All-fiber multi-group gas concentration monitoring method

Abstract

The invention provides an all-fiber multi-group gas concentration monitoring method, which comprises a plurality of groups of detection units and a controller, and each group of detection unit comprises a tunable laser, a laser detector, a detection chamber and a harmonic detector; a light output port of the tunable laser is connected to a light input port of the detection chamber through an optical fiber, an input end of the detector is connected to a light output port of the detection chamber through an optical fiber, an output end of the detector is connected to the harmonic detector, and an output end of the harmonic detector is connected to the controller. The control output end of the controller is connected to the control input end of the tunable laser; the controller determines the concentration of the detected sample gas according to the following method: the controller determines the light intensity value of the output laser of the DFB laser; the controller receives the light intensity value of the laser which is determined by the harmonic detector and passes through the sample gas in the detection chamber; and the controller determines the concentration of the sample gas according to the light intensity value passing through the detection chamber.

Description

Technical Field

[0001] The invention relates to a gas concentration monitoring method, and in particular to an all-optical fiber multi-group gas concentration monitoring method. Background Art

[0002] In industrial applications, the accuracy of gas concentration detection provides reliable data support for industrial production and environmental management.

[0003] In the prior art, spectroscopy is generally used to detect the concentration of target gas in sample gas (referred to as sample gas). The existing spectroscopy method has a relatively complex system structure and low stability. If the structure is simplified, it is difficult to ensure the accuracy of gas monitoring, and it is difficult to measure multiple gases simultaneously in the prior art.

[0004] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an all-fiber multi-group gas concentration monitoring method, which can detect multiple gas concentrations at the same time and effectively ensure the accuracy of the final detection results. The structure is simpler than the existing technology, with high stability and strong portability.

[0006] The present invention provides an all-fiber multi-group gas concentration monitoring method, comprising multiple groups of detection units and a controller, wherein each group of detection units comprises a tunable laser, a laser detector, a detection chamber and a harmonic detector;

[0007] The light output port of the tunable laser is connected to the light input port of the detection chamber through an optical fiber, the input end of the detector is connected to the light output port of the detection chamber through an optical fiber, the output end of the detector is connected to the harmonic detector, the output end of the harmonic detector is connected to the controller, and the control output end of the controller is connected to the control input end of the tunable laser;

[0008] The controller determines the concentration of the sample gas to be measured according to the following method:

[0009] The controller determines the light intensity value of the output laser of the DFB laser;

[0010] The controller receives the light intensity value of the laser after the harmonic detector determines that the laser passes through the sample gas in the detection chamber;

[0011] The controller determines the concentration of the sample gas based on the light intensity value after passing through the detection chamber.

[0012] Furthermore, the harmonic detector determines the intensity of the laser light after passing through the sample gas chamber:

[0013]

[0014] Where: I(v,t) is the light intensity after passing through the sample gas chamber, I0 is the light intensity of the tunable laser output, n is the light intensity modulation coefficient of the tunable laser, v f is the wavelength modulation amplitude, △v is the half-height full width of the absorption line, w is the sinusoidal modulation frequency coefficient of the tunable laser, L is the total optical path of the absorption path, C is the concentration of the measured gas in the sample gas, and a0 is the absorption coefficient of the pure gas at the center of the absorption line.

[0015] Further, the controller determines the concentration of the sample gas according to the light intensity value after passing through the detection chamber, specifically including:

[0016] The controller expands the light intensity value I(v, t) after passing through the sample gas chamber using the Fourier series, and extracts the quadratic term in the Fourier series of the light intensity value I(v, t):

[0017] I 2f = -ka0LCI0;

[0018] Where: I 2f The quadratic term in the Fourier series representing the light intensity value I(v,t), k is the coefficient;

[0019] The quadratic term I in the Fourier series of the light intensity value I(v,t) 2f The concentration value C of the measured gas in the sample gas is obtained by solving the problem.

[0020] Further, the coefficient k is determined by the following method:

[0021]

[0022] Further, the controller determines the control signal of the tunable laser according to the following method:

[0023] Input reference gas into the sample gas chamber;

[0024] The controller controls the tunable laser to output a laser signal, and the laser signal passes through the sample gas chamber and the harmonic detector detects the light intensity value;

[0025] Control signal to build concentration signal model:

[0026]

[0027] Where: C is the concentration of the measured gas in the reference gas, a(v) is the absorption coefficient of unit concentration when the laser wavelength is v, I0(v) is the light intensity of the laser output, and I(v) is the light intensity of the harmonic detector output;

[0028] The controller will As the control input signal of the tunable laser.

[0029] Furthermore, the absorption coefficient a(v) per unit concentration at a laser wavelength v is determined by the following method:

[0030]

[0031] Where: v is the wavelength of the laser, v c is the central absorption peak of the laser.

[0032] The beneficial effects of the present invention are as follows: through the present invention, multiple gas concentrations can be detected simultaneously, and the accuracy of the final detection result can be effectively ensured. Moreover, the structure is simpler than the prior art, with high stability and strong portability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0034] Figure 1 It is a schematic diagram of the structure of the present invention.

[0035] Figure 2 It is a schematic diagram of the process of the present invention.

[0036] Figure 3 It is a schematic diagram of the sample gas chamber structure of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below:

[0038] The present invention provides an all-fiber multi-group gas concentration monitoring method, comprising multiple groups of detection units and a controller, wherein each group of detection units comprises a tunable laser, a laser detector, a detection chamber and a harmonic detector;

[0039] The light output port of the tunable laser is connected to the light input port of the detection chamber through an optical fiber, the input end of the detector is connected to the light output port of the detection chamber through an optical fiber, the output end of the detector is connected to the harmonic detector, the output end of the harmonic detector is connected to the controller, and the control output end of the controller is connected to the control input end of the tunable laser;

[0040] The controller determines the concentration of the sample gas to be measured according to the following method:

[0041] The controller determines the light intensity value of the output laser of the DFB laser;

[0042] The controller receives the light intensity value of the laser after the harmonic detector determines that the laser passes through the sample gas in the detection chamber;

[0043] The controller determines the concentration of the sample gas according to the light intensity value after passing through the detection chamber, wherein the tunable laser adopts the existing TDLAS laser, and the harmonic detector adopts the existing equipment, which will not be elaborated here. Through the above structure, multiple gas concentrations can be detected at the same time, and the accuracy of the final detection result can be effectively ensured. Moreover, the structure is simpler than the existing technology, with high stability and strong portability. Of course, in practice, a corresponding display is also provided to connect with the controller to display information such as spectrum and concentration waveform changes.

[0044] like Figure 3 As shown, Figure 3 The structure of the sample gas chamber is shown in the figure, 1 is the sample gas input port, 4 is the laser input port, 3 is the laser output port, 5 is the chamber of the sample gas chamber, and 2 is the shell of the sample gas chamber.

[0045] In this embodiment, the harmonic detector determines the light intensity of the laser after passing through the sample gas chamber:

[0046]

[0047] Where: I(v,t) is the light intensity after passing through the sample gas chamber, I0 is the light intensity of the tunable laser output, n is the light intensity modulation coefficient of the tunable laser, v f is the wavelength modulation amplitude, △v is the half-height full width of the absorption line, w is the sinusoidal modulation frequency coefficient of the tunable laser, L is the total optical path of the absorption path, C is the concentration of the measured gas in the sample gas, and a0 is the absorption coefficient of the pure gas at the center of the absorption line.

[0048] In this embodiment, the controller determines the concentration of the sample gas according to the light intensity value after passing through the detection chamber, specifically including:

[0049] The controller expands the light intensity value I(v, t) after passing through the sample gas chamber using the Fourier series, and extracts the quadratic term in the Fourier series of the light intensity value I(v, t):

[0050] I 2f = -ka0LCI0;

[0051] Where: I 2f The quadratic term in the Fourier series representing the light intensity value I(v,t), k is the coefficient;

[0052] The quadratic term I in the Fourier series of the light intensity value I(v,t) 2f The concentration value C of the measured gas in the sample gas is obtained by solving the problem.

[0053] In this embodiment, the coefficient k is determined by the following method:

[0054]

[0055] In this embodiment, the controller determines the control signal of the tunable laser according to the following method:

[0056] Input reference gas into the sample gas chamber;

[0057] The controller controls the tunable laser to output a laser signal, and the laser signal passes through the sample gas chamber and the harmonic detector detects the light intensity value;

[0058] Control signal to build concentration signal model:

[0059]

[0060] Where: C is the concentration of the measured gas in the reference gas, a(v) is the absorption coefficient of unit concentration when the laser wavelength is v, I0(v) is the light intensity of the laser output, and I(v) is the light intensity of the harmonic detector output;

[0061] The controller will As the control input signal of the tunable laser.

[0062] The absorption coefficient a(v) per unit concentration at a laser wavelength v is determined by the following method:

[0063]

[0064] Where: v is the wavelength of the laser, v c is the central absorption peak of the laser.

[0065] In the drawings, dotted lines represent optical signals.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An all-fiber multi-group gas concentration monitoring method, characterized in that: It includes multiple groups of detection units and a controller, each group of detection units includes a tunable laser, a laser detector, a detection chamber and a harmonic detector; The light output port of the tunable laser is connected to the light input port of the detection chamber through an optical fiber, the input end of the detector is connected to the light output port of the detection chamber through an optical fiber, the output end of the detector is connected to the harmonic detector, the output end of the harmonic detector is connected to the controller, and the control output end of the controller is connected to the control input end of the tunable laser; The controller determines the concentration of the sample gas to be measured according to the following method: The controller determines the light intensity value of the output laser of the DFB laser; The controller receives the light intensity value of the laser after the harmonic detector determines that the laser passes through the sample gas in the detection chamber; The controller determines the concentration of the sample gas based on the light intensity value after passing through the detection chamber.

2. The all-fiber multi-group gas concentration monitoring method according to claim 1, characterized in that: The harmonic detector determines the intensity of the laser light after passing through the sample gas cell: Where: I(v,t) is the light intensity after passing through the sample gas chamber, I0 is the light intensity of the tunable laser output, n is the light intensity modulation coefficient of the tunable laser, v f is the wavelength modulation amplitude, △v is the half-height full width of the absorption line, w is the sinusoidal modulation frequency coefficient of the tunable laser, L is the total optical path of the absorption path, C is the concentration of the measured gas in the sample gas, and a0 is the absorption coefficient of the pure gas at the center of the absorption line.

3. The all-fiber multi-group gas concentration monitoring method according to claim 2, characterized in that: The controller determines the concentration of the sample gas according to the light intensity value after passing through the detection chamber, specifically including: The controller expands the light intensity value I(v, t) after passing through the sample gas chamber using the Fourier series, and extracts the quadratic term in the Fourier series of the light intensity value I(v, t): and 2f =-ka0LCI0; Where: I 2f The quadratic term in the Fourier series representing the light intensity value I(v,t), k is the coefficient; The quadratic term I in the Fourier series of the light intensity value I(v,t) 2f The concentration value C of the measured gas in the sample gas is obtained by solving the problem.

4. The all-fiber multi-group gas concentration monitoring method according to claim 3, characterized in that: The coefficient k is determined as follows:

5. The all-fiber multi-group gas concentration monitoring method according to claim 1, characterized in that: The controller determines the control signal of the tunable laser according to the following method: Input reference gas into the sample gas chamber; The controller controls the tunable laser to output a laser signal, and the laser signal passes through the sample gas chamber and the harmonic detector detects the light intensity value; Control signal to build concentration signal model: Where: C is the concentration of the measured gas in the reference gas, a(v) is the absorption coefficient of unit concentration when the laser wavelength is v, I0(v) is the light intensity of the laser output, and I(v) is the light intensity of the harmonic detector output; The controller will As the control input signal of the tunable laser.

6. The all-fiber multi-group gas concentration monitoring method according to claim 5, characterized in that: The absorption coefficient a(v) per unit concentration at a laser wavelength v is determined by the following method: Where: v is the wavelength of the laser, v c is the central absorption peak of the laser.

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