CN210571955U

CN210571955U - Device for realizing methyl measurement and imaging based on photolysis laser induced fluorescence

Info

Publication number: CN210571955U
Application number: CN201920367299.2U
Authority: CN
Inventors: 李博; 刘吉绪; 高强; 张大源
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2019-03-19
Filing date: 2019-03-19
Publication date: 2020-05-19
Anticipated expiration: 2029-03-19

Abstract

The utility model discloses a device based on photodissociation laser induction fluorescence realizes methyl measurement and formation of image, include: a first nanosecond laser for outputting CH₃Photolytic laser of (2) to convert CH₃Photolysis to CH at low energy level; a second nanosecond laser for outputting CH₃Photolysis of the detection laser of the product CH to excite CH from a low level to a high level; the beam combiner is used for realizing the spatial coincidence of the photolysis laser and the detection laser; a lens device for converting the superposed laser beams into laser sheets to realize CH alignment₃Imaging the plane of (a); burner, is CH₃The generating device is used for generating combustion flame of hydrocarbon fuel; camera for photolyzing fluorescence of product CHAnd collecting optical signals. The utility model discloses the experimental system is simple, can realize CH₃The interference-free on-line measurement is realized, the photolysis efficiency is high, and the yield is high; can realize CH in flow field₃Single transient imaging of (2).

Description

Device for realizing methyl measurement and imaging based on photolysis laser induced fluorescence

Technical Field

The utility model relates to a methyl measurement and imaging technology field especially relate to a device based on photodissociation laser induction fluorescence realizes methyl measurement and formation of image.

Background

Methyl (CH)₃) Is an important intermediate component in the fields of fuel combustion, atmospheric chemistry, chemical vapor deposition, ultrafast kinetics and the like. In the chemical industry, CH₃Is a key precursor for synthesizing diamond based on Chemical Vapor Deposition (CVD) technology, and in recent years, with the great breakthrough of CVD single crystal diamond rapid synthesis technology, related researchers are gradually focusing on synthesizing diamond with larger size, and the process needs to realize the CH synthesis₃On-line measurement of spatial distribution. In the field of combustion, in particular natural gas (CH)₄) Combustion of CH₃Also plays an important role. First, CH₃Is considered to be a main component for initiating a combustion reaction radical chain process, and is mainly used for ignition, flame propagation and the like of hydrocarbon fuels. Secondly, there are studies showing the generation of Polycyclic Aromatic Hydrocarbons (PAH) and Soot (Soot) and CH during combustion₃Related, therefore, to improve fuel combustion efficiency and reduce pollutant emissions, CH is required₃Intensive studies were conducted. Third, Direct Numerical Simulation (DNS) results show CH in the combustion field₃Has a correlation with the local heat release rate of the flame, which means to the CH in the combustion field₃Visualization can deduce the distribution information of the combustion heat release rate. It can be seen that the development of corresponding test techniques achieves CH in the convection field or combustion field₃The measurement and imaging of (A) have important significance in many fields.

CH₃As an intermediate component in chemical reaction processes, the survival life is extremely short and cannot be measured by conventional sampling methods, which are currently known for CH₃The measurement method mainly includes optical measurement, and mainly includes methods such as mass spectrometry, absorption spectrometry, Degenerate Four-wave Mixing (DFWM) and Resonance Enhanced Multi-photon Ionization (REMPI) according to the measurement principle. The above measurement means can realize CH₃But inThere are certain inevitable problems in the measurement process. Lower spatial resolution such as absorption spectroscopy; the DFWM technology is based on three-order nonlinear optical effect, and the experimental system is relatively complex; measuring CH by REMPI method₃Physical probes or electrodes required for collecting electrons or ions can interfere a reaction flow field; coherent microwave Rayleigh scattering technology based on REMPI (REMPI) can realize CH₃Concentration measurement and CH realization by point-by-point scanning₃But still does not solve the problem of low spatial resolution.

Laser-induced Fluorescence (LIF) technology is one of the most commonly used methods for flow field component measurement and imaging. The technology is characterized in that a component to be measured is subjected to resonance excitation by using laser with a specific wavelength, so that the component to be measured undergoes transition from a low energy level to a high energy level, and then the purpose of component measurement is achieved by collecting a fluorescence signal released in the process that the component to be measured spontaneously transitions from the high energy level back to the low energy level. CH (CH)₃Lack of a suitable excitation diagnostic strategy for CH directly due to strong pre-dissociation of the excited state of the electron₃LIF measurement. In response to the above problems, researchers developed an indirect measurement of CH₃The method of (1), Laser photodissociation-induced Fluorescence (LPIF), has a core idea of using Laser to irradiate CH with Laser₃The photolysis generates a CH photolysis product at a high energy level, the unstable CH at the high energy level can spontaneously transit to a low energy level, a fluorescence signal is released in the transition process, and the CH can be indirectly realized by collecting the fluorescence signal₃The measurement of (2). Desgroup et al]Based on the technology, the intermediate component CH is successfully combusted under the low-pressure condition₃By means of a multi-photon process with a laser having a wavelength of 205nm₃Photolysis to CH (A) at a high energy level²Δ), then CH (A)²Delta) transition back to CH (X)²Π) emits fluorescence with a wavelength near 431nm, and CH is realized by collecting fluorescence signals₃The measurement of (2). However, due to the problems of limited laser energy of 205nm laser, low photolysis efficiency in a multi-photon process and the like, only CH in the region to be detected is realized₃Point measurement of (2). Li et al improved on the above problem by using a wavelength of 212.8nThe Laser of m replaces the Laser of 205nm, and the Planar Laser-induced Fluorescence (PLIF) technology is combined to realize the CH coupling₃Two-dimensional imaging of (2). Although the laser energy is improved, only CH is obtained due to the problem of low photolysis efficiency of a multi-photon process₃Multiple mean imaging of (1) failing to achieve CH₃Single transient imaging of (2).

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a device based on photodissociation laser-induced fluorescence realizes methyl measurement and formation of image to the technical defect who exists among the prior art.

For realizing the utility model discloses a technical scheme that the purpose adopted is:

a device for realizing methyl measurement and imaging based on photolysis laser-induced fluorescence comprises: a first nanosecond laser for outputting CH₃Photolytic laser of (2) to convert CH₃Photolysis to CH at low energy level;

a second nanosecond laser for outputting CH₃Photolysis of the detection laser of the product CH to excite CH from a low level to a high level;

the beam combiner is used for realizing the spatial coincidence of the photolysis laser and the detection laser;

a lens device for converting the superposed laser beams into laser sheets to realize CH alignment₃Imaging the plane of (a);

burner, is CH₃The generating device is used for generating combustion flame of hydrocarbon fuel;

and a camera for collecting a fluorescence signal of the photolysis product CH.

The device for realizing methyl measurement and imaging based on photolysis laser induced fluorescence further comprises a light beam cut-off device for collecting laser penetrating through a region to be measured and avoiding damage caused by incidence on a human body or other objects.

The camera is an ICCD camera.

Compared with the prior art, the beneficial effects of the utility model are that:

the utility model discloses the experimental system is simple, canCan realize CH₃Interference-free online measurement; photolytic laser is the conversion of CH by a single photon process₃Photolysis to low level CH (X)²Π), high photolysis efficiency and high yield; the photolysis laser induction fluorescence method measuring device can realize CH in a flow field₃Single-frame transient imaging of (2); the device measures CH₃The spatial resolution of (2) is higher; CH (CH)₃The signal-to-noise ratio (SNR) of the visualization of (a) is high.

Drawings

Fig. 1 is a schematic structural diagram of an apparatus for performing methyl measurement and imaging based on photolysis laser-induced fluorescence.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, the device for realizing methyl measurement and imaging based on photolysis laser induced fluorescence of the present invention comprises;

nanosecond laser 1 for outputting CH₃Photolytic laser of (2) to convert CH₃Photolysis to CH at low energy level;

nanosecond laser 2 for outputting CH₃Photolysis of the detection laser of the product CH to excite CH from a low level to a high level;

the beam combiner 3 is used for realizing the spatial coincidence of the photolysis laser and the detection laser;

a lens device 4 for converting the laser beam combined by the beam combining mirror 3 into a laser sheet to realize the CH alignment₃Imaging the plane of (a);

burner 5, denoted CH₃The generating device is used for generating combustion flame of hydrocarbon fuel to form a flow field to be measured, and flow field parameters such as the equivalence ratio, the flow velocity and the like of the flame can be adjusted through the control system;

the beam cut-off device 6 is used for collecting the laser penetrating through the area to be detected and avoiding the laser from being incident on a human body or other objects to cause damage;

an ICCD camera 7 for fluorescence signal acquisition of the photolysis product CH.

The lens device 4 is a lens combination to realize the above function, i.e. the laser beam combined by the beam combining mirror 3 is converted into a laser sheet to realize CH alignment₃The plane imaging of (2) is enough, and the plane imaging can be specifically selected according to the actual situation.

The utility model discloses a brand-new indirect measurement CH₃The measuring device of (1). The working principle is as follows: two beams of laser are adopted to jointly act on an area to be detected, one beam of laser is used as photolysis laser, and CH is subjected to single photon process₃Photolysis to CH (X) at a low energy level²Π), another laser as a probing laser for CH₃Photolysis product of CH (X)²II) is excited from low energy level to high energy level, CH with high energy level is unstable and can spontaneously transit to low energy level, a fluorescence signal with the wavelength near 431nm can be released in the transition process, and CH can be indirectly realized by collecting the fluorescence signal of CH₃And (4) measuring and imaging.

In the embodiment, it is preferable to use laser light having a wavelength of 212.8nm as CH₃The photolysis laser of (1) employs a laser having a wavelength of 387nm as the photolysis product CH (X)²Π), converting the laser beam into a laser sheet through a lens to realize CH alignment₃Is imaged.

The utility model discloses based on photodissociation laser induced fluorescence realizes that the working process of the device of methyl measurement and formation of image is as follows:

(1) a nanosecond laser 1 generates photolysis laser with the wavelength of 212.8nm, and another nanosecond laser 2 generates detection laser with the wavelength of 387 nm; (2) the two beams of laser pass through the reflector and the beam combiner 3 to realize spatial coincidence; (3) the laser after the beam closing is converted into a laser sheet by a laser beam through the lens device 4, and the focusing position of the laser sheet is adjusted to be positioned in the area of the flow field to be measured. (4) CH in flow field to be measured₃First, the light is decomposed by a photolysis laser with the wavelength of 212.8nm to generate CH (X) at a low energy level through single-photon process photolysis²Π), after which the molecule is excited again to CH (B) at a high energy level by a detection laser having a wavelength of 387nm²Σ^-) High level of CH (B)²Σ^-) CH (X) transitioning back to low energy level²Π) to release fluorescent signal with wavelength near 431nmNumber (n). (5) The released fluorescent signal is captured by an ICCD camera 7 equipped with a filter and transmitted to a control system, and then the captured fluorescent signal is analyzed and processed.

According to the actual measurement effect, the time sequence (time interval between photolysis laser and detection laser) between the two beams of laser, the ICCD camera shooting parameter, the flow velocity of the flow field to be measured, the flame equivalence ratio and other parameters can be adjusted through the control system to carry out optimization.

The utility model discloses a CH₃The measuring device has the following advantages:

the experimental system is simple and can realize CH₃Interference-free online measurement; photolytic laser is the conversion of CH by a single photon process₃Photolysis to low level CH (X)²Π), high photolysis efficiency and high yield; the photolysis laser induction fluorescence method measuring device can realize CH in a flow field₃Single-frame transient imaging of (2); the device measures CH₃The spatial resolution of (2) is higher; CH (CH)₃The signal-to-noise ratio (SNR) of the visualization of (a) is high.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A device for realizing methyl measurement and imaging based on photolysis laser induced fluorescence is characterized by comprising:

a first nanosecond laser for outputting CH₃Photolytic laser of (2) to convert CH₃Photolysis to CH at low energy level;

a lens device for converting the superposed laser beams into laser sheets to realize CH alignment₃OfSurface imaging;

and a camera for collecting a fluorescence signal of the photolysis product CH.

2. The apparatus of claim 1, further comprising a beam stop for collecting the laser beam transmitted through the area to be measured to avoid damage to human body or other objects.

3. The apparatus according to claim 1, wherein the camera is an ICCD camera.