CN111855654B - Method for evaluating multiphase flow reinforced stirring and mixing effects - Google Patents

Method for evaluating multiphase flow reinforced stirring and mixing effects Download PDF

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CN111855654B
CN111855654B CN202010517208.6A CN202010517208A CN111855654B CN 111855654 B CN111855654 B CN 111855654B CN 202010517208 A CN202010517208 A CN 202010517208A CN 111855654 B CN111855654 B CN 111855654B
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multiphase flow
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王�华
杨凯
徐建新
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Kunming University of Science and Technology
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Abstract

The invention provides a method for evaluating multiphase flow reinforced stirring and mixing effects. The method adopts a statistical method to calculate the 0 th Betty number of the multiphase mixed fluid mixing pattern, obtains the time sequence of the 0 th Betty number of the multiphase flow mixing sample, and carries out logistic fitting on the time sequence. Judging the mixing effect under the working condition according to the size of the area S enclosed by the 0 th Betty number time sequence logistic curve and the abscissa; the larger the 0 th wittig number is, the better the mixing effect is; the more closely the logistic fit curve inflection point is to the vertical axis, the better the mixing effect. That is, the larger the area S of the region surrounded by the logistic curve of the 0 th witterion time series and the abscissa, the better the mixing effect. The method is simple and reliable, is suitable for the characterization of multiphase flow mixing effect, particularly for the evaluation of multiphase stirring mixing effect in the fields of metallurgy and chemical industry, and has high practical value.

Description

Method for evaluating multiphase flow reinforced stirring and mixing effects
Technical Field
The invention relates to the technical field of chemical and metallurgical engineering, in particular to a method for evaluating multiphase flow reinforced stirring and mixing effects.
Background
The gas-liquid-solid three-phase system is a very common multiphase flow reaction or separation system in the industrial production process, and has wide application in a plurality of industrial processes such as petroleum, chemical industry, energy sources, metallurgy and the like. The reinforced stirring and mixing are key steps of a plurality of process technologies, and in the chemical reaction, the reinforced stirring and mixing are used for accelerating the reaction process and saving the reaction time; in the physical reaction, the intensified mixing is used for preventing solid particles from depositing, so that the solid particles reach a suspension state in a liquid phase, and the mixing energy consumption is reduced. The stirring process can be accurately controlled by mastering the quality of the multiphase mixing effect, and a large amount of manpower, material resources and financial resources are saved. The evaluation of multiphase flow reinforced stirring mixing effect is one of the research difficulties in the multiphase flow field.
At present, the evaluation of multiphase flow stirring and mixing effects at home and abroad is mainly studied from two angles of macroscopic and microscopic. The macro evaluation method includes measuring stirring power, and the micro evaluation method includes measuring a mixing process velocity field. Measuring the stirring power is not accurate enough to evaluate the mixing effect, and measuring each phase velocity field is too complex. In recent years, a Planar Laser Induced Fluorescence (PLIF) measurement method is widely used, and the method not only can display the mixing effect difference of each planar position in a flow field in real time, but also can intuitively and clearly reflect the change rule of a mixing state along with time. Although some students studied transient tracer distribution, concentration variation and macroscopic mixing characteristics in stirred tanks by PLIF measurement methods, the application of this method has strong limitations. The requirement on working medium selection is high.
Based on the problems existing in the prior art, an evaluation method for evaluating multiphase flow mixing effect, which is visual and has a wide application range, is needed.
Disclosure of Invention
The invention aims to provide a method for evaluating multiphase flow reinforced stirring and mixing effects, which solves the problems in the prior art and can intuitively evaluate the multiphase flow reinforced stirring and mixing effects.
In order to achieve the above object, the present invention provides the following solutions: the invention provides a method for evaluating multiphase flow reinforced stirring and mixing effects, which comprises the following steps:
building a test bed: adding an object to be mixed into a transparent container, inserting a stirring rod into the object to be mixed, mounting an air supply device at the bottom of the transparent container, and mounting an image acquisition device near the transparent container;
collecting an image: starting the image acquisition device, the stirring rod and the gas supply device, and spraying gas by the gas supply device, wherein the gas moves in the object to be mixed from bottom to top, and the stirring rod stirs the object to be mixed, so that multiphase flow reinforced stirring is formed; the image acquisition device acquires a video of the stirring process in the length of T time;
image gray level and binarization processing: carrying out framing treatment on the video in the stirring process, and carrying out image gray scale and binarization treatment on the image subjected to framing treatment to obtain an image subjected to binarization treatment;
calculating a zero-dimensional Betty number time sequence: calculating a time sequence of the zero-dimensional Betty number of the binarized image;
logistics fitting: and performing logistic fitting on the time sequence of the zero-dimensional Betty number in an OXY rectangular coordinate system to obtain a fitted logistic curve, and calculating the area S of the logistic curve and the transverse axis of the OXY rectangular coordinate system.
Preferably, the object to be stirred is transparent or semitransparent liquid, and the image acquisition device is a high-speed camera or a particle velocimeter.
Preferably, the air supply device is an oxygen gun, and the oxygen gun is connected with an air pump, and the air pump is used for providing oxygen flow with pressure for the oxygen gun.
Preferably, the oxygen lance is at an angle of 0-180 ° to the bottom of the transparent vessel.
Preferably, the bottom of the stirring rod is fixedly connected with a plurality of blades, the blades are used for stirring the object to be stirred when rotating, and the stirring rod is powered by a motor.
Preferably, the image acquisition device adopts a high-speed camera, and the imaging rate is 11000 frames/second.
Preferably, the zeroth-dimensional Betty number is calculated by Chomp International software.
The invention discloses the following technical effects:
the method provided by the invention solves the defects of the existing method for evaluating the mixing effect, provides a new index for evaluating the mixing effect, is intuitive and has strong applicability, and relates to the fields of chemical industry, metallurgy and the like, for example, the method can be used for researching the leaching stirring process of hydrometallurgy and also can be used for researching the water model research of pyrometallurgy.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a test apparatus of the present invention;
FIG. 2 is a schematic representation of the test results of the present invention.
Wherein, 1 is the air pump, 2 is the oxygen rifle, 3 is the stirring rod, 4 is the blade, 5 is the whiteboard, and 6 is high-speed camera.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Referring to fig. 1-2, the present invention provides a method for evaluating the effect of multiphase flow enhanced stirring and mixing, and in order to enable those skilled in the art to more clearly understand the present embodiment, the theory related to the present embodiment is first described below.
G is an Abelian group, and the group is a beta-form group,
Figure SMS_1
for a free Abbe group in algebra, from the classification point of view analysis, the Abbe group generated by isomorphic finite element is through the unique finite number set +.>
Figure SMS_2
Wherein r is free Abelian group
Figure SMS_3
Is called Betty number, ++>
Figure SMS_4
Called flexible coefficients, in algebraic topology, betty number b of topological space 0 ,b 1 ,b 2 .. it is an important invariant, and the value is a non-negative integer or infinity. Intuitively see b 0 Is the number of connected components b 1 Is the maximum number of cuts that maintain communication by cutting the space along the closed curve. Higher order b k Can be defined by coherent groups. Wherein b 0 The 0 th wittig number represents the number of connected components in the region, that is, the number of blocks in the region, and if the number of blocks in the region is sufficiently large, the effect of multiphase mixing is sufficiently good.
The invention utilizes the combination of the 0 th witterion number and the logistic fitting curve to characterize the multiphase mixing effect. The logistic regression is also called logistic regression analysis, is a generalized linear regression analysis model, and is commonly used in the fields of data mining, automatic disease diagnosis, economic prediction and the like. And calculating the 0 th Betty number of the multiphase mixed fluid mixed pattern by adopting a statistical method, obtaining a time sequence of the 0 th Betty number of the multiphase flow mixed sample, and carrying out logistic fitting. Judging the mixing effect under the working condition according to the size of the area S enclosed by the 0 th Betty number time sequence logistic curve and the abscissa; the larger the 0 th wittig number is, the better the mixing effect is; the more closely the logistic fit curve inflection point is to the vertical axis, the better the mixing effect. That is, the larger the area S of the region surrounded by the logistic curve of the 0 th witterion time series and the abscissa, the better the mixing effect.
The following description will be made in detail with reference to fig. 1-2, wherein an object to be mixed is added into a transparent container, a stirring rod 3 is inserted into the object to be mixed, a blade 4 is installed at the bottom of the stirring rod 3, a gas supply device is installed at the bottom of the transparent container, the gas supply device comprises a gas pump 1 and an oxygen lance 2, the oxygen lance 2 is uniformly installed at the bottom of the transparent container, the gas pump 1 and the oxygen lance 2 are connected through a pipeline, and the gas pump 1 provides gas flow with certain pressure for the oxygen lance.
A high-speed camera 6 is arranged near the transparent container, the high-speed camera 6, the stirring rod 3 and the air supply device are started, the imaging speed of the high-speed camera 6 is 11000 frames/second, the air supply device sprays air, the air moves in an object to be mixed from bottom to top, and the stirring rod 3 drives the blades 4 to rotate, so that the object to be mixed is stirred, and multiphase flow reinforced stirring is formed. The high speed camera 6 captures video of the stirring process for a length of T.
And carrying out framing treatment on the video in the stirring process, and carrying out image gray scale and binarization treatment on the picture subjected to framing treatment to obtain an image subjected to binarization treatment. Then, the time series of the zeroth-dimension Betty number is calculated, and the time series of the zeroth-dimension Betty number of the binarized image is calculated.
And then carrying out logistic fitting on the time sequence of the zero-dimensional Betty number in an OXY rectangular coordinate system to obtain a fitted logistic curve, and calculating the area S of the logistic curve and the transverse axis of the OXY rectangular coordinate system, as shown in figure 2.
Wherein the logistic equation is defined as follows:
Figure SMS_5
in the above formula, t represents a time variable, a, b and c are parameters of the model, and when the trend is complete, a >0, b <0 and c >0. In this embodiment, a Rhodes method is adopted for estimating the parameters of the logistics equation, and the specific contents are as follows:
Figure SMS_6
is provided with
Figure SMS_7
And then obtaining parameter estimation values of the equation by using a common least square method, and further obtaining estimation values of a, b and c parameters in the logistics equation.
The method is simple, reliable, visual and visual, and particularly suitable for evaluating multiphase flow stirring and mixing effects in the metallurgical and chemical fields, and has high practical value.
The figure 1 of the invention is only for illustrating the method for evaluating multiphase flow reinforced stirring mixing effect of the invention, when the method is specifically applied, bottom blowing can not be adopted at the bottom of the transparent container, solid components can also be adopted in the stirred solution, and the figure 1 does not limit the application scene of the method.
In the description of the present invention, it should be understood that the terms "longitudinal," "transverse," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate or are based on the orientation or positional relationship shown in the drawings, merely to facilitate description of the present invention, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.
The above embodiments are merely illustrative of the preferred embodiments of the present invention, and not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solution of the present invention should fall within the protection scope of the present invention without departing from the design spirit of the present invention.

Claims (7)

1. A method for evaluating multiphase flow enhanced stirring mixing effect, which is characterized by comprising the following steps:
building a test bed: adding an object to be mixed into a transparent container, inserting a stirring rod into the object to be stirred, mounting an air supply device at the bottom of the transparent container, and mounting an image acquisition device near the transparent container;
collecting an image: starting the image acquisition device, the stirring rod and the air supply device, and spraying air by the air supply device, wherein the air moves in the object to be stirred from bottom to top, and the stirring rod stirs the object to be stirred, so that multiphase flow reinforced stirring is formed; the image acquisition device acquires a stirring process video with the time length of T;
image gray level and binarization processing: carrying out framing treatment on the video in the stirring process, and carrying out image gray scale and binarization treatment on the image subjected to framing treatment to obtain an image subjected to binarization treatment;
calculating the 0 th witterion time series: calculating a time sequence of the 0 th wittig number of the binarized image;
logistics fitting: performing logistic fitting on the time sequence of the 0 th Betty number in an OXY rectangular coordinate system to obtain a fitted logistic curve, and calculating the area S of the logistic curve and the transverse axis of the OXY rectangular coordinate system;
judging the mixing effect under the working condition according to the size of the area S; when the 0 th Betty number is larger, the mixing effect is better, namely the larger the area S of a region surrounded by a logistic curve of the 0 th Betty number time sequence and an abscissa is, the better the mixing effect is;
wherein the logistic equation is defined as follows:
Figure QLYQS_1
t is a time variable, a, b and c are parameters of the model, and a is a when the trend is complete>0,b<0,c>0;
The method for estimating the parameters of the logistics equation adopts a Rhodes method, and comprises the following specific contents:
Figure QLYQS_2
is provided with->
Figure QLYQS_3
Obtaining the parameter estimation value of the equation by using a common least square method, and estimating the parameter estimation values of a, b and c in the logistics equation according to the parameter estimation value.
2. The method for evaluating multiphase flow intensified mixing according to claim 1, wherein the object to be mixed is transparent or semitransparent liquid, and the image acquisition device is a high-speed camera or a particle velocimeter.
3. The method for evaluating multiphase flow intensified mixing according to claim 1, wherein the air supply device is an oxygen lance, and an air pump is connected to the oxygen lance, and the air pump is used for providing pressurized oxygen flow to the oxygen lance.
4. The method for evaluating multiphase flow intensified mixing according to claim 3, wherein the oxygen lance is at an angle of 0-180 ° to the bottom of the transparent vessel.
5. The method for evaluating multiphase flow intensified mixing effects according to claim 1, wherein a plurality of blades are fixedly connected to the bottom of the stirring rod, the blades are used for stirring the object to be stirred during rotation, and the stirring rod is powered by a motor.
6. The method for evaluating multiphase flow intensified mixing effects according to claim 1, wherein the image acquisition device is a high-speed camera with an imaging rate of 11000 frames/second.
7. The method for evaluating multiphase flow intensified mixing according to claim 1, wherein the 0 th wittig number is calculated by ChomP international software.
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Parameters Estimation for Logistic Curve and Application;Hu Xiaohua;《数学理论与应用》;第31卷(第4期);全文 *
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