RU2578515C2 - Method of determination of volume of atmospheric emissions from natural fires - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: method includes synchronous surface shooting by a digital video camera and a hyper spectrometer installed on the space carrier, separation by methods of spatial differentiation of function of brightness of the video image of the fire outline, calibration of brightness of pixels inside the outline, calculation by hyper spectrometer measurements of concentration of harmful emissions from the fire by reference attenuation of the light beam which has passed twice the atmosphere in the oxygen absorption band 761…767 nanometres and its attenuation in the visible range. The volume of emissions is determined from the expression V = m_Σ·S·H·A, where m_Σ - average concentration of harmful emissions from the fire, S - the area of the fire outline, N - height of the source of emissions (forest crop), A - meteorological coefficient of height temperature stratification of the atmosphere.

EFFECT: possibility of quantitative determination of volume of emissions.

8 dwg, 1 tbl

Description

The invention relates to the field of ecology, in particular to remote methods for monitoring natural environments, and can find application in systems of sanitary and epidemiological control of industrial regions and regional centers of the Ministry of Emergencies.

Industrial progress is inevitably associated with an increase in atmospheric emissions of so-called “greenhouse gases”, causing a positive trend in the average temperature of the Earth. The latter causes a significant increase in natural fires on a global scale. The consequences of natural fires (forest, peat) in particular, led to the formation of smogs in the European part of Russia in 2010 for up to 2 months, which increased the level of daily mortality in Moscow by several times.

Air pollution control is an integral part of the responsibilities of the states that have signed the Kyoto Protocol on environmental environmental monitoring.

A known method of assessing the state of the atmosphere by calculating the index of its state. Usually, the state index q _{Σ is} calculated for five components that determine the main contribution to air pollution [see, for example, “Methodology for calculating atmospheric air concentrations of substances contained in enterprise emissions”. All-Union normative document, OND-86, USSR, Hydrometeoizdat, Leningrad, 1987, pp. 4-5 - analogue]

where m _i [mg / m ³ ] is the average annual concentration of the i-th substance in the atmosphere;

CH _i - the maximum permissible sanitary norm of the i-th substance in atmospheric air, according to GOST 12.1.005-88 “General sanitary and hygienic requirements for the air of the working area”;

j is an indicator of the degree of isoefficiency of the harmful substance equal to 0.85; one; 1.3; 1.5 for substances of IV, III, II and I hazard classes, respectively.

There is a method for solving inverse problems of determining the source emission power M [g / s] at a given level of maximum surface concentration q [g / m ³ ] with other fixed emission parameters [see there is OND-86, p. 17, ... Solving inverse problems, formulas 2.41, 2.42 - analogue]

for f> 100

where H is the height of the source of emission (for terrestrial sources H = 2 m);

A - meteorological coefficient of altitude stratification of the atmosphere, at which the concentration of harmful substances in the atmosphere is maximum. For Moscow, Tula, Ryazan, Kostroma, Vladimir, Ivanovo reg. A = 140;

F is a dimensionless coefficient that takes into account the sedimentation rate of harmful substances in the atmosphere [for finely dispersed aerosols F = 1, for finely dispersed F≈3];

, f_c - см. аналог стр 6. формулы 2.3; 2.4; 2.5; 2.6];m (f), n (f) - coefficients that take into account the conditions for the exit of the gas-air mixture from the mouth, depending on the intermediate parameters [f, ν _m , $${\nu }_{m.}^{\text{'}\text{'}}$$

, f _c - see the analogue of page 6. of formula 2.3; 2.4; 2.5; 2.6];

η is a dimensionless coefficient taking into account the influence of the terrain (for a height difference of up to 50 m η → 1);

- расход газовоздушной смеси, D[м] - диаметр устья, $$V_{\mathrm{one}}=\frac{\mathrm{<figure-callout\; id="2"\; label="\pi \; D"\; filenames="00000023.png,00000025.png"\; state="\{\{state\}\}">\pi \; </figure-callout>}{D}^{}{}^2}{\mathrm{four}}{\nu }_0$$

- the flow rate of the gas-air mixture, D [m] is the diameter of the mouth,

ν ₀ is the average gas velocity of the air mixture;

ΔТ is the difference between the temperature of the gas-air mixture and the temperature of the surrounding air.

The disadvantages of the analogue are:

- the impossibility of directly using the formula for areal sources, which include a natural fire;

- a large amount of methodological error, equal to the sum of the relative errors of each parameter of the original formula, which makes the direct use of the analogue unacceptable.

The closest analogue to the claimed technical solution is the "Method for determining the concentration of carbon dioxide in the atmosphere." Patent RU No. 2422807 of 06/27/2011

In the closest analogue method, an equal number of adjacent spectral absorption bands of oxygen O ₂ and carbon dioxide CO ₂ in the near infrared range are selected by laboratory ground measurements, spectrometric measurements are carried out from a space carrier on the selected spectral bands of the light flux reflected from the underlying surface and transmitted twice atmosphere, calculate the energy of the recorded signals in the oxygen band

and carbon dioxide

calculate the total attenuation loss in the O ₂ and CO ₂ bands as the difference between the energy of the reference, according to Planck, solar spectrum in the same bands W _etal (O ₂ ) and W _etal (CO ₂ ) and the energy of the recorded signals

ΔW (O ₂ ) = W _etal (O ₂ ) -W (O ₂ ); ΔW (CO ₂ ) = W _etal (CO ₂ ) -W (CO ₂ ),

and the concentration of carbon dioxide in the atmosphere along the flight path of the carrier in each frame of spectrometric measurements is calculated from the ratio

where O ₂ [%] is the oxygen concentration in the atmosphere, equal to 21%;

I _i (O ₂ ), I _i (CO ₂ ) - the amplitudes of the recorded signals of each of the gases;

λ _i is the average wavelength of the spectral line;

n is the number of spectral lines in each band.

The disadvantages of the closest analogue are:

- the locality of the obtained measurement results, tied only to the path of a narrow sounding beam;

- a one-component assessment of atmospheric carbon dioxide pollution, while emissions from a natural fire contain many harmful substances, including mainly highly dispersed aerosols.

The problem solved by the claimed method consists in highlighting the fire contour on a generalized image of the underlying surface, calibrating the brightness pixels inside the fire contour according to standard spectrometric measurements in the values of total atmospheric pollution q _Σ [mg / m ³ ], calculating the emission volume V [tons] as a product the area S of the fire contour by the average statistical value m _Σ [mg / m ³ ] of the total pollution and the meteorological coefficient of atmospheric stratification A = 140 and the height N [m] of the source of emissions.

The problem is solved in that the method for determining the amount of atmospheric emissions from natural fires includes synchronous shooting of the underlying surface with a digital video camera and hyperspectrometer mounted on a space carrier, with the position of the spectrometer entrance slit aligned with the central portion of the video image frame, the spatial brightness differentiation of the brightness function I (x , y), a gradient contour fire in the video image, the calculation of the concentration q _Σ [mg / ^m3] of harmful emissions from a fire on the measured thrust With an spectrometer, the reference attenuation of a light beam that has twice passed through the atmosphere in an oxygen absorption band of 761 ... 767 nm, the concentration of which in the atmosphere is considered known, and its attenuation in the visible range, plotting a histogram of the pixel brightness inside the loop and calibrating them in measured concentration values for pixels in the central part of the frame video images, determination of the volume of emissions V [tons] = m _Σ · S · A · H, where m _Σ [mg / m ³ ] is the average concentration of total pollution over all calibrated pixels of the fire circuit, S [m ² ] - fire contour area, A - meteorological coefficient of altitude temperature stratification of the atmosphere, N [m] - height of the source of emissions.

The invention is illustrated by drawings, where

FIG. 1 - the original video image of the fire with the coaxial position of the slit of the spectrometer in the frame;

FIG. 2 - a characteristic profile of radio brightness temperatures over a fire;

FIG. 3 - selected contours of the gradients of the brightness function of the video image;

FIG. 4 - a method for measuring the attenuation of a light flux that has twice passed through the atmosphere;

FIG. 5 - reference, according to Planck, the solar spectrum (1), normalized relative to the maximum, and the spectrogram (2) of a real fire (one of the implementation);

FIG. 6 - absorption band of the light flux by atmospheric oxygen molecules;

FIG. 7 - a histogram of brightness pixels in the fire circuit and their calibration in the values of the concentration of harmful impurities [mg / m ³ ];

FIG. 8 is a functional diagram of a device that implements the method.

Natural fires occur under anticyclone conditions, cloudless or cloudless weather. A selectable sign of a forest (peat) fire is a plume of smoke, which is clearly visible in the image in cloudless weather and whose area is ten times the area of ignition. In reflected solar radiation, a plume of smoke appears to be a lighter (whitish) band starting from the front of the fire, FIG. 1. In addition to a plume of smoke, a fire is characterized by a red-hot surface of burning wood (front flame) and cooling coals (burned out, rear part).

In the figure of FIG. Figure 2 shows the characteristic profile of radio brightness temperatures above a fire.

. Более 99% энергии излучения пожара приходится на невидимую инфракрасную область спектра. Максимум теплового излучения пожара (Т°К∈[1000°…1500°] приходится на интервал 2…3 мкм. Поэтому в диапазоне длин волн λ<2 мкм пожар не оказывает влияние на отраженное солнечное излучение. Дымы пожаров - это высокодисперсные аэрозоли с твердыми частицами. По изменению спектральной яркости определяют полосу размывания дыма по мере удаления от фронта источника. Изображение пожара содержит всю информацию о мощности источника: размеру площади задымления, концентрации аэрозолей и других вредных продуктов горения.In accordance with the Wien displacement law, the wavelength corresponding to the maximum of the thermal radiation of a heated body is determined from the relation $${\lambda }_{\max }\left[m\mathrm{to}m\right]=\left[\mathrm{from}=2898\text{μm}\right]/T_{\max }^{°}K$$

. More than 99% of the radiation energy of the fire falls on the invisible infrared region of the spectrum. The maximum thermal radiation of the fire (T ° K∈ [1000 ° ... 1500 °] falls on the interval 2 ... 3 μm. Therefore, in the wavelength range λ <2 μm, the fire does not affect the reflected solar radiation. Smoke fires are highly dispersed aerosols with solid particles. By the change in spectral brightness, the smoke erosion band is determined as the distance from the source front. The image of the fire contains all the information about the source power: the size of the smoke area, the concentration of aerosols and other harmful combustion products.

The visual perception of the image by the human operator occurs at the level of the outline drawing. A contour drawing of a plume of smoke from a fire is obtained by calculating the gradient of the scalar brightness function I (x, y) of the video image at each image point as

[see, for example, “Derivative in direction,” in the textbook N.S. Piskunov. "Differential and integral calculus for technical colleges, 5th ed., Vol. 1, Science, M., 1964, pp. 264-268]. The directional derivatives of the brightness function define the vector field of the gradients. To obtain a contour drawing, a regular operator with a window aperture of | 2 × 2 | item;

i, j i, j + 1 i + 1, j i + 1, j + 1

Window elements are connected along diagonals (two mutually orthogonal directions) by a subtraction operation. The Roberts operator is calculated at each point:

R (i, j) = | I (i, j) -I (i + 1, j + 1) | - | I (i + 1, j) -I (i, j + 1) |,

displays points for which R (i, j) ≥ threshold [see, for example. Duda P.O., Hart P.E. “Pattern Recognition and Scene Analysis”, trans. from English, M., Mir, 1976 § 7-3, “Spatial differentiation”, pp. 287-288, Fig. 7.3].

At large values of the threshold value, the loss of essential information and the disappearance of the edge of the contour pattern are possible. With small threshold values, an unacceptable number of false lines appears, multi-circuit. The threshold value in each case is selected based on the range of values (image brightness function). The highlighted contours in the fire image (FIG. 1) are illustrated by the drawing of FIG. 3. Based on the image scale, the resolution of one pixel is determined. The number of pixels of the image of the fire highlighted against the underlying surface determines the area (S) of the distribution of combustion products and the power of the emission source.

The algorithm considered above is implemented by the following program.

The program for selecting contours in the image of the fire.

The highlighted contours of the fire image are illustrated in FIG. 3. The brightness of the pixels inside the selected contour depends on the emission power, the size of the fire and the train, the front or rear of the fire displayed in the frame [see, for example, L.I. Chapursky. “Reflective properties of natural objects in the range 400 ... 2500 nm”, part I, Min. Defense of the USSR, 1986, pp. 105-107, “Results of measurements and calculations of the QWS of air haze”]. The next task is to calibrate the brightness pixels in the values of the concentration of harmful emissions from the fire. In the claimed method, the measurement of the concentration of harmful emissions is carried out according to the operations of the closest analogue, based on the analysis of the absorption of a light beam that has twice passed the atmosphere in the oxygen absorption band (O ₂ ), the concentration of which in the atmosphere is 21%, and its absorption by harmful emissions in the visible range. The method of spectrometric measurements of the absorption of the light flux that has twice passed through the atmosphere is illustrated in Fig. 4. To calculate the absolute value of signal attenuation along the propagation path in the spectral bands of measurements, a reference is needed for comparison. The Planck function of the solar spectrum I (λ) is used as a reference. The reference (according to Planck) function of the solar spectrum, normalized in intensity, is illustrated in the graph of FIG. 5.

The attenuation energy of the light flux due to the absorption of harmful emissions along the propagation path twice through the atmosphere is calculated from the relations

ΔW (O ₂ ) = W _etal- W (O ₂ ); ΔW (po) = W _etal -W (po)

where W (i) is the energy of the signals in the spectral bands of the measurements,

W _etal is the energy of the reference (according to Planck) solar spectrum in the same spectral bands.

. Полную эталонную энергию светового потока вычисляют по соотношению Рэлея [см., например, Заездный В.М., «Основы расчетов по статистической радиотехнике», Связь-издат, М., 1964 г., стр. 93-94]The energy of one quantum (according to Planck's quantum theory) w = hν, where h is the Planck constant, ν is the frequency. Since the wavelength λ = c / ν (c is the speed of light), the quantum energy $$w=\frac{hc}{\lambda }$$

. The full reference energy of the luminous flux is calculated by the Rayleigh ratio [see, for example, Zaezdny VM, “Fundamentals of calculations on statistical radio engineering”, Sviaz-izdat, M., 1964, pp. 93-94]

where I (λ _i ) is the amplitude of the reference signal on the spectral line λ _i ;

n is the number of spectral lines in the attenuation band on which measurements are made.

The stability of the measurement result, independent of systematic errors, the height of the Sun, the azimuth of sounding, is also achieved by using the method of ratios of measured values, namely

In view of the foregoing, priority is given to the correct choice of spectral absorption bands for oxygen (O ₂ ) and harmful fire emissions.

The absorption band of atmospheric oxygen ≈764 nm, which is closest to the band of the visible range, was chosen as the comparison channel. The oxygen absorption (transmission) band is illustrated by the graph of FIG. 6.

According to the calculated total concentration of harmful emissions, for the pixels of the central portion of the video frame, they are calibrated for the entire selected circuit. The histogram of pixel luminance and the calculated values of the total pixel pollution of the central portion are illustrated in the graph of FIG. 7. Specific calculations of quantities are presented in an example implementation.

An example implementation of the method.

The claimed method can be implemented according to the scheme of FIG. 8. The functional diagram of the device comprises a spacecraft (SC) of observation 1 of the Resource type. A digital video camera 2 is installed on the spacecraft to obtain an image of the underlying surface 3 of the visible range (such as “DCS 760”) and a coaxial hyperspectrometer 4 (such as “Astrogon”) with the position of the entrance slit corresponding to the central portion of the video camera image. Frame-by-frame shooting of the planned regions 3 is carried out according to commands from the onboard control complex (BCC) 5 from the Flight Control Center (MCC) 6 via the command control radio line 7. The measurement results are recorded in the buffer memory 8 and according to the BCC commands, in the spacecraft radio visibility zones from ground points, reset via the mobile communication channel 9 to the information reception points (PLI) 10. After the preliminary processing of the frames according to service signs (number of revolution, time of shooting, site coordinates) on the means 11 information distributed to the Thematic Processing Center 12, where through the input device 13 it is entered into the PC 14 in a standard set of elements: processor 15, hard drive 16, random access memory (RAM) 17, display 18, printer 19, keyboard 20. Results of measurements of the concentration of harmful impurities along the flight path, the spacecraft are displayed on the Internet server 21.

The Astrogon-1 hyperspectrometer has three parallel spectral channels, in the visible 0.3 ... 0.4; 0.4 ... 0.65 μm and a near infrared range of 0.65 ... 0.9 μm with a spectral resolution of 1 ... 50 nm, a quantization resolution of 12 bits and a field of view of 0.11 ° [see, for example, “Small spacecraft "Volcano-Astrogon" with a high-resolution hyperspectrometer. " Engineering note, CANCER, NIIEM, STC "Reagent", pp. 8-10].

The minimum brightness of the pixels inside the image path was I _min = 19, the maximum I _max = 242, the average I _cp = 116.

With the initial data of the sensing paths and oxygen absorption bands (Fig. 6), the Planck reference function of the solar spectrum (Fig. 5 (1)) and the signal amplitudes measured by the hyperspectrometer (Fig. 5 (2)), the calculated values of the parameters took the values presented in Table .one

Table 1 Measurement path Band of measurements, nm Energy of a reference signal, rel. Signal Energy ΔW signal attenuation Concentration,% About ₂ Middle IR range 7 0.14 0.08 0.06 21% Fire emissions Visible Range 300 0.454 0.4494 0.0046 1.6%

Based on the measured percentage [%] content of harmful impurities of the fire in the air atmosphere, their maximum concentration is calculated for the pixels of the central part of the image frame, in which the standard attenuation of the light flux in atmospheric oxygen was measured.

It is known that one mole of any gas occupies a volume of 22.4 liters. The molar weights of the oxides of the combustion products CO ₂ = 44 g, NO ₂ = 46 g, SO ₂ = 64 g ... In a first approximation (taking into account highly dispersed aerosols), the average molar weight of the combustion products is taken to be ~ 50 g / mol. The concentration of harmful impurities is calculated from the ratio

The minimum concentration of harmful impurities along the blurry edges of the smoke plume m _min = 0.29 g / m ³ .

The average concentration of harmful impurities inside the fire circuit

. $${\overline{m}}_{\sum }=1.72{\text{g / <figure-callout id="3" label="m" filenames="00000025.png" state="{{state}}">m</figure-callout>}}^{\text{3}}$$

.

.The video image scale of FIG. 1 M: 1 cm = 1000 m. The area of the fire contour (number of pixels × pixel resolution) is: (Fig. 3) S = 56 · 10 ⁶ m ² . The average height (stand) of the source of emissions [see, for example, N.P. Anuchin. “Forest taxation”, 5th edition, Moscow, Timber industry, 1982, pp. 206-213, § 44. The average height of the stands H = 15 m]. Fire release volume $$V=\overline{m}\cdot S\cdot A\cdot H\approx 2.04\cdot {10}^5\text{t}\text{about}\text{n}\text{n}$$

.

The effectiveness of the proposed method is characterized by the ability to remotely determine the amount of emissions from natural fires and the documentary (register of measurements + fire video image) of the results of the estimates.

Claims (1)

The method for determining the volume of atmospheric emissions from natural fires includes synchronous shooting of the underlying surface with a digital video camera and hyperspectrometer mounted on a space carrier, with the position of the spectrometer entrance slit coaxial to the central portion of the video image frame, spatial isolation of the brightness function I (x, y), gradient contour fire in the video image, the calculation of the concentration q _Σ [mg / ^m3] of harmful emissions from a fire on the measured reference hyperspectrometer damped light beam that has twice passed the atmosphere in the oxygen absorption band of 761 ... 767 nm, the concentration of which in the atmosphere is considered to be known, and its attenuation in the visible range, the construction of a histogram of the pixel brightness inside the loop and their calibration in the values of the measured concentration for pixels of the central portion of the video image frame, determination of the emission volume V [t] = m _Σ · S · A · N, where m _Σ [mg / m ³ ] is the average concentration of total pollution over all calibrated pixels of the fire circuit, S [m ² ] is the area of the fire circuit, A - meteorologist cal factor altitude temperature stratification of the atmosphere, H [m] - the height of the emission source.

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