IE20230209U1 - A long pulse libs-raman-lif multi-spectral combined in-situ detection system and its detection method - Google Patents
A long pulse libs-raman-lif multi-spectral combined in-situ detection system and its detection method Download PDFInfo
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- 238000001514 detection method Methods 0.000 title claims abstract description 52
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 17
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- 238000001499 laser induced fluorescence spectroscopy Methods 0.000 abstract description 24
- 238000001069 Raman spectroscopy Methods 0.000 abstract description 23
- 238000005516 engineering process Methods 0.000 abstract description 23
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Abstract
The present invention provides a long pulse LIBS-Raman-LIF multi-spectral joint in-situ detection system, integrating Laser-Induced Breakdown Spectroscopy (LIBS), Raman Spectroscopy (Raman) and Laser Induced Fluorescence (LIF) in a working chamber to realize the simultaneous detection of anions, cations, gas molecules, solid particles and other substances in the combustion field. The all-solid-state long pulse laser is used as the excitation light source and focused on the combustion field through the front optical path. The front optical path has remote zooming function, the generated spectral signal is collected by LIBS spectrometer and Raman-LIF spectrometer through the front optical path. The present invention realizes the combination of key device sharing and multi-spectral technology, and provides a more comprehensive and effective technical means for in-situ detection of high temperature combustion flow field.
Description
A LONG PULSE LIBS-RAMAN-LIF MULTI-SPECTRAL COMBINED IN-SITU
DETECTION SYSTEM AND ITS DETECTION METHOD
TECHNICAL FIELD
[01] The present invention belongs to the field of aerospace and laser spectroscopy,
and specifically relates to a long pulse LIBS-Raman-LIF multi-spectral combined in-situ
detection system and its detection method.
BACKGROUND ART
[02] In recent years, China 's aerospace technology is developing continuously, solid
rocket motor technology has the advantages of simple structure, high reliability and low
cost, which is widely used as the main power device of missile weapons. Therefore, the
continuous upgrading of solid motors has also received more and more attention. The
primary chamber is one of the core components of the aerospace engine. The reliability
and life of the engine depend largely on the reliability and effectiveness of the combustion
chamber. Engine energy conversion is realized by the combustion of solid propellant, but
the conversion process is complex, often accompanied by unstable combustion problems.
Wherein, the component information in the combustion process is one of the key
parameters that are of great concern to the current engine test. On-line testing the main
component concentration of combustion field airflow, and the analysis and determination
of the content of each component in the gas flow after oxygen supplementation are of
great significance for the performance evaluation of solid rocket motors and the
improvement of solid propellants. However, the engine combustion process is highly
dynamic and has a great disturbance to the surrounding environment. At present, there is
still a lack of fast in-situ sensing technology for on-line and non-contact detection of
combustion field components.
[03] Laser-Induced Breakdown Spectroscopy (LIBS) technology is to focus the high-
power pulsed laser on the surface of the sample by means of an optical system. When the
pulsed laser power density on the surface of the sample is large enough to produce plasma,
the qualitative analysis of the element components and quantitative analysis of the content
in any physical form of the sample can be realized by collecting the plasma emission
spectrum through the optical path system. Compared with the traditional in-situ testing
technology, LIBS technology has many advantages such as a simple experimental system,
no sample pretreatment, fast analysis speed, and simultaneous detection of multiple
elements. It has been widely used in many fields and has broad application prospects in
the field, especially in extreme environmental detection. In recent years, LIBS technology
has been widely used in flame combustion diagnosis. It is a promising spectral analysis
technology in the aerospace field.
[04] Laser Raman Spectroscopy (Raman) technology is a non-destructive molecular
spectroscopy technique. The low-energy laser is used to act on the surface of the sample,
by receiving the scattering spectrum generated by the material, the scattered light with
different frequencies from the incident light is analyzed to obtain the fingerprint
information of the molecular vibration and rotational energy levels, which can achieve
rapid identification and qualitative detection of the corresponding substances. At present,
the multi-component measurement of combustion field generally uses spontaneous
Raman scattering technology. It can often obtain the Raman signal of the main
components of the combustion field by single pulse measurement to complete the
quantitative measurement of the main components of the flow field. At present, this
technology has been successfully applied to the measurement of various combustion flow
field components.
[05] Laser Induced Fluorescence (LIF) technology uses a specific wavelength laser to
excite molecules to undergo electronic energy level transitions. When absorbed by the
relevant molecules, it will spontaneously emit fluorescence. At present, Laser Induced
Fluorescence technology is commonly used to measure the concentration and temperature
of free radicals in the flame field.
[06] The general optical system design is only for one or more specific detection
distances. Because when the detection distance changes, the spot size of laser aggregation,
energy density and systemic optical efficiency will change, thereby leading to the
collection of plasma spectra with different spectral intensities and characteristics during
zoom detection, resulting in different degrees of error in the experimental results. Besides,
in high dynamic high temperature combustion field, the combustion field temperature of
the engine is up to 3000K. Most current instrumentation cannot withstand such high
temperatures, the real conditions of engine combustion field cannot be restored only by
theoretical simulation, and analysis results are not available. Therefore, the development
of non-contact remote zoom in-situ sensing technology for combustion field detection is
an urgent problem to be solved.
SUMMARY
[07] The technical problem to be solved by the present invention is to provide a long
pulse LIBS-Raman-LIF multi-spectral combined in-situ detection system and its
detection method in view of the deficiency of the above existing technologies. The system
realizes the organic integration of multi-spectral technology. For the choice of excitation
light source, LIBS technology often uses high power laser pulses, Raman and LIF
technology often use continuous laser. LIBS detection cannot be achieved by continuous
laser, while Raman and LIF detection can be realized by pulsed laser. The advantage of
using pulsed laser for LIF detection is that it can better suppress the background and
perform time-resolved detection of the spectrum.
[08] In order to solve the above technical problems, the technical scheme adopted by
the present invention is: a long pulse LIBS-Raman-LIF multi-spectral combined in-situ
detection system and its detection method, including a working chamber/ cabin. An all-
solid-state long pulse laser, LIBS-Raman-LIF front optical path, LIBS spectrometer,
Raman-LIF spectrometer and electronic control system are set up in the working chamber.
The all-solid-state long pulse laser is the excitation light source. The laser emitted by the
all-solid-state long pulse laser is focused on the flame of the combustion flow field after
passing through the LIBS-Raman-LIF front optical path. The all-solid-state long pulse
laser, LIBS-Raman-LIF front optical path, LIBS spectrometer, Raman-LIF spectrometer
are all electrically connected to the electronic control system. LIBS-Raman-LIF front
optical path includes a laser beam splitter, LIBS front optical path and Raman-LIF front
optical path. The LIBS front optical path and Raman-LIF front optical path share a laser
beam splitter. The angle between the laser beam splitter and the incident light is 45°. The
LIBS focus window and Raman-LIF focus window are set at the front of the working
cabin. The LIBS focus window is set corresponding to the LIBS front optical path, and
the Raman-LIF focus window is set corresponding to the Raman-LIF front optical path.
[09] Preferably, the laser beam splitter is a Nd:YAG laser beam splitter with a
projection to reflection ratio of 9 : l.
[10] Preferably, the LIBS front optical path includes the first long-wave dichroic
mirror, the first concave lens and the first double lens combination. These three
combinations are arranged on the right side of the laser beam splitter from left to right
along the laser travel direction. The first long-wave dichroic mirror is set in parallel with
the laser beam splitter. A broadband reflector is arranged in parallel above the first long-
wave-pass dichroic mirror. The first fiber coupling lens is set on the left side of the
broadband reflector. The first fiber coupling lens couples the signal light to the fiber and
transmits it to the LIBS spectrometer. The cut-off wavelength of the first long wave-pass
dichroic mirror is 900 nm. The 1064 nm laser beam through the laser beam splitter passes
through the first long-wave-pass dichroic mirror and the first concave mirror in turn. After
passing through the first concave lens and the first double lens combination, the laser is
focused into the combustion field. The generated LIBS signal becomes a parallel spectral
signal after the first double lens combination and the first concave lens. The first long-
wave dichroic mirror is reflected to the broadband reflector, and the signal light is coupled
to the fiber by the first fiber coupling lens and transmitted to the LIBS spectrometer, so
as to realize the detection of the LIBS signal.
[11] Preferably, the Raman-LIF front optical path includes the second long-wave
dichroic mirror, the second concave lens, and the second double lens combination. The
second long-wave dichroic mirror is set parallelly below the laser beam splitter. And a
frequency doubling crystal is set between the second long-wave dichroic mirror and the
laser beam splitter. The second concave lens and the second double lens combination are
set in turn on the right of the second long-wave two-way mirror. A long-pass filter and
the second fiber coupling lens are arranged in turn on the left side of the second long-
wave pass dichroic mirror. The second fiber coupling lens couples the optical signal to
the fiber and transmits it to the Raman-LIF spectrometer. The cut-off wavelength of the
second long wave-pass dichroic mirror is 535 nm. The 1064 nm laser reflected by the
laser beam splitter is converted into 532 nm laser after passing through the frequency-
doubled crystal, through the second long-wave dichroic mirror and the second concave
lens in turn, the 532 nm laser is focused into the combustion field after passing through
the second concave lens and the second double lens combination. The generated Raman
and LIF signals become parallel spectral signals through the second double lens
combination and the second concave lens, through the second long-pass dichroic mirror
and through the long-pass filter, the second fiber coupling lens is coupled to the fiber
and transmitted to the Raman-LIF spectrometer, so as to realize the detection of Raman-
LIF signal.
[12] Preferably, the electronic control system includes control module, power supply
module and transmission module. The power supply module and transmission module are
connected to the control module.
[13] Preferably, the wavelength of the fundamental frequency light emitted by the all-
solid-state long pulse laser is 1064 nm. The pulse width of nanosecond laser is 100ns, and
the maximum pulse energy is 250m]. The frequency-doubled crystal is located at the
reflection end of the laser beam splitter. The frequency-doubled crystal is used to convert
the fundamental frequency light into a laser with a wavelength of 5 32 nm.
[14] Preferably, the diameter of the first concave lens and the second concave lens is
inch. The first double lens combination and the second double lens combination are
composed of crescent lens and convex lens with the same diameter. The diameter of the
first double lens combination and the second double lens combination is 4 inches.
[15] Preferably, the first concave lens and the second concave lens are installed on the
first linear motor and the second linear motor respectively. The distance between the
concave lens and the double lens combination is adjusted by the linear motor to change
the actual focusing distance of the laser, so as to realize the remote zoom function of the
combustion field. The moving accuracy of the first linear motor and the second linear
motor is 20 H m. The first linear motor and the second linear motor are electrically
connected to the control module.
[16] Preferably, the LIBS spectrometer has a spectral range of 200-880 nm and a
spectral resolution of 0.3 nm; the Raman-LIF spectrometer has a spectral range of 0-45 00
cm '1 and a spectral resolution of 10 cm'l. LIBS front optical path forms LIBS spectrum,
and LIBS spectrum induces atomic and cationic spectra. Raman spectrum and LIF
spectrum are formed by Raman-LIF front optical path. Raman spectroscopy provides
Raman active anion and molecular spectra. The LIF spectrum provides a molecular
spectrum with fluorescent activity.
[17] A long-pulse LIBS-Raman—LIF multi-spectral joint in-situ detection method,
includes the following steps:
[18] S1. the all-solid-state long pulse laser is turned on to emit laser pulses, and the
laser is focused on the combustion field flame through the LIBS-Raman-LIF front optical
path;
[19] S2. the spectral signal is collected by LIBS spectrometer and Raman-LIF
spectrometer, LIBS spectrometer (3) adopts external trigger mode, the LIBS spectrometer
is triggered by the Q-switched output signal of the all-solid-state long pulse laser, the time
interval after laser pulse emission is tl, turning on the LIBS spectrometer, the acquisition
time is t2, and then turning off the LIBS spectrometer to obtain the LIBS spectral signal;
the Raman-LIF spectrometer adopts the internal trigger mode, after turning on the all-
solid-state long pulse laser, turning on the Raman-LIF spectrometer by the control module,
the acquisition time is t3, and then turning off the Raman-LIF spectrometer to obtain
the Raman-LIF spectral signal.
[20] Preferably, the value of tl is preferably 1 H s, the value of t2 is preferably lms,
and the value of t3 is preferably Is; the spectrum acquisition is divided into time and
space acquisition modes, wherein, in the time-resolved mode, the combustion field is
detected at a fixed point without changing the position of the concave lens, and the time-
varying process of the plasma information in the combustion field is obtained; In the
spatial resolution mode, the distance between the concave lens and the double lens
combination is adjusted by linear motor control, and the plasma radiation information of
the combustion field at different spatial positions is analyzed.
[21] Preferably, for the process of LIBS detection, the plasma induced by pulsed laser
has a strong continuous background radiation at the initial stage. This requires setting a
certain time delay to avoid the interference of continuous background radiation to obtain
discrete characteristic spectral signals. Therefore, a certain time interval tl is required
before the laser pulse and LIBS spectrometer. And the time interval tl is preferentially set
to l 11 s. LIBS spectrum acquisition needs to set a certain acquisition time t2, which can
be set 1 - 50 ms. Since plasma radiation usually lasts for few tens of H s, the time interval
t2 is preferred to 1 ms. Compared to LIBS detection, Raman and LIF detection do not
need to set a time delay. The spectrometer is in the internal trigger mode, and the
corresponding acquisition time t3 needs to be set. Since the laser used is a pulsed laser,
the acquisition of Raman and LIF signals requires a relatively long integration time to
improve the detection sensitivity. The acquisition time t3 can be set between 1 and 60 s.
However, the combustion field is in a dynamic process. Integral time should not be too
long, time interval t3 preferably set Is.
[22] Compared with the existing technology, the invention has the following
advantages:
[23] 1. The present invention integrates laser-induced breakdown spectroscopy, laser
Raman spectroscopy and laser-induced fluorescence spectroscopy into the same sealed
cabin to form a multi-spectral joint detection device. Through the optical path
optimization design, the use of the device is reduced, the volume of the device is reduced,
and the miniaturization and integration of the device are realized. At the same time,
through multi-spectral fusion, comprehensive multi-component spectral information can
be provided for combustion field detection, which provides a new technical means for on-
line detection of combustion field components.
[24] 2.The present invention is based on the remote zoom joint detection optical path
of the same all-solid-state single pulse laser as the common excitation light source of
LIBS, Raman and LIF. And the selected laser pulse width is 100 ns long pulse. It is
beneficial to obtain higher intensity spectral signal and improve the detection sensitivity
of multispectral technology. The laser with fundamental frequency of 1064 nm is emitted
into different optical paths through the laser beam splitter. One of the light paths is
converted into a 532 nm laser by a frequency-doubled crystal. Different optical paths
complete the excitation and collection of LIBS and Raman-LIF signals respectively,
which improves the space utilization of the device. Combined with the structure of
Galileo telescope system, the remote and spatial resolution detection of combustion field
is realized by the combination of concave lens and double lens, which further improves
the practical application ability of multi-spectral combined technology.
[25] 3. The present invention adopts Galileo telescope system to change the actual
focusing distance of the laser by adjusting the distance between the lenses, thereby
realizing the remote spatial resolution measurement of the combustion field. The present
invention adopts a Galileo telescope system structure composed of a concave lens and a
double lens. The concave lens is installed on the linear motor displacement platform, and
the optical path structure is simulated and analyzed by using the optical path design
software. The correlation function between the displacement of the concave lens and the
telemetry distance is fitted, and the function is input into the control program. The
controller adjusts the moving distance of the linear motor to complete the remote spatial
resolution measurement of the combustion field.
[26] 4. At present, most of the commonly used pulse lasers are short pulses with a
pulse width of about 10 ns, resulting in low LIBS detection sensitivity. The present
invention uses a long pulse laser with a pulse width of 100 ns, which can effectively
increase the interaction time between the laser and the plasma and improve the LIBS
detection sensitivity. But for Raman and LIF spectra, based on the pulse laser, the long
pulse laser is also beneficial to enhance the Raman and LIF spectra. At the same time, the
present invention adopts multi-spectral filsion method, wherein, LIBS spectral excitation
induces the generation of atomic and cationic spectra, Raman spectrum excitation
produces Raman active anions and molecular spectra, LIF spectra provide molecular
spectra with fluorescent activity. The three spectra are integrated with each other and
complement each other, providing multi-component and multi-spectral information for
combustion field detection and diagnosis.
[27] The following is a further detailed description of the invention in combination
with drawings and implementation examples.
BRIEF DESCRIPTION OF THE DRAWINGS
[28] FIG. 1 is the overall structure diagram of the present invention.
[29] FIG. 2 is the structure diagram of LIBS-Raman-LIF front optical path in the
present invention.
[30] Label description of drawings:
[31] 1: all-solid-state long pulse laser; 2: LIBS-Raman-LIF front optical path;
[32] 2-1: LIBS front optical path;
[33] 2-2: Raman-LIF front optical path; 3: LIBS spectrograph; 4: Raman-LIF
spectrometer ;
[34] 5: electronic control system; 6: laser beam splitter;
[35] 7: the first long-wave dichroic mirror;
[36] 8: the first concave lens; 9: the first linear motor;
[37] 10: the first double lens combination;
[38] 11: broadband reflector; 12: the first fiber coupling lens;
[39] 13: frequency-doubled crystal;
[40] 14: the second long-wave dichroic mirror; 15: the second concave lens;
[41] 16: the second linear motor;
[42] 17: the second double lens combination; 18: long-pass filter;
[43] 19: the second fiber coupling lens;
[44] 20: working space; 21-1: LIBS focus window; 21-2: Raman-LIF focus window.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[45] As shown in FIGS 1 and 2, the present invention includes a working chamber.
All-solid-state long pulse laser 1, LIBS-Raman-LIF front optical path 2, LIBS
spectrometer 3, Raman-LIF spectrometer 4 and electronic control system 5 are set in the
working cabin. All-solid-state long pulse laser 1 is the excitation light source. The laser
emitted by the all-solid-state long pulse laser 1 is focused on the combustion flow field
flame after passing through the LIBS-Raman-LIF front optical path 2. All-solid-state long
pulse laser 1, LIBS-Raman-LIF front optical path 2, LIBS spectrometer 3, Raman-LIF
spectrometer 4 are all electrically connected to the electronic control system 5. LIBS-
Raman-LIF front optical path 2 includes laser beam splitter 6, LIBS front optical path 2-
land Raman-LIF front optical path 2-2. LIBS front optical path 2-1 and Raman-LIF front
optical path 2-2 share a laser beam splitter 6. The angle between the laser beam splitter
and the incident light is 45°. LIBS focus window 2 l -l and Raman-LIF focus window 2 l -
are set at the front of the working cabin 20. The LIBS focus window 21-1 is set
corresponding to the LIBS front optical path 2-1, and the Raman-LIF focus window 21-
is set corresponding to the Raman-LIF front optical path 2-2.
[46] In this example, the laser beam splitter is a Nd: YAG laser beam splitter with a
projection to reflection ratio of 9 : l.
[47] In this example, LIBS front optical path 2-l includes the first long-wave dichroic
mirror 7, the first concave lens 8 and the first double lens combination 10. These three
combinations are arranged on the right side of the laser beam splitter 6 from left to right
along the laser travel direction. The first long-wave dichroic mirror 7 is set in parallel
with the laser beam splitter 6. A broadband reflector 11 is arranged in parallel above the
first long-wave-pass dichroic mirror 7. The first fiber coupling lens 12 is set on the left
side of the broadband reflector 11. The first fiber coupling lens 12 couples the signal light
to the fiber and transmits it to the LIBS spectrometer 3. The cut-off wavelength of the
first long wave-pass dichroic mirror 7 is 900 nm. The 1064 nm laser beam through the
laser beam splitter 6 passes through the first long-wave-pass dichroic mirror 7 and the
first concave lens 8 in turn. After through the first concave lens 8 and the first double lens
combination 10, the laser is focused into the combustion field. The generated LIBS signal
becomes a parallel spectral signal after the first double lens combination 10 and the first
concave lens 8. The first long-wave dichroic mirror 7 is reflected to the broadband
reflector 11, and the signal light is coupled to the fiber by the first fiber coupling lens 12
and transmitted to the LIBS spectrometer 3, so as to realize the detection of LIBS signal.
[48] In this example, the Raman-LIF front optical path 2-2 includes the second long-
wave dichroic mirror 14, the second concave lens 15, and the second double lens
combination 17. The second long-wave dichroic mirror 14 is set parallelly below the laser
beam splitter 6. And a frequency-doubling crystal 13 is set between the second long-wave
dichroic mirror 14 and the laser beam splitter 6. The second concave lens 15 and the
second double lens combination 17 are set in turn on the right of the second long-wave
two-way mirror 14. A long-pass filter 18 and the second fiber coupling lens 19 are
arranged in turn on the left side of the second long-wave pass dichroic mirror 14. The
second fiber coupling lens 19 couples the optical signal to the fiber and transmits it to the
Raman-LIF spectrometer 4. The cut-off wavelength of the second long wave-pass
dichroic mirror 14 is 535 nm. The 1064 nm laser reflected by the laser beam splitter 6 is
converted into 5 32 nm laser after passing through frequency-doubled crystal 13, through
the second long-wave dichroic mirror 14 and the second concave lens 15 in turn, the 532
nm laser is focused into the combustion field after passing through the second concave
lens 15 and the second double lens combination 17. The generated Raman and LIF signals
become parallel spectral signals through the second double lens combination l7 and the
second concave lens 15, through the second long-pass dichroic mirror 14 and through the
long-pass filter 18, the second fiber coupling lens 19 is coupled to the fiber and
transmitted to the Raman-LIF spectrometer 4, so as to realize the detection of Raman-LIF
signal.
[49] In this example, the electronic control system 5 includes control module, power
supply module and transmission module. The power supply module and transmission
module are connected to the control module.
[50] In this example, the wavelength of the fundamental frequency light emitted by
the all-solid-state long pulse laser is 1064 nm. The pulse width of nanosecond laser is
ns, and the maximum pulse energy is 25 OmJ . The frequency-doubled crystal is located
at the reflection end of the laser beam splitter. The frequency-doubled crystal is used to
convert the fundamental frequency light into a laser with a wavelength of 5 32 nm.
[51] In this example, the diameter of the first concave lens 8 and the second concave
lens 15 is 1 inch. The first double lens combination 10 and the second double lens
combination 17 are composed of crescent lens and convex lens with the same diameter.
The diameter of the first double lens combination 10 and the second double lens
combination 17 is 4 inches.
[52] In this example, the first concave lens 8 and the second concave lens 15 are
installed on the first linear motor 9 and the second linear motor 16 respectively. The
distance between the concave lens and the double lens combination is adjusted by the
linear motor to change the actual focusing distance of the laser, so as to realize the remote
zoom filnction of the combustion field. The moving accuracy of the first linear motor 9
and the second linear motor 16 is 20 ll m. The first linear motor 9 and the second linear
motor 16 are electrically connected to the control module.
[53] In this example, the LIBS spectrometer 3 has a spectral range of 200-880 nm and
a spectral resolution of 0.3 nm; the Raman-LIF spectrometer 4 has a spectral range of 0-
cm '1 and a spectral resolution of 10 cm'l. LIBS front optical path 2-1 forms LIBS
spectrum, and LIBS spectrum induces atomic and cationic spectra. Raman spectrum and
LIF spectrum are formed by Raman-LIF front optical path. Raman spectroscopy provides
Raman active anion and molecular spectra. The LIF spectrum provides a molecular
spectrum with fluorescent activity.
[54] When the device system is used, the following steps are included:
[55] S1. the all-solid-state long pulse laser is turned on to emit laser pulses, and the
laser is focused on the combustion field flame through the LIBS-Raman-LIF front optical
path;
[56] S2. the spectral signal is collected by LIBS spectrometer (3) and Raman-LIF
spectrometer (4), LIBS spectrometer (3) adopts external trigger mode, the LIBS
spectrometer (3) is triggered by the Q-switched output signal of the all-solid-state long
pulse laser (1), the time interval after laser pulse emission is t1, turning on the LIBS
spectrometer (3), the acquisition time is t2, and then turning off the LIBS spectrometer
(3) to obtain the LIBS spectral signal; the Raman-LIF spectrometer (4) adopts the internal
trigger mode, after turning on the all-solid-state long pulse laser (1), turning on the
Raman-LIF spectrometer (4) by the control module, the acquisition time is t3, and then
turning off the Raman-LIF spectrometer (4) to obtain the Raman-LIF spectral signal.
[57] Wherein, the value of tl is preferably 1 H s, the value of t2 is preferably lms, and
the value of t3 is preferably Is; the spectrum acquisition is divided into time and space
acquisition modes, wherein, in the time-resolved mode, the combustion field is detected
at a fixed point without changing the position of the concave lens, and the time-varying
process of the plasma information in the combustion field is obtained; In the spatial
resolution mode, the distance between the concave lens and the double lens combination
is adjusted by linear motor control, and the plasma radiation information of the
combustion field at different spatial positions is analyzed.
[58] Wherein, for the process of LIBS detection, the plasma induced by pulsed laser
has strong continuous background radiation at the initial stage. This requires setting a
certain time delay to avoid the interference of continuous background radiation to obtain
discrete characteristic spectral signals. Therefore, a certain time interval tl is required
before the laser pulse and LIBS spectrometer. And the time interval tl is preferentially set
to l 11 s. LIBS spectrum acquisition needs to set a certain acquisition time t2, which can
be set 1 ~50 ms. Since plasma radiation usually lasts for few tens of H s, the time interval
t2 is preferred to 1 ms. Compared to LIBS detection, Raman and LIF detection do not
need to set time delay. The spectrometer is in the internal trigger mode, and the
corresponding acquisition time t3 needs to be set. Since the laser used is a pulsed laser,
the acquisition of Raman and LIF signals requires a relatively long integration time to
improve the detection sensitivity. The acquisition time t3 can be set between 1 and 60 s.
However, the combustion field is in a dynamic process. Integral time should not be too
long, time interval t3 is preferably set to ls.
[59] The above is only a better embodiment of the invention and does not impose any
restriction on the invention. Any simple modification, change and equivalent change
made to the above implementation cases according to the essence of the invention
technology are still within the protection scope of the technical scheme of the invention.
Claims (5)
1. A long pulse LIBS-Raman-LIF multi spectral combined in-situ detection system, including a working chamber; all-solid-state long pulse laser 1, LIBS-Raman-LIF front optical path 2, LIBS spectrometer 3, Raman LIF spectrometer 4 and electronic control system 5 are set in the working chamber; the all-solid-state long pulse laser 1 is the excitation light source, the laser emitted by the all solid-state long pulse laser 1 is focused on the combustion flow field flame after passing through the LIBS-Raman-LIF front optical path 2; the all-solid state long pulse laser 1, LIBS-Raman-LIF front optical path 2, LIBS spectrometer 3, the Raman-LIF spectrometer 4 are all electrically connected to the electronic control system 5; the LIBS-Raman-LIF front optical path 2 includes a laser beam splitter 6; LIBS front optical path 2-1 and Raman-LIF front optical path 2 2 share the laser beam splitter 6; the angle between the laser beam splitter and the incident light is 45°; LIBS focus window 21 1 and Raman-LIF focus window 21 2 are set at the fron of the working chamber 20-; the LIBS focus window 21 l is set corresponding to the LIBS front optical path 2 l, and the Raman-LIF focus window 21 2 is set corresponding to the Raman-LIF front optical path 2 2.
2. The long pulse LIBS-Raman-LIF multi spectral combined in-situ detection system according to claim 1, wherein the LIBS front optical path 2 5. includes first long- Wave dichroic mirror 7, first concave lens 8 and first double lens combination 10; these three combinations are arranged on the right side of the laser beam splitter 6 from left to right along the laser travel direction; the first long-wave dichroic mirror 7 is set in parallel with the laser beam splitter 6; a broadband reflector 11 is arranged in parallel above the first long-wave pass dichroic mirror 7; first fiber coupling lens 12 is set on the left side of the broadband reflector 11; the first fiber coupling lens 12 couples the signal light to the fiber and transmits it to the LIBS spectrometer 3; the cut-off wavelength of the first long wave-pass dichroic mirror 7 is 900 nm.
3. The long pulse LIBS-Raman-LIF multi spectral combined in-situ detection system according to claim 2, wherein the Raman-LIF front optical path 2-2 includes second long wave dichroic mirror 14, a second concave lens 15, and a second double lens combination 17; the second long wave dichroic mirror 14 is set parallelly below the laser beam splitter 6, and a frequency doubling crystal 13 is set between the second long wave dichroic mirror 14 and the laser beam splitter 6; the second concave lens 15 and the second double lens combination 17 are set in turn on the right of the second long wave two-way mirror 14; a long pass filter 18 and second fiber coupling lens 19 are arranged in turn on the left side of the second long wave pass dichroic mirror 14; the second fiber coupling lens 19 couples the optical signal to the fiber and transmits it to the Raman-LIF spectrometer 4; the cut-off wavelength of the second long wave-pass dichroic mirror 14 is 535 nm.
4. The long pulse LIBS-Raman-LIF multi spectral combined in-situ detection system according to claim 1, wherein the electronic control system 5 includes a control module, a power supply module and a transmission module; the power supply module and the transmission module are connected to the control module.
5. A method for LIBS-Raman-LIF multi spectral joint in-situ detection for combustion field components using the long pulse LIBS-Raman-LIF multi spectral combined in situ detection system according to any of the claims 1-4, including the following steps: S l. the all-solid-state long pulse laser is turned on to emit laser pulses, and the laser is focused on the combustion field flame through the LIBS-Raman-LIF front optical path; S2. the spectral signal is collected by LIBS spectrometer (3) and Raman-LIF spectrometer (4), LIBS spectrometer (3) adopts an external trigger mode; the LIBS spectrometer (3) is triggered by the Q-switched output signal of the all-solid-state long pulse laser (1), the time interval after laser pulse emission is tl; turning on the LIBS spectrometer (3), the acquisition time is t2; and then turning off the LIBS spectrometer (3) to obtain the LIBS spectral signal; the Raman-LIF spectrometer (4) adopts an internal trigger mode, after turning on the all-solid-state long pulse laser (1), turning on the Raman LIF spectrometer (4) by the control module, the acquisition time is t3; and then turning off the Raman-LIF spectrometer (4) to obtain the Raman-LIF spectral signal. ANNE RYAN & CO. AGENTS FOR THE APPLICANTS 21-1 21-2 Single pulse afl-soHd-statelaser LIBS pectrograp Raman-LIF pectrograp Electronic control module FIG.1 --_--------..----- : oo -. '. fl :1, 3 1"}: 1| . 18 14 16 ((
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310008953.1A CN115980006B (en) | 2023-01-04 | 2023-01-04 | Long-pulse LIBS-Raman-LIF multispectral combined in-situ detection system and detection method thereof |
Publications (2)
| Publication Number | Publication Date |
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| IES87458Y1 IES87458Y1 (en) | 2023-12-20 |
| IE20230209U1 true IE20230209U1 (en) | 2023-12-20 |
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| CN106645078A (en) * | 2016-09-20 | 2017-05-10 | 中国海洋大学 | LIBS (laser-induced breakdown spectroscopy)-Raman combined underwater in-situ detection device and detection method |
| CN211553759U (en) * | 2020-02-20 | 2020-09-22 | 中国海洋大学 | Raman-fluorescence-laser induced breakdown spectroscopy combined system |
| CN111487228A (en) * | 2020-03-20 | 2020-08-04 | 江苏大学 | Device for synchronously measuring combustion intermediate products and main components |
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| CN115980006B (en) | 2024-01-09 |
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