JP2009150909A - Gas concentration flux measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas concentration flux measuring system with high responsibility and excellent in measurement stability capable of selecting broad areas, such as forest and the like as measuring objects, without impacts of coexisting materials. <P>SOLUTION: The gas concentration flux measuring apparatus includes a laser light source, a laser output controlling device, a wavelength modulation controlling device, a first light receiving device, a first DC component detector, a first wavelength modulation demodulator, an optical system, a reference cell, a second light receiving device, a second DC component detector, a second wavelength modulation demodulator, a third wavelength modulation demodulator, an analyzer, an accumulator, a thermometry means, a pressure measuring means, and a flow rate measuring means measuring separately flow rate components in the two horizontal directions and the flow rate component in the vertical direction of the gas flow in a measuring domain directly to output those measurement signal to the analyzer, and the analyzer implements an analysis based on eddy correlation law using signal input from the flow rate measuring means to acquire momentum flux and concentration of measuring object gas from the analytic results. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

To evaluate the amount of CO ₂ absorbed in forests, to conduct environmental surveys such as the survey of the amount of global warming gas (GHG) generated from the ground, or to use CO ₂ underground disposal plants, gas storage facilities, pipelines, etc. The present invention relates to a gas concentration flux measuring device used for detecting gas leakage.

In recent years, global warming problems due to greenhouse gases (GHG: CO ₂ , CH ₄ , N ₂ O, etc.) have attracted attention, and various GHG emissions / leakage from the ground surface and industrial plants, and CO ₂ absorption in forests. Understanding is increasingly important.

  As shown in FIG. 15A, the simplest method for grasping the amount of gas emission (flux) per unit area from the ground surface is to lay down a container 101 with a minute hole on the ground 100, and first in the container 101 In this method, the concentration of the measurement target gas is measured and the gas concentration is measured again after a predetermined time has elapsed. The gas concentration flux amount can be estimated from the concentration difference and the contact area / volume of the container.

In addition, in forest CO ₂ flux measurement that has begun to be carried out actively in various places in recent years, an observation tower 91 is installed in the forest, and the velocimeter 51 and the CO ₂ concentration meters 93 and 96 having good time response on the tower 91 are installed. Atmospheric observation is performed, and the measurement results of both are analyzed by the eddy correlation method, and the amount of forest CO ₂ flux (that is, the amount of CO ₂ absorbed by the forest) is derived. For example, the present inventors have reported continuous observation of CO ₂ flux in Non-Patent Document 1.

Specifically, as shown in FIG. 15B, an ultrasonic current meter 51 with very good time response is generally used for wind speed measurement. Regarding the CO ₂ concentration measurement, a closed path type CO ₂ concentration meter 96 using a sampling tube 95 is generally used, but in recent years, an open path type CO ₂ meter 93 using an infrared light source with good time response is used. (Measurement length is less than 1m) is also being used.

  Furthermore, a technology for measuring a wide range of momentum flux (= {vertical transport amount of atmospheric mass (average density) x horizontal velocity component}) using a laser is developed and applied to forest measurement, although it is not a gas concentration flux itself. Is underway. In this measurement technique, as shown in FIG. 15C, two observation towers 91 and 92 are installed apart from each other in the forest, and a laser beam is transmitted from the light source unit 111 installed on one tower 91 so as to pass through the upper part of the forest. The main irradiation is performed, and the time change (scintillation) of each laser transmittance is measured by the light receiving unit 112 installed on the other tower 92.

  As shown in FIG. 15D, the basic configuration of this conventional apparatus includes two pairs of laser oscillators 113 and 114 / light receiving apparatuses 115 and 116 on a tower and an analysis unit 122 provided in a measurement chamber. The two laser beams that have passed through the measurement region 100 are received by the light receiving devices 115 and 116, respectively, and the received light signals 101 and 102 are sent to the analysis unit 122. The analysis unit 122 first analyzes the dispersion and covariance in order to grasp the turbulent state of the atmosphere on the optical path, and then obtains the kinetic energy and heat dissipation rate ε using an analysis method based on the Monin-Obukhov similarity law. Furthermore, momentum flux and sensible heat flux (including latent heat flux in some cases) are obtained.

By the way, it is known that in the atmospheric boundary layer, turbulent flow is generated by friction and thermal action of the ground surface, and turbulent transport is dominant in the transport of various physical quantities to the sky. In the Monin-Obukhov similarity law (hereinafter referred to as MOS), various statistics (average value, variance, covariance, spectrum, etc.) of atmospheric variables in this region are z / L (z: measured height, L: Monin-Obukhov It shows that it becomes a universal function. Therefore, when this similarity law holds, the atmospheric turbulent state (in this case, the time change of the laser transmittance → the disturbance of the atmospheric density (second-order density structure function Dn ² )) is measured, and the measurement result is The analysis (atmospheric turbulence state → kinetic energy spectrum → energy dissipation rate) is sequentially performed based on the MOS to derive the momentum flux.

  As described above, regarding the derivation of the momentum flux, it is assumed that the MOS is established in the upper part of the forest, and the atmospheric turbulence state is analyzed from the scintillation state of the laser using the method described in Non-Patent Document 2, and from the result, The amount of momentum flux on the optical path is derived (scintillation method).

Nakaya Ko et al. “Introduction of continuous observation of CO2 flux in the eastern mountain birch forest of Mt. Asama” 2002 CGER Flux Research Meeting (November 14, 2002), p. 58 Thiermann, V. "A displaced-beam scintillometer for line-averaged measurements of surface layer turbulence". Tenth symposium of turbulence and diffusion, 29 Sept -2 Oct, 1992, Portland, OR., Published by the American Meteorological Society, Boston, MA .: p244-p247 (1992).

However, when the gas concentration flux is measured using the above-described conventional method, there are various problems as described below.
(1) The current gas concentration meter does not completely satisfy the necessary conditions used for flux measurement.
The following characteristics are required for gas concentration measurement used for flux measurement such as forest CO ₂ absorption measurement, except for the measurement that does not take into account the time variation of the flux amount, which is shown at the beginning of the prior art.
(i) High responsiveness Flux detection using the eddy correlation method requires the fastest possible responsiveness.

(ii) No influence of coexisting substances In order to detect trace components, it is required that substances other than the target gas are not affected.

(iii) Measurement stability Since long-time continuous measurement is required, measurement stability is required.

  The normally used sampling-type closed-path gas concentration meter 96 has a problem in its responsiveness due to its measurement delay and dilution effect due to its structure.

Moreover, since it is easily affected by coexisting substances (H ₂ O, solid particles), pretreatment (dehumidification and dust removal) is always required, making it difficult to improve responsiveness.

In addition, the open-pass gas concentration meter 93 that has been introduced for the purpose of improving responsiveness uses an infrared light source having a wide emission amplitude as a light source, and thus is easily affected by a coexisting gas (particularly, H ₂ O). In addition, due to the problem of the light source, there is still a problem in measurement stability.

(2) Continuous gas concentration measurement over a wide area is impossible.
In the current closed path gas concentration meter 96, the measurement range is limited only to the region near the sampling position. In addition, due to the problem of the light source, the measurement length of the open path gas concentration meter 93 is only 1 m or less at most. Therefore, the conventional method cannot measure gas concentration fluctuations over a wide area of 1 m or more, for example, 10 m, 100 m, or 1 km. Even in the conventional method, if a large number of measuring devices are arranged side by side, it is theoretically possible to measure a wide range of gas concentrations. However, when a large number of measuring devices are installed, these devices themselves become obstacles and change the state of the measurement region (concentration, flux, etc.), so accurate wide-area flux measurement is impossible.

  The present invention has been made in order to solve the above-described problems, and is intended for measurement of a wide area such as a forest, is not affected by coexisting substances, is highly responsive, and has excellent measurement stability. The purpose is to provide.

  In the application specification of the above-mentioned Japanese Patent Application No. 2003-009785, the present inventors have used a wavelength modulation type non-contact gas concentration measurement technique (wavelength-tunable semiconductor laser absorption spectroscopy) using a near-infrared semiconductor laser of room temperature oscillation as a light source. A gas concentration monitoring system using Tunable Diode Laser Absorption Spectroscopy (hereinafter referred to as TDLAS)) is proposed, which is i) very good time response, ii) coexisting substances (solid particles, etc.) Iii) measurement technology with advantages such as stable measurement such as stable wavelength, and (b) a simple gas concentration measurement technology with time responsiveness. A laser that can be used for flux measurement (b) or used for gas concentration measurement by TDLAS and that can control the wavelength and polarization plane is combined with a high current meter. By using the means for applying hex measurement, it is possible to gas concentration flux measuring to effectively solve the above problems. The present inventors have completed the present invention described below by paying attention to such a function of TDLAS.

(1) The gas concentration flux measuring apparatus of the first means according to the present invention is:
At least one light source that oscillates a laser beam having an absorption wavelength specific to the measurement target gas toward the measurement region;
A laser output control device for controlling the output operation of the light source;
A wavelength modulation control device that outputs a modulation signal for modulating the oscillation wavelength of the laser emitted from the light source, and outputs a reference signal synchronized with the modulation;
A first light receiving device that receives the laser that has passed through the measurement region and outputs a signal corresponding to the received light intensity;
A first DC component detector that removes the AC component as the modulation signal from the signal output from the first light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the first light receiving device, and measurement in the measurement region is performed. A first wavelength modulation demodulator that outputs a signal proportional to the target gas concentration;
An optical system that distributes the laser emitted from the light source to two or more;
A reference cell in which the measurement target gas having a known concentration is sealed, and is arranged at a position where a laser that is distributed by the optical system and is not directed to the measurement region passes through the sealed gas;
A second light receiving device that receives the laser that has passed through the sealed gas in the reference cell and outputs a signal corresponding to the received light intensity;
A second DC component detector that removes an AC component as the modulation signal from the signal output from the second light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the second light receiving device, A second wavelength modulation demodulator that outputs a signal proportional to the concentration of the enclosed gas;
Based on the reference signal from the wavelength modulation control device, the odd harmonic component of the modulation signal applied to the laser is detected from the signals output from the second light receiving device, and the laser wavelength is measured. A third wavelength modulation demodulator that outputs a reference signal for fixing to the absorption wavelength of the target gas;
Based on signals output from the first DC component detector, the first wavelength modulation demodulator, the second DC component detector, and the second wavelength modulation demodulator, the An analyzer that calculates the measurement gas concentration and solid particle concentration and outputs the calculation results;
The modulation signal from the wavelength modulation controller and the reference signal for fixing the laser wavelength from the third wavelength modulation demodulator are added, and the added signal is externally controlled to the laser output controller An adder that outputs as a signal;
Temperature measuring means for measuring the temperature of the measurement region and outputting a signal corresponding to the measured value to the analysis device;
A pressure measuring means for measuring the pressure in the measurement region and outputting a signal corresponding to the measured value to the analysis device, and a gas concentration flux measuring device comprising:
Furthermore, it has a flow velocity measurement means for directly measuring each of the two horizontal flow velocity components and the vertical flow velocity component of the gas flow in the measurement region, and outputting these measurement signals to the analysis device,
The analysis device performs an analysis based on a vortex correlation law using a signal input from the flow velocity measurement means, and uses the analysis result to calculate the momentum flux in the measurement region, the concentration flux of the measurement target gas, and the measurement target gas. The density is obtained by calculation.

(2) Moreover, the gas concentration flux measuring apparatus of the second means according to the present invention is:
At least one first laser light source that oscillates laser light having an absorption wavelength specific to the measurement target gas toward the measurement region;
A laser output control device for controlling an output operation of the laser light source;
A wavelength modulation controller for outputting a modulation signal for modulating the oscillation wavelength of the laser emitted from the laser light source, and outputting a reference signal synchronized with the modulation;
A first light receiving device that receives the laser that has passed through the measurement region and outputs a signal corresponding to the received light intensity;
A first DC component detector that removes the AC component as the modulation signal from the signal output from the first light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the first light receiving device, and measurement in the measurement region is performed. A first wavelength modulation demodulator that outputs a signal proportional to the target gas concentration;
An optical system that distributes the laser emitted from the first laser light source into two or more;
A reference cell in which the measurement target gas having a known concentration is sealed, and is arranged at a position where a laser that is distributed by the optical system and is not directed to the measurement region passes through the sealed gas;
A second light receiving device that receives the laser that has passed through the sealed gas in the reference cell and outputs a signal corresponding to the received light intensity;
A second DC component detector that removes an AC component as the modulation signal from the signal output from the second light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the second light receiving device, A second wavelength modulation demodulator that outputs a signal proportional to the concentration of the enclosed gas;
Based on the reference signal from the wavelength modulation control device, the odd harmonic component of the modulation signal applied to the laser is detected from the signals output from the second light receiving device, and the laser wavelength is measured. A third wavelength modulation demodulator that outputs a reference signal for fixing to the absorption wavelength of the target gas;
Based on signals output from the first DC component detector, the first wavelength modulation demodulator, the second DC component detector, and the second wavelength modulation demodulator, the An analyzer that calculates the measurement gas concentration and solid particle concentration and outputs the calculation results;
The modulation signal from the wavelength modulation controller and the reference signal for fixing the laser wavelength from the third wavelength modulation demodulator are added, and the added signal is externally controlled to the laser output controller An adder that outputs as a signal;
Temperature measuring means for measuring the temperature of the measurement region and outputting a signal corresponding to the measured value to the analysis device;
A pressure measuring means for measuring the pressure in the measurement region and outputting a signal corresponding to the measured value to the analysis device, and a gas concentration flux measuring device comprising:
A second light source for irradiating the measurement area with a laser;
A third light receiving device that receives a laser beam emitted from the second light source and transmitted through the measurement region, and outputs a signal corresponding to the received light intensity to the analysis device;
The analysis device obtains the time change of the laser transmittance using the signal input from the third light receiving device, derives the time change of the gas density from the obtained time change of the laser transmittance, and further calculates the gas density. Analyzes based on the Monin-Obukhov similarity law to understand the state of turbulence of the measurement target gas from time changes, and using the analysis results, the momentum flux in the measurement region, the concentration flux of the measurement target gas, and the measurement target The gas concentration is obtained by calculation.

(3) Moreover, the gas concentration flux measuring apparatus of the third means according to the present invention is:
A first light source that oscillates a laser beam having an absorption wavelength unique to the measurement target gas toward the measurement region;
A laser output control device for controlling an output operation of the first light source;
A wavelength modulation control device that outputs a modulation signal for modulating the oscillation wavelength of the laser emitted from the first light source and outputs a reference signal synchronized with the modulation;
A first light receiving device that receives the laser that has passed through the measurement region and outputs a signal corresponding to the received light intensity;
A first DC component detector that removes the AC component as the modulation signal from the signal output from the first light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the first light receiving device, and measurement in the measurement region is performed. A first wavelength modulation demodulator that outputs a signal proportional to the target gas concentration;
An optical system that distributes the laser emitted from the first light source to two or more;
A reference cell in which the measurement target gas having a known concentration is sealed, and is arranged at a position where a laser that is distributed by the optical system and is not directed to the measurement region passes through the sealed gas;
A second light receiving device that receives the laser that has passed through the sealed gas in the reference cell and outputs a signal corresponding to the received light intensity;
A second DC component detector that removes an AC component as the modulation signal from the signal output from the second light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the second light receiving device, A second wavelength modulation demodulator that outputs a signal proportional to the concentration of the enclosed gas;
Based on the reference signal from the wavelength modulation control device, the odd harmonic component of the modulation signal applied to the laser is detected from the signals output from the second light receiving device, and the laser wavelength is measured. A third wavelength modulation demodulator that outputs a reference signal for fixing to the absorption wavelength of the target gas;
Based on signals output from the first DC component detector, the first wavelength modulation demodulator, the second DC component detector, and the second wavelength modulation demodulator, the An analyzer that calculates the measurement gas concentration and solid particle concentration and outputs the calculation results;
The modulation signal from the wavelength modulation controller and the reference signal for fixing the laser wavelength from the third wavelength modulation demodulator are added, and the added signal is externally controlled to the laser output controller An adder that outputs as a signal;
Temperature measuring means for measuring the temperature of the measurement region and outputting a signal corresponding to the measured value to the analysis device;
A pressure measuring means for measuring the pressure in the measurement region and outputting a signal corresponding to the measured value to the analysis device, and a gas concentration flux measuring device comprising:
A second light source that oscillates a laser beam having an absorption wavelength specific to the measurement target gas toward the measurement region;
A third light receiving device that receives a laser beam oscillated from the second light source and transmitted through the measurement region, and that outputs a signal corresponding to the received light intensity;
A third DC component detector that removes an AC component as the modulation signal from the signal received from the third light receiving device and outputs a DC component of the received light intensity to the analysis device;
The analysis device uses the signal input from the third DC component detector to obtain a time change in laser transmittance, derives a time change in gas density from the obtained time change in laser transmittance, In order to grasp the turbulence state of the measurement target gas from the change in density over time, an analysis based on the Monin-Obukhov similarity law is performed, and the momentum flux of the measurement region, the concentration flux of the measurement target gas, and The measurement target gas concentration is obtained by calculation.

(4) The gas concentration flux measuring apparatus of the fourth means according to the present invention is:
A single light source that oscillates a laser beam with an absorption wavelength specific to the measurement target gas toward the measurement region;
A laser output control device for controlling the output operation of the light source;
A wavelength modulation control device that outputs a modulation signal for modulating the oscillation wavelength of the laser emitted from the light source, and outputs a reference signal synchronized with the modulation;
A first light receiving device that receives the laser that has passed through the measurement region and outputs a signal corresponding to the received light intensity;
A first DC component detector that removes the AC component as the modulation signal from the signal output from the first light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the first light receiving device, and measurement in the measurement region is performed. A first wavelength modulation demodulator that outputs a signal proportional to the target gas concentration;
An optical system that distributes the laser emitted from the light source to two or more;
A reference cell in which the measurement target gas having a known concentration is sealed, and is arranged at a position where a laser that is distributed by the optical system and is not directed to the measurement region passes through the sealed gas;
A second light receiving device that receives the laser that has passed through the sealed gas in the reference cell and outputs a signal corresponding to the received light intensity;
A second DC component detector that removes an AC component as the modulation signal from the signal output from the second light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the second light receiving device, A second wavelength modulation demodulator that outputs a signal proportional to the concentration of the enclosed gas;
Based on the reference signal from the wavelength modulation control device, the odd harmonic component of the modulation signal applied to the laser is detected from the signals output from the second light receiving device, and the laser wavelength is measured. A third wavelength modulation demodulator that outputs a reference signal for fixing to the absorption wavelength of the target gas;
Based on signals output from the first DC component detector, the first wavelength modulation demodulator, the second DC component detector, and the second wavelength modulation demodulator, the An analyzer that calculates the measurement gas concentration and solid particle concentration and outputs the calculation results;
The modulation signal from the wavelength modulation controller and the reference signal for fixing the laser wavelength from the third wavelength modulation demodulator are added, and the added signal is externally controlled to the laser output controller An adder that outputs as a signal;
Temperature measuring means for measuring the temperature of the measurement region and outputting a signal corresponding to the measured value to the analysis device;
A pressure measuring means for measuring the pressure in the measurement region and outputting a signal corresponding to the measured value to the analysis device, and a gas concentration flux measuring device comprising:
An optical system that distributes the laser emitted from the single light source to two or more;
A polarization plane rotating device that rotates a polarization plane of one or more of the distributed lasers;
A third light receiving device for receiving a laser whose polarization plane is rotated by the polarization plane rotating device and outputting a signal corresponding to the received light intensity;
A third DC component detector that removes an AC component as the modulation signal from the signal received from the third light receiving device and outputs a DC component of the received light intensity to the analysis device;
The analysis device uses the signal input from the third DC component detector to obtain a time change in laser transmittance, derives a time change in gas density from the obtained time change in laser transmittance, In order to grasp the turbulence state of the measurement target gas from the change in density over time, an analysis based on the Monin-Obukhov similarity law is performed, and the momentum flux of the measurement region, the concentration flux of the measurement target gas, and The measurement target gas concentration is obtained by calculation.

(5) Moreover, the gas concentration flux measuring apparatus of the 5th means which concerns on this invention in any one of the 1st thru | or 4 WHEREIN:
The light source and the first light receiving device are housed in the same container.

(6) Moreover, the gas concentration flux measuring apparatus of the 6th means which concerns on this invention in the 5th means,
Further, the temperature measuring means and the pressure measuring means are also housed in the same container.

(7) Moreover, the gas concentration flux measuring apparatus of the 7th means which concerns on this invention in the 1st means,
An ultrasonic velocity meter is used as the flow velocity measuring means, and the ultrasonic velocity meter is housed in the same container.

  In the present specification, the “momentum flux” refers to the vertical transport amount of the entire gas in the measurement region in the horizontal direction (eg, average atmospheric density × horizontal wind speed). In addition, the “gas concentration flux” refers to a vertical transport amount of only the measurement target gas in the measurement region.

  Regarding the combination of the wavelength modulation TDLAS and the scintillation method, the following two can be mentioned.

(I) Combination of a TDLAS device and a scintillation measuring device As shown in FIG. 7, for example, a wide-area gas concentration measuring device in wavelength-modulated TDLAS and a wide-area momentum flux measuring device by a scintillation method are combined. -By integrating based on the Obukhov similarity law, it is possible to measure gas concentration flux over a wide area.

(Ii) A combination in which the scintillation technique is directly incorporated into the TDLAS gas concentration measurement technique. For example, as shown in FIGS. 9, 11, and 13, the function of the scintillation technique is added to the wavelength modulation TDLAS, and a wide range gas concentration flux measurement is performed by a single device. Enable the device.

  Next, the procedure for deriving the momentum flux by the scintillation method is shown in FIGS. 16A and 16B. Non-patent document 2 explains in detail the basic principle regarding the derivation of the momentum flux by the scintillation method. In the derivation procedures shown in FIGS. 16A and 16B, the notation is different from that in Non-Patent Document 2, but the basic idea is the same.

When the laser beam passes through the measurement area, if the gas (atmosphere) in that area is disturbed, the laser beam is bent slightly due to the change in refractive index, and the laser beam blinks (laser scintillation) at the light receiving part. Is done. In the scintillation method, this blink is measured by two light receiving sections, and as shown in FIG. 16A, the minimum unit (internal scale) of atmospheric turbulence from the respective variances (B1, B2) and covariances (B). L ₀ , momentum energy dissipation rate ε, and atmospheric density ρ variation degree (density structure function) Cn ² are obtained.

The result is analyzed based on the Monin-Obukhov similarity law, and the frictional velocity u * of the atmosphere is obtained using the equation shown in FIG. 16B. Next, the momentum flux M (= ρ · (u *) ² ) is obtained using the result and the atmospheric density ρ.

  Next, a procedure for deriving the gas concentration flux will be described with reference to FIGS. 17A and 17B.

Similar to the measurement by the normal scintillation method, the internal scale L ₀ , the kinetic energy dissipation rate ε, and the density structure function Cn ² are obtained from the laser scintillation measurement results, and measured by TDLAS as shown in FIG. 17A. The measurement target gas concentration g in the region is obtained, and from the result, the degree of variation (gas concentration structure function) of the measurement target gas in the measurement region is obtained, and similarly, the temperature structure function Cr ² is obtained from the temperature measurement result.

  The above measurement results are analyzed based on the Monin-Obukhov similarity rule, and the friction ratio concentration G * of the atmosphere is obtained using the equation shown in FIG. 17B. Next, the concentration flux G (= ρ · u * · G *) of the measurement target gas is obtained using the result, the atmospheric friction velocity u *, and the atmospheric density ρ.

  According to the present invention, not only can the gas concentration flux measurement technology improve the measurement accuracy by overcoming the problems of the prior art, but also real-time wide-area gas concentration flux that is impossible only by the combination of the prior art. Measurement is possible. For this reason, environmental measurement and leakage monitoring using the present invention can significantly reduce labor and cost compared to the conventional method combined with the conventional method. Ultimately, forest management and safety of various plants can be achieved. Sophisticated management can be achieved.

  Further, according to the present invention, the number of laser oscillation devices and the number of light receiving devices can be reduced by switching the polarization plane of the laser between vertical polarization and horizontal polarization.

  Further, according to the present invention, the following advantages of the wavelength modulation TDLAS device as the gas concentration measuring device are fully exhibited.

  (i) Time response is very good.

  Since the wavelength modulation TDLAS measurement is an optical measurement, gas sampling and pre-processing required in the prior art are unnecessary. For this reason, it is possible to measure gas concentration flux over a wide area, which is impossible with the combination of the prior arts, and realize real-time measurement for good time response.

  Compared with the conventional optical measurement method, the concentration measurement sensitivity can be greatly improved by wavelength modulation, and the gas concentration flux with sufficient sensitivity even if the measurement time constant is lowered (time response is increased). Can be measured.

  (ii) Not affected by coexisting substances.

  Since a laser with a very narrow wavelength line width is used as the light source, it is not affected by the coexisting gas. The influence of solid particles can be removed by wavelength modulation measurement, and it is resistant to dirt, and can be measured without problems even under bad conditions such as rain.

  (iii) The measurement stability is good.

  In the present invention, the improvement in measurement stability has been proven by using multiple stages of wavelength modulation. Furthermore, since wavelength-modulated TDLAS is an optical measurement using a laser, it is possible to perform real-time measurement of a wide range of gas concentrations, which was very difficult with conventional gas concentration measurement techniques. Therefore, real-time measurement of gas concentration flux over a wide area is possible by combining this wavelength modulation TDLAS technique with a wide-area momentum flux measurement technique based on the scintillation method.

The block diagram which shows the part of the basic gas concentration measuring apparatus integrated in this invention apparatus. The block diagram which shows the gas concentration flux measuring apparatus (combination of two laser light sources and two light-receiving devices) of this invention. 1 is a configuration block diagram showing a gas concentration flux measuring device (combination of one laser light source and two light receiving devices; polarization plane modulation method) of the present invention. The block diagram which shows the gas concentration flux measuring device (combination of one laser light source and one light-receiving device; external control polarization plane modulation system) as an examination example of the present invention. (A) is a configuration block diagram showing a gas concentration flux measuring apparatus (Example 1; CO ₂ concentration flux measuring example on a forest observation tower) of the present invention, and (b) is a schematic layout diagram of the apparatus. Measurement results characteristic diagram showing the (combined forest CO ₂ concentration flux measurement result of the ultrasonic current meter) of Example 1. (A) is a configuration block diagram showing a gas concentration flux measuring device of the present invention (Example 2; a wide-area CO ₂ concentration flux measuring example between forest observation towers), and (b) is a schematic layout diagram of the device. Characteristic diagram showing a (regional CO ₂ flux measurement result between combinations forest observation by towers scintillation method) measurement results in Example 2. (A) is a configuration block diagram showing a gas concentration flux measuring device of the present invention (Example 3; a wide-area CO ₂ concentration flux measuring example between forest observation towers), and (b) is a schematic layout diagram of the device. Characteristic diagram showing a (regional CO ₂ flux measurement result between the forest observation towers by the semiconductor laser type gas concentration flux measuring device) measurement results of Example 3. (A) is a configuration block diagram showing a gas concentration flux measuring device of the present invention (Example 4; a wide-area CO ₂ concentration flux measuring example between forest observation towers), and (b) is a schematic layout diagram of the device. Characteristic diagram showing a (regional CO ₂ flux measurement result between the forest observation towers by the semiconductor laser type gas concentration flux measuring device) measurement results of Example 4. (A) is a configuration block diagram showing a gas concentration flux measuring device (consideration example 1: wide-area CO ₂ concentration flux measuring example between forest observation towers) as a study example of the present invention, and (b) is a schematic layout diagram of the device. . Characteristic diagram showing a (regional CO ₂ flux measurement result between the forest observation towers by the semiconductor laser type gas concentration flux measuring device) Study Example 1 of the measurement results. Schematic diagram of a conventional sampling device. Schematic diagram of a conventional apparatus used in the CO ₂ absorption quantity measurement in forest. The schematic diagram of the conventional apparatus which measures the momentum flux in a forest by the scintillation method. The schematic diagram of the conventional apparatus which measures momentum flux by the scintillation method. The flowchart which shows the derivation | leading-out procedure of the momentum flux by a scintillation method. The flowchart which shows the derivation | leading-out procedure (continuation of FIG. 16A) of the momentum flux by a scintillation method. The flowchart which shows the derivation | leading-out procedure of the gas concentration flux by this invention. The flowchart which shows the derivation | leading-out procedure (continuation of FIG. 17A) of the gas concentration flux by this invention.

  Hereinafter, various preferred embodiments of the present invention will be described with reference to the accompanying drawings.

(Basic configuration of gas concentration measurement)
First, a basic configuration of a gas concentration measuring apparatus using TDLAS will be described with reference to FIG. The gas concentration measuring device 10 includes a light source unit 2, a light receiving unit 3, DC component detectors 4 and 12, a wavelength modulation demodulator 5, a wavelength modulation control device 6, wavelength modulation demodulators 7 and 8, an adder 9, and an LD control device. 11, an A / D converter 13 and a computer 14. The light source section 2 is covered with an optical system container 2a having an outer periphery excellent in weather resistance, and the semiconductor laser light source 21, the reference cell 25, and a part of the laser light are transmitted toward the optical window 23 and a part thereof is reflected A mirror 24 that reflects the laser light reflected by the half mirror 22 toward the reference cell 25, and a reference light receiving unit 26 that receives the laser light from the reference cell 25.

  The semiconductor laser light source 21 is provided in the LD module together with a Peltier element for adjusting the temperature of the laser element. The semiconductor laser element is connected to the drive circuit of the LD control device 11 so that its temperature and current are controlled. The oscillation signal S1 sent from the LD control device 11 to the light source 21 is feedback-controlled by a signal S13 from the adder 9. In this embodiment, the case where a semiconductor laser element is employed as the light source 21 is described as an example. However, the light source of the present invention is not limited to the semiconductor laser element, and other wavelength modulation is possible. The present invention can be applied to all laser oscillators, and can also be applied to all light and electromagnetic waves other than lasers when wavelength modulation is possible. Further, the LD control device 11 may be manually controlled or externally controlled.

  In the measurement region 100, a temperature measuring device T1 and a pressure measuring device P1 are provided, and the temperature measuring signal S2 and the pressure measuring signal S3 are respectively sent to the computer 14 which is an analysis unit via the A / D converter 13. ing.

  The measurement light receiving unit 3 is arranged so that the optical axis thereof coincides with the optical axis of the light source unit 2, and receives the laser light transmitted through the measurement region 100. A first DC component detector 4 and a first wavelength modulation demodulator 5 are provided at the subsequent stage of the measurement light receiving unit 3. The first DC component detector 4 removes the AC component as the modulation signal from the signal S4 output from the light receiving unit 3, and outputs the DC component signal S5 of the received light intensity to the computer 14 as the analyzing unit.

  The first wavelength modulation demodulator 5 is based on the reference signal S10 from the wavelength modulation control device 6 and the even harmonics of the wavelength modulation signal added to the laser from the signal S4 output from the first light receiving device. The component is detected, and a signal S6 proportional to the measurement target gas concentration in the measurement region is output.

  The wavelength modulation control device 6 is provided in front of the first wavelength modulation demodulator 5 for concentration measurement, the second wavelength modulation demodulator 7 for concentration calibration, and the adder 9. 7 outputs the wavelength modulation reference signal S10, and outputs the wavelength modulation signal S11 to the adder 9.

The reference cell 25 is a position where a measurement target gas (for example, CO ₂ gas) having a known concentration is sealed, and a laser which is distributed by the optical systems 22 and 24 and is not directed to the measurement region 100 transmits through the sealed gas. Is arranged.

  The second light receiving device 26 is arranged after the reference cell 25, receives the laser beam that has passed through the sealed gas in the reference cell 25, and outputs a signal S7 corresponding to the received light intensity to the second DC component detector 12. Output to.

  The second DC component detector 12 removes an AC component as a modulation signal from the signal S7 output from the second light receiving device 26, and outputs a DC component signal S8 of the received light intensity to the analysis unit 14.

  The second wavelength modulation demodulator 7 is based on the reference signal S10 from the wavelength modulation control device 6, and the even-order harmonics of the wavelength modulation signal applied to the laser from the signal S7 output from the second light receiving device 26. A wave component is detected, and a signal S9 proportional to the concentration of the enclosed gas in the reference cell 25 is output to the analysis unit 14.

  Based on the reference signal S10 from the wavelength modulation control device 6, the third wavelength modulation demodulator is an odd-order harmonic component of the wavelength modulation signal applied to the laser from the signal S7 output from the second light receiving device. And a reference signal S12 for fixing the laser wavelength to the absorption wavelength of the measurement target gas is output to the adder 9.

  The analysis device includes a temperature measuring device T1, a pressure measuring device P1, a first DC component detector 4, a first wavelength modulation demodulator 5, a second DC component detector 12, and a second wavelength modulation demodulator 7. Based on the output signals S2, S3, S5, S6, S8, and S9, the gas concentration and solid particle concentration in the measurement region are calculated, and the calculation results are recorded and output on the display.

  The adder 9 adds the modulation signal S11 from the wavelength modulation control device 6 and the laser wavelength fixing signal S12 from the third wavelength modulation demodulator 8, and adds the addition signal S13 to the laser output control device 11. Output as a control signal.

The gas concentration is verified as follows.
Inside the reference cell 25, a standard gas having a known gas concentration is sealed or passed at a constant pressure. First, the known gas concentration in the reference cell 25, the known optical length of the reference cell 25, and the known optical length of the measurement region are input to the computer 14 which is an analysis unit. The computer 14 calls a predetermined mathematical expression from the memory, assigns the three input data to corresponding parameters of the predetermined mathematical expression, and obtains a gas concentration value by calculation. The obtained gas concentration value is continuously recorded and a state of changing every moment is displayed on the display screen.

  The above is the part responsible for gas concentration measurement in the device of the present invention. In addition to the gas concentration measurement part, the apparatus of the present invention further includes a part responsible for flux measurement described below.

(Gas concentration flux measurement 1)
(Combination of two light sources and two light-receiving units for measurement)
FIG. 2 is a diagram illustrating an overall configuration of the gas concentration flux measuring apparatus according to the embodiment. In addition, description of the part which the gas concentration flux measuring apparatus 10B of this embodiment overlaps with the gas concentration measuring apparatus 10 mentioned above is abbreviate | omitted.

  The gas concentration flux measuring apparatus 10A includes another laser light source 21A in addition to the semiconductor laser light source 21 in the light source unit 2A. For this reason, the optical container 2a is provided with two optical windows 23a and 23b arranged side by side. The oscillation laser of the first light source 21 is emitted from one optical window 23a to the measurement region 100 and from the other optical window 23b. The oscillation laser of the second light source 21A is emitted to the measurement region 100. The first and second light sources 21 and 21A are aligned with each other so that the two laser beam optical axes are substantially parallel.

  The light receiving unit 3 </ b> A includes a second measurement light receiving unit 32 in addition to the first measurement light receiving unit 31. The first measurement light receiving unit 31 receives the laser oscillated from the first light source 21 and outputs a signal S 41 to the first DC component detector 41. The second measurement light receiving unit 32 receives the laser oscillated from the second light source 21 </ b> A and outputs the signal S <b> 42 to the third DC component detector 42.

  The third DC component detector 42 removes the AC component as the modulation signal from the light reception signal S42 and outputs the atmospheric turbulence component signal S52 to the analysis unit 14. In parallel with this, the first DC component detector 41 removes the AC component as the modulation signal from the light reception signal S42 and outputs the measurement unit light reception intensity signal S51 to the analysis unit 14.

  Based on the reference signal S10 from the wavelength modulation control device 6, the wavelength modulation demodulator 5 detects even-order harmonic components of the wavelength modulation signal added to the laser from the signal S41 output from the first light receiving device. Then, a signal S61 proportional to the measurement target gas concentration in the measurement region is output.

  The analyzing unit 14 includes a temperature measuring device T1, a pressure measuring device P1, a first DC component detector 41, a first wavelength modulation demodulator 5, a second DC component detector 12, and a second wavelength modulation demodulator 7. Based on the signals S2, S3, S51, S52, S61, S8, and S9 respectively output from the third DC component detector 42, the gas concentration and the solid particle concentration in the measurement region are calculated according to the MOS rule. The momentum flux in the measurement area is calculated, and the calculation results are continuously recorded and displayed on the display.

(Gas concentration flux measurement 2)
(Combination of a single light source and two light-receiving units for measurement)
FIG. 3 is a diagram illustrating an overall configuration of a gas concentration flux measuring apparatus according to another embodiment. In addition, description of the part which the gas concentration flux measuring apparatus 10B of this embodiment overlaps with the above-mentioned apparatuses 10 and 10A is abbreviate | omitted.

  The gas concentration flux measuring device 10B includes a polarization plane rotating device 27 and laser distributing optical systems 22a, 22b, 24a, and 24b in the light source unit 2B. Two half mirrors 22 a and 22 b are inserted between the light source 21 and the polarization plane rotating device 27. The first half mirror 22a reflects part of the laser light oscillated from the single light source 21, and distributes it to the reference cell 25 via the mirror 24a. The second half mirror 22b reflects a part of the light transmitted through the first half mirror 22a and emits the reflected light from the first optical window 23a to the measurement region via the mirror 24b. A part of the light transmitted through the first half mirror 22 a is transmitted, and the transmitted light is distributed to the polarization plane rotating device 27. The polarization plane rotation device 27 has a built-in Faraday rotator that rotates longitudinally polarized light by 90 ° and alternately converts it into laterally polarized light. The laser beam whose polarization plane is modulated by the polarization plane rotating device 27 is emitted from the second optical window 23 b to the measurement region 100. The optical systems 22a, 22b, 24a, 24b and the polarization plane rotating device 27 are aligned with each other so that the two laser beam optical axes are substantially parallel.

  The light receiving unit 3 </ b> A includes a second measurement light receiving unit 32 in addition to the first measurement light receiving unit 31. The first measurement light receiving unit 31 receives the oscillation laser and outputs a signal S41 to the first DC component detector 41. The second measurement light receiving unit 32 receives the polarization plane modulation laser and outputs the signal S 42 to the third DC component detector 42.

  The third DC component detector 42 removes the AC component as the modulation signal from the light reception signal S42 and outputs the atmospheric turbulence component signal S52 to the analysis unit 14. In parallel with this, the first DC component detector 41 removes the AC component as the modulation signal from the light reception signal S42 and outputs the measurement unit light reception intensity signal S51 to the analysis unit 14.

  Based on the reference signal S10 from the wavelength modulation control device 6, the wavelength modulation demodulator 5 detects even-order harmonic components of the wavelength modulation signal added to the laser from the signal S41 output from the first light receiving device. Then, a signal S61 proportional to the measurement target gas concentration in the measurement region is output.

  The analyzing unit 14 includes a temperature measuring device T1, a pressure measuring device P1, a first DC component detector 41, a first wavelength modulation demodulator 5, a second DC component detector 12, and a second wavelength modulation demodulator 7. Based on the signals S2, S3, S51, S52, S61, S8, and S9 respectively output from the third DC component detector 42, the gas concentration and the solid particle concentration in the measurement region are calculated according to the MOS rule. The momentum flux in the measurement area is calculated, and the calculation results are continuously recorded and displayed on the display.

(Gas concentration flux measurement 3)
(Combination of a single light source and a single light receiver for measurement)
FIG. 4 is a diagram showing an overall configuration of a gas concentration flux measuring apparatus as an examination example of the present invention. In addition, description of the part which 10C of gas concentration flux measuring apparatuses of this examination example overlaps with the above-mentioned apparatus 10, 10A, 10B is abbreviate | omitted.

  The gas concentration flux measuring device 10C includes an externally controlled polarization plane rotating device 27A in the light source unit 2C. The half mirror 22a reflects a part of the laser light oscillated from the single light source 21, distributes the reflected light to the reference cell 25 via the mirror 24, and transmits a part of the oscillated laser light. To the externally controlled polarization plane rotating device 27A. When the modulation control signal S14 is input from the polarization plane modulation control device 15 provided outside, the externally controlled polarization plane rotating device 27A receives longitudinal polarization (0 °) and horizontal polarization (90 at a predetermined timing by the Faraday rotator. °) to switch between. The laser light is polarized plane-modulated by the externally controlled polarization plane rotating device 27A, then emitted from the optical window 23 toward the measurement region 100, and received by the light receiving unit 3. That is, in the apparatus of this examination example, flux measurement and concentration measurement are simultaneously performed by timing control in which one laser beam oscillated from the single light source 21 is alternately switched between vertical polarization and horizontal polarization.

  The light receiving unit 3 outputs the light reception signal S4 to each of the first polarization plane modulation demodulator 17a, the second polarization plane modulation demodulator 17b, and the wavelength modulation demodulator 5 (for density measurement).

  The polarization plane modulation control device 15 outputs a modulation control signal S14 to the externally controlled polarization plane rotation device 27A, and also includes a signal phase converter 16, a first polarization plane modulation demodulator 17a, and a third polarization plane modulation demodulator 18. The polarization plane modulation reference signal S15 is output to each of the signals.

  When the polarization plane modulation reference signal S15 is input from the polarization plane modulation controller 15, the signal phase converter 16 converts the phase of the signal and outputs the phase conversion signal S16 to the second polarization plane modulation demodulator 17b.

  The wavelength modulation demodulator 5 detects an even harmonic component of the wavelength modulation signal applied to the laser from the light reception signal S4 based on the reference signal S10 from the wavelength modulation control device 6, and measures the measurement target gas in the measurement region. A signal S 6 proportional to the density is output to the third polarization plane modulation demodulator 18.

  When the polarization plane modulation reference signal S15 is input from the polarization plane modulation control device 15, the first polarization plane modulation demodulator 17a detects a signal synchronized with the polarization plane modulation from the received light signal S4 and transmits the signal through the measurement region. A signal proportional to the received light intensity of the vertically polarized laser is output to the analyzer 14 as a measurement unit laser absorption signal S18.

  When the phase conversion signal S16 is input from the signal phase converter 16, the second polarization plane modulation demodulator 17b detects a signal synchronized with the polarization plane modulation from the received light signal S4 and transmits the horizontally polarized light transmitted through the measurement region. A signal proportional to the received light intensity of the laser is output to the analyzer 14 as a measurement unit laser absorption amount signal S17.

  When the polarization plane modulation reference signal S15 is input from the polarization plane modulation control device 15, the third polarization plane modulation demodulator 18 sets a signal proportional to the intensity of the received light signal S4 of the laser that has passed through the measurement region. The measurement signal S62 is output to the analysis device 14.

  Here, the wavelength modulation reference signal S10 output from the wavelength modulation control device 6 and the polarization plane modulation reference signal S15 output from the polarization plane modulation control device 15 are the wavelength modulation demodulator 5 or the third polarization plane modulation demodulator. These modulation frequencies need to be different so as not to interfere with each other. For example, as shown in FIG. 4, when the third polarization plane modulation demodulator 18 is provided in the subsequent stage of the wavelength modulation demodulator 5, the frequency λ2 (for example, 100 Hz) of the polarization plane modulation reference signal S15 is set to the wavelength modulation reference signal S10. It is desirable to set it sufficiently smaller than the frequency λ1 (for example, 10 kHz). On the other hand, when the arrangement of the demodulators 5 and 18 is reversed, that is, when the third polarization plane modulation demodulator 18 is provided in the preceding stage of the first wavelength modulation demodulator, the polarization plane modulation reference signal S15. Is preferably set sufficiently larger than the frequency λ1 (10 kHz) of the wavelength modulation reference signal S10.

  The analyzing unit 14 includes a temperature measuring device T1, a pressure measuring device P1, a first polarization plane demodulator 17a, a second polarization plane demodulator 17b, a third polarization plane demodulator 18, and a first wavelength modulation demodulator 5. Based on the signals S2, S3, S17, S18, S62, S8, and S9 respectively output from the second wavelength modulation demodulator 7, the gas concentration and the solid particle concentration in the measurement region are calculated according to the MOS rule. The momentum flux in the measurement area is calculated, and the calculation results are continuously recorded and displayed on the display.

[Example]
As Example 1, an example in which CO ₂ flux and concentration are measured on a forest observation tower using a gas concentration flux measuring device that combines a TDLAS gas concentration measuring device and an ultrasonic velocimeter will be described.

Example 1
In Example 1, in order to verify the gas concentration flux measurement according to the present invention, as shown in FIG. 5B, a wavelength variable TDLAS gas concentration measuring device and an ultrasonic current meter are incorporated in one container 2b. The measuring unit 2D was installed on the forest observation tower 91, the measurement results of both were analyzed by the eddy correlation method, and the CO ₂ concentration flux on the forest observation tower 91 was measured. The gas in the measurement region 100 is introduced into the measurement unit 2D on the forest observation tower 91 through the sampling pipe 95. Further, a CO ₂ meter 93 and a pre-processor 94 were respectively provided on the gas sampling end side of the sampling pipe 95, and the CO ₂ concentration was actually measured for comparison confirmation, and the sampling gas was pre-processed by a predetermined method. Further, the control / analysis unit 19D is provided in the observation room 90 near the tower.

  As shown in FIG. 5 (a), the gas concentration flux measuring device 10D includes a measuring unit 2D and a control / analyzing unit 19D. Between the measuring unit 2D and the control / analyzing unit 19D using a communication cable or a wireless telegraph device. Signals can be sent and received. The configuration of the wavelength tunable TDLAS type gas concentration measuring device 20 incorporated in the measuring unit 2D is substantially the same as the wavelength modulation TDLAS type gas concentration measuring device shown in FIG. 1, but in this embodiment, the gas concentration measuring accuracy is improved. For the purpose of improvement, the control / analysis unit 19D has a double wavelength modulation mechanism (wavelength modulation waveform generators 61 and 62) and a zero concentration measurement unit (DC detector 65c, zero reference unit 29c) for monitoring the zero concentration point. ) Has been added.

  Specifically, the measurement unit 2D installed on the tower 91 includes a TDLAS optical system unit 20 that oscillates a laser, a light receiving device (PD-G) 29a that receives the laser that has passed through the measurement region 100, and an ultrasonic anemometer. 51 is provided.

  The measuring unit 2D is entirely covered with a protective container 2b. The TDLAS optical system unit 20 is entirely surrounded by an optical container 2a having excellent weather resistance in order to improve environmental resistance. An optical window 23 for emitting laser light is attached to the optical system container 2a. A light receiving device (PD-G) 29 a made of a photodiode is arranged to face the optical window 23. The open end of the sampling tube 91 is introduced into the measuring unit 2D, is located between the light receiving device (PD-G) 29a and the optical window 23, and a sampling gas (atmosphere in the forest) is supplied between the two. It is like that. In this embodiment, the distance L1 from the optical window 23 to the light receiving device (PD-G) 29a is set to about 2 m.

Next, the control / analysis unit 19D installed in the observation room next to the forest observation tower includes an LD control device 11 that controls the laser oscillation of the LD 28 and a first waveform generator (for modulating the laser light). No. 1-FG) 61, second waveform generator (No. 1-FG, No. 2-FG) 62, each light receiving device (PD-G, PD-R, PD-Z) 29a, 29b, 29c A direct current detector (LPF) that detects a direct current component from the received light signal and outputs the received light intensity signals S23, S22, S21, and a reference from the first wavelength modulation waveform generator 61 from each received light signal A first phase sensitive detector (No. 1-PSD-) 63 for detecting and outputting only a signal synchronized with the harmonic frequency component of the modulation frequency based on the signal; From the output signal of 1-PSD, no. Based on the 2-FG reference signal, a phase sensitive detector (No. 1-PSD) 63 for detecting and outputting only a signal synchronized with the harmonic frequency component of the modulation frequency, and A / D for capturing each signal Conversion unit 13, A / D conversion signal is analyzed, personal computer (PC) 14 that analyzes and records CO ₂ concentration and CO ₂ concentration flux in the atmosphere, 1-FG61 and No.1. 2-FG62 modulation signal, No. 2 And an adder 9 that adds the wavelength-fixed signals from the 2-PSD-FB 64d and outputs the signals as an external control signal of the LD control device 11.

Furthermore, in this embodiment, a wavelength sweep waveform generator (FG) 66 for sweeping the laser wavelength around the CO ₂ absorption wavelength, and a changeover switch (switch SW) for switching the signal to a laser wavelength fixed signal. 67 is added.

  An ultrasonic velocimeter 51, a semiconductor pressure sensor 53, and a temperature sensor 52 are accommodated in the measurement unit 2D. These ultrasonic velocimeters 51 and sensors 52, 53 are attached in the vicinity of the gas outlet of the sampling pipe 91, and the flow velocity measurement signal S 19, the temperature measurement signal S 2 and the pressure measurement signal S 3 are passed through the A / D converter 13. And output to the personal computer 14 respectively.

The single semiconductor laser (LD) 28 can adjust the laser oscillation wavelength to one of the absorption wavelengths of CO ₂ . The optical system includes a first half mirror 22a, a second half mirror 22b, and a reflection mirror 24. The first half mirror 22a transmits and distributes a part of the laser light oscillated from the light source 28, emits it from the optical window 23 toward the light receiving device for measurement (PD-G) 29a, and oscillates the laser light. Is reflected and distributed to the second half mirror 22b. The second half mirror 22b reflects a part of the distributed light and further distributes it to the reference cell 25, and transmits a part of the distributed light to pass through the reflective mirror 24 to the zero reference part (PD-Z). Distribute to 29c. The reference cell 25 is filled with CO ₂ gas (CO ₂ = 1%, N 2 = 99%) at a specified concentration for concentration calibration and fixation of the laser wavelength to the CO ₂ absorption wavelength. The light transmitted through the reference cell 25 enters the reference light receiving device (PD-R) 29b, and a light reception signal is output to the direct current detector (LPF) 65b of the control / analysis unit 19D. The DC detector (LPF) 65b outputs a signal S22 obtained by removing an AC component as a modulation signal from the received light signal to the personal computer 14. On the other hand, when a light reception signal enters the DC detector (LPF) 65c of the control / analysis unit 19D from the zero reference unit (PD-Z) 29c, the DC detector (LPF) 65c generates an alternating current as a modulation signal from the light reception signal. The signal S21 from which the component has been removed is output to the personal computer 14.

  The light receiving device for measurement (PD-G) 29a outputs a light receiving signal to each of the DC detector (LPF) 65c and the first phase sensitive detector (No. 1-PSD-G) 63a of the control / analyzer 19D. To do. When the received light signal is input to the DC detector (LPF) 65c, the DC detector (LPF) 65c outputs to the personal computer 14 a signal S23 obtained by removing the AC component as a modulation signal from the received light signal. The first phase sensitive detector (No. 1-PSD-G) 63a is output from the light receiving device 29a based on the wavelength modulation reference signal from the first wavelength modulation waveform generator (No. 1-FG) 61. The even-order harmonic component of the wavelength modulation signal applied to the laser is detected from the detected signal, and a signal proportional to the concentration of the sealed gas in the reference cell is detected by the second phase sensitive detector (No. 2-PSD-G). ) Output to 64a. Further, the second phase sensitive detector (No. 2-PSD-G) 64a is based on the wavelength modulation reference signal from the second wavelength modulation waveform generator (No. 2-FG) 62, and receives from the light receiving device 29a. An odd harmonic component of the wavelength modulation signal applied to the laser is detected from the output signals, and a signal S24 proportional to the concentration of the sealed gas in the reference cell is output to the personal computer.

  The wavelength sweep waveform generator 66 applies a ramp wave having a frequency of 0.5 Hz or 0.01 Hz, for example, to the injection current of the semiconductor laser element in order to slowly sweep the laser oscillation wavelength in the absorption spectrum unique to the measurement target gas. It is supposed to be. When measuring a change in gas concentration over a long period of time, the sweep of the laser oscillation wavelength by the wavelength sweep waveform generator 66 is stopped and the laser oscillation wavelength is locked to a predetermined wavelength. A wavelength sweep signal S28 is output from the wavelength sweep waveform generator 66 to the personal computer 14.

  The two wavelength modulation waveform generators 61 and 62 apply sine waves having different frequencies to the injection current of the semiconductor laser element 28 so as to modulate the laser oscillation wavelength. For example, a sine wave (f = 10 kHz) signal of 10 kHz, for example, is applied as a first modulation frequency f from one wavelength modulation waveform generator 61 to the LD controller 11 via the adder 9, and the other wavelength modulation is performed. From the waveform generator 62, for example, a sine wave (w = 500 Hz = 0.5 kHz) signal of 500 Hz is applied to the LD controller 11 via the adder 9 as the second modulation frequency w.

  The adder 9 includes a sweep signal S29 from the wavelength sweep waveform generator 66, modulation signals S25 and S26 having different frequencies f and w from the two wavelength modulation waveform generators 61 and 62, and two-stage phase sensitive detectors 63a to 63a. A third-order differential demodulated signal S27 having a frequency of 2f + w from 63d and 64a to 64d is superimposed and applied to the injection current of the semiconductor laser element.

  When a ramp wave having a sweep wavelength is applied from the wavelength sweep waveform generator 66 to the injection current, and sine waves of different frequencies f and w are applied from the wavelength modulation waveform generators 61 and 62 to the injection current, they are thereby applied. The lasing wavelength is doubly modulated at two different frequencies f and w. As a result, the signal receiving this laser beam includes the modulation frequencies f and w and their harmonics, so that the signals are demodulated by the phase sensitive detectors 63a to 63d at the double frequency 20 kHz (2f). Then, the phase sensitive detectors 64 a to 64 d demodulate at a double frequency 1 kHz (2 w), and a fourth-order differential signal (2 f + 2 w) on which these are superimposed is sent to the personal computer 14.

  The signals demodulated at the double frequency 20 kHz (2f) by the phase sensitive detectors 63a to 63d are demodulated at the frequency w by the phase sensitive detectors 64a to 64d. The third derivative signal (2f + w) on which these are superimposed is sent to the adder 9 through the changeover switch 67, and the laser oscillation wavelength is feedback controlled to the absorption center wavelength of the measurement target gas based on this signal.

  The wind speed on the tower 91 is measured by the ultrasonic anemometer 51, and the wind speed signal (S) is output to the control / analysis unit 19D of the observation room 90. As shown in the figure, the measurement region 100 is the atmosphere above the tower having a measurement length of 2 m (= L1). In addition, the pressure in the measurement region 100 is measured by the semiconductor pressure sensor 53, the measurement signal S3 is output to the measurement chamber, the temperature in the measurement region is measured by a thermocouple, and the temperature signal S2 is measured. It is output. Note that the temperature and pressure may be measured with a laser using the characteristics of the absorption spectrum of the target gas without using a sensor.

  For measurement of the absorption spectrum, a wavelength sweep waveform generator (FG) 66 applies a ramp wave of, for example, 0.5 Hz or 0.01 Hz to the injection current, and slowly sweeps the laser wavelength. The laser wavelength is locked to measure the long-term density change.

Furthermore, in the present embodiment, for comparison with the conventional measurement, the air is sampled from almost the same position as the measurement region of the present invention, pre-processed by the pre-processor 94, and then the conventional CO ₂ meter 93. Measurement was performed, and vortex correlation analysis was performed together with the measurement result of the ultrasonic velocimeter 51, and the CO ₂ concentration flux was simultaneously measured.

FIG. 6 is a characteristic diagram showing the measurement results of Example 1 with the measurement time on the horizontal axis and the measured CO ₂ concentration flux (mg / m ² · S) on the vertical axis. In the figure, the solid line A1 shows the result of Example 1 measured by the apparatus of the present invention, and the broken line B1 shows the result of the comparative example measured by the conventional sampling method utilization apparatus.

Both the results are almost the same, and it was demonstrated that the CO ₂ concentration flux measurement according to the present invention is possible. Furthermore, in the situation where the photosynthesis / respiration switching of plants occurs immediately after dawn or just after sunset, and the momentum flux changes greatly from minus to plus, the measurement result (characteristic line A1) of this example is Although the situation is clearly captured, the measurement result (characteristic line B1) of the conventional technique is a result that is somewhat leveled. The cause of this is thought to be the response delay of the conventional CO ₂ meter 93 due to the dilution effect or the like. As described above, the conventional apparatus cannot sufficiently capture the fast fluctuation in the measurement region, and tends to underestimate the flux amount more than the actual one. On the other hand, the CO ₂ concentration flux measurement by the apparatus of the present invention can accurately capture fast fluctuations in the measurement region, and its effectiveness has been proved.

(Example 2)
Next, an example in which the wide-area CO ₂ flux between the forest observation towers combining the wide-area gas concentration measurement device and the scintillation technique in TDLAS is measured as Example 2 will be described with reference to FIG. In addition, description of the part which a present Example overlaps with said Example is abbreviate | omitted.

In this second embodiment, in order to demonstrate wide-area gas concentration flux measurement according to the present invention, a variable wavelength TDLAS gas concentration measurement device and a scintillation method momentum flux measurement device are installed in combination on a forest observation tower, and both are measured. The results were analyzed based on the Monin-Obukhov similarity law, and the wide-area CO ₂ concentration flux between forest observation towers was measured.

  FIG. 7 shows an apparatus system of the second embodiment. The configuration of the wavelength tunable TDLAS gas concentration measuring devices 2E and 19E is substantially the same as the device systems 2D and 19D of the first embodiment shown in FIG. 5, and the control / analyzing unit 19E installed in the observation room 90 Is substantially the same as the control / analysis unit 19D of the first embodiment shown in FIG. However, in the apparatus of the second embodiment, the measurement length is greatly increased to 81 m, which is equal to the distance between the forest observation towers 91 and 92, for wide-area gas concentration measurement.

  Specifically, the light source unit 2E installed on the first observation tower 91 includes the TDLAS optical system unit 20 having substantially the same configuration as that of the first embodiment and the scintillation measurement unit 70 shown in FIG. 15D. ing. The light source unit 2E outputs the reference light reception signal S22, the zero light reception signal S21, and the intensity modulation reference signal S24 of the scintillation measurement unit 70 toward the control / analysis unit 19E of the observation room 90, and at the same time, the TDLAS optical system unit 20 The LD control signal S1 is transmitted from the control / analysis unit 19E of the observation room 90. Two laser oscillators 71 and 72 are housed in the scintillation measurement unit 70, and the oscillated laser beams are emitted to the measurement region 100 through the optical windows 73a and 73b, respectively, and are respectively received by the light receiving unit 3E on the second tower 92. Light is received.

  In this embodiment, the semiconductor pressure sensor 53 and the thermocouple 52 are installed on the first forest monitoring tower 91, and the measured values are represented as the pressure and temperature of the measurement region. In some cases, the average pressure and average temperature in the measurement region are measured with a laser using the characteristics of the spectrum.

  Next, the light receiving unit 3E installed on the second forest observation tower 92 receives a laser beam emitted from the TDLAS optical system unit 20 of the light source unit 2E on the first tower 91 and transmitted through the atmosphere. (PD-G) 35 and light receiving devices (PD-S1, PD-S2) 33, 34 for receiving the laser emitted from the scintillation measuring unit 70, and the respective light receiving signals S23, S191, S192. (G, S1, S2) is output to the control / analysis unit 19E of the observation room 90 for analysis.

  In the present embodiment, signal transmission from the light source unit 2E and the light receiving unit 3E on the towers 91 and 92 to the observation room 90 is performed by a normal electric wiring cable. However, the present invention is not limited to this. In addition, in order to cope with the case where the measurement length becomes longer, it is possible to adopt an optical fiber transmission method or a wireless transmission method in which communication facilities can be easily installed.

FIG. 8 is a characteristic diagram showing the measurement results of Example 2 with the measurement time on the horizontal axis and the measured CO ₂ concentration flux (mg / m ² · S) on the vertical axis. In the figure, the solid line A2 indicates the result of Example 2 measured by the apparatus of the present invention, and the broken line B2 combines the concentration measurement by the conventional CO ₂ meter and the flux measurement by the ultrasonic velocimeter on the first observation tower 91. The results of Comparative Example 1 are shown, and the two-dot chain line C2 shows the result of Comparative Example 2 in which the concentration measurement by the conventional CO ₂ meter and the flux measurement by the ultrasonic velocity meter on the second observation tower 92 are combined. As is apparent from the figure, the measurement result (characteristic line A2) of Example 2 is a smoother curve than the result of the comparative example (characteristic lines B2 and C2). This is due to the fact that there is no obstacle (no disturbance) between the light source unit and the light receiving unit in the device of the present invention. On the other hand, the measurement result of the comparative example using the conventional apparatus has a lot of jaggedness in the change curve. This is because in the prior art, a large number of measurement devices are installed in the measurement region, so that from the perspective of a certain measurement device, another measurement device becomes an obstacle, and the measurement device itself causes a disturbance.

Although the measurement result (characteristic line A2) of the wide-area CO ₂ concentration flux according to the present invention cannot be directly verified with the measurement result (characteristic line B2, C2) of the comparative example using the conventional technology, the measurement result of the present invention is The results of the measurement using the conventional technology on each tower almost coincided with each other, and it was proved that the present invention is suitable for real-time measurement of wide-area CO ₂ concentration flux.

(Example 3)
As Example 3, an example in which a wide-area CO ₂ flux between forest observation towers is measured using a semiconductor laser type gas concentration flux measurement device will be described with reference to FIG. In addition, description of the part which a present Example overlaps with said Example is abbreviate | omitted.

In this third embodiment, in order to demonstrate wide-area gas concentration flux measurement according to the present invention, a semiconductor laser gas concentration flux that is a single device of a wavelength tunable TDLAS gas concentration measuring device in which a scintillation method function is added on a forest observation tower. A measurement device was installed, and the measurement results were analyzed based on the Monin-Obukhov similarity law, and the wide-area CO ₂ concentration flux between the forest observation towers was measured. In Example 3, as in Example 2, the measurement length was 81 m, which is equal to the distance between the towers.

  FIG. 9 shows an apparatus system of the third embodiment. The configuration of the wavelength tunable TDLAS gas concentration measuring devices 2F and 3F is substantially the same as the typical device configuration shown in FIG. 2 and, like the first and second embodiments, in order to improve measurement sensitivity and measurement stability, A dual wavelength modulation mechanism and a zero point measurement mechanism are added. The control / analysis unit 19F installed in the observation room 90 is almost the same as the control / analysis unit 19D of the second embodiment shown in FIG.

  Specifically, the light source unit 2F installed on the first forest observation tower 91 is a laser separate from the gas concentration measurement light source 11a in the basic configuration of the TDLAS optical system unit 20 of the first and second embodiments. An oscillation device 11b is incorporated. From the light source part 2F, the reference part light reception signal S23 and the zero part light reception signal S21 are output to the control / analysis part 19F of the observation room 90, and at the same time, the control signals of the respective light source parts LD are output from the observation room 90. It is transmitted from the control / analysis unit 19F. In this embodiment, the semiconductor pressure sensor 53 and the thermocouple 52 are installed on the first forest monitoring tower 91, and the measured values are represented as the pressure and temperature of the measurement region 100. In some cases, the average pressure and the average temperature in the measurement region 100 are measured with a laser using the characteristics of the absorption spectrum.

  Next, the light receiving unit 3F installed on the second observation tower 92 is received by each laser receiving device (PD-G, PD-) emitted from the optical unit 20 and transmitted through the atmosphere between the towers 91 to 92. S) 29a and 29d, and the received light signals S20 and S23 are output to the control / analysis unit 19F of the observation room 60 for analysis. In this embodiment, this signal transmission is performed using a normal electric wiring cable. However, when the measurement length is further increased, optical fiber transmission and wireless transmission that are easy to install in a facility are possible.

FIG. 10 is a characteristic diagram showing the measurement results of Example 3 with the measurement time on the horizontal axis and the measured CO ₂ concentration flux (mg / m ² · S) on the vertical axis. In the figure, the solid line A3 shows the result of Example 3 measured by the apparatus of the present invention, and the broken line B3 is a combination of the concentration measurement by the conventional CO ₂ meter and the flux measurement by the ultrasonic velocimeter on the first observation tower 91. The results of Comparative Example 1 are shown, and the two-dot chain line C3 shows the result of Comparative Example 2 in which the concentration measurement by the conventional CO ₂ meter and the flux measurement by the ultrasonic velocimeter on the second observation tower 92 are combined. As is apparent from the figure, the measurement result (characteristic line A3) of the third embodiment is a smoother change curve than the result of the comparative example (characteristic lines B3 and C3). This is due to the fact that there is no obstacle (no disturbance) between the light source unit and the light receiving unit in the device of the present invention. On the other hand, the measurement result of the comparative example using the conventional apparatus has a lot of jaggedness in the change curve. This is because in the prior art, a large number of measurement devices are installed in the measurement region, so that from the perspective of a certain measurement device, another measurement device becomes an obstacle, and the measurement device itself causes a disturbance.

Although the measurement result (characteristic line A3) of the wide-area CO ₂ concentration flux according to the present invention cannot be directly verified by the measurement result (characteristic line B3, C3) of the comparative example using the conventional technology, the measurement result of the present invention is The results of the measurement using the conventional technology on each tower almost coincided with each other, and it was proved that the present invention is suitable for real-time measurement of wide-area CO ₂ concentration flux.

Example 4
As Example 4, wide area CO ₂ flux measurement between forest observation towers using a semiconductor laser type gas concentration flux measurement device will be described with reference to FIG. In addition, description of the part which a present Example overlaps with said Example is abbreviate | omitted.

In the fourth embodiment, in order to demonstrate wide-area gas concentration flux measurement according to the present invention, a semiconductor laser type that is a single unit of a wavelength tunable TDLAS type gas concentration measurement device in which a scintillation method function is added to the forest observation towers 91 and 92. Gas concentration flux measurement devices 2G and 3G were installed, and the measurement results were analyzed based on the Monin-Obukhov similarity law, and the wide-area CO ₂ concentration flux between the forest observation towers 91 and 92 was measured. In the present embodiment, the measurement length is 81 m, which is equal to the distance between the towers, as in the second embodiment.

  FIG. 10 shows an apparatus system of the fourth embodiment. The configuration of the wavelength tunable TDLAS type gas concentration measuring device is substantially the same as the typical device configuration shown in FIG. 3, but in the same way as in Examples 1 and 2, in order to improve measurement sensitivity and measurement stability, the dual wavelength Added modulation mechanism and zero point measurement mechanism.

  Specifically, the light source unit 2G installed on the first forest observation tower 91 distributes the measurement laser into two in the basic structure of the TDLAS optical system unit of the first and second embodiments. The polarization plane rotator 27G that oscillates toward the measurement region is added after the laser polarization plane is rotated by 90 °, and the reference light reception signal S22 and the zero light reception signal S21 are used to control the observation chamber 90. At the same time, an LD control signal to the TDLAS optical system unit 20 is transmitted from the control / analysis unit 19G of the observation room 90. The polarization plane rotator 27G incorporates a Faraday rotator and rotates the polarization plane of the laser light oscillated from the light source 28 by 90 ° to convert the laser polarization plane from vertical polarization to horizontal polarization.

  In this embodiment, the semiconductor pressure sensor 53 and the thermocouple 52 are installed on the first forest monitoring tower 91, and the measured values are represented as the pressure and temperature of the measurement region 100. In some cases, the average pressure and average temperature in the measurement region are measured with a laser using the characteristics of the absorption spectrum.

  Next, the light receiving unit 3G installed on the second forest observation tower 92 has two light receiving devices that receive two laser beams emitted from the optical unit 20 and transmitted through the atmosphere between the towers 91 and 92 ( PD-G, PD-S) 29a and 29d, and the received light signals (G, S) are output to the control / analysis unit of the observation room for analysis. In the present embodiment, this signal transmission is performed using a normal electric wiring cable. However, if the measurement length is further increased, it is possible to perform transmission using an optical fiber method or a wireless method that facilitates installation of a communication facility. The control / analysis unit 19G installed in the observation room 90 later is substantially the same as that of the second embodiment shown in FIG.

FIG. 12 is a characteristic diagram showing the measurement results of Example 4 with the measurement time on the horizontal axis and the measured CO ₂ concentration flux (mg / m ² · S) on the vertical axis. In the figure, the solid line A4 shows the result of Example 4 measured by the apparatus of the present invention, and the broken line B4 combines the concentration measurement by the conventional CO ₂ meter and the flux measurement by the ultrasonic velocimeter on the first observation tower 91. The results of Comparative Example 1 are shown, and the two-dot chain line C4 shows the result of Comparative Example 2 in which the concentration measurement by the conventional CO ₂ meter and the flux measurement by the ultrasonic velocity meter on the second observation tower 92 are combined.

Although the measurement result of the wide-area CO ₂ concentration flux according to the present invention cannot be directly verified with the measurement result of the prior art, the measurement result of the present invention is almost the same as the measurement result of the conventional technique on each tower. Thus, it can be said that the present invention has proved that real-time measurement of wide-area CO ₂ concentration flux is possible.

(Examination example 1)
A case where wide-area CO ₂ flux measurement between forest observation towers using a semiconductor laser type gas concentration flux measurement device will be described as Study Example 1 of the present invention with reference to FIG. In addition, description of the part which this examination example overlaps with said Example is abbreviate | omitted.

In this examination example 1, in order to demonstrate wide-area gas concentration flux measurement according to this examination example, a semiconductor laser that is a single unit of a wavelength tunable TDLAS type gas concentration measuring apparatus having a scintillation method function added to the forest observation towers 91 and 92 The gas concentration flux measuring apparatus 10H was installed, and the measurement result was analyzed based on the Monin-Obukhov similarity law, and the wide-area CO ₂ concentration flux between the forest observation towers 91 and 92 was measured. In the present study example 1 as well, the measurement length was 81 m, which is equal to the distance between the towers, as in the second embodiment.

  FIG. 13 shows an apparatus system of Study Example 1. The configuration of the wavelength tunable TDLAS gas concentration measuring device is substantially the same as the typical device configuration shown in FIG. 4 because the polarization plane modulation frequency is sufficiently lower than the wavelength modulation frequency. Similarly, a dual wavelength modulation mechanism and a zero point measurement mechanism are added to improve measurement sensitivity and measurement stability.

  Specifically, the light source unit 2H installed on the first forest observation tower 91 has a polarization plane modulation function for adding a polarization plane modulation function to the basic structure of the TDLAS optical system unit of the first and second embodiments. The apparatus 59 and the optical unit 20 to which the modulation control device 58 is added. The reference part light reception signal S22, the zero part light reception signal S21, and the polarization plane modulation reference signal S37 are directed to the control / analysis part 19H of the observation room 90. At the same time, an LD control signal to the optical system unit 20 is transmitted from the control / analysis unit 19H of the observation room 90. In this embodiment, the semiconductor pressure sensor 53 and the thermocouple 52 are installed on the first forest monitoring tower 91, and the measured values are represented as the pressure and temperature of the measurement region. In some cases, the average pressure and average temperature in the measurement region are measured with a laser using the characteristics of the spectrum.

  The control / analysis unit 19H installed in the observation room 90 is the same as that of the second embodiment shown in FIG. 7 in that the polarization is obtained from the signal output from the second phase sensitive detector (No. 2-PSD-G) 64a. Based on the surface modulation reference signal S37, a third phase sensitive detector (No. 3-PSD-G) 64e for detecting a signal component synchronized with the modulation, and the received light signal of the PD-G The first phase sensitive detector (No. 1-PSD-S) 63a for extracting the received light intensity signal, or the phase sensitive detector (No. 1 for extracting the received light intensity signal of the transversely polarized laser from the received light signal of the PD-G) .2-PSD-S) 64f and a phase shifter 68 for outputting a signal S36 for shifting the phase of the polarization plane modulation reference signal S37 are added, and a DC component detection device for the received light intensity signal is omitted instead.

  The light receiving unit 2H installed on the second forest observation tower 92 includes a light receiving device (PD-G) 29 that receives a laser beam emitted from the optical unit 20 and transmitted through the atmosphere between the towers 91 and 92. The light reception signal S22 is output to the control / analysis unit 19H of the observation room 90 for analysis. In this study example, this signal transmission was performed using a normal electrical wiring cable. However, if the measurement length is further increased, it is possible to use an optical fiber transmission system or a wireless transmission system that facilitates installation of communication facilities. is there.

FIG. 14 is a characteristic diagram showing the measurement results of Study Example 1, with the measurement time on the horizontal axis and the measured CO ₂ concentration flux (mg / m ² · S) on the vertical axis. In the figure, the solid line A5 shows the result of the study example 1 measured by this study example device, and the broken line B5 shows the concentration measurement by the conventional CO ₂ meter and the flux measurement by the ultrasonic velocimeter on the first observation tower 91. The combined result of Comparative Example 1 is shown, and the two-dot chain line C5 shows the result of Comparative Example 2 that combines the concentration measurement by the conventional CO ₂ meter and the flux measurement by the ultrasonic velocimeter on the second observation tower 92. .

Although the measurement result of wide-area CO ₂ concentration flux in this study example cannot be directly verified with the measurement result of the conventional technology, the measurement result in this study example is almost the same as the result of measurement in the conventional technology on each tower. It can be said that it was demonstrated that real-time measurement of wide-area CO ₂ concentration flux was possible in this study example.

The gas concentration flux measuring apparatus of the present invention is used for monitoring the abundance of global warming gas (GHG) over a wide area. For example, the evaluation of CO ₂ absorption in forests, and the amount of GHG generated on the ground surface and ground. used in environmental research surveys, etc., or CO ₂ underground disposal plants, gas storage facilities, is also used for detection of gas leakage, such as pipelines.

DESCRIPTION OF SYMBOLS 10 ... Gas concentration measuring device 10A-10H ... Gas concentration flux measuring device 11, 11a, 11b ... LD control device (laser output control device)
12 ... Second DC component detector (for reference)
13 ... A / D converter 14 ... Data analysis / recording / display unit (analyzer; personal computer)
DESCRIPTION OF SYMBOLS 15 ... Polarization surface modulation control apparatus 16 ... Signal phase converter 17a, 17b, 18 ... Polarization surface modulation demodulator 19D-19H ... Control / analysis part 2, 2A-2H ... Light source part (measurement part)
2a ... Optical system container, 2b ... Protective container 20 ... Optical system unit 21 ... Laser light source 22, 22a-22c ... Half mirror 23, 23a, 23b ... Optical window 24 ... Mirror 25 ... Reference cell 26, 29b ... Light receiver for reference (Second light receiving device)
27, 27A, 27G... Polarization plane modulation device (polarization plane rotation device)
28, 28a, 28b ... Laser diode (LD)
29a ... Photodiode (first light receiving device)
29b ... Photodiode (second light receiving device)
29c, 29d ... photodiode (third light receiving device)
3, 3A to 3H, 31, 33, 34... First measurement light receiving unit (first light receiving device)
32, 33, 34... Second light receiving unit for measurement (third light receiving device)
3a: Optical container 4, 41, 42: First DC component detector (for measurement)
5 ... First wavelength modulation demodulator (for concentration measurement)
6 ... Wavelength modulation control device 7 ... Second wavelength modulation demodulator (for concentration calibration)
8 ... Third wavelength modulation demodulator (for laser wavelength fixed signal)
DESCRIPTION OF SYMBOLS 9 ... Adder 51 ... Ultrasonic anemometer 52 ... Temperature sensor 53 ... Pressure sensor 58 ... Polarization plane modulation controller 59 ... Polarization plane modulator (polarization plane rotator)
61, 62 ... Wavelength modulation waveform generators 63a to 63d, 64a to 64d ... Phase sensitive detectors 65a to 65d ... Low pass filter 66 ... Wavelength sweep waveform generator 67 ... Changeover switch 70 ... Scintillation measurement unit 71, 72 ... Laser oscillator 73a , 73b ... optical window 90 ... observation room 91 ... tower 93 ... open path type CO ₂ meter 95 ... sampling tube 96 ... closed path type CO ₂ monitor 100 ... measurement region T1 ... temperature instruments P1 ... pressure meter S1~ S192 ... Signal

Claims (7)

At least one light source that oscillates a laser beam having an absorption wavelength specific to the measurement target gas toward the measurement region;
A laser output control device for controlling the output operation of the light source;
A wavelength modulation control device that outputs a modulation signal for modulating the oscillation wavelength of the laser oscillated from the light source, and outputs a reference signal synchronized with the modulation;
A first light receiving device that receives the laser that has passed through the measurement region and outputs a signal corresponding to the received light intensity;
A first DC component detector that removes the AC component as the modulation signal from the signal output from the first light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the first light receiving device, and measurement in the measurement region is performed. A first wavelength modulation demodulator that outputs a signal proportional to the target gas concentration;
An optical system for distributing the laser emitted from the light source to two or more;
A reference cell in which the measurement target gas having a known concentration is sealed, and is arranged at a position where a laser that is distributed by the optical system and is not directed to the measurement region passes through the sealed gas;
A second light receiving device that receives the laser that has passed through the sealed gas in the reference cell and outputs a signal corresponding to the received light intensity;
A second DC component detector that removes an AC component as the modulation signal from the signal output from the second light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the second light receiving device, A second wavelength modulation demodulator that outputs a signal proportional to the concentration of the enclosed gas;
Based on the reference signal from the wavelength modulation control device, the odd harmonic component of the modulation signal applied to the laser is detected from the signals output from the second light receiving device, and the laser wavelength is measured. A third wavelength modulation demodulator that outputs a reference signal for fixing to the absorption wavelength of the target gas;
Based on signals output from the first DC component detector, the first wavelength modulation demodulator, the second DC component detector, and the second wavelength modulation demodulator, the An analyzer that calculates the measurement gas concentration and solid particle concentration and outputs the calculation results;
The modulation signal from the wavelength modulation controller and the reference signal for fixing the laser wavelength from the third wavelength modulation demodulator are added, and the added signal is externally controlled to the laser output controller An adder that outputs as a signal;
Temperature measuring means for measuring the temperature of the measurement region and outputting a signal corresponding to the measured value to the analysis device;
A pressure measuring means for measuring the pressure in the measurement region and outputting a signal corresponding to the measured value to the analysis device, and a gas concentration flux measuring device comprising:
Furthermore, it has a flow velocity measurement means for directly measuring each of the two horizontal flow velocity components and the vertical flow velocity component of the gas flow in the measurement region, and outputting these measurement signals to the analysis device,
The analysis device performs an analysis based on a vortex correlation law using a signal input from the flow velocity measurement means, and uses the analysis result to calculate the momentum flux in the measurement region, the concentration flux of the measurement target gas, and the measurement target gas. A gas concentration flux measuring device characterized in that the concentration is obtained by calculation. At least one first laser light source that oscillates laser light having an absorption wavelength specific to the measurement target gas toward the measurement region;
A laser output control device for controlling an output operation of the laser light source;
A wavelength modulation controller for outputting a modulation signal for modulating the oscillation wavelength of the laser emitted from the laser light source, and outputting a reference signal synchronized with the modulation;
A first light receiving device that receives the laser that has passed through the measurement region and outputs a signal corresponding to the received light intensity;
A first DC component detector that removes the AC component as the modulation signal from the signal output from the first light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the first light receiving device, and measurement in the measurement region is performed. A first wavelength modulation demodulator that outputs a signal proportional to the target gas concentration;
An optical system that distributes the laser emitted from the first laser light source into two or more;
A reference cell in which the measurement target gas having a known concentration is sealed, and is arranged at a position where a laser that is distributed by the optical system and is not directed to the measurement region passes through the sealed gas;
A second light receiving device that receives the laser that has passed through the sealed gas in the reference cell and outputs a signal corresponding to the received light intensity;
A second DC component detector that removes an AC component as the modulation signal from the signal output from the second light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the second light receiving device, A second wavelength modulation demodulator that outputs a signal proportional to the concentration of the enclosed gas;
Based on the reference signal from the wavelength modulation control device, the odd harmonic component of the modulation signal applied to the laser is detected from the signals output from the second light receiving device, and the laser wavelength is measured. A third wavelength modulation demodulator that outputs a reference signal for fixing to the absorption wavelength of the target gas;
Based on signals output from the first DC component detector, the first wavelength modulation demodulator, the second DC component detector, and the second wavelength modulation demodulator, the An analyzer that calculates the measurement gas concentration and solid particle concentration and outputs the calculation results;
The modulation signal from the wavelength modulation controller and the reference signal for fixing the laser wavelength from the third wavelength modulation demodulator are added, and the added signal is externally controlled to the laser output controller An adder that outputs as a signal;
Temperature measuring means for measuring the temperature of the measurement region and outputting a signal corresponding to the measured value to the analysis device;
A pressure measuring means for measuring the pressure in the measurement region and outputting a signal corresponding to the measured value to the analysis device, and a gas concentration flux measuring device comprising:
A second light source for irradiating the measurement area with a laser;
A third light receiving device that receives a laser beam emitted from the second light source and transmitted through the measurement region, and outputs a signal corresponding to the received light intensity to the analysis device;
The analysis device obtains the time change of the laser transmittance using the signal input from the third light receiving device, derives the time change of the gas density from the obtained time change of the laser transmittance, and further calculates the gas density. Analyzes based on the Monin-Obukhov similarity law to understand the state of turbulence of the measurement target gas from time changes, and using the analysis results, the momentum flux in the measurement region, the concentration flux of the measurement target gas, and the measurement target A gas concentration flux measuring apparatus characterized by obtaining a gas concentration by calculation. A first light source that oscillates a laser beam having an absorption wavelength unique to the measurement target gas toward the measurement region;
A laser output control device for controlling an output operation of the first light source;
A wavelength modulation control device that outputs a modulation signal for modulating the oscillation wavelength of the laser emitted from the first light source and outputs a reference signal synchronized with the modulation;
A first light receiving device that receives the laser that has passed through the measurement region and outputs a signal corresponding to the received light intensity;
A first direct current component detector that removes an alternating current component as the modulation signal from the signal output from the first light receiving device and outputs a direct current component of received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the first light receiving device, and measurement in the measurement region is performed. A first wavelength modulation demodulator that outputs a signal proportional to the target gas concentration;
An optical system that distributes the laser emitted from the first light source to two or more;
A reference cell in which the measurement target gas having a known concentration is sealed, and is arranged at a position where a laser that is distributed by the optical system and is not directed to the measurement region passes through the sealed gas;
A second light receiving device that receives the laser that has passed through the sealed gas in the reference cell and outputs a signal corresponding to the received light intensity;
A second DC component detector that removes an AC component as the modulation signal from the signal output from the second light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the second light receiving device, A second wavelength modulation demodulator that outputs a signal proportional to the concentration of the enclosed gas;
Based on the reference signal from the wavelength modulation control device, the odd harmonic component of the modulation signal applied to the laser is detected from the signals output from the second light receiving device, and the laser wavelength is measured. A third wavelength modulation demodulator that outputs a reference signal for fixing to the absorption wavelength of the target gas;
Based on signals output from the first DC component detector, the first wavelength modulation demodulator, the second DC component detector, and the second wavelength modulation demodulator, the An analyzer that calculates the measurement gas concentration and solid particle concentration and outputs the calculation results;
The modulation signal from the wavelength modulation controller and the reference signal for fixing the laser wavelength from the third wavelength modulation demodulator are added, and the added signal is externally controlled to the laser output controller An adder that outputs as a signal;
Temperature measuring means for measuring the temperature of the measurement region and outputting a signal corresponding to the measured value to the analysis device;
A pressure measuring means for measuring the pressure in the measurement region and outputting a signal corresponding to the measured value to the analysis device, and a gas concentration flux measuring device comprising:
A second light source that oscillates a laser beam having an absorption wavelength specific to the measurement target gas toward the measurement region;
A third light receiving device that receives a laser beam oscillated from the second light source and transmitted through the measurement region, and that outputs a signal corresponding to the received light intensity;
A third DC component detector that removes an AC component as the modulation signal from the signal received from the third light receiving device and outputs a DC component of the received light intensity to the analysis device;
The analysis device uses the signal input from the third DC component detector to obtain a time change in laser transmittance, derives a time change in gas density from the obtained time change in laser transmittance, In order to grasp the turbulence state of the measurement target gas from the change in density over time, an analysis based on the Monin-Obukhov similarity law is performed, and the momentum flux of the measurement region, the concentration flux of the measurement target gas, and A gas concentration flux measuring apparatus characterized in that the gas concentration to be measured is obtained by calculation. A single light source that oscillates a laser beam with an absorption wavelength specific to the measurement target gas toward the measurement region;
A laser output control device for controlling the output operation of the light source;
A wavelength modulation control device that outputs a modulation signal for modulating the oscillation wavelength of the laser emitted from the light source, and outputs a reference signal synchronized with the modulation;
A first light receiving device that receives the laser that has passed through the measurement region and outputs a signal corresponding to the received light intensity;
A first DC component detector that removes the AC component as the modulation signal from the signal output from the first light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the first light receiving device, and measurement in the measurement region is performed. A first wavelength modulation demodulator that outputs a signal proportional to the target gas concentration;
An optical system that distributes the laser emitted from the light source to two or more;
A reference cell in which the measurement target gas having a known concentration is sealed, and is arranged at a position where a laser that is distributed by the optical system and is not directed to the measurement region passes through the sealed gas;
A second light receiving device that receives the laser that has passed through the sealed gas in the reference cell and outputs a signal corresponding to the received light intensity;
A second DC component detector that removes an AC component as the modulation signal from the signal output from the second light receiving device and outputs a DC component of the received light intensity;
Based on the reference signal from the wavelength modulation control device, an even-order harmonic component of the modulation signal applied to the laser is detected from signals output from the second light receiving device, A second wavelength modulation demodulator that outputs a signal proportional to the concentration of the enclosed gas;
Based on the reference signal from the wavelength modulation controller, the odd harmonic component of the modulation signal applied to the laser is detected from the signals output from the second light receiving device, and the laser wavelength is measured. A third wavelength modulation demodulator that outputs a reference signal for fixing to the absorption wavelength of the target gas;
Based on signals output from the first DC component detector, the first wavelength modulation demodulator, the second DC component detector, and the second wavelength modulation demodulator, the An analyzer that calculates the measurement gas concentration and solid particle concentration and outputs the calculation results;
The modulation signal from the wavelength modulation controller and the reference signal for fixing the laser wavelength from the third wavelength modulation demodulator are added, and the added signal is externally controlled to the laser output controller An adder that outputs as a signal;
Temperature measuring means for measuring the temperature of the measurement region and outputting a signal corresponding to the measured value to the analysis device;
A pressure measuring means for measuring the pressure in the measurement region and outputting a signal corresponding to the measured value to the analysis device, and a gas concentration flux measuring device comprising:
An optical system that distributes the laser emitted from the single light source to two or more;
A polarization plane rotating device that rotates a polarization plane of one or more of the distributed lasers;
A third light receiving device for receiving a laser whose polarization plane is rotated by the polarization plane rotating device and outputting a signal corresponding to the received light intensity;
A third DC component detector that removes an AC component as the modulation signal from the signal received from the third light receiving device and outputs a DC component of the received light intensity to the analysis device;
The analysis device uses the signal input from the third DC component detector to obtain a time change in laser transmittance, derives a time change in gas density from the obtained time change in laser transmittance, In order to grasp the turbulence state of the measurement target gas from the change in density over time, an analysis based on the Monin-Obukhov similarity law is performed, and the momentum flux of the measurement region, the concentration flux of the measurement target gas, and A gas concentration flux measuring apparatus, wherein the gas concentration to be measured is calculated. The apparatus according to claim 1, wherein the light source and the first light receiving device are accommodated in the same container. 6. The apparatus according to claim 5, wherein the temperature measuring means and the pressure measuring means are also housed in the same container. 2. The apparatus according to claim 1, wherein an ultrasonic current meter is used as the flow velocity measuring means, and the ultrasonic current meter is accommodated in the same container.

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