Raman spectrum device and method for non-contact measurement of gas composition and temperature

Abstract

The invention discloses a Raman spectrum device and method for non-contact measurement of gas temperature. The Raman spectrum device comprises a laser, a focusing lens, a temperature detection area, a collection lens, a coupling lens and a spectrometer, the focusing lens focuses laser emitted by the laser on the temperature detection area, the laser is processed by the temperature detection area to generate a Raman spectrum signal, and the Raman spectrum signal penetrates through the collecting lens and is focused on the slit of the spectrometer through the coupling lens. On the basis of a spectrograph, focused Raman spectrum signals are collected, a Raman spectrum chart is formed, then the quantitative mathematical relation between Raman rotation peaks in the Raman spectrum chart and the temperature is obtained, and non-contact measurement of the temperature of the gas is achieved. According to the Raman spectrum device and method for non-contact measurement of the gas temperature, low-detection-limit and high-sensitivity monitoring of temperature changes in the environment can be achieved, and new application is provided for application of the Raman spectrum technology in the field of non-contact extreme environment monitoring.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental monitoring, and in particular relates to a Raman spectroscopy device and method for non-contact measurement of gas temperature. Background Art

[0002] Accurate measurement of high-temperature gas temperature field is of great significance in the fields of explosion process control, fuel engine performance diagnosis, fire safety and fire control. However, the complex flow field changes during fuel gas combustion seriously limit the application of traditional temperature measurement technology. At present, the commonly used temperature measurement methods are contact measurement and non-contact measurement. Among them, contact measurement is divided into pressure temperature measurement, optical fiber temperature measurement, thermocouple temperature measurement, etc. Non-contact measurement mainly includes acoustic temperature measurement, laser interferometry, radiation temperature measurement, Raman scattering and laser absorption spectroscopy technology temperature measurement. After comparison, non-contact temperature measurement has a higher temperature upper limit because it does not directly contact, so non-contact temperature measurement has greater advantages, which can achieve low detection limit and high sensitivity monitoring of temperature changes in the test environment, and provide new technical guarantees for the application in the field of non-contact extreme environment monitoring.

[0003] The non-contact measurement technology can detect the vibration or rotation performance of each bond of the molecule under different environmental conditions. The signal is relatively stable, and it can realize real-time and accurate identification of material components and detection of vibration / rotation performance. Since the vibration and rotation performance of the gas in the test environment will change under different ambient temperature conditions, but it can be displayed in the Raman spectrum of the gas to be tested, non-contact and high-precision detection of the ambient temperature to be tested can be achieved based on the change of the gas Raman spectrum signal. In addition, the Raman spectroscopy system is simple to install, does not require pretreatment of the sample, is non-destructive, and has a fast analysis speed, which can meet the needs of real-time on-site detection. Raman spectroscopy temperature measurement technology is a non-contact optical temperature measurement technology based on the quantitative relationship between the Raman rotation peak of fuel gas and temperature. It has the characteristics of non-invasiveness and high reliability. It has great application potential in the measurement of temperature fields with limited optical windows and involving complex flow and heat exchange processes.

[0004] Raman spectroscopy directly reflects the vibration and rotational energy level information of molecules. It can not only directly measure the information of combustion materials, combustion products and intermediate products, but also accurately measure the combustion temperature through the Raman spectral information during the combustion process. The main principle of temperature measurement is that the intensity of the gas rotational Raman spectrum is closely related to its temperature. As the temperature rises, the intensity of the low quantum number rotational Raman signal decreases, and the high quantum number Raman signal increases. Therefore, the relationship between the intensity of the high and low quantum number Raman signals and the temperature can be established for temperature measurement. Based on this principle, conventional laser temperature radar uses the zero-order rotational Raman spectrum of nitrogen to measure the atmospheric space-time temperature. The zero-order rotational Raman signal is relatively strong and easy to detect. If the laser radar principle is used, only the temperature of the combustion process can be measured, and it is impossible to measure the combustion process products and temperature at the same time.

[0005] At present, the country pays great attention to areas such as explosion process control, fire safety and fire control. The standards for real-time and accurate monitoring of temperature under extreme environmental conditions are becoming more and more stringent. Therefore, temperature measurement and analysis instruments or analysis technologies with non-contact, high sensitivity and strong anti-interference capabilities have become one of the important trends in the development of modern instruments. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a Raman spectroscopy device and method for non-contact measurement of gas composition and temperature. By establishing a high-sensitivity gas Raman spectroscopy system, the gas molecule vibration Raman spectrum and rotation Raman spectrum are measured simultaneously, the gas composition and concentration are identified and quantified based on the vibration Raman spectrum, and the gas temperature is measured by the rotation Raman spectrum. The spectrum of the Raman signal of the gas at different temperatures is fully utilized to establish a quantitative mathematical relationship between the Raman vibration peak area and the concentration of the object to be measured, and the rotation peak area and the temperature of the environment to be measured, and finally realize the non-contact Raman method detection of the gas composition and temperature in the environment to be measured. This detection method has the advantages of high sensitivity, low detection limit and non-contact detection, and provides a new idea for the application of Raman spectroscopy technology in the field of extreme environmental temperature monitoring. To solve the problems existing in the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides a Raman spectroscopic device for non-contact measurement of gas temperature, comprising: a laser, a focusing lens, a temperature detection area, a collection lens, a coupling lens, a multi-reflection cavity and a spectrometer;

[0008] The focusing lens focuses the laser light emitted by the laser on the temperature detection area, and generates a Raman spectrum signal after being processed in the temperature detection area. The Raman spectrum signal passes through the collecting lens and is focused on the slit of the spectrometer through the coupling lens.

[0009] Optionally, the wavelength model of the laser is selected from any one of 266nm, 355nm and 532nm.

[0010] Optionally, the temperature detection area is used to generate Raman spectrum signals when laser interacts with typical gases under different temperature conditions.

[0011] Optionally, typical gases detected by the temperature detection zone include but are not limited to hydrogen and methane.

[0012] Optionally, the collection lens has the same focal point as the coupling lens and is used to laterally collect the Raman spectrum signal generated by the temperature detection area.

[0013] Optionally, the spectrometer adopts a Raman spectrometer to collect focused Raman spectral signals and disperse them into spectra of different wavelengths to form a Raman spectrum graph, and then non-contact measurement of gas temperature is achieved by analyzing the quantitative mathematical relationship between the Raman rotation peak and temperature in the Raman spectrum graph.

[0014] The present invention also provides a method for non-contact measurement of gas temperature, based on a Raman spectroscopic device for non-contact measurement of gas temperature, comprising the following steps:

[0015] Based on laser emitting laser;

[0016] Focusing the laser on the temperature detection area based on a focusing lens;

[0017] Based on multiple reflection cavity mirrors, the interaction distance between laser and gas sample is increased and the signal intensity is improved.

[0018] Generate Raman spectrum signals under different temperature conditions based on the temperature detection zone;

[0019] The Raman spectrum signal is collected based on a collecting lens and focused onto the slit of the spectrometer through a coupling lens;

[0020] The spectrometer collects focused Raman spectrum signals to form a Raman spectrum graph, and then obtains a quantitative mathematical relationship between the Raman rotation peak and the temperature in the Raman spectrum graph to achieve non-contact measurement of the temperature of the gas.

[0021] Optionally, the process of achieving non-contact measurement of gas temperature includes:

[0022] The least squares method is used to capture the Raman rotation peaks in the Raman spectrum for principal component analysis. The dimensionality reduction idea is used to retain nonlinear information, the spectral information of the mixture is reduced in dimension, and then a quantitative mathematical relationship between the Raman rotation peak and temperature is established. Based on the quantitative mathematical relationship, the gas temperature is measured non-contactly.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] 1) The present invention applies Raman spectroscopy technology to the monitoring of gas composition and temperature in extreme environments.

[0025] 2) Compared with the research technology in the research background, the present invention can make full use of Raman spectroscopy technology to determine the temperature of the gas in the environment to be measured based on Raman scattering optical analysis, thereby realizing non-contact temperature measurement of the gas in the environment to be measured.

[0026] 3) The present invention has a lower detection limit and higher sensitivity for measuring the gas temperature in the environment to be measured.

[0027] 4) The present invention utilizes non-contact temperature measurement using Raman spectroscopy technology, which has a higher upper limit of temperature detection compared to traditional contact temperature measurement methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0029] Figure 1 A diagram of a Raman spectroscopic device for non-contact measurement of gas temperature according to an embodiment of the present invention;

[0030] Figure 2 This is a Raman frequency shift spectrum of nitrogen within the low temperature detection range of an embodiment of the present invention;

[0031] Figure 3 A temperature measurement standard curve diagram within the low temperature detection range of an embodiment of the present invention;

[0032] Figure 4 This is a Raman frequency shift spectrum of nitrogen within the high temperature detection range of an embodiment of the present invention;

[0033] Figure 5 A temperature measurement standard curve diagram within the high temperature detection range of an embodiment of the present invention;

[0034] Figure 6 This is a Raman spectrum of air at 25°C according to an embodiment of the present invention;

[0035] Among them, 1. laser, 2. focusing lens, 3. temperature detection area, 4. collecting lens, 5. coupling lens, 6. spectrometer, 7. cavity mirror ①, 8. cavity mirror ②. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] In the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention, and do not specifically refer to any part or element in the present invention and should not be understood as limitations on the present invention.

[0040] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meanings of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0041] As introduced in the background technology, traditional contact gas temperature detection technology is susceptible to changes in the complex flow field during the combustion of fuel gas, which affects the detection sensitivity and the upper temperature limit of the detection area, severely limiting the application of traditional temperature measurement technology. In order to solve the above technical problems, the present invention proposes a Raman spectroscopy device and method for non-contact measurement of gas temperature.

[0042] A Raman spectroscopic device for non-contact measurement of gas temperature, such as Figure 1As shown, it mainly includes: laser 1, focusing lens 2, temperature detection area 3, collecting lens 4, coupling lens 5 and spectrometer 6. The focusing lens 2 focuses the laser emitted by the laser 1 on the temperature detection area 3, and the Raman spectrum signal after passing through the detection area passes through the collecting lens 4 and is focused on the slit of the spectrometer 6 through the coupling lens 5. The spectrometer 6 collects relevant Raman spectrum signals, makes full use of the spectrum of the Raman signal of the gas at different temperatures, establishes the quantitative mathematical relationship between the Raman vibration peak area and the concentration of the object to be detected, and the rotation peak area and the temperature of the environment to be detected, and finally realizes the non-contact Raman method detection of the gas composition and temperature in the environment to be detected. The detection method has the advantages of high sensitivity, low detection limit and non-contact detection.

[0043] The wavelength of the laser 1 in the present invention can be selected as 266nm, 355nm or 532nm, and the laser emitted by the laser is focused on the temperature detection area through a focusing lens.

[0044] In the present invention, the collecting lens 4 and the coupling lens 5 have the same focus, so that the spectral signal emitted from the temperature detection area is collected laterally (90°).

[0045] The focus of the coupling lens 5 in the present invention must be on the slit of the spectrometer.

[0046] The spectrometer 6 in the present invention is a Raman spectrometer, and its spectrum collection range is matched with the laser.

[0047] Typical gases detectable in the temperature detection zone 3 of the present invention include hydrogen and methane.

[0048] A method for non-contact measurement of gas temperature described in the present invention comprises the following steps:

[0049] Based on the laser 1, laser is emitted;

[0050] Focusing the laser on the temperature detection area 3 based on the focusing lens 2;

[0051] Based on the temperature detection zone 3, Raman spectrum signals under different temperature conditions are generated;

[0052] The Raman spectrum signal is collected based on the collecting lens 4 and focused onto the slit of the spectrometer 6 through the coupling lens 5;

[0053] The spectrometer 6 collects the focused Raman spectrum signal to form a Raman spectrum graph, and then obtains the quantitative mathematical relationship between the Raman rotation peak and the temperature in the Raman spectrum graph to achieve non-contact measurement of the gas temperature.

[0054] Based on the multi-reflection cavity mirror 7 and cavity mirror 8, the laser is confined in the multi-reflection cavity composed of cavity mirror 7 and cavity mirror 8, so as to increase the interaction distance between the laser and the material and improve the Raman signal intensity.

[0055] The feasible process of realizing non-contact measurement of gas temperature includes: using the least squares method to capture the Raman rotation peak in the Raman spectrum for principal component analysis, using the dimensionality reduction approach to retain nonlinear information, reducing the dimensionality of the mixture spectrum information, and then establishing a quantitative mathematical relationship between the Raman rotation peak and the temperature, and non-contactly measuring the gas temperature based on the quantitative mathematical relationship.

[0056] The following is a specific implementation example of the device of the present invention for non-contact measurement of gas composition and temperature:

[0057] (1) A sealed heatable container with a quartz window is placed in the temperature detection zone 3, and the temperatures are adjusted to 25°C, 45°C, 55°C, 63°C, 70°C, 78°C and 95°C respectively. The Raman spectrometer for non-contact gas temperature measurement of the present invention is used, and the wavelength of the laser 1 is selected as 532nm model, and the 2250-2600cm -1 The Raman signal of nitrogen under different temperature conditions within the Raman spectrum range, according to the relationship between the ratio of the high and low quantum number rotation Raman scattering signal intensity and temperature:

[0058]

[0059] Where P1(T, z) is the intensity of the high quantum number rotation Raman signal, and P2(T, z) is the intensity of the low quantum number rotation Raman signal.

[0060] The calculation results are:

[0061]

[0062] Where n1(J,z) and n2(J,z) are the numbers of high and low quantum number Raman scattered photons, and A and B are system parameters.

[0063] Since the rotation peaks are numerous and complex, the least square method is used to capture the principal components for analysis when processing the data. The nonlinear information of the Raman spectrum is retained by using the dimensionality reduction method, and the spectral information of the mixture is reduced in dimension. Figure 2 The area ratio of region 1 to region 2 is used to establish a linear correlation with temperature, and a standard curve is drawn to establish a Raman quantitative analysis method for gas temperature within the low-temperature detection range. Region 1 and region 2 are determined based on the difference between high and low quantum numbers. Region 1 represents a low quantum number, and the intensity of the low quantum number decreases with increasing temperature; region 2 represents a high quantum number, and the intensity of the high quantum number increases with increasing temperature. Figure 3 The experimental results show that the correlation coefficient R of the standard curve of temperature detection in the low temperature detection range of the established quantitative analysis method is 2 It is 0.994.

[0064] (2) A sealed heatable container with a quartz window is placed in the temperature detection zone 3, and the temperatures are adjusted to 105°C, 118°C, 130°C, 140°C, 150°C and 160°C respectively. The Raman spectrometer for non-contact gas temperature measurement of the present invention is used, and the wavelength of the laser 1 is selected as 532nm model, and the 2250-2600cm -1 The Raman signal of nitrogen under different temperature conditions within the Raman spectrum range is used to determine the relationship between the Raman rotation peak of nitrogen and temperature in different Raman spectrum ranges. Figure 4 The linear correlation between the area ratio of region 1 (low quantum number) and region 2 (high quantum number) and temperature is established, a standard curve is drawn, and a Raman quantitative analysis method for gas temperature in the high temperature detection range is established, such as Figure 5 The experimental results show that the correlation coefficient R of the standard curve of temperature detection in the low temperature detection range of the established quantitative analysis method is 2 is 0.997.

[0065] (3) The Raman spectrum of air at 25°C is as follows Figure 6 As shown in the figure, the Raman peak position corresponds to the material composition one by one, so the Raman spectrum is also called the "fingerprint" spectrum, which can identify the material composition. -1 ), nitrogen (2331cm -1 ) and water vapor (3650cm -1 ) Raman peak position, and the concentration of the substance can be quantified through its signal intensity.

[0066] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A Raman spectroscopic device for non-contact measurement of gas temperature, characterized in that: include: Laser, focusing lens, temperature detection area, collection lens, coupling lens and spectrometer; The focusing lens focuses the laser light emitted by the laser on the temperature detection area, and generates a Raman spectrum signal after being processed in the temperature detection area. The Raman spectrum signal passes through the collecting lens and is focused on the slit of the spectrometer through the coupling lens.

2. The Raman spectroscopic device for non-contact measurement of gas temperature according to claim 1, characterized in that: The wavelength model of the laser is selected from any one of 266nm, 355nm and 532nm.

3. The Raman spectroscopic device for non-contact measurement of gas temperature according to claim 1, characterized in that: The temperature detection area is used for the laser to interact with typical gases under different temperature conditions to generate Raman spectrum signals.

4. The Raman spectroscopic device for non-contact measurement of gas temperature according to claim 3, characterized in that: Typical gases detected by the temperature detection zone include, but are not limited to, hydrogen and methane.

5. The Raman spectroscopic device for non-contact measurement of gas temperature according to claim 1, characterized in that: The collecting lens has the same focal point as the coupling lens and is used to laterally collect the Raman spectrum signal generated by the temperature detection area.

6. The Raman spectroscopic device for non-contact measurement of gas temperature according to claim 1, characterized in that: The spectrometer adopts a Raman spectrometer to collect focused Raman spectrum signals and disperse them into spectrums of different wavelengths to form a Raman spectrum graph, and then realizes non-contact measurement of gas temperature by analyzing the quantitative mathematical relationship between the Raman rotation peak and temperature in the Raman spectrum graph.

7. A method for non-contact measurement of gas temperature, characterized in that: The Raman spectroscopic device for non-contact measurement of gas temperature according to any one of claims 1 to 6 comprises the following steps: Based on laser emitting laser; Focusing the laser on the temperature detection area based on a focusing lens; Generate Raman spectrum signals under different temperature conditions based on the temperature detection zone; The Raman spectrum signal is collected based on a collecting lens and focused onto the slit of the spectrometer through a coupling lens; The spectrometer collects focused Raman spectrum signals to form a Raman spectrum graph, and then obtains a quantitative mathematical relationship between the Raman rotation peak and the temperature in the Raman spectrum graph to achieve non-contact measurement of the temperature of the gas.

8. The method for non-contact measurement of gas temperature according to claim 7, characterized in that: The process of achieving non-contact measurement of gas temperature includes: The least squares method is used to capture the Raman rotation peaks in the Raman spectrum for principal component analysis. The dimensionality reduction idea is used to retain nonlinear information, the spectral information of the mixture is reduced in dimension, and then a quantitative mathematical relationship between the Raman rotation peak and temperature is established. Based on the quantitative mathematical relationship, the gas temperature is measured non-contactly.

9. The method for non-contact measurement of gas temperature according to claim 8, characterized in that: The quantitative mathematical relationship between the Raman rotation peak and temperature is: Among them, n1(J,z), n2(J,z) are the numbers of high and low quantum number Raman scattered photons, A and B are system parameters, and T(z) is the temperature.

Images