RU2516581C1 - Method to assess parameters of spray of dispersion-capable process liquid and plant for its realisation - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: by recorded pulse light image of cut plane with small thickness of the spray part, they determine parameters of drop spray in this part of the spray by means of a system of dispersion units based on the formula of the volume of ball (sphere) of a drop, for this purpose in the specified image they perform sorting and counting of number of drops of standard classes of ranges of microscopic dimensions in their adjacent sequence. For realisation of the method a double-laser plant is developed with digital devices of image signal processing and a computer.

EFFECT: invention makes it possible to expand functional capabilities of the method and the plant due to measurement of speeds of dispersed drops and production of results of assessment of spray parameters by means of analysis of values of reduced integral volumes of drops per unit of area with sorting by sequence of adjacent ranges of drop size.

4 cl, 4 dwg, 1 tbl

Description

Technical field

The invention relates to instrumentation, in particular to optoelectronic methods for monitoring and controlling the parameters of dispersed media.

State of the art

A close analogue is known - optical-electronic “Method for express analysis of the characteristics of the fuel flame” (patent for invention No. 2259554, published August 27, 2005), which consists in the fact that the rapid analysis of the flame is achieved by determining the local distribution of droplets by size in various points of the torch at its cross section by the laser plane. As such distributions, a two-parameter Rosin-Rammler dependence is used to describe the structure of dispersed media. The parameters D _cp , μm (the characteristic average diameter of the droplets) and n (the Rosin-Rammler distribution constant of droplets by size) characterizing the dispersion of the distributed fuel are determined. The installation for implementing this method is also described there.

The main disadvantages of this invention, which do not allow sufficiently effective application of this method and apparatus for measuring and evaluating parameters, regulating and designing spray devices (RU) to obtain dispersed flames of process fluids with different predetermined degrees of dispersion, are as follows:

- there is no such important characteristic of dispersed flows as the velocity of droplets in different parts of the spray torch. Drops of the same size (especially liquid fuel), but moving at different speeds, will give a different final effect;

- the volume of liquid at a predetermined flow rate (for example, ml / s) is fed to the inlet of the switchgear, and the so-called “medium-dispersed” size D _cp ., μm, which is not linearly related to the dispersed microvolume (μm ³ ) of the dispersed liquid, is determined at the output , therefore, the parameter D _cp. , microns, cannot serve as a determinant of the dispersed microvolume obtained at the outlet of the switchgear;

- “average” diameters for all dispersed droplets of a spherical liquid torch with sizes D≥5.0 μm, which are technologically applicable in industry, medicine, agriculture (and in a number of other branches of science and technology), - do not exist in nature: microvolumes of droplets calculated by virtual "average" diameters are practically poorly mathematically correlated with microvolumes calculated by their actual diameters.

Disclosure of invention

The objective of the invention is to overcome the disadvantages of this analogue in terms of expanding the functionality of the method and installation by measuring the velocities of dispersed droplets and obtaining the results of the evaluation of the parameters of the spray pattern by analyzing the values of the integral droplet volumes per unit area sorted by a sequence of adjacent droplet size ranges.

, где ⌀ - телесный угол схождения лучей. Также по зарегистрированному импульсному световому изображению рассеченной плоской с малой толщиной части факела распыла определяют параметры распыла капель в данной части факела с помощью системы единиц дисперсности на основе формулы объема шара (сферы) капли Q=0,524·D³, где D - диаметр шара диспергированной капли. Для этого в указанном изображении производят сортировку и подсчет количества капель стандартных (по ОСТ 10.6.1-2000) классов диапазонов микроскопических размеров в их смежной последовательности. В каждом классе от первого минимального до последнего максимального последовательно определяют в общем случае дробный коэффициент приведенного количества n_привi капель класса на единицу площади изображения. Умножают эту величину на объем Q_i шара капли своего класса для получения величины приведенного на единицу площади суммарного объема капель своего класса. Полученные дискретные величины приведенных на единицу площади суммарных объемов капель всех классов n_привiQ_i (i=1…i_max) и общую сумму этих объемов Σn_привiQ_i при i=1…i_max используют в дальнейшей математической статистической и/или интегральной обработке для определения базового параметра-коэффициента поли- или монодисперности исследуемой части факела распыла. В качестве базового параметра поли- или монодисперности исследуемой части факела распыла используют выборочное статистическое стандартное (среднее квадратичное) отклонение, характеризующее степень разброса суммарных объемов капель классов от монодисперсного состояния. В общем случае чем эта неотрицательная величина меньше, тем исследуемая часть факела является более монодисперсной.To solve this problem, a method is proposed for estimating the parameters of a spray torch of a dispersion-capable process liquid, which consists in the fact that a fluid torch obtained from a spray device in a predetermined location and direction is "dissected" by a laser light plane formed from a pulsed beam of a pulsed laser using an optical system in in the form of a flat light beam with a uniform distribution of its intensity. Register with a photo recorder and transmit to a computer for further processing a pulsed light image of the dissected part of the torch and determine the dispersion dispersion parameters of the droplets in this part of the torch. In addition, the velocity of the droplet droplets is determined using the laser-Doppler effect, for which use the radiation of an additional continuous laser, which is divided into two intersecting rays using an optical scheme. In the region of their intersection, a measuring volume is formed with a spatially periodic distribution of the light intensity, while the frequency of the light scattered by the moving drop differs from the frequency of the incident light of the laser by an amount that depends on the speed of the drop and is uniquely associated with it. This radiation is collected in a large solid angle with a lens and fed through a diaphragm to a photodetector, where an electronic spectral analysis of the scattered light frequencies is performed using a spectrum analyzer and the center frequency of the spectrum f _D is determined, and the laser radiation wavelength £ is also recorded. The speed of the droplet is determined by the formula: $$V=f_D\frac{\pounds }{2\sin \varnothing /2}$$

where ⌀ is the solid angle of convergence of the rays. Also, according to the recorded pulsed light image of the dissected flat part of the spray torch with a small thickness, the droplet spray parameters are determined in this part of the torch using a system of dispersion units based on the formula of the volume of the ball (sphere) of the drop Q = 0.524 · D ³ , where D is the diameter of the ball of the dispersed drop . To do this, the specified image is sorted and counted the number of drops of standard (according to OST 10.6.1-2000) classes of ranges of microscopic sizes in their adjacent sequence. In each class of the first minimum to the maximum of the last sequentially determined in the general case, a fractional coefficient of the reduced number n _privi class drops per unit image area. Multiply this value by the volume Q _{i of the} ball of a droplet of its class to obtain the value given per unit area of the total volume of drops of its class. The obtained discrete values of the total volume of droplets of all classes reduced per unit area n _privi Q _i (i = 1 ... i _max ) and the total amount of these volumes Σn _privi Q _i for i = 1 ... i _max are used in further mathematical statistical and / or integral processing to determine the base parameter-coefficient of poly- or monodispersity of the studied part of the spray torch. As a basic parameter of the poly- or monodispersity of the studied part of the spray torch, a selective statistical standard (mean square) deviation is used, which characterizes the degree of dispersion of the total volumes of class drops from the monodisperse state. In the general case, the smaller this non-negative value, the more studied part of the torch is more monodisperse.

Also can receive a system of light images of portions of the torch, primarily perpendicular to the main axis of the flame propagation spray and define the parameters spray droplets in these parts of the torch individually or together integrally around the torch with the actuating total volumes n _privi Q _i droplets all classes per unit area of images.

The apparatus for implementing the method for estimating the parameters of the spray torch of a dispersion-capable process fluid includes a laser pulse light source, a spray device for generating a spray torch, an optical system for generating and directing to the studied part of the spray torch a flat light beam with a uniform distribution of its intensity from the laser pulse light source, digital photorecorder for receiving a pulse image of the studied part of the spray torch, computers for storage and processing digital signals recorded images. Moreover, the setup additionally contains a continuous laser, an optical circuit of its beam divider with a variable pitch and a variable-pitch control device, a digital photodetector with an electronic analyzer of the frequency spectrum of the spatially periodic distribution of the intensity of the scattered light in the measurement volume in the studied part of the spray torch to determine the velocities of droplets with using the laser Doppler effect.

List of figures

figure 1 - schematic diagram of the proposed installation;

figure 2 - diagram of the expiration of the jet with the internal rarefaction zone of RU;

figure 3 is a diagram of an example of the distribution of speeds of dispersed droplets in the torch RU;

Fig. 4 is a graph of an example of a distribution of integral volume of monodispersed droplets given per unit area of a sequence of adjacent size ranges.

The implementation of the invention

Figure 1 diagrams of the proposed installation for implementing the method, the positions indicated: 1 - continuous He-Ne laser LGN-503; 2 is an optical diagram of a beam splitter with a variable pitch and a variable pitch control device; 3 - a lens with a digital photorecorder (3a); 4 - spectrum analyzer; 5 - pulsed laser LGI-215; 6 - rotary heads; 7 - combined lenses; 8 is a digital photorecorder for receiving a pulse image aligned on a plane cutting a torch and perpendicular to this plane; 9 - spray device (RU); 10 - a computer for storing and processing digital data of the dispersion of the cross sections of the torch and the speeds of the dispersed droplets using the laser-Doppler effect.

Both ruby pulsed (LGI-215) and continuous He-Ne (LGN-503) lasers are part of one measuring holographic setup UIG-12, but are structurally located separately and also work separately. The He-Ne laser is mounted directly on the holographic table plate and is focused on the nozzle torch, and the pulsed laser is mounted under the plate, from where, using the rotary heads 6, it is also focused on the same nozzle torch. The “laser knife” method was used in the setup: the beam of a pulsed ruby laser 5 is converted into a flat thin light beam (0.5 ... 1 mm) with a uniform distribution of its intensity using an optical system 7, which is a combination of a short-focus cylindrical lens and a long-focus telescopic system with variable focal length. The “laser knife” pulse (5 microseconds) cuts through the torch of the working nozzle in a given place. All drops falling into the section plane are recorded by a digital photorecorder 8 located strictly perpendicular to this plane and aligned with it. Since the working thickness of the "laser knife" is from 0.5 to 1 mm, and the size of the drops is at least an order of magnitude smaller, the bulk of the drops (90 ... 95%) are fully illuminated and give fairly objective information about their true size. Drops that fall into the plane of the “laser knife” are not cut by it, they are only illuminated for 5 microseconds and enable non-destructive testing to evaluate their size using a photographic recorder, followed by processing and calculation.

An example of the method

At the installation, comparative studies of the torches of pneumatic nozzles of the “G-2m” type were carried out with and without swirling spraying compressed air. By dividing the torch zone along the axis and in the transverse direction into sections and measuring the velocity of the gas flow and liquid droplets in each of them, a picture of the liquid and gas flows was visualized. Figure 2 presents a diagram of the expiration of the jet with the internal rarefaction zone from the RU - a diagram of the expiration of the air flow from the annular gap of the nozzle with a swirl of compressed air. The air was spun in order to increase the angle of the torch and reduce its range. Studies have shown that when compressed air swirls near the cut-off of the liquid nozzle, a region of reduced pressure forms (zone I) with circulating regions of reverse currents (zone II). The reduced pressure in it bends the trajectory of the jet, which quickly adjoins the axis of symmetry. The size of the reverse current region does not exceed 3 ... 5 gauges of the liquid nozzle. When spraying liquid in a swirling stream of compressed atomizing air (P = 1 bar), droplet speeds were experimentally measured and their significant differences were revealed in different parts of the nozzle plume, the distribution of which is shown in Fig. 3. The swirling of the spraying air contributes to the intensive expansion of the plume from the nozzle exit, an increase in the opening angle from 17 ... 19 ° (direct untwisted flow) to 45 ... 55 °, and rapid attenuation of the velocity along the axis.

The information obtained using laser technology on the velocities of droplets of the sprayed liquid and the velocity fields of the entire torch becomes another important characteristic for evaluating the effectiveness of a particular reactor and ways to improve its design, which opens up the possibility of developing new ones. So, for example, during the operation of fuel injectors, a difference in the velocities of droplets of the same size in different parts of the flame two or more times can lead to incomplete combustion, because At the same time, processes of intense evaporation and combustion are underway. New switchgear should be developed not only with the aim of achieving a monodisperse spray, but also with such droplet speeds that ensure their maximum combustion, taking into account the volume and design of the combustion chamber. This approach is able to provide the highest energy efficiency and reduce liquid fuel consumption.

Thus, the use of laser technology in the study of the torch allowed:

- evaluate the speed of the droplets (for one of the pneumatic nozzles, this speed in different parts of the torch varied in the range of 70 ... 120 m / s);

- detect the zone of reverse currents near the liquid nozzle for swirling flows;

- see the area of the unbroken stream, where the stream of liquid begins to disintegrate into drops;

- detect the non-monotonic distribution of the concentration of drops in the cross section of the torch, and these concentrations in different parts of the torch can vary by an order of magnitude.

Also in the method it is proposed to use a system of units of dispersion (poly - or monodispersity), due to the following paradigms:

- as the size, volumetric average, median-mass and other “average” droplet diameters cannot, by definition, be system-forming units of dispersion measurements, since all of them are not a quantitative, physico-chemical, energy, economic measure of dispersion-capable liquid systems (DGS) and they cannot be instrumentally measured.

- as the aggregate states of a substance, any DFS is characterized by droplet microvolumes and their number (quantity) depending on the degree of dispersion of these microvolumes in the total volume of DFS, and for rationing a comparative analysis - bringing this amount to a unit area

- in the physical and mathematical sense, polydispersity is the quadratic deviation of droplet volumes from monodisperse. This deviation (the practical dispersion of droplets by their number (quantity), size and volume, depending on the degree of dispersion of the volumes) should be called the coefficient of poly- or monodispersity, mathematically equal to the square root of the dispersion.

As the main systemic unit of dispersion, a dispersed cubic micron with a dimension of μm ³ is taken - the microvolume of the ball (sphere) of the drop in accordance with the classical formula of the volume of the ball: Q = 0.524 · D ³ , where D is the diameter of the dispersed drop in microns. Extra-systemic units of dispersion volume: 1 l = 10 ¹⁵ μm ³ ; 1 ml = 10 ¹² μm ³ .

In the example implementation of the method in the table and figure 4 presents the results of measurements recorded on the proposed installation data and evaluation of the parameters of the spray torch dispersion-capable process fluid.

Table Class
owl
between
current (by
OST 10.6.1-2000) The diameter range of the droplets of the class, microns The average diameter of the droplets of the class, microns The reduced number of drops per unit area, pcs / cm ² The given volume in the class, μm ³ / cm ² % fraction of liquid enclosed in class drops 1-3 14-41 28 303.60 3.310 ⁶ 0.32 3-5 42-69 56 239.30 20.2 · 10 ⁶ 2.13 5-7 70-97 84 121.40 34.410 ⁶ 3.40 7-9 98-125 112 60.71 41.0 · 10 ⁶ 4.13 9-11 126-153 140 41.67 55.410 ⁶ 5.52 11-13 154-181 168 41.67 95.210 ⁶ 9.60 13-15 182-209 196 23.81 86.710 ⁶ 8.70 15-17 210-237 224 19.44 107,0 · 106 10.60 17-19 238-265 252 11.61 85.0 · 106 9.00 19-21 266-293 280 6.55 69.2 · 106 7.00 21-23 294-321 308 4.17 58.8106 5.80 23-25 322-349 336 3.21 58.6106 5.80 25-27 350-377 364 2.14 50,0 · 106 5.03 27-29 378-405 392 1,67 48.5106 4.87 29-31 406-433 420 1.19 29.0 · 106 4.30 31-33 434-461 448 0.83 36.2 · 106 3.62 33-35 462-489 476 0.65 33.8106 3.42 35-37 490-517 504 0.48 29.6106 2.95 37-39 518-545 532 0.30 21.8 · 106 2.20 39-41 546-573 560 0.12 10.2 · 106 1.01 41-43 574-601 588 0.06 5.6106 0.60 Amount - - - 979.5106 one hundred

According to the integral (additive) volumes given per unit area (1 cm ² ) (the volume of droplets per their number per unit area) and the classical formulas of the sample characteristics, the standard deviation (square root of the dispersion), taken as the coefficient of poly- or monodispersity, It turned out to be 2.87.

According to other proprietary formulas and derived dispersion units for estimating the coefficient of poly- or monodispersity, the value of the coefficient of poly- or monodispersity also turns out to be quite close to the value obtained by the classical formulas, namely, 2.98. This result was obtained by processing the table data using the following author's formulas and dispersion units.

The unit of the degree of dispersion of the microvolumes of the liquid is the geometric (general) coefficient of poly - or monodispersity of the liquid cooling liquid K _{p / m} according to the formula:

где: $$K_{P/m}=\sqrt{{\mathrm{TO}}_{\mathrm{one,}PR\mathrm{and}\mathrm{at}}\cdot {\mathrm{TO}}_{2\mathrm{about}bbemn}},$$

Where:

- K ₁ , _priv - quadratic deviation of the given diameters of the droplets from monodisperse:

$${\mathrm{TO}}_{\mathrm{one}}{}_{,PR\mathrm{and}\mathrm{at}}=\frac{d_{PR\mathrm{and}\mathrm{at},max}}{d_{PR\mathrm{and}\mathrm{at},mix}}$$

K ₂ , _volume is the quadratic deviation of the microvolumes of the droplets and the number (number) of droplets contained in the additive (integral) microvolume from the monodisperse:

$${\mathrm{TO}}_{2\mathrm{about}bbem}=\frac{{\displaystyle \sum \left(n\cdot d_i^3{}_{,PR\mathrm{and}\mathrm{at}}\right)\max }}{{\displaystyle \sum \left(n\cdot d_i^3{}_{,PR\mathrm{and}\mathrm{at}}\right)mix}}\cdot K_{\mathrm{one}}^{-\mathrm{one}},PR\mathrm{and}\mathrm{at}$$

The established units of measurement give the basis to formulate a coherent system of communication equations: a dispersion measurement system in accordance with the law of conservation of mass of matter and the canons of the international system of units.

$$\{\begin{array}{l}{Q}_{\mathrm{one,}\max }+{\mathrm{<figure-callout\; id="2"\; label="Q"\; filenames="00000006.png,00000009.png"\; state="\{\{state\}\}">Q</figure-callout>}}_{2\min }=Q_{\mathrm{about}bu}\mathrm{,one\; hundred}\%\\ \frac{Q_{\mathrm{about}bu}}{0.524{\displaystyle \sum _{D\min }^{D\max }n\cdot D_i^3{}_{,PR\mathrm{and}\mathrm{at}}\cdot KP/m}}\\ {\mathrm{TO}}_{P/m}=\sqrt{\frac{{\displaystyle \sum \left(n\cdot d_i^3{}_{,PR\mathrm{and}\mathrm{at}}\right)}\approx 90\%}{{\displaystyle \sum \left(n\cdot d_i^3{}_{,PR\mathrm{and}\mathrm{at}}\right)\approx 10\%}}}\end{array}=\mathrm{1,0};gde:$$

Note: ≈90% (max) and ≈10% (min) are the distribution of the volumes of liquid contained in the corresponding cumulative integral volumes of drops (according to OST 10.6.1-2000).

The calculated results of the table data according to the above author's formulas were obtained as follows:

K _{1, pr} = 3.44

K _{2, volume} = 2.59

K _{p / m} = 2.98

According to the practical work of the authors, finding the K _{p / m} value in the range 1 ... 2 means a close to monodisperse state of the droplets, in the range 2 ... 5 it means the boundary state between mono-and polydisperse,> 5 - the polydisperse state of the studied part of the torch. In this case, we must strive for an exceptionally monodisperse state of DZhS.

The proposed method allows the designer and tester to obtain, based on the polydispersity analysis, the desired degree of dispersion of liquids at the outlet of the reactor during calculations, design, bench testing and implementation of energy characteristics, for example:

- the velocity of the flow of droplets per unit time (m / s);

- deposition of droplets microvolumes and their number (quantity) per unit area (l / ha; ml / cm ² ; μm ³ / cm ² );

- the distribution of microvolumes of droplets and their number (number) over the working volume of the combustion chamber (μm ³ / volume c.c.)

Claims (4)

1. A method for evaluating the parameters of a spray torch of a dispersion-capable process fluid, which consists in the fact that the fluid torch obtained from the spraying device in the specified location and direction is "cut" with a laser light plane formed from a pulsed beam of a pulsed laser using an optical system in the form of a plane light beam with a uniform distribution of its intensity, register with a photorecorder and transmit to a computer for further processing a pulsed light image of the dissected part of the ph ate and determine the parameters of the dispersion spray of droplets in this part of the torch, characterized in that they additionally determine the speeds of the droplet droplets using the laser-Doppler effect, for this use the radiation of an additional continuous laser, which is divided into two intersecting rays using an optical scheme, their intersection regions form a measuring volume with a spatially periodic distribution of light intensity, while the frequency of light scattered by a moving drop is different I from the frequency of the incident light of the laser by an amount depending on the speed of the droplet and uniquely associated with it, this radiation is collected in a large solid angle using a lens and fed through a diaphragm to a digital photodetector, where an electronic spectral analysis of the frequencies of the scattered light is performed using a spectrum analyzer and determine the center frequency of the spectrum f _D , also fix the value of the wavelength £ of the laser radiation, and the drop velocity is determined by the formula: $$V=f_D\frac{\pounds }{2\sin \varnothing /2}$$

, where ⌀ is the solid angle of convergence of the rays, as well as the parameters of the droplet atomization in this part of the torch using the system of dispersion units based on the ball volume formula Q = 0.524 · D ³ , where D - the diameter of the ball of a dispersed droplet, for this purpose, the specified image is sorted and counted the number of drops of standard class ranges of microscopic sizes in their adjacent sequence, in each class from Vågå minimum to the last maximum sequentially define generally fractional ratio given number n _{pref i} class per unit image area drops multiply this value by the amount Q _i of the ball in its class drop to obtain the value indicated on the unit area of the total volume of its class droplets obtained discrete values given per unit area of the total volume of all droplets classes _privi n Q _i (i = 1 ... i _max) and the total amount of these volumes Σn _privi Q _i when i = 1 ... i _max used in further mathematical eskoy statistical and / or an integrated processing for determining basic parameter coefficient monodispernosti poly- or of the measured part of the spray. 2. The method according to claim 1, characterized in that as the basic parameter of the poly- or monodispersity of the studied part of the spray torch, a selective statistical standard (mean square) deviation is used that characterizes the degree of dispersion of the total volumes of class drops from a monodisperse state: in general, than this non-negative value is less, the studied part of the torch is more monodisperse. 3. The method according to claim 1 or 2, characterized in that they obtain a system of light images of various parts of the torch, primarily perpendicular to the main axis of propagation of the spray torch and determine the parameters of the spray droplets in these parts of the torch, both individually and collectively integrally throughout with the reduction of the total volumes n _add Q _i drops of all classes to the total image area unit. 4. Installation for evaluating the parameters of the spray pattern of a dispersion-capable process fluid, including a laser pulsed light source, a spray device for generating a spray pattern, an optical system for generating and directing a flat light beam with a uniform intensity distribution over the entire plane from laser pulsed light source, a digital photo recorder receiving a pulsed image of the studied part of the spray pattern, computers for storage and Processing of digital signals of registered images, characterized in that the installation further comprises a continuous laser, an optical scheme of its beam divider with a variable pitch and a variable-pitch control device, a digital photodetector with an electronic analyzer of the frequency spectrum of the spatially periodic distribution of the intensity of the scattered light in the measurement volume in the studied part spray pattern for determining droplet velocity using the laser Doppler effect.

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