CN102889959A - Device for measuring gas pressure based on Rayleigh-Brillouin scattering spectral characteristic - Google Patents

Abstract

The invention relates to a novel method and an experiment device for measuring gas pressure based on a Rayleigh-Brillouin scattering spectrum of gas. Sound speed under different pressure intensities can be measured by detecting Brillouin frequency shift amount in the Rayleigh-Brillouin scattering spectrum at different temperatures, so the pressure can be measured. 355nm single-mode laser, 532nm single-mode laser and 1,064nm single-mode laser are emitted into the gas of a scattering pool, and interact with various gas molecules in the gas, a scattering signal passes through a Fabry-Perot (F-P) scanning interferometer and is received by a photon detector, the Rayleigh-Brillouin scattering spectrum of the gas can be obtained, and the gas pressure can be accurately measured at different temperatures by analysis and computation of a spectral function.

Description

A kind of device based on Rayleigh-Brillouin scattering spectral characteristic measurement gaseous tension

Technical field:

The present invention relates to a kind of device of the spectrum measurement gaseous tension based on gas Rayleigh-Brillouin scattering.

Technical background:

In commercial production, general working pressure table, pressure transducer, mercury atmospheric pressure meter, the baroceptor measurement gas pressure such as the atmospheric pressure meter of absolute pressure sensor.When measuring high pressure, high temperature gas flow, baroceptor when measuring facing to more impact.Therefore, in measuring process, the pressure of baroceptor can not well be measured actual pressure.And the instantaneous measurement of the gases at high pressure difficult point in the pressure survey especially, main cause is, and temperature is high, and pressure is large, and temperature variation is fast.

The common method of measuring at present high temperature and high pressure gas is divided into contact and contactless.During with contact type measurement pressure, because sensing element is to the disturbance of pressure field, the inertia of sensor and the limitation in pressure measurement zone, so its measurement result is not satisfactory.Non-contact type pressure testing method, particularly optics manometry, because the advantage such as its measurement range is large, measured pressure field soon, is not disturbed in response and transient response is good, thereby in the superiority that has uniqueness aspect the measurement of pressure field.

Mentioned in the literary composition a kind of novel, realize method to the pressure real-time measuring of high-temperature gas by measuring the atmosphere Brillouin shift.Because the Brillouin shift of high-temperature gas becomes one to one relation with atmospheric temperature, therefore as long as measure accurately the size that the Brillouin shift amount of high-temperature gas can obtain pressure.

Summary of the invention:

In order to realize the accurate measurement of high-temperature gas pressure, we have proposed a kind of method of utilizing Rayleigh-Brillouin scattering spectrum measurement pressure.The method is by formula (1), measure the Brillouin shift under the uniform temperature, realize the measurement of the velocity of sound, theory shows, the temperature of ideal gas and the velocity of sound are obeyed formula (2), obey formula (3) so can shift temperature and Brillouin's frequency displacement onto:

$\mathrm{\Δv}=\±\frac{2\mathrm{nv}}{\mathrm{\λ}}\sin \frac{\mathrm{\θ}}{2}---\left(1\right)$

$v=\sqrt{\frac{\mathrm{\γ}*R*T}{m}}---\left(2\right)$

$p=\frac{{\mathrm{<figure-callout\; id="2"\; label="ml"\; filenames="HSA00000781203400011.png"\; state="\{\{state\}\}">ml</figure-callout>}}^2{\mathrm{Dv}}^{2}N}{{4\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000781203400011.png"\; state="\{\{state\}\}">N</figure-callout>}}^2\mathrm{gsi}{n}^2\frac{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="HSA00000781203400011.png"\; state="\{\{state\}\}">q</figure-callout>}}{2}{\mathrm{VN}}_A}---\left(3\right)$

Δ v is the Brillouin shift in the medium in the formula (1), and n is medium refraction index, and v is the velocity of sound in the medium, and λ is laser wavelength of incidence, and θ is scattering angle, ± be corresponding Stokes and anti-Stokes light.

V is the velocity of sound in the medium in the formula (2), and γ is the specific heat capacity of ideal gas, and R is ideal gas constant, and T is gas temperature, and m is the molecular weight of air.

Therefore, as long as experimentally determined frequency displacement Δ v, can obtain according to formula (3) pressure of gas.V in the formula (3) is gas volume, and N is molecular number, N _ABe Avogadro's number.

The invention provides a kind of experimental provision of new measurement gas pressure, realized the measurement at the gaseous tension of high temperature.

Detection system of the present invention comprises: pouring-in pulsed laser comprises 355nm, 532nm, three kinds of long wavelength lasers (1) of 1064nm, convex lens (2,4,6,10,12,15,17), collimation and filter system (11), polaroid (5), slit (3,9,16,18), scattering cell (7), scanning interferometer (13), energy recovery pond (8), signal detecting device (14).

The technical matters scheme that the present invention solves is: laser instrument (1) output wavelength is 355nm, the narrow band light of the vertical polarization of 532nm and 1064nm, converge through convex lens (2), pass through again slit (3) filtering, arrive convex lens (4) and collimate, through polaroid (5), arrive again convex lens (6), arrive in the scattering cell (7), interact with gas molecule, produce signal, finally see through scattering cell and enter energy recovery pond (8).The scattered signal that device produces from 180 ° of probe gas ponds (7), for being coupled in the beam splitting system (13) of guaranteeing that scattered signal can maximal efficiency, scattered signal collimates through convex lens (6), through 1/2nd slides (15), again by polaroid (5), optical slits (9) after filtration, collimation and filtering system (10,11), converged in the scanning interferometer (13) by convex lens (12), final scattered signal is scattered signal detecting device (14) and computing machine is observed.，

The technical advantage of this new method and detection system is apparent.One, adopting Rayleigh-Brillouin scattering frequency spectrum to come the pressure of Calculation of Gas, namely utilize the Brillouin shift formula after obtaining scattering, obtain in real time gaseous tension by computer program, is that a kind of new spectroscopic methodology that utilizes comes the method for gaging pressure.Two, detection system has very high reliability and degree of accuracy, is mainly reflected in: 1. adopt 355nm, 532nm and 1064nm laser can obtain obvious Brillouin scattering peak, realize the accurate Calculation of pressure.2. adopt the scan-type f-p interferometer that places under the constant temperature as the high resolving power beam splitting system, realize the accurate measurement to Brillouin shift.3. the f-p interferometer is placed constant temperature oven, having reduced external environment affects it, has improved the reliability and stability of detection system.4. scattering cell places the regulating box that temperature and pressure can be regulated, and can simulate different pressures, and the gas of temperature is realized the pressure survey under the different temperatures.5. scattering cell adopts the design of Brewster window, has greatly weakened the reflected light in the pond, has strengthened scattered signal.6. use photon detector and photon collection card detecting light spectrum image, can obtain high sensitivity, high-resolution spectrum picture.

Description of drawings:

Accompanying drawing 1 has provided the sniffer schematic diagram of Rayleigh-Brillouin scattering spectral characteristic.

Accompanying drawing 2 has provided collimation in the device and the schematic diagram of filtering system.

Accompanying drawing 3 has provided the experimental spectrum figure that photon detector gathers.

Embodiment

Embodiment 1:

As shown in Figure 1, this device comprises: pouring-in pulsed laser (1), convex lens (2,4,6,10,12,15,17), collimation and filter system (11), polaroid (5), slit (3,9,16,18), scattering cell (7), scanning interferometer (13), energy recovery pond (8), signal detecting device (14).

Laser instrument (1) output wavelength is 355nm, the narrow band light of the vertical polarization of 532nm and 1064nm, converge through convex lens (2), pass through again slit (3) filtering, arriving convex lens (4) collimates, through polaroid (5), enter energy recovery pond (8).The scattered signal that device produces from 180 ° of probe gas ponds (7), for being coupled in the beam splitting system (13) of guaranteeing that scattered signal can maximal efficiency, scattered signal collimates through convex lens (6), by polaroid (5), optical slits (9) after filtration, collimation and filtering system (10,11), converged in the scanning interferometer (13) by convex lens (12), final scattered signal is scattered acquisition of signal dress arm (14) and computing machine is observed.

Embodiment 2:

As shown in Figure 2, filter system (7) comprising: convex lens (15,17) and slit (16,18).

In order in experiment, to detect faint scattered signal, realize the detection of brillouin scattering signal, scattered signal must be coupled in the high-resolution beam splitting system (11) as much as possible, so designed slit slit 9, lens 10 (D in beam splitting system ₁₀=0.1mm, f ₁₁=80mm) and optical filtering and spot diameter integration system (11), signal at first passes through slit 9 (D ₁₀=0.1mm) reduce the space divergence angle, there are lens 10 (f=80mm) to collimate, then focused on slit 16 (D16=100um) by lens 15 (fl5=50mm) and carry out spatial filtering, again collimated by lens 17 (fl7=50mm) at last, for so that spot diameter be limited in the scanner acceptable scope, it is carried out spot diameter by slit 18 (D18=2mm) proofread and correct, finally allow hot spot be coupled in the f-p to greatest extent.

Accompanying drawing 3 is that the detection system of using accompanying drawing 1 and accompanying drawing 2 to form is carried out Rayleigh-brillouin frequency spectrometry and obtained the spectrogram that photon detector collects.As shown in Figure 3, as long as measure brillouin scattering signal, just can obtain gaseous tension according to the Brillouin shift formula.

Claims (6)

1. device based on Rayleigh-Brillouin scattering spectrum measurement gaseous tension, this device comprises pouring-in pulsed laser (1), convex lens (2,4,6,10,12,15,17), collimation and filter system (11), polaroid (5), slit (3,9,16,18), scattering cell (7), scanning interferometer (13), energy recovery pond (8), signal detecting device (14).

Laser instrument (1) output wavelength is 355nm, the narrow band light of the vertical polarization of 532nm and 1064nm, converge through convex lens (2), pass through again slit (3) filtering, arrive convex lens (4) and collimate, through polaroid (5), arrive again convex lens (6), arrive in the scattering cell (7), interact with gas molecule, produce signal, finally see through scattering cell and enter energy recovery pond (8).The scattered signal that device produces from 180 ° of probe gas ponds (7), for being coupled in the beam splitting system (13) of guaranteeing that scattered signal can maximal efficiency, scattered signal collimates through convex lens (6), by polaroid (5), optical slits (9) after filtration, collimation and filtering system (10,11), be collimated in the scanning interferometer (13) by convex lens (12), the final scattered signal that produces is scattered signal detecting device (14) and carries out observation and the record of image and data by computing machine.

This experimental technique has very high spectral resolution, and the lot of advantages such as detection accuracy height have high-strength using value in real life, for certain basis has been established in later on this class methods detection.

2. the device based on Rayleigh-Brillouin scattering spectrum measurement gaseous tension as claimed in claim 1, it is characterized in that: the design of scattering cell (7), one, can be by regulating external pressure, temperature is simulated the gas of different temperatures and pressure, realize the measurement of different pressures under the different temperatures Adopt Brewster window, can greatly reduce the reflected light of scattering cell, the interference that reduces parasitic light just can obtain obvious scattered signal

3. the device based on Rayleigh-Brillouin scattering spectrum measurement gaseous tension as claimed in claim 1, it is characterized in that: survey the selection of 100um slit (16) in the light path, implementation space filtering, the parasitic light of filtering scattered signal, the detection of scattered signal can realize.

4. the device based on Rayleigh-Brillouin scattering spectrum measurement gaseous tension as claimed in claim 1, it is characterized in that: the placement of f-p scanning interferometer and the selection of parameter, realized the detection of feeble signal, one, f-p is placed the controlled constant temperature oven of temperature, can guarantee stability and reliability that f-p uses; Two, the major parameter of f-p is: Free Spectral Range 30GHZ, and two specular reflectances of the front and back plated film of f-p all are 99%, centre wavelength is 355nm, 532nm and 1064nm etc., bandwidth is 130MHZ, fineness is 130.

5. the device based on Rayleigh-Brillouin scattering spectrum measurement gaseous tension as claimed in claim 1, one of them key is the selection of slit (16), the size of slit is the power of the signal that detects of impact and the intensity of noise directly.

6. the device based on Rayleigh-Brillouin scattering spectrum measurement gaseous tension as claimed in claim 1, carry out visual inspection less than the experiment of 1064nm light the time, carry out first the calibration of light path with green glow, so that the state of light path is surveyed carrying out 1064nm light when the state of the best.

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