CN116626334A - Laser-induced breakdown spectroscopy in-situ velocity measurement system and method based on Doppler frequency shift - Google Patents
Laser-induced breakdown spectroscopy in-situ velocity measurement system and method based on Doppler frequency shift Download PDFInfo
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- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/26—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
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- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
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- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/18—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the time taken to traverse a fixed distance
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Abstract
The invention provides a Doppler frequency shift-based laser-induced breakdown spectroscopy in-situ velocity measurement system and method, comprising a working cabin body, a single-pulse all-solid-state laser, a photoelectric detector, an oscilloscope, a LIBS front-end light path, a LIBS spectrometer, an ICCD camera, a DG535 time sequence controller and an electronic control module, wherein the working cabin body is provided with a laser-induced breakdown spectroscopy in-situ velocity measurement system; the single-pulse all-solid-state laser, the LIBS spectrometer and the ICCD camera are electrically connected with the DG535 time sequence controller, and the photoelectric detector is electrically connected with the oscilloscope; the LIBS front-end light path comprises a laser spectroscope, a dichroic mirror, a concave lens, a double-lens combination, a broadband beam splitter prism, an optical fiber coupling lens, a broadband reflecting mirror, a convex lens, a microscope objective and a neutral density filter. The invention combines the laser-induced breakdown spectroscopy technology and the Doppler frequency shift effect, simultaneously adopts an image method to assist in providing flow speed support for LIBS detection, integrates all equipment and devices into the same instrument, and builds a complete LIBS flow speed detection system.
Description
Technical Field
The invention belongs to the technical field of aerospace science and technology and combustion flow field diagnosis and measurement, and particularly relates to a laser-induced breakdown spectroscopy in-situ velocity measurement system and method based on Doppler frequency shift.
Background
With the continuous development of the national aerospace technology, higher requirements are put forward on the progress of the propulsion technology of the aerospace vehicle, and the research of a hypersonic flight power system is a key field of technological competition of various countries at present, so that the hypersonic flight power system is an important strategic resource of the country. The combustion plume of the rocket engine is combustion and cracking products discharged by the spray pipe after the propellant is ignited, the plume speed is an important parameter for revealing the engine performance, the fuel combustion condition can be effectively inverted and the engine running state can be analyzed through the flow speed monitoring way, and the method is an important basis for engine performance evaluation, optimization design and propellant improvement.
Currently, flame flow rate measurement in combustion fields can be divided into two modes, namely contact type measurement and non-contact type measurement. The contact measurement mainly comprises a speed measuring tube, a hot wire anemometer and other means, but the means have the defects of slow response time, low spatial resolution, interference with a plume field and the like. In contrast, non-contact measurement includes optical methods and acoustic velocity methods, and in contrast, optical measurement techniques mainly have been paid attention to, such as Particle Image Velocimetry (PIV), laser Doppler Velocimetry (LDV), tunable semiconductor laser absorption spectroscopy (TDLAS), and Planar Laser Induced Fluorescence (PLIF) techniques.
In the actual detection of a high-dynamic combustion field, the PLIF technology has high response speed and high spatial resolution, but trace particles are required to be added, so that the trace particles are difficult to uniformly distribute in the flow field due to uncontrollable combustion of a solid propellant, and particle signals are easy to annihilate by stronger flame radiation signals; the TDLAS spectrum technology has high spectrum resolution, but requires the combustion plume to pass through an optical reflection cavity thereof, and has complex field operation and longer response time; although PIV technology can carry out full-field measurement, trace particles are needed to be added, and the sampling frequency is low; therefore, the above measurement methods have certain limitations in practical application.
Disclosure of Invention
The invention aims to solve the technical problems of the prior art, and provides a laser-induced breakdown spectroscopy in-situ velocity measurement system and a method based on Doppler frequency shift.
In order to solve the technical problems, the invention adopts the following technical scheme: the laser-induced breakdown spectroscopy in-situ speed measurement system based on Doppler frequency shift is characterized by comprising a working cabin body, a single-pulse all-solid-state laser, a photoelectric detector, an oscilloscope, a LIBS front-end light path, a LIBS spectrometer, an ICCD camera, a DG535 time sequence controller and an electronic control module, wherein the single-pulse all-solid-state laser, the photoelectric detector, the oscilloscope, the LIBS front-end light path, the LIBS spectrometer, the ICCD camera and the DG535 time sequence controller are arranged in the working cabin body; the single-pulse all-solid-state laser, the LIBS spectrometer and the ICCD camera are electrically connected with the DG535 time sequence controller, and the photoelectric detector is electrically connected with the oscilloscope;
the LIBS front-end light path comprises a laser spectroscope, a dichroic mirror, a concave lens, a double-lens combination, a broadband beam splitter prism, an optical fiber coupling lens, a broadband reflecting mirror, a convex lens, a micro objective lens and a neutral density filter;
pulse laser emitted by the single-pulse all-solid-state laser sequentially passes through a laser spectroscope and a dichroic mirror, is focused in combustion field flame through a concave lens and a double-lens combination to generate an LIBS signal, the LIBS signal reversely passes through the double-lens combination and the concave lens and becomes parallel plasma radiation light, the parallel plasma radiation light is reflected by the dichroic mirror, the plasma radiation light is divided into a beam of transmitted light and a beam of reflected light by a broadband beam splitting prism, and the reflected light couples the plasma radiation spectrum signal to an optical fiber through an optical fiber coupling lens and transmits the optical fiber to a LIBS spectrometer to finish the spectrum information detection of the combustion field LIBS signal; meanwhile, the transmitted light sequentially passes through a broadband reflector and a convex lens, is focused to a focus position of the convex lens, is converted into a plasma image signal through a micro objective lens, is amplified in multiple, and is attenuated through a neutral density filter, and then the acquisition of plasma image information of a combustion field LIBS signal is completed through an ICCD camera;
the photoelectric detector is used for receiving the pulse laser reflected by the laser spectroscope and then transmitting a pulse laser signal to the oscilloscope for displaying the laser pulse width.
Preferably, the concave lens is arranged on the linear motor, the linear motor is electrically connected with the electronic control module, and the electronic control module controls the movement mode of the linear motor, so that the distance between the concave lens and the double lens combination is controlled, and the actual focusing distance of laser is changed.
Preferably, the electronic control module comprises a control module, a power supply module and a communication module, wherein the control module, the power supply module and the communication module are electrically connected; the control module is used for controlling the linear motor, and the power supply module is electrically connected with the single-pulse all-solid-state laser, the photoelectric detector, the oscilloscope, the LIBS spectrometer, the ICCD camera, the DG535 time sequence controller and the electronic control module and is used for supplying power; the communication module is used for communicating the LIBS spectrometer, the ICCD camera and the control module through USB.
Preferably, the double-lens combination is composed of a crescent lens and a convex lens, and the crescent lens is arranged close to one side of the concave lens.
Preferably, the laser spectroscope is a Nd-YAG laser spectroscope, and the transmission and reflection ratio of the spectroscope is 9:1, a step of; the cut-off wavelength of the dichroic mirror is 900nm; the transmission and reflection ratio of the broadband beam splitter prism is 5:5.
in addition, the invention also provides a Doppler frequency shift-based laser-induced breakdown spectroscopy in-situ speed measurement method, which is carried out by means of the speed measurement system and comprises the following steps:
turning on single pulse all solid state laser to continuously emit laser pulse, focusing the laser pulse in flame of combustion field via LIBS pre-optical path, triggering LIBS spectrometer by DG535 time sequence controller, and after laser pulse emission, keeping a certain time t 1 Then, opening the LIBS spectrometer, and starting to collect spectrum information of LIBS signals of the combustion field, wherein the spectrum signal collection duration is t 2 Obtaining a combustion field LIBS signal spectrum signal; the ICCD camera is triggered by DG535 time sequence controller and is separated by a certain time t after laser pulse is emitted 3 After that, the ICCD camera is turned on to start to collect plasma image information, and the time length for collecting the plasma image information is t 4 。
Preferably, the LIBS signal spectrum information acquisition and the plasma image information acquisition of the combustion field are divided into two modes, wherein one is a time resolution acquisition mode, and the time change process of the plasma radiation information of the combustion field is obtained by carrying out fixed-point detection on the combustion field without changing the distance between the concave lens and the double lens combination in the time resolution acquisition mode; the other is a space resolution acquisition mode, and in the space resolution acquisition mode, the distance between the concave lens and the double lens combination is regulated and controlled, so that longitudinal space plasma radiation information of the combustion field is obtained, and the space velocity change process of the combustion field under different space positions is analyzed.
Preferably t 1 The value range of (2) is 0-100 mu s; t is t 2 The value range of (2) is 0.1-5 mu s; t is t 3 The value range of (2) is 0-1 mu s; t is t 4 The range of the value of (2) is 0-1 mu s.
The invention combines an optical system with a single-pulse all-solid-state laser, a LIBS spectrometer, an ICCD camera and other devices to provide a novel integrated detection system for detecting the flow rate of a combustion field and a novel method for completing in-situ measurement of the flow rate of the combustion field by using the system.
According to the invention, a laser-induced breakdown spectroscopy technology is combined with an optical Doppler effect, plasma spectrum information and images are collected simultaneously by means of an optical path system, the change of plasma image information along with the flow velocity is analyzed through spectrum preprocessing and a spectrum peak identification algorithm, and a flame flow velocity accurate inversion method based on the Doppler frequency shift of the laser-induced breakdown spectroscopy assisted by the image information is developed.
According to the invention, the distance between the concave lens and the double lens is adjusted to change the actual focusing distance of the laser, so that the remote space resolution measurement of the flow velocity of the combustion field is realized. According to the invention, the concave lens is arranged on the linear motor, and the linear motor is controlled by the electronic control module, so that the distance is automatically adjusted, and the space resolution measurement of the flow velocity of the combustion field is completed.
Compared with the prior art, the invention has the following advantages:
1. the invention combines the laser-induced breakdown spectroscopy technology and the Doppler frequency shift effect, simultaneously adopts an image method to assist in providing flow velocity support for LIBS detection, integrates all equipment and devices into the same instrument, builds a complete LIBS flow velocity detection system, reduces the use of the devices to the greatest extent by optimizing an optical path, greatly reduces the volume of the instrument, and provides a new thought and technological breakthrough for LIBS flow velocity measurement of a combustion field.
2. The invention designs a set of remote zooming flow velocity detection light path which is based on the same light path system and completes the collection of LIBS spectrum information and image information, and after the emitted 1064nm laser pulse excites flame of a combustion field, the generated plasma signal is equally divided into transmitted light and reflected light through a broadband beam splitting prism, and the LIBS spectrum instrument and an ICCD camera are respectively used for completing the collection and the simultaneous detection of the flow velocity spectrum information and the image of the combustion field.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
Fig. 1 is a schematic diagram of a detection device disclosed in embodiment 1 of the present invention.
Fig. 2 is a schematic diagram of the structure of the LIBS pre-optical path disclosed in embodiment 1 of the present invention.
Wherein, 1-a single pulse all-solid-state laser; 2-a photodetector; 3-an oscilloscope; 5-LIBS spectrometer; 6-ICCD camera; 7-DG 535 timing controller; 8-a laser spectroscope; 9-a dichroic mirror; 10-concave lens; 11-a linear motor; 12-a dual lens assembly; 13-broadband beam-splitting prism; 14-a fiber coupling lens; 15-a broadband mirror; 16-convex lens; 17-a microobjective; 18-a neutral density filter; 19-an electronic control module; 20-a working cabin body.
Detailed Description
Example 1
As shown in fig. 1 and 2, a laser induced breakdown spectroscopy in-situ velocity measurement system based on doppler shift of the present embodiment effectively combines laser induced breakdown spectroscopy LIBS technology and optical doppler effect, including: the system comprises a working cabin body 20, a single-pulse all-solid-state laser 1, a photoelectric detector 2, an oscilloscope 3, a LIBS front-end light path, a LIBS spectrometer 5, an ICCD camera 6, a DG535 time sequence controller 7 and an electronic control module 19, wherein the single-pulse all-solid-state laser 1, the photoelectric detector 2, the oscilloscope 3, the LIBS front-end light path, the LIBS spectrometer 5, the ICCD camera 6 and the DG535 time sequence controller 7 are arranged in the working cabin body 20; the single-pulse all-solid-state laser 1, the LIBS spectrometer 5 and the ICCD camera 6 are electrically connected with the DG535 time sequence controller 7, and the photoelectric detector 2 is electrically connected with the oscilloscope 3;
the single-pulse all-solid-state laser 1 is used as an excitation light source and is focused in combustion field flame through an LIBS (laser induced polarization beam) front-end light path, wherein the LIBS front-end light path comprises a laser spectroscope 8, a dichroic mirror 9, a concave lens 10, a double-lens combination 12, a broadband spectroprism 13, an optical fiber coupling lens 14, a broadband reflecting mirror 15, a convex lens 16, a micro objective lens 17 and a neutral density filter 18; the optical elements in the LIBS pre-optical path are arranged in the working cabin body 20 according to the following working process; pulse laser emitted by the single-pulse all-solid-state laser 1 sequentially passes through a laser spectroscope 8 and a dichroic mirror 9, is focused in combustion field flame through a concave lens 10 and a double-lens combination 12 to generate an LIBS signal, the LIBS signal reversely passes through the double-lens combination 12 and the concave lens 10 and becomes parallel plasma radiation light, the parallel plasma radiation light is reflected by the dichroic mirror 9, the plasma radiation light is divided into a beam of transmitted light and a beam of reflected light by a broadband spectroscope 13, and the reflected light couples the plasma radiation spectrum signal to an optical fiber by an optical fiber coupling lens 14 and transmits the optical fiber to the LIBS spectrometer 5 to finish the spectrum information detection of the combustion field LIBS signal; meanwhile, the transmitted light sequentially passes through the broadband reflector 15 and the convex lens 16, is focused to the position of one focal length of the convex lens 16, is converted into a plasma image signal through the micro objective lens 17, is amplified in multiple, and is attenuated through the neutral density filter 18, and then the ICCD camera 6 is used for completing the acquisition of plasma image information of a combustion field LIBS signal;
the photodetector 2 is used for receiving the pulse laser light reflected by the laser beam splitter 8, and then transmitting a pulse laser signal to the oscilloscope 3 for displaying the laser pulse width.
In this embodiment, the concave lens 10 is mounted on the linear motor 11, the linear motor 11 is electrically connected with the electronic control module 19, and the electronic control module 19 controls the movement mode of the linear motor 11, so as to control the distance between the concave lens 10 and the double-lens combination 12, and change the actual focusing distance of the laser.
In this embodiment, the fundamental wavelength of light emitted by the single-pulse all-solid-state laser 1 is 1064nm, the pulse width of the generated nanosecond laser is less than 10ns, and the maximum pulse energy exceeds 200mJ. The LIBS spectrometer 5 has a spectral range of 200-880nm and a spectral resolution of 0.3nm. The ICCD camera 6 comprises a spectrum acquisition mode and an image acquisition mode.
In this embodiment, the electronic control module 19 includes a control module, a power supply module, and a communication module, where the control module, the power supply module, and the communication module are electrically connected; the control module is used for controlling the linear motor 11, and the power supply module is electrically connected with the single-pulse all-solid-state laser 1, the photoelectric detector 2, the oscilloscope 3, the LIBS spectrometer 5, the ICCD camera 6, the DG535 time sequence controller 7 and the electronic control module 19 and supplies power; the communication module is used for communicating the LIBS spectrometer 5, the ICCD camera 6 and the control module through USB.
In this embodiment, the dual-lens assembly 12 is composed of a crescent lens and a convex lens, and the crescent lens is disposed near the concave lens 10, which can greatly reduce spherical aberration to improve focusing quality of laser.
The diameter of the double lens assembly 12 is 4 inches and the diameters of the concave lens 10, the fiber coupling lens 14 and the convex lens 16 are all 1 inch. The magnification of the microscope objective 17 is 40.
In this embodiment, the laser beam splitter 8 is a nd:yag laser beam splitter, and the transmittance and reflectance of the beam splitter are 9:1, a step of; the cut-off wavelength of the dichroic mirror 9 is 900nm; the transmittance and reflectance of the broadband light splitting prism 13 is 5:5.
in this embodiment, the photodetector 2 is a photodiode.
Example 2
The laser-induced breakdown spectroscopy in-situ speed measurement method based on Doppler frequency shift in the embodiment is performed by means of the speed measurement system in embodiment 1, and comprises the following steps:
the operating parameters of the single-pulse all-solid-state laser 1 and the LIBS spectrometer 5 are first set.
The single-pulse all-solid-state laser 1 is selected to be in an internal trigger mode, the single-pulse all-solid-state laser 1 is turned on, the normal operation of the single-pulse all-solid-state laser 1 is always kept, laser pulses are continuously emitted, the laser pulses are focused in flame of a combustion field through a LIBS front-end optical path, the LIBS spectrometer 5 adopts an external trigger mode, the external trigger mode is triggered by the DG535 time sequence controller 7, as strong continuous background radiation exists in the initial stage of plasma induced by pulse laser, a certain time delay is required to be set to avoid the interference of the continuous background radiation so as to obtain discrete characteristic spectrum signals, and a certain time t is required to be spaced after the laser pulses are emitted 1 After that, the LIBS spectrometer 5 is opened, the LIBS signal spectrum information of the combustion field is started to be collected, and the spectrum signal collection duration is t 2 Obtaining a combustion field LIBS signal spectrum signal; the ICCD camera 6 adopts an external trigger mode, the ICCD camera 6 is triggered by the DG535 time sequence controller 7, and a certain time t is spaced after the laser pulse is transmitted 3 After that, the ICCD camera 6 is turned on to start to collect plasma image information, and the time length for collecting the plasma image information is t 4 。
Pulse laser emitted by the single-pulse all-solid-state laser 1 sequentially passes through a laser spectroscope 8 and a dichroic mirror 9, is focused in combustion field flame through a concave lens 10 and a double-lens combination 12 to generate an LIBS signal, the LIBS signal reversely passes through the double-lens combination 12 and the concave lens 10 and becomes parallel plasma radiation light, the parallel plasma radiation light is reflected by the dichroic mirror 9, the plasma radiation light is divided into a beam of transmitted light and a beam of reflected light by a broadband spectroscope 13, and the reflected light couples the plasma radiation spectrum signal to an optical fiber by an optical fiber coupling lens 14 and transmits the optical fiber to the LIBS spectrometer 5 to finish the spectrum information detection of the combustion field LIBS signal; meanwhile, the transmitted light sequentially passes through the broadband reflector 15 and the convex lens 16, is focused to the position of one focal length of the convex lens 16, is converted into a plasma image signal through the micro objective lens 17, is amplified in multiple, and is attenuated through the neutral density filter 18, and then the ICCD camera 6 is used for completing the acquisition of plasma image information of a combustion field LIBS signal;
the photodetector 2 is used for receiving the pulse laser light reflected by the laser beam splitter 8, and then transmitting a pulse laser signal to the oscilloscope 3 for displaying the laser pulse width.
In this embodiment, the concave lens 10 is mounted on the linear motor 11, the linear motor 11 is electrically connected with the electronic control module 19, and the electronic control module 19 controls the movement mode of the linear motor 11, so as to control the distance between the concave lens 10 and the double-lens combination 12, and change the actual focusing distance of the laser.
In the embodiment, the LIBS signal spectrum information acquisition and the plasma image information acquisition of the combustion field are divided into two modes, wherein one is a time resolution acquisition mode, and the interval between the concave lens 10 and the double lens combination 12 is not changed in the time resolution acquisition mode, so that the combustion field is subjected to fixed-point detection, and the time change process of the plasma radiation information of the combustion field is acquired; the other is a space resolution acquisition mode, and in the space resolution acquisition mode, the distance between the concave lens 10 and the double lens combination 12 is regulated and controlled, so that longitudinal space plasma radiation information of the combustion field is obtained, and the space flow velocity change process of the combustion field under different space positions is analyzed.
In this embodiment, t 1 The range of the value is 0-100 mu s, and t is preferably selected in the experimental process 1 Set to 0.5 mus; t is t 2 The range of the value is 0.1-5 mu s, and the plasma irradiation usually lasts for tens of microseconds, t is in the experimental process 2 The priority is set to 1ms. The method comprises the steps of carrying out a first treatment on the surface of the t is t 3 The range of the value of (2) is 0-1 mu s, t is in the experimental process 3 Preferably 0.1 mus; t is t 4 The range of the value is 0-1 mu s, and t is preferably selected in the experimental process 4 Set at 50 mus.
The above description is only of the preferred embodiments of the present invention, and is not intended to limit the present invention. Any simple modification, variation and equivalent variation of the above embodiments according to the technical substance of the invention still fall within the scope of the technical solution of the invention.
Claims (8)
1. The laser-induced breakdown spectroscopy in-situ speed measurement system based on Doppler frequency shift is characterized by comprising a working cabin body (20) and a single-pulse all-solid-state laser (1), a photoelectric detector (2), an oscilloscope (3), a LIBS front-end light path, a LIBS spectrometer (5), an ICCD camera (6), a DG535 time sequence controller (7) and an electronic control module (19) which are arranged in the working cabin body (20); the single-pulse all-solid-state laser (1), the LIBS spectrometer (5) and the ICCD camera (6) are electrically connected with the DG535 time sequence controller (7), and the photoelectric detector (2) is electrically connected with the oscilloscope (3);
the LIBS front-end light path comprises a laser spectroscope (8), a dichroic mirror (9), a concave lens (10), a double-lens combination (12), a broadband beam splitting prism (13), an optical fiber coupling lens (14), a broadband reflecting mirror (15), a convex lens (16), a micro objective lens (17) and a neutral density filter (18);
pulse laser emitted by the single-pulse all-solid-state laser (1) sequentially passes through a laser spectroscope (8) and a dichroic mirror (9), is focused in combustion field flame through a concave lens (10) and a double-lens combination (12) to generate LIBS signals, the LIBS signals reversely pass through the double-lens combination (12) and the concave lens (10) and become parallel plasma radiation light, the parallel plasma radiation light is reflected by the dichroic mirror (9), the plasma radiation light is divided into a beam of transmitted light and a beam of reflected light by a broadband beam splitting prism (13), and the reflected light couples the plasma radiation spectrum signals to an optical fiber by an optical fiber coupling lens (14) and transmits the optical fiber to a LIBS spectrometer (5) to finish combustion field LIBS signal spectrum information detection; meanwhile, the transmitted light sequentially passes through a broadband reflector (15) and a convex lens (16), is focused to a double focal length of the convex lens (16), is converted into a plasma image signal through a micro objective lens (17), is amplified in multiple, and is attenuated through a neutral density filter (18), and then the acquisition of plasma image information of a combustion field LIBS signal is completed through an ICCD camera (6);
the photoelectric detector (2) is used for receiving the pulse laser reflected by the laser spectroscope (8) and then transmitting a pulse laser signal to the oscilloscope (3) for displaying the laser pulse width.
2. The laser-induced breakdown spectroscopy in-situ velocity measurement system based on Doppler shift according to claim 1, wherein the concave lens (10) is mounted on a linear motor (11), the linear motor (11) is electrically connected with an electronic control module (19), and the electronic control module (19) controls the movement mode of the linear motor (11), so that the distance between the concave lens (10) and the double-lens combination (12) is controlled, and the actual focusing distance of laser is changed.
3. The laser-induced breakdown spectroscopy in-situ velocity measurement system based on the Doppler shift according to claim 2, wherein the electronic control module (19) comprises a control module, a power supply module and a communication module, and the control module, the power supply module and the communication module are electrically connected; the control module is used for controlling the linear motor (11), and the power supply module is electrically connected with the single-pulse all-solid-state laser (1), the photoelectric detector (2), the oscilloscope (3), the LIBS spectrometer (5), the ICCD camera (6), the DG535 time sequence controller (7) and the electronic control module (19) and is used for supplying power; the communication module is used for communicating the LIBS spectrometer (5), the ICCD camera (6) and the control module through USB.
4. The doppler shift-based laser induced breakdown spectroscopy in-situ velocimetry system of claim 1, wherein the dual lens assembly (12) is comprised of a curved crescent lens and a convex lens, the crescent lens being disposed adjacent to one side of the concave lens (10).
5. The doppler shift-based laser-induced breakdown spectroscopy in-situ velocity measurement system according to claim 1, wherein the laser spectroscope (8) is a nd:yag laser spectroscope, and the transmittance and reflectance of the spectroscope are 9:1, a step of; the cut-off wavelength of the dichroic mirror (9) is 900nm; the transmission and reflection ratio of the broadband light splitting prism (13) is 5:5.
6. a laser-induced breakdown spectroscopy in-situ speed measurement method based on doppler shift, the speed measurement method being performed by means of the speed measurement system according to any one of claims 1 to 5, the speed measurement method comprising:
the single-pulse all-solid-state laser (1) is turned on to continuously emit laser pulses, the laser pulses are focused in flame of a combustion field through a LIBS (laser induced breakdown spectroscopy) pre-light path, a LIBS spectrometer (5) is triggered by a DG535 time sequence controller (7), and a certain time t is reserved after the laser pulses are emitted 1 Then, a LIBS spectrometer (5) is opened to start to collect the spectrum information of the LIBS signal of the combustion field, and the spectrum signal collecting duration is t 2 Obtaining a combustion field LIBS signal spectrum signal; the ICCD camera (6) is triggered by the DG535 time sequence controller (7) and is separated by a certain time t after the laser pulse is emitted 3 After that, an ICCD camera (6) is turned on to start to collect plasma image information, and the time length for collecting the plasma image information is t 4 。
7. The Doppler frequency shift-based laser induced breakdown spectroscopy in-situ velocity measurement method is characterized in that the LIBS signal spectrum information acquisition and the plasma image information acquisition of the combustion field are divided into two modes, wherein one is a time resolution acquisition mode, and in the time resolution acquisition mode, the space between the concave lens (10) and the double lens combination (12) is not changed, so that the combustion field is subjected to fixed-point detection, and the time change process of the plasma radiation information of the combustion field is obtained; the other is a space resolution acquisition mode, and in the space resolution acquisition mode, the distance between the concave lens (10) and the double lens combination (12) is regulated so as to obtain longitudinal space plasma radiation information of the combustion field, and the longitudinal space plasma radiation information is used for analyzing the space flow velocity change process of the combustion field at different space positions.
8. The Doppler shift-based laser induced breakdown spectroscopy in-situ velocimetry method as claimed in claim 6, wherein t is 1 The value range of (2) is 0-100 mu s; t is t 2 The value range of (2) is 0.1-5 mu s; t is t 3 The value range of (2) is 0-1 mu s; t is t 4 The range of the value of (2) is 0-1 mu s.
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