostic unit so as to acquire the translation temperature in the flow field;
the second diagnosis unit collects the radiation luminescence in the flow field to obtain the electronic temperature in the flow field in the test device;
the system further comprises: and the signal trigger unit is used for controlling the first diagnosis unit and the second diagnosis unit.
In one possible embodiment, the assay device comprises: the device comprises a high-frequency plasma heater, a spray pipe and a test chamber;
the high-frequency induction plasma heater is connected with the test chamber through the spray pipe and used for enabling plasma generated in the high-frequency induction plasma heater to form a flow field for test model examination in the test chamber through the spray pipe, and the test chamber is provided with a plurality of optical detection windows.
In one possible embodiment, the first diagnostic unit comprises: the system comprises a TDLAS signal modulation and data processing module, a controller, a semiconductor laser, an optical fiber coupler, an F-P interferometer, a collimator and a photoelectric detector;
the TDLAS signal modulation and data processing module is used for receiving a first instruction output by the signal trigger unit and sending a control signal generated according to the first instruction to the controller;
the controller is used for tuning a laser signal to be output in the semiconductor laser according to the control signal;
the semiconductor laser is used for outputting a laser signal to the optical fiber coupler;
the optical fiber coupler is used for dividing the laser signal into a first laser signal and a second laser signal, wherein the first laser signal is transmitted to the collimator through a first optical fiber, the collimator transmits the first laser signal to a flow field in the test device and then transmits the first laser signal through the test device, the transmitted first laser signal is received by the receiver, the receiver transmits the first laser signal to the photoelectric detector through a third optical fiber to perform conversion of a transmitted light intensity signal, and the photoelectric detector is also used for transmitting the transmitted light intensity signal to the TDLAS signal modulation and data processing module;
the optical fiber coupler is also connected with the F-P interferometer through a second optical fiber and is used for transmitting the second laser signal to the F-P interferometer for time scale-wavelength scale relation calibration, and the F-P interferometer is also used for sending the calibrated time scale-wavelength scale relation to the TDLAS signal modulation and data processing module;
and the TDLAS signal modulation and data processing module is also used for determining a translation temperature value in the flow field according to the received relation between the time scale and the wavelength scale and the transmission light intensity signal.
In one possible embodiment, the second diagnostic unit comprises: the device comprises a data analysis module, a spectrometer and an acquisition module;
the data analysis module is used for receiving a second instruction output by the signal trigger unit and sending the second instruction to the spectrometer;
the spectrometer is used for controlling the acquisition module according to the second instruction;
the collection module is used for collecting the radiant luminescence of a plurality of measuring points in a flow field and transmitting the radiant luminescence to the spectrometer through a fourth optical fiber;
the spectrometer is also used for converting the radiant luminescence into a corresponding spectral image and sending the spectral image to the data analysis module;
and the data analysis module is also used for determining the electronic temperature value at the measuring point according to the relation between the spectral line radiation intensity and the corresponding spectral line high-level energy.
In one possible embodiment, the first optical fiber and the second optical fiber are single mode optical fibers, the third optical fiber is a multimode optical fiber, and the fourth optical fiber is a silica optical fiber.
In a second aspect, the present invention further provides a method for diagnosing imbalance of a flow field of a high frequency induction wind tunnel, which adopts a system for diagnosing imbalance of a flow field of a high frequency induction wind tunnel, and comprises the following steps:
plasma generated in the high-frequency induction plasma heater forms a flow field for checking a test model in the test chamber through the spray pipe;
acquiring a translation temperature value in the flow field through a first diagnostic unit;
acquiring an electronic temperature value within the flow field by a second diagnostic unit;
and effectively evaluating the unbalance of the flow field according to the translation temperature value and the electronic temperature value.
In one possible implementation manner, the DLAS signal modulation and data processing module receives a first instruction output by a signal trigger unit, generates a control signal according to the first instruction, and sends the control signal to the controller;
the controller tunes a laser signal to be output in the semiconductor laser according to the control signal;
the semiconductor laser outputs a laser signal to the optical fiber coupler;
the optical fiber coupler divides the laser signal into a first laser signal and a second laser signal, wherein the first laser signal is transmitted to a collimator, the collimator transmits the first laser signal to a flow field in the test device and then transmits the first laser signal through the test device, the transmitted first laser signal is received by the receiver, the first laser signal is transmitted to the photoelectric detector through a third optical fiber to convert a transmission light intensity signal, and the transmission light intensity signal is transmitted to the TDLAS signal modulation and data processing module through the photoelectric detector;
the optical fiber coupler transmits the second laser signal to the F-P interferometer for time scale-wavelength scale relation calibration, and the F-P interferometer sends the calibrated time scale-wavelength scale relation calibration to the TDLAS signal modulation and data processing module;
and the TDLAS signal modulation and data processing module determines a translation temperature value in the flow field according to the received relation between the time scale and the wavelength scale and the transmission light intensity signal.
In a possible embodiment, the TDLAS signal modulation and data processing module determines a translational temperature value in a flow field according to the received relationship between the time scale and the wavelength scale and the transmitted light intensity signal, and specifically includes:
and the TDLAS signal modulation and data processing module extracts a baseline signal based on the transmission light intensity signal, compares the transmission light intensity signal with the baseline signal and takes a logarithm as a fitting object to perform Gauss curve fitting.
Converting the time domain and the frequency domain of the transmitted light intensity signal through the received relation between the time scale and the wavelength scale to obtain the Doppler broadening of a curve, and acquiring a translation temperature mean value along the optical path according to the relation between the Doppler broadening and the translation temperature;
the relationship between the Doppler broadening and the translation temperature is as follows:
Figure BDA0002043381180000051
wherein: c is the speed of light, M is the molar mass of the absorbing component, and k is glassZeeman constant, v0The center frequency of the atomic absorption line.
In a possible embodiment, obtaining, by the second diagnostic unit, an electronic temperature value within the flow field specifically includes:
the data analysis module receives a second instruction output by the signal trigger unit and sends the second instruction to the spectrometer;
the spectrometer controls the acquisition module according to the second instruction;
the collection module collects the radiant luminescence of a plurality of measuring points in the flow field and transmits the radiant luminescence to the spectrometer;
the spectrometer converts the radiant luminescence into a corresponding spectral image and sends the spectral image to the data analysis module;
and the data analysis module determines the electronic temperature value at the measuring point according to the relation between the spectral line radiation intensity and the corresponding spectral line high-level energy.
In one possible embodiment, the data analysis module is configured to, based on the relationship between the spectral line radiation intensity and the corresponding spectral line high-level energy:
Figure BDA0002043381180000052
wherein λ is the center wavelength of the spectral line, gkIs the degeneracy of high energy level of spectral line, A is the Einstein spontaneous emissivity coefficient of spectral line, k is Boltzmann constant, TeIs the electron temperature at the measurement point, C is a constant;
the determining the electronic temperature value at the measurement point specifically includes:
taking spectrograms corresponding to a plurality of measuring points as background spectrums when the test device does not work;
subtracting the background spectrum from the spectrograms corresponding to the plurality of measuring points when the test device works to obtain a spectrogram without background interference;
selecting a plurality of spectral lines in the spectrogram without background interference, determining elements corresponding to each spectral line and a spectral constant thereof, selecting a target element to perform fitting integration on the target element, and obtaining an integrated intensity value of the corresponding spectral line;
and obtaining the electronic temperature value of the measuring point by adopting a boltzmann plotting method according to the plurality of spectral lines of the target element.
Has the advantages that:
the wind tunnel flow field characteristic diagnosis system and method provided by the embodiment of the invention realize synchronous measurement of the electronic temperature and the translation temperature of the high-temperature flow field in the high-frequency induction plasma heater and after passing through the spray pipe, and further can realize quantitative evaluation of the non-equilibrium characteristic of the high-frequency induction plasma heating wind tunnel flow field.
The method is based on a non-contact spectroscopy measurement means, does not interfere the operation of the wind tunnel, can be very helpful for deepening the understanding of the flow field characteristics of the high-frequency induction plasma in online quantitative diagnosis of the electron temperature and the translation temperature, and provides a direct quantitative evaluation basis for the interrelation of the flow field characteristics with power supply parameters, gas medium parameters and gas quantity parameters in the operation of the high-frequency induction plasma heater.
The invention relates to the coupling of two measurement technologies of an emission spectrum temperature measurement technology and a laser absorption spectrum technology, and the complementation of measurement data, which is a great innovation for the application of the existing high-frequency induction plasma flow field diagnosis technology, in particular to the prior verification for ensuring the operation reliability of a spectrum diagnosis system under the severe measurement environment of a megawatt high-frequency induction plasma heating wind tunnel.
The invention can realize the two-dimensional distribution of electron temperature and translation temperature on the cross section of the plasma flow field by adopting the displacement mechanism, and can be directly used for evaluating the uniformity of the high-frequency induction plasma flow field.
Drawings
FIG. 1 is a schematic diagram of a systematic diagnosis of flow field imbalance of a high frequency induction wind tunnel according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a spectral diagnostic system provided in an embodiment of the present invention;
fig. 3 is a flowchart of a method for diagnosing imbalance of a flow field of a high-frequency induction wind tunnel according to an embodiment of the present invention;
FIG. 4 shows a plurality of measurement cycles of transmitted laser signals obtained by a second diagnostic unit in an embodiment of the present invention;
FIG. 5 is a chart of atomic oxygen and nitrogen spectra at a certain measurement point collected by the first diagnostic unit in the embodiment of the present invention;
FIG. 6 is a graph illustrating the integrated intensity processing of the 777.2nm emission spectrum of an oxygen atom in an example of the present invention;
FIG. 7 is an electron temperature and translational temperature distribution of high temperature air flow under a set of operating conditions of a wind tunnel flow field in an embodiment of the present invention;
notation of the reference numerals:
the system comprises a high-frequency induction plasma heater, a 2-spray pipe, a 3-optical detection window, a 4-spectrum diagnosis device, a 5-second diagnosis unit, a 6-first diagnosis unit, a 7-signal trigger synchronization unit, an 8-displacement mechanism, a 9-radiation collection lens, a 10-quartz optical fiber, an 11-spectrometer, a 12-data analysis module, a 13-TDLAS signal modulation and data processing module, a 14-controller, a 15-semiconductor laser, a 16-optical fiber coupler, a 17-single-mode optical fiber, an 18-F-P interferometer, a 19-collimator, a 20-receiver, a 21-multimode optical fiber and a 22-photoelectric detector.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, technical methods in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any creative effort, shall fall within the scope of the present invention.
It should be noted that, if directional indications (such as up, down, left, right, front, back, etc.) are involved in the embodiment of the present invention, the directional indications are only used for explaining the relative positional relationship between the components in a certain posture, the motion situation, etc., and if the certain posture is changed, the directional indications are changed accordingly.
Taking a 1MW high frequency induction plasma heating wind tunnel as an example, as shown in fig. 1, a high frequency induction plasma heating wind tunnel flow field imbalance diagnosis system includes: a test device and a spectral diagnostic device 4.
In this embodiment, the test apparatus includes: the device comprises a high-frequency induction plasma heater 1, a spray pipe 2, a test chamber and a vacuum system.
The high-frequency induction plasma heater 1 is connected with the test chamber through the spray pipe 2 and used for enabling plasma generated in the high-frequency induction plasma heater 1 to form a flow field in the test chamber through the spray pipe 2, and the test chamber is further connected with a vacuum system used for collecting air flow;
the test chamber is provided with a plurality of optical detection windows 3, and a spectrum diagnosis device 4 for evaluating the unbalance of the flow field is arranged outside the optical detection windows 3.
In the embodiment, the high-frequency induction plasma heater induces an alternating electric field through an alternating magnetic field generated by current loaded in a water-cooling copper coil outside a quartz tube, so that a test gas medium entering the high-frequency induction plasma heater is heated, the gas is ionized, and high-temperature plasma is generated; and a high-temperature flow field which can be used for test model examination is formed after passing through the spray pipe, and the airflow passing through the test model is collected by a vacuum system.
In this embodiment, fig. 2 is a schematic diagram of a spectral diagnostic system provided in an embodiment of the present invention, and as shown in fig. 2, the spectral diagnostic apparatus 4 includes: a first diagnostic unit 6, a second diagnostic unit 5 and a signal triggering unit 7.
The first diagnostic unit 6 includes: a TDLAS signal modulation and data processing module 13, a controller 14, a semiconductor laser 15, an optical fiber coupler 16, an F-P interferometer 17, a collimator 19, a receiver 20 and a photoelectric detector 20;
the TDLAS signal modulation and data processing module 13 is configured to receive the first instruction output by the signal triggering unit 7, generate a control signal according to the first instruction, and send the control signal to the controller 14;
wherein, the control signal can be a periodic sawtooth wave or a sine signal.
A controller 14 for tuning a wavelength of a laser signal to be output in the semiconductor laser 15 according to a control signal;
the wavelength of the tuned laser signal is specifically as follows: the size and the frequency of the tuning current can be respectively changed by changing the amplitude and the frequency of the sawtooth wave or the sine signal, on the other hand, the wavelength of the laser signal output by the semiconductor laser is changed by the controller through temperature modulation, and the required central wavelength and the tuning wavelength range of the semiconductor laser can be obtained through coupling of the two modes.
A semiconductor laser 15 for outputting a laser signal to the optical fiber coupler 16;
the line width of a semiconductor laser spectral line is less than 10MHz, the central wavelength is 777.19nm, and the line width is at least one of the following: a DFB type semiconductor laser, an external cavity semiconductor laser or a VCSEL type semiconductor laser.
The optical fiber coupler 16 is used for dividing a laser signal into a first laser signal and a second laser signal, and transmitting the first laser signal to the collimator 19 through a first optical fiber, wherein the first optical fiber is a single-mode optical fiber 17, the length of the single-mode optical fiber is 5-10m, the core diameter of the single-mode optical fiber is 0.4mm, and the central wavelength of the single-mode optical fiber is 780 nm; a 650-plus 1050nm antireflection film is arranged in the collimator 19 and is used for adjusting the first laser signal into high-collimation laser and transmitting the high-collimation laser, the first laser signal is transmitted by the testing device after passing through a flow field of the testing device, the transmitted first laser signal is received by the receiver 20, a narrow-band filter is arranged in the receiver 20 and is used for filtering background radiation on the first laser signal, the bandwidth of the narrow-band filter is 2-10nm, the central wavelength of the filter is 780nm, the receiver 20 also transmits the first laser signal to the photoelectric detector 22 through a third optical fiber, wherein the third optical fiber is a multimode optical fiber 21, the length of the multimode optical fiber is 5-10m, the core diameter is 0.4mm, and the central wavelength is 780 nm; the photodetector 22 is configured to convert the first laser signal into a transmission light intensity signal, and transmit the transmission light intensity signal to the TDLAS signal modulation and data processing module 13; the photoelectric detector is a silicon-based or indium gallium arsenic photoelectric detector.
The optical fiber coupler 16 is further connected to the F-P interferometer 18 through a second optical fiber, and is configured to transmit a second laser signal to the F-P interferometer 18 for time scale-wavelength scale relationship calibration, and the F-P interferometer 18 is further configured to send the calibrated time scale-wavelength scale relationship calibration to the TDLAS signal modulation and data processing module 13; wherein the second optical fiber is a single mode optical fiber, the length of the second optical fiber is 5-10m, the core diameter is 0.4mm, and the central wavelength is 780 nm.
The TDLAS signal modulation and data processing module 13 is further configured to obtain a translation temperature value in the flow field according to the received relationship between the time scale and the wavelength scale and the transmitted light intensity signal.
Here, it should be noted that: the optical fiber coupler 16 is used for splitting the input laser, the splitting ratio is 10:90, the laser occupying 10% of the power is output to the F-P interferometer 18 for calibrating the time domain-frequency domain relation of the laser, and the laser occupying 90% of the power is output to the collimator 19 for flow field diagnosis. The collimator 19 and the receiver 20 are both fixed on the displacement mechanism, and the translation temperature tomography of the plasma flow field section can be realized by combining the displacement mechanism.
The second diagnostic unit includes: a data analysis module 12, a spectrometer 11 and an acquisition module;
the data analysis module 12 is configured to receive the second instruction output by the signal triggering unit 7, and send the second instruction to the spectrometer 11; the spectrometer 11 is used for controlling the acquisition module according to the second instruction; wherein the spectrometer is a common C-T type grating spectrometer or a fiber spectrometer or a echelle spectrometer, the wavelength range covers 500-900nm, and the spectral resolution is less than 0.2 nm. The collection module is used for collecting the radiant luminescence of a plurality of measuring points in the flow field and transmitting the radiant luminescence to the spectrometer 11 through a fourth optical fiber;
wherein, collection module includes displacement mechanism 8 and acquisition lens 9, acquisition lens 9 is fixed in on the displacement mechanism 8, and displacement mechanism 8 is for can following the vertical direction lift, can follow the accurate electronic platform of horizontal direction translation, has good motion accuracy and straightness accuracy, and electronic platform passes through motor drive and follows perpendicular or horizontal orbital motion with predetermined translation speed, and its repeated positioning accuracy is less than 10um, and scanning speed covers 0.5-10mm/s, and concrete parameter can be according to experimental demand settlement. The radiation collecting lens 9 is used for collecting high-temperature gas radiation in a plasma flow field, and can realize the adjustment of a focal length of 1-5m under the condition of fixing a measuring solid angle, wherein the solid angle range is 1-10 mrad. The fourth optical fiber is a quartz optical fiber with the length of 10m and the core diameter of 0.2-0.8 mm.
The spectrometer 11 is further configured to convert the radiant light into a corresponding spectral image, and send the spectral image to the data analysis module 12;
the data analysis module 12 is further configured to obtain an electronic temperature value of the flow field according to the spectral image.
The emission spectrum data analysis module is a general name of a computer and analysis software, the analysis software is an analysis program compatible with a spectrometer development environment, and can be compiled based on C, C + +, Fortran or LabVIEW development environment, and the function is to analyze and process acquired spectrum data on line, perform fitting integration on a plurality of spectral lines and obtain a measuring point electronic temperature value in real time.
Fig. 3 is a flowchart of a method for diagnosing imbalance of a flow field of a high-frequency induction wind tunnel according to an embodiment of the present invention, and as shown in fig. 3, the method includes:
s101, enabling plasma generated in the high-frequency induction plasma heater to form a flow field for checking a test model in a test chamber through a spray pipe;
s102, acquiring a translation temperature value in the flow field through a first diagnosis unit;
the method specifically comprises the following steps:
the TDLAS signal modulation and data processing module receives a first instruction output by a signal trigger unit, generates a control signal according to the first instruction, and sends the control signal to a controller;
the controller tunes a laser signal to be output in the semiconductor laser according to the control signal;
the semiconductor laser outputs a laser signal to the optical fiber coupler;
the optical fiber coupler divides the laser signal into a first laser signal and a second laser signal, wherein the first laser signal is transmitted to a collimator, passes through a flow field through the collimator and is sent to a receiver, the first laser signal is transmitted to a photoelectric detector after being filtered by the receiver, the photoelectric detector converts the first laser signal into a transmission light intensity signal, and transmits the transmission light intensity signal to the TDLAS signal modulation and data processing module;
the optical fiber coupler transmits the second laser signal to the F-P interferometer for time scale-wavelength scale relation calibration, and the F-P interferometer sends the calibrated time scale-wavelength scale relation calibration to the TDLAS signal modulation and data processing module;
the TDLAS signal modulation and data processing module converts the time domain and the frequency domain of the transmitted light intensity signal according to the received time scale-wavelength scale relation to obtain the Doppler broadening of an oxygen atom 777.19nm spectral line, and obtains a translation temperature value along a measuring optical path according to the relation between the Doppler broadening and the translation temperature.
Furthermore, by combining a displacement mechanism, the translation temperature tomography of the plasma flow field section can be realized.
According to the theory of spectral line broadening, the mechanisms causing the spectral line broadening are mainly uniform broadening and non-uniform broadening which are respectively expressed by Lorentz broadening and Gauss broadening. For a typical flow field state of a high-frequency induction plasma heating wind tunnel, the total pressure is several kpa, the total temperature of airflow is more than 5000K, the Gauss broadening influence is far greater than Lorentz broadening under the state, the real line type of the whole absorption spectrum line obtained by using the TDLAS technology can be directly fitted by using the Gauss line type, and then the Gauss broadening delta v is obtainedDUsing Δ vDCan be directly used for calculating translation temperature Ttr
Figure BDA0002043381180000121
Wherein c is the speed of light, M is the molar mass of the absorbing component, k is the Boltzmann constant, v0The center frequency of the atomic absorption line.
The TDLAS signal modulation and data processing module performs time domain and frequency domain conversion on the transmitted light intensity signal through the received time scale-wavelength scale relation to obtain Doppler broadening of an oxygen atom 777.19nm spectral line, and obtains a translation temperature value along a measuring optical path according to the relation between the Doppler broadening and the translation temperature, and the TDLAS signal modulation and data processing module specifically comprises the following steps of:
and the TDLAS signal modulation and data processing module extracts a baseline signal based on the transmission light intensity signal, compares the transmission light intensity signal with the baseline signal and takes a logarithm as a fitting object to perform Gauss curve fitting.
And converting the time domain and the frequency domain of the transmitted light intensity signal through the received relation between the time scale and the wavelength scale to obtain the Doppler broadening of the curve, and acquiring the translation temperature mean value along the optical path according to the relation between the Doppler broadening and the translation temperature.
The baseline signal is data without atomic oxygen spectral line absorption in the single-period transmitted light intensity signal, 5-fold polynomial fitting is carried out to obtain the baseline signal, and the definition of the wavelength range without atomic oxygen spectral line absorption is based on 4-6 times of the full width at half maximum of the atomic oxygen spectral line in the transmitted light intensity signal.
Fig. 4 shows a plurality of measurement periods of transmitted laser signals obtained by the first diagnostic unit in an embodiment of the present invention, where a peak in the graph is a typical absorption peak absorbed by a spectral line to be measured, and a Gauss broadening is obtained by extracting a baseline and Gauss fitting, so that a translation temperature diagnosis can be implemented according to equation (1).
S103, acquiring an electronic temperature value in the flow field through a second diagnosis unit;
the method specifically comprises the following steps:
the data analysis module receives a second instruction output by the signal trigger unit and sends the second instruction to the spectrometer;
the spectrometer controls the acquisition module according to the second instruction;
the collection module collects the radiant luminescence of a plurality of measuring points in the flow field and transmits the radiant luminescence to the spectrometer;
the spectrometer converts the radiant luminescence into a corresponding spectral image and sends the spectral image to the data analysis module;
and the data analysis module calculates the electron temperature at the measuring point according to the relation between the spectral line radiation intensity and the corresponding spectral line high-level energy.
Furthermore, a spectrogram of a plurality of measuring points in a flow field space is obtained by combining a displacement mechanism, so that the electronic temperature distribution of the flow field of the high-frequency induction plasma heating wind tunnel is obtained.
According to the atomic spectrum theory, the integral radiation intensity I of an atomic spectral line and the high-level energy E of the corresponding spectral linekThe relationship between them is as follows:
Figure BDA0002043381180000131
wherein λ is the center wavelength of the spectral line, gkIs the degeneracy of high energy level of spectral line, A is the Einstein spontaneous emissivity coefficient of spectral line, k is Boltzmann constant, TeC is a constant, which is the electron temperature at the measurement point. From formula (2), with EkThe linear relation is formed, and the electron temperature at the measuring point can be calculated by adopting a boltzmann plotting method, namely drawing a straight line graph to calculate the slope based on the spectral intensity of a plurality of emission spectral lines of a certain atom.
Therefore, the method for calculating the electron temperature at the measuring point according to the relation between the radiation intensity of the spectral line and the high-level energy of the corresponding spectral line based on the spectrogram obtained by a single measuring point comprises the following steps:
taking spectrograms corresponding to a plurality of measuring points as background spectrums when the test device does not work;
subtracting the background spectrum from the spectrograms corresponding to the plurality of measuring points when the test device works to obtain a spectrogram without background interference;
selecting a plurality of spectral lines in the spectrogram without background interference, determining elements corresponding to each spectral line and a spectral constant thereof, selecting a target element to perform fitting integration on the target element, and obtaining an integrated intensity value of the corresponding spectral line;
and obtaining the electronic temperature value of the measuring point by adopting a boltzmann plotting method according to the plurality of spectral lines of the target element.
FIG. 5 is a diagram of the second diagnostic unit acquiring atomic oxygen and nitrogen spectra at a certain measurement point according to an embodiment of the present invention. As shown in FIG. 5, based on the extremely high spectral resolution of the spectrometer, the emission lines of oxygen atoms at 615.7nm, 645.6nm, 777.2nm and 844.6nm are clear and isolated, so that the electron temperature measured by the system is guaranteed to have extremely high accuracy, and in addition, the characteristic radiation spectrum of nitrogen atoms with high resolution is captured at the same time, so that the system can be used for electron temperature measurement and can be verified with the measurement result based on the oxygen atoms.
FIG. 6 is a graphical representation of the integrated intensity processing of the 777.2nm emission spectrum for oxygen atoms in one embodiment of the invention. And (3) integrating the fitting data (shown by shading in figure 6) to obtain the intensity I of the oxygen emission spectral line, and obtaining the electron temperature value of the measuring point by obtaining the integral intensity of a plurality of emission spectral lines and adopting a boltzmann plot method.
And S104, evaluating the unbalance of the flow field according to the translation temperature value and the electronic temperature value.
Fig. 7 shows the electron temperature and translational temperature distribution of the high-temperature air flow under a group of operating conditions of the flow field of the high-frequency induction plasma heating wind tunnel, as shown in fig. 7, in the same measurement area, the mean value of the electron temperature is 6650K, the mean value of the translational temperature is 2590K, the electron temperature is obviously higher than the translational temperature, the unbalanced characteristic of the flow field is quantitatively analyzed, and in addition, the device can be used for real-time monitoring of the operating state of the high-frequency induction heater according to the temperature fluctuation characteristic.
The wind tunnel flow field characteristic diagnosis system and method provided by the embodiment of the invention realize synchronous measurement of the electronic temperature and the translation temperature of the high-temperature flow field in the high-frequency induction plasma heater and after passing through the spray pipe, and further realize quantitative evaluation of the non-equilibrium characteristic of the high-frequency induction plasma heating wind tunnel flow field.
The method is based on a non-contact spectroscopy measurement means, does not interfere the operation of the wind tunnel, can be very helpful for deepening the understanding of the flow field characteristics of the high-frequency induction plasma in online quantitative diagnosis of the electron temperature and the translation temperature, and provides a direct quantitative evaluation basis for the interrelation of the flow field characteristics with power supply parameters, gas medium parameters and gas quantity parameters in the operation of the high-frequency induction plasma heater.
The invention relates to the coupling of two measurement technologies of an emission spectrum temperature measurement technology and a laser absorption spectrum technology, and the complementation of measurement data, which is a great innovation for the application of the existing high-frequency induction plasma flow field diagnosis technology, in particular to the prior verification for ensuring the operation reliability of a spectrum diagnosis system under the severe measurement environment of a megawatt high-frequency induction plasma heating wind tunnel.
The invention can realize the two-dimensional distribution of electron temperature and translation temperature on the cross section of the plasma flow field by adopting the displacement mechanism, and can be directly used for evaluating the uniformity of the high-frequency induction plasma flow field.
The embodiments of the present invention have been described in detail, but the present invention is not limited to the embodiments described above as examples. It will be appreciated by those skilled in the art that various equivalent changes and modifications can be made without departing from the spirit and scope of the invention, and it is intended to cover all such modifications and alterations as fall within the true spirit and scope of the invention.

Claims (1)

1. A high-frequency induction wind tunnel flow field unbalance diagnosis method adopts a wind tunnel flow field characteristic diagnosis system, and is characterized in that the system comprises: a test device, a first diagnostic unit and a second diagnostic unit;
the collimator of the first diagnostic unit emits a laser signal, the laser signal is transmitted by the testing device after passing through a flow field of the testing device, and the transmitted laser signal is received by the receiver of the first diagnostic unit so as to acquire the translation temperature in the flow field;
the second diagnosis unit collects the radiation luminescence in the flow field to obtain the electronic temperature in the flow field in the test device;
wherein, the test device includes: the device comprises a high-frequency plasma heater, a spray pipe and a test chamber;
the high-frequency induction plasma heater is connected with the test chamber through the spray pipe and is used for enabling plasma generated in the high-frequency induction plasma heater to form a flow field for test model examination in the test chamber through the spray pipe, and a plurality of optical detection windows are arranged on the test chamber;
the first diagnostic unit includes: the system comprises a TDLAS signal modulation and data processing module, a controller, a semiconductor laser, an optical fiber coupler, an F-P interferometer, a collimator and a photoelectric detector;
the TDLAS signal modulation and data processing module is used for receiving a first instruction output by a signal trigger unit and sending a control signal generated according to the first instruction to the controller;
the controller is used for tuning a laser signal to be output in the semiconductor laser according to the control signal;
the semiconductor laser is used for outputting a laser signal to the optical fiber coupler;
the optical fiber coupler is used for dividing the laser signal into a first laser signal and a second laser signal, wherein the first laser signal is transmitted to the collimator through a first optical fiber, the collimator transmits the first laser signal to a flow field in the test device and then transmits the first laser signal through the test device, the transmitted first laser signal is received by the receiver, the receiver transmits the first laser signal to the photoelectric detector through a third optical fiber to perform conversion of a transmitted light intensity signal, and the photoelectric detector is also used for transmitting the transmitted light intensity signal to the TDLAS signal modulation and data processing module;
the optical fiber coupler is also connected with the F-P interferometer through a second optical fiber and is used for transmitting the second laser signal to the F-P interferometer for time scale-wavelength scale relation calibration, and the F-P interferometer is also used for sending the calibrated time scale-wavelength scale relation to the TDLAS signal modulation and data processing module;
the TDLAS signal modulation and data processing module is further used for determining a translation temperature value in the flow field according to the received relation between the time scale and the wavelength scale and the transmission light intensity signal;
the second diagnostic unit includes: the device comprises a data analysis module, a spectrometer and an acquisition module;
the data analysis module is used for receiving a second instruction output by the signal trigger unit and sending the second instruction to the spectrometer;
the spectrometer is used for controlling the acquisition module according to the second instruction;
the collection module is used for collecting the radiant luminescence of a plurality of measuring points in a flow field and transmitting the radiant luminescence to the spectrometer through a fourth optical fiber;
the spectrometer is also used for converting the radiant luminescence into a corresponding spectral image and sending the spectral image to the data analysis module;
the data analysis module is also used for determining an electronic temperature value at a measuring point according to the relation between the spectral line radiation intensity and the corresponding spectral line high-level energy;
the first optical fiber and the second optical fiber are both single-mode optical fibers, the third optical fiber is a multimode optical fiber, and the fourth optical fiber is a quartz optical fiber;
the method comprises the following steps:
plasma generated in the high-frequency induction plasma heater forms a flow field for checking a test model in the test chamber through the spray pipe;
acquiring a translation temperature in the flow field through a first diagnostic unit;
acquiring, by a second diagnostic unit, an electron temperature within the flow field;
evaluating the unbalance of the flow field according to the translation temperature and the electron temperature;
the acquiring, by the first diagnostic unit, the translational temperature value in the flow field specifically includes:
the TDLAS signal modulation and data processing module receives a first instruction output by a signal trigger unit, generates a control signal according to the first instruction, and sends the control signal to a controller;
the controller tunes a laser signal to be output in the semiconductor laser according to the control signal;
the semiconductor laser outputs a laser signal to the optical fiber coupler;
the optical fiber coupler divides the laser signal into a first laser signal and a second laser signal, wherein the first laser signal is transmitted to a collimator, the collimator transmits the first laser signal to a flow field in the test device and then transmits the first laser signal through the test device, the transmitted first laser signal is received by the receiver, the first laser signal is transmitted to the photoelectric detector through a third optical fiber to convert a transmission light intensity signal, and the transmission light intensity signal is transmitted to the TDLAS signal modulation and data processing module;
the optical fiber coupler transmits the second laser signal to the F-P interferometer for time scale-wavelength scale relation calibration, and the F-P interferometer sends the calibrated time scale-wavelength scale relation calibration to the TDLAS signal modulation and data processing module;
the TDLAS signal modulation and data processing module determines a translation temperature value in the flow field according to the received relation between the time scale and the wavelength scale and the transmission light intensity signal;
the TDLAS signal modulation and data processing module determines the translational temperature in the flow field according to the received relationship between the time scale and the wavelength scale and the transmitted light intensity signal, and specifically includes:
the TDLAS signal modulation and data processing module extracts a baseline signal of the transmission light intensity signal based on the transmission light intensity signal, compares the transmission light intensity signal with the baseline signal and takes a logarithm as a fitting object to perform Gauss curve fitting;
converting the time domain and the frequency domain of the transmitted light intensity signal through the received relation between the time scale and the wavelength scale to obtain the Doppler broadening of a curve, and acquiring a translation temperature mean value along the optical path according to the relation between the Doppler broadening and the translation temperature;
the relationship between the Doppler broadening and the translation temperature is as follows:
Figure FDA0002448006420000051
wherein: c is the speed of light and M is the molar absorption of the componentThe mass, k is the Boltzmann constant, v0Is the central frequency, Δ v, of the atomic absorption lineDTo widen, TtrIs translation temperature;
acquiring the electron temperature in the flow field through a second diagnostic unit, which specifically comprises:
the data analysis module receives a second instruction output by the signal trigger unit and sends the second instruction to the spectrometer;
the spectrometer controls the acquisition module according to the second instruction;
the collection module collects the radiant luminescence of a plurality of measuring points in the flow field and transmits the radiant luminescence to the spectrometer;
the spectrometer converts the radiant luminescence into a corresponding spectral image and sends the spectral image to the data analysis module;
the data analysis module determines an electronic temperature value at a measuring point according to the relation between the spectral line radiation intensity and the corresponding spectral line high-level energy;
the relationship between the spectral line radiation intensity and the corresponding spectral line high-level energy is as follows:
Figure FDA0002448006420000061
wherein I is atomic spectral line integral radiation intensity, lambda is spectral line central wavelength, EkHigh level energy of spectral line, gkIs the degeneracy of high energy level of spectral line, A is the Einstein spontaneous emissivity coefficient of spectral line, k is Boltzmann constant, TeIs the electron temperature at the measurement point, C is a constant;
the determining the electron temperature at the measurement point specifically comprises:
taking spectrograms corresponding to a plurality of measuring points as background spectrums when the test device does not work;
subtracting the background spectrum from the spectrograms corresponding to the plurality of measuring points when the test device works to obtain a spectrogram without background interference;
selecting a plurality of spectral lines in the spectrogram without background interference, determining elements corresponding to each spectral line and a spectral constant thereof, selecting a target element to perform fitting integration on the target element, and obtaining an integrated intensity value of the corresponding spectral line;
and obtaining the electronic temperature value of the measuring point by adopting a boltzmann plotting method according to the plurality of spectral lines of the target element.
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