Lower-layer prevalent star stirring flow strengthening method based on external electric field coupling effect

Abstract

The invention discloses a lower-layer prevalent star stirring flow strengthening method based on an external electric field coupling effect, which comprises the following steps of: arranging a stirring paddle in a cylindrical stirring tank, and starting stirring to form a chaotic mixing area and a mixing isolation area; the height of the stirring paddle is kept unchanged, the stirring paddle is eccentrically arranged in the stirring tank, the stirring tank is placed on a rotatable disc, and planetary stirring motion is formed through revolution motion of the disc and rotation motion of the stirring paddle; a non-uniform electric field is introduced between the upper surface and the lower surface of the stirring tank, so that charges enter fluid through molecular polarization, and a chaotic mixing region crosses the boundary of a mixing isolation region under the driving of electric field force to realize mixing enhancement. The method effectively solves the problems of non-uniform mixing, high energy consumption and the like in the current stirring process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fluid machinery, and particularly relates to a laminar flow planetary stirring flow intensification method based on external electric field coupling. BACKGROUND

[0002] In industrial production, stirring technology is a core operation, and the purpose is to realize uniform mixing of the medium in the stirring tank. The technology is widely used in chemical industry, metallurgy, pharmaceutical industry, food processing and wastewater treatment fields, and common stirring methods include mechanical stirring, airflow stirring and external field stirring, among which mechanical stirring is the most efficient and convenient. In order to improve the stirring efficiency, the following methods are currently mainly used: 1. Based on stirring tank structure optimization: for example, a double-arm planetary stirring tank, a swash plate impeller stirring paddle, a combined paddle, or an intruding geometric baffle is arranged in the tank. This kind of method can improve the mixing efficiency from the mechanism, but due to the complex stirring structure, it also increases the manufacturing cost and process difficulty; 2. Based on flow direction regulation: under the condition of self-rotation plus rotation, a flow field mainly in the form of global axial flow is formed in the stirring tank, which promotes frequent spatial displacement between different fluid layers, thereby strengthening the mixing. Under the same energy input condition, this method can realize faster mixing and save time, but the requirement for energy input is higher; 3. Based on enhancing fluid disordered motion: under the condition of central stirring, periodically adjusting the stirring paddle speed can effectively enhance the disordered motion of the fluid in a short period of time, and improve the mixing efficiency by about 15%. However, the enhancement effect gradually weakens over time, and the space for further improving the mixing degree is limited. Although the existing methods have made good progress in improving the mixing uniformity, there are still isolated mixing regions (IMR) in the stirring tank. SUMMARY

[0003] The application provides a laminar flow planetary stirring flow intensification method based on external electric field coupling to solve the problems in the prior art.

[0004] To achieve the above purpose, the application provides a laminar flow planetary stirring flow intensification method based on external electric field coupling, which comprises the following steps: The stirring paddle is arranged in the cylindrical stirring tank, and stirring is started to form a chaotic mixing region and an isolated mixing region; The height of the stirring paddle is kept unchanged, and the stirring paddle is arranged eccentrically in the stirring tank, and the stirring tank is arranged on a rotatable disc, and the planetary stirring motion is formed by the revolution motion of the disc and the rotation motion of the stirring paddle; A non-uniform electric field is introduced between the upper and lower surfaces of the stirring tank, so that the electric charges enter the fluid through molecular polarization, and the chaotic mixing region crosses the boundary of the isolated mixing region under the driving of the electric field force, thereby realizing mixing intensification.

[0005] Optionally, the center of the stirring paddle is arranged in the stirring tank, and the center of the paddle is located at one-half of the height of the tank.

[0006] Optionally, the eccentricity of the stirring paddle is one-fourth of the diameter of the stirring tank.

[0007] Optionally, the introduction of the non-uniform electric field comprises connecting the upper surface of the stirring tank to a high-voltage power supply and connecting the lower surface to the ground, so as to establish an axial non-uniform electric field in the tank.

[0008] Optionally, the formation and change of the chaotic mixing region and the mixing isolated region are observed by injecting tracer particles into the fluid and recording the motion trajectories of the tracer particles.

[0009] Optionally, the expression of the electric field force is as follows: ; In the formula, , is the vacuum permittivity, is the relative permittivity, is the applied electric field, is the unit tensor, represents a Hamiltonian operator, is a matrix transposition symbol.

[0010] Optionally, the working medium in the stirring tank is glycerol.

[0011] Compared with the prior art, the present application has the following advantages and technical effects: The present application introduces an external electric field, and charges enter the fluid through a molecular polarization mechanism. Under the action of the electric field, the charge carriers interact with the surrounding fluid elements, so that the fluid elements are driven by the electric field force. The electric field force is coupled with the inertial force, viscous force and surface tension of the fluid, and the original flow field structure is further reconstructed. This coupling effect promotes the easy mixing region (CMR) to cross the IMR boundary, and realizes a higher degree of mixing. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of this application and their description together with the drawings serve to explain the application. In the drawings: Figure 1 are schematic diagrams of the central stirring and planetary stirring arrangement schemes of the embodiments of the present application and a three-dimensional schematic diagram of the IMR structure; wherein (a) is a central stirring arrangement scheme, (b) is a planetary stirring arrangement scheme, and (c) is a three-dimensional schematic diagram of the IMR structure; Figure 2Schematic diagram of the center stirring and planetary stirring scheme under the application of an external electric field of the embodiment of the application; wherein (a) is the center stirring scheme, and (b) is the planetary stirring scheme; Figure 3 The streamline diagram and the concentration distribution diagram of the center stirring scheme of the embodiment of the application before the application of an electric field and the streamline diagram and the concentration distribution diagram after the application of an electric field; wherein (a) is the streamline diagram and the concentration distribution diagram before the application of an electric field, and (b) is the streamline diagram and the concentration distribution diagram after the application of an electric field; Figure 4 The streamline diagram and the concentration distribution diagram of the planetary stirring scheme of the embodiment of the application before the application of an electric field and the streamline diagram and the concentration distribution diagram after the application of an electric field; wherein (a) is the streamline diagram and the concentration distribution diagram before the application of an electric field, and (b) is the streamline diagram and the concentration distribution diagram after the application of an electric field; Figure 5 The streamline diagram and the concentration distribution diagram of the center stirring scheme and the planetary stirring scheme under different electric field configuration forms (coil grounding mode) of the embodiment of the application, wherein (a) is the streamline diagram and the concentration distribution diagram of the center stirring, and (b) is the streamline diagram and the concentration distribution diagram of the planetary stirring. In the figure, c is a tracer particle; and V is an applied electric potential. DETAILED DESCRIPTION

[0013] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0014] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a group of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown herein.

[0015] Embodiment one In this embodiment, a laminar planetary stirring flow strengthening method based on external electric field coupling is provided, which comprises the following steps: The stirring paddle is arranged in the cylindrical stirring tank, and the stirring is started to form a chaotic mixing area and a mixing isolation area; The height of the stirring paddle is kept unchanged, and the stirring paddle is arranged eccentrically in the stirring tank, and the stirring tank is placed on a rotatable disc, and the planetary stirring motion is formed by the revolution motion of the disc and the rotation motion of the stirring paddle; A non-uniform electric field is introduced between the upper and lower surfaces of the stirring tank, so that the electric charges enter the fluid through molecular polarization, and the chaotic mixing area is driven to cross the boundary of the mixing isolation area under the driving of the electric field force, so that the mixing is strengthened.

[0016] Specifically, it comprises: I. The center of the stirring paddle is arranged in a cylindrical stirring tank, and the center of the paddle blade is placed at one-half of the height of the tank. Glycerol is added as a working medium in the tank, tracer particles are injected, and the movement trajectory of the tracer particles is recorded. During the central stirring of the laminar flow, the fluid molecules undergo repeated stretching and folding, forming a chaotic mixing region (CMR) and an isolated mixing region (IMR) inside the stirring tank. II. The height of the stirring paddle in step I is kept unchanged, and the stirring paddle is arranged eccentrically at one-fourth of the diameter of the stirring tank. The stirring tank is arranged on a rotatable disc, and a planetary stirring motion is formed by the combination of the revolution motion of the disc and the rotation motion of the stirring paddle , so as to break the original symmetrical structure of the flow field and significantly improve the mixing degree of the fluid. III. A non-uniform electric field is introduced between the upper and lower surfaces of the stirring tank. Charges enter the fluid through molecular polarization, and under the further driving of the electric field, the charge carriers interact with the surrounding fluid elements, so as to make the CMR region cross the IMR boundary and achieve a higher degree of mixing.

[0017] Further, step I is specifically as follows: The center of the stirring paddle is arranged in a cylindrical stirring tank, and the center of the paddle blade is placed at one-half of the height of the tank. Glycerol is added as a working medium in the tank, tracer particles are injected, and the movement trajectory of the tracer particles is recorded. During the central stirring of the laminar flow, the periodic motion of the stirring paddle forms a symmetrical "doughnut" shaped dynamic isolated flow field on both sides of the stirring paddle, i.e. an IMR region. Near the IMR region, the fluid can be divided into two parts, i.e. a main flow and a secondary flow. The secondary flow has an independent dynamic stable structure, and is independent of and does not interfere with the main flow. Influenced by the flow characteristics, the fluid in the IMR region can only rely on molecular diffusion to realize internal material exchange, and cannot effectively mix with the external fluid, thereby leading to a decrease in the overall mixing quality, and even mixing failure.

[0018] Further, step II is specifically as follows: The height of the stirring paddle in step I is kept unchanged, and the stirring paddle is arranged eccentrically at one-fourth of the diameter of the stirring tank. The stirring tank is arranged on a rotatable disc, and a planetary stirring motion is formed by the combination of the revolution motion of the disc and the rotation motion of the stirring paddle , tracer particles are injected, and the movement trajectory of the tracer particles is recorded. The planetary arrangement scheme significantly increases the sweeping area of the stirring paddle, effectively breaks the original symmetrical structure of the flow field, and promotes the sufficient mixing between the fluid media in different regions.

[0019] Furthermore, step three specifically involves: A non-uniform electric field is introduced between the upper and lower surfaces of the stirred tank. Charges enter the fluid through molecular polarization, and at this time, the charges are subjected to the electric field force. The electric field force can be described by the divergence of Maxwell's stress tensor, i.e.: ; In the formula, , The vacuum permittivity, The relative permittivity, For an external electric field, For unit tensors, Represents the Hamiltonian operator. This is the matrix transpose. Driven further by the electric field, the charge carriers interact with the surrounding fluid elements, causing the CMR region to cross the IMR boundary and achieve a higher degree of mixing.

[0020] The following explanation is provided in conjunction with the accompanying drawings: 1. Position the agitator inside the cylindrical mixing tank, ensuring the center of the agitator blades is located at half the height of the tank. Figure 1 In (a) of the text, after injecting glycerol as the working medium and adding tracer particles into the tank, the stirring process is started, and the movement trajectory of the tracer particles is recorded. When the fluid in the tank is in a laminar flow state, due to the periodic movement of the stirring paddle, the fluid molecules undergo repeated stretching and folding, and a symmetrical, "donut"-shaped dynamic isolation region is formed on both the upper and lower sides. Figure 1 (b) in the text is called the isolated mixing region (IMR). 2. Keeping the height of the agitator constant, position it eccentrically at one-quarter of the diameter of the mixing tank, and place the mixing tank on a rotatable disc. The rotation of the disc (equivalent to the rotational speed of the inner wall of the mixing tank) will influence the overall rotational speed. , Figure 1 (c) and the rotational motion of the agitator ( The combination of these elements creates planetary mixing motion, and tracer particles are injected to record their trajectories. This planetary arrangement significantly increases the sweeping area of ​​the impellers, effectively breaking the original symmetrical structure of the flow field, thereby promoting thorough mixing of the fluid medium in different regions. III. Figure 2 As shown, the central stirring ( Figure 2 (a) in the middle, planetary stirring ( Figure 2In scheme (b) of the above, the upper surface of the stirred tank is connected to a high-voltage power supply, and the lower surface is grounded, thus forming a non-uniform electric field throughout the entire tank. Charges enter the fluid via molecular polarization, and under the further drive of the electric field, the charge carriers interact with the surrounding fluid micro-elements, causing the CMR region to cross the IMR boundary, achieving a higher degree of mixing. Tracer particles are injected into the upper, middle, and lower cross-sectional annular sections of the stirred impeller, respectively. Figure 2 It records the trajectory of the tracer particles. Figure 3 The diagram shows the central stirring scheme before the electric field is applied ( Figure 3 (a) in the middle, (b) after ( Figure 3 By comparing the streamline diagram and concentration distribution diagram inside the stirred tank in (b) of the figure, it can be found that when there is no electric field, there are four flow isolation zones (blue rings) around the stirred tank, and the fluid inside them does not exchange substances with the external fluid, resulting in poor mixing effect; after the electric field is added, the flow isolation zones disappear and the mixing effect is significantly improved.

[0021] For planetary stirring schemes ( Figure 4 When there is no electric field ( Figure 4 In (a) of the mixture, compared to the central stirring scheme, the flow isolation zone also disappears, and the mixing effect is significantly improved, but there is still an unmixed area (blue) at the edge of the mixing tank; with the introduction of an electric field, the unmixed area at the edge of the mixing tank is further reduced. Figure 4 (b) in the example further enhances the blending effect. Figure 5 The diagrams show the streamlines and tracer particle concentration distribution within the tanks of both the central stirring and planetary stirring systems with coil grounding. As the grounding method changes, the electric field distribution within the tank also changes, increasing the disturbance of the electric field force and intensifying the mass exchange of the fluid within the tank, thus improving mixing efficiency. For example, in the central stirring system, with the change in the electric field configuration (coil grounding), the fluid within the stirring tank is almost completely mixed, with only a small amount of unmixed area remaining at the left and right edges of the tank bottom. Figure 5 (a) In the planetary mixing scheme, compared to the central mixing scheme, the unmixed area on the right edge of the tank bottom disappears ( Figure 5 (b) in the example further improves the mixing efficiency.

[0022] This invention proposes a laminar planetary stirring flow enhancement method based on external electric field coupling, achieving a new approach to efficient mixing. In this method, planetary stirring effectively breaks the symmetrical structure of the flow field by expanding the sweeping range of the stirring impeller, resulting in a flow pattern dominated by global axial flow within the stirred tank. This promotes spatial displacement and mixing between different fluid layers, thereby improving the mixing degree to some extent. However, this method still cannot completely break the IMR structure, and there is still considerable room for improvement in the mixing effect.

[0023] By introducing an external electric field, the charges enter the fluid via the molecular polarization mechanism. Under the action of the electric field, the charge carriers interact with the surrounding fluid elements, causing the fluid elements to be driven by the electric field force. This electric field force is coupled with the inertial force, viscous force and surface tension of the fluid, etc., and further reconstructs the original flow field structure. This coupling effect promotes the easy mixing zone (CMR) to cross the IMR boundary, realizing a higher degree of mixing.

[0024] The above merely provides the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements easily thought of by those skilled in the art within the technical scope disclosed by the present application shall be encompassed within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for enhancing the stirring flow of a lower layer of a planet based on the coupling of an external electric field, characterized by, The method comprises the following steps: arranging a stirring paddle in a cylindrical stirring tank, starting stirring to form a chaotic mixing area and a mixing isolation area; keeping the height of the stirring paddle unchanged, eccentrically arranging the stirring paddle in the stirring tank, and placing the stirring tank on a rotatable disc to form a planetary stirring motion through the revolution of the disc and the rotation of the stirring paddle; introducing a non-uniform electric field between the upper and lower surfaces of the stirring tank to make charges enter the fluid through molecular polarization, and drive the chaotic mixing area to cross the boundary of the mixing isolation area under the driving of the electric field force to realize mixing intensification.

2. The method of claim 1, wherein, The center of the stirring paddle is arranged in the stirring tank with the center of the paddle blade located at one-half of the height of the tank.

3. The method of claim 1, wherein, The eccentricity of the stirring paddle is one-fourth of the diameter of the stirring tank.

4. The method of claim 1, wherein, The introduction of the non-uniform electric field comprises connecting the upper surface of the stirring tank to a high-voltage power supply and the lower surface to the ground to establish an axial non-uniform electric field in the tank.

5. The method of claim 1, wherein, The formation and change of the chaotic mixing area and the mixing isolation area are observed by injecting tracer particles into the fluid and recording the motion trajectories of the tracer particles.

6. The method of claim 5, wherein, The expression of the electric field force is: ； wherein , is the vacuum permittivity, is the relative permittivity, is the applied electric field, is the unit tensor, denotes the Hamiltonian operator, is the matrix transpose symbol.

7. The method of claim 1, wherein, The working medium in the stirring tank is glycerol.

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