A rolox triangular baffle structure passive micromixer

Abstract

The application discloses a Luoluo triangle baffle structure passive micro-mixer and relates to the technical field of mixers, aiming to solve the problem that micro-mixers can be divided into passive and active types according to different mixing principles, the active micro-mixer mainly relies on an external energy device to affect fluid flow to complete mixing, and the passive micro-mixer only relies on the change of the micro-channel structure shape to disturb fluid to complete mixing, the passive micro-mixer is widely applied due to simple structure, simple manufacturing and easy integration; the asymmetrically arranged rectangular and Luoluo triangle baffles on the channel are used to destroy the laminar flow of fluid, to promote the change of the flow direction of mixed working medium to form secondary flow and vortex flow to promote the mixing between two-component fluids, the Luoluo triangle obstacle is used to make the cross-section area of the micro-channel shrink sharply, to promote the generation of vortex flow, to enhance the mixing effect, to make the change degree of the flow direction of fluid working medium greater, and to increase the contact area of two-component solute particles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mixers, in particular to a passive micromixer with a LuGre triangle baffle structure. BACKGROUND

[0002] Microfluidic chip, which integrates the functions of traditional laboratory into a chip with micron or nanometer scale, has been widely used in biomedical, environmental detection and chemical synthesis due to its real-time, high efficiency, low cost and convenience. As an indispensable part of microfluidic chip, micro-mixer plays an important role in mixing two or more liquids quickly, and has attracted extensive attention. The channel geometry of micro-mixer is usually tens to hundreds of microns, and the Reynolds number Re of fluid is small under the structure size, which leads to the laminar flow of fluid. At this time, the mixing between fluids mainly depends on molecular diffusion, and the effect of convection diffusion is not significant, which greatly prolongs the mixing time. Therefore, it is of great significance to design a micro-mixer that can mix quickly and efficiently under low Reynolds number.

[0003] At present, according to the different mixing principles, micro-mixers can be divided into passive and active types. The active micro-mixer mainly relies on external energy equipment to affect the flow direction of fluid to complete the mixing, while the passive micro-mixer only relies on the change of micro-channel structure to disturb the fluid to complete the mixing. Passive micro-mixers are widely used due to their simple structure, easy manufacturing and easy integration.

[0004] In 2008, Xia et al. Xia H M, Wan S, Shu C, et al. Chaotic micromixers using two-layer crossing channels to exhibit fast mixing at low Reynolds numbers. Lab on a Chip, 2005, 5(7):748-755. The three-dimensional structure of the microchannel is adopted by two-layer crossing channels. The concentrated fluid is converted into multiple small fluids through multiple stretching, folding, splitting and recombination, which increases the contact area between fluids and promotes mixing, and fast mixing can still be achieved when Re is much lower than 1. Liu Zhaomiao, Wang Wenkai, Pang Yan. Influence of extended cavity on mixing performance of square wave type micro-mixer. Chinese Journal of Mechanics, 2018, v. 5002: 66-74. A square wave type micro-mixer with an extended cavity is proposed. The influence of the size parameters of the narrow slit and the extended cavity on the mixing performance is studied, and a passive micro-mixer with a narrow slit and an obstacle arranged in a five-sided mixing cavity is designed in subsequent work Liu Zhaomiao, Zhao Sheng, Wang Wenkai, et al. Influence of geometric configuration on mixing performance of planar chaotic micro-mixer. Analytical Chemistry, 2019, 479: 1321-1329. The jet characteristics of the fluid and the vortex principle of the baffle are used to strengthen the fluid disturbance and effectively promote the fluid mixing. Liu Yang, Mao Haiyang, Fan Wenbing, et al. Design and simulation of a passive micro-mixer with baffle structure. Micro and Nano Electronic Technology, 2018, 554: 258-264. Based on the T-shaped straight channel micro-mixer, the channel is bent and a rectangular baffle is added at the corner, and a finite element model is established for research. The results show that the cross-sectional size of the bending part is sharply contracted, which makes the fluid accelerate, forms a large centrifugal force and a large vortex in the channel behind the baffle, increases the disturbance to the fluid, and can achieve 95% high-efficiency mixing when Re = 5-60.

[0005] The above documents show that the mixing effect of fluid in the microchannel is not significant at low Reynolds number, and the pressure drop increases significantly with the increase of fluid flow rate. It is difficult to design a micro-mixer with simple structure, low power loss and good mixing performance at low Reynolds number. Therefore, it is of great significance to explore a micro-mixer with good comprehensive mixing performance. SUMMARY

[0006] In view of the problems existing in the prior art, the application discloses a passive micromixer with a Luoluo triangle baffle structure, which adopts the technical scheme that a channel is internally provided with a first channel inlet, a second channel inlet, a channel outlet, a contraction channel, a front mixing cavity and a mixing unit; the first channel inlet and the second channel inlet are arranged in the channel from left to right, the front mixing cavity is arranged between the first channel inlet and the second channel inlet, the mixing unit is arranged beside the channel outlet, the mixing unit is connected with the front mixing cavity, a plurality of groups of rectangular obstacles are arranged in the mixing unit, the rectangular obstacles further include a first rectangular obstacle and a second rectangular obstacle, the first rectangular obstacle and the second rectangular obstacle are arranged on the inner top surface and the inner bottom surface of the mixing unit respectively, and a focusing channel is formed between the first rectangular obstacle and the second rectangular obstacle; the rectangular obstacles divide the mixing unit into a plurality of cavities, Luoluo triangle obstacles are arranged between the rectangular obstacles, the Luoluo triangle obstacles are arranged in multiple groups and diagonally, and the mixing unit is divided into a left upper cavity, a right upper cavity, a left lower cavity and a right lower cavity, and the left upper cavity, the right upper cavity, the left lower cavity and the right lower cavity are communicated with the focusing channel.

[0007] As a preferred technical scheme of the application, the channel is T-shaped, and the first channel inlet, the second channel inlet and the front mixing cavity are arranged at an angle of 90 degrees.

[0008] As a preferred technical scheme of the application, the first rectangular obstacle and the second rectangular obstacle are arranged in a staggered manner, so that the cross-section of the fluid flowing in two directions is suddenly changed and accelerated, and the fluids can quickly converge.

[0009] As a preferred technical scheme of the application, the Luoluo triangle obstacles include a first Luoluo triangle obstacle and a second Luoluo triangle obstacle, and the first Luoluo triangle obstacle and the second Luoluo triangle obstacle are arranged diagonally.

[0010] As a preferred technical scheme of the application, the Luoluo triangle obstacle includes an equilateral triangle and a circular arc, and the Luoluo triangle obstacle is formed by a circle with the center at the vertex of the equilateral triangle and three circular arcs with the same radius as the equilateral triangle.

[0011] As a preferred technical scheme of the application, a contraction channel is formed between the Luoluo triangle obstacle and the mixing unit, and the contraction channel is communicated with the left upper cavity, the right upper cavity, the left lower cavity and the right lower cavity, so that the fluids can converge in the contraction channel and be mixed.

[0012] The beneficial effects of the present application: the present application designs a passive micro-mixer with higher mixing performance based on the innovative design of the Rulox triangle, which is based on the T-shaped micro-mixer and arranged asymmetrically on the main channel by rectangular and Rulox triangle baffles, which can destroy the laminar flow of the fluid, promote the change of the flow direction to form secondary flow and vortex to promote the mixing of two-component fluid, and the Rulox triangle obstacle can make the cross-sectional area of the micro-channel contract sharply, promote the generation of vortex, enhance the mixing effect, cause the flow direction of the fluid to change more greatly, and increase the contact area of the two-component solute particles; the rectangular obstacle and the Rulox triangle obstacle jointly interfere with the flow direction of the fluid in the horizontal plane, promote the vortex, increase the disturbance to the fluid, and increase the mixing efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. In all the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0014] Figure 1 It is a structural schematic diagram of the present application;

[0015] Figure 2 It is a structural schematic diagram of the Rulox triangle obstacle of the present application;

[0016] Figure 3 It is a curve diagram of the mixing efficiency of the present application changing with the direction angle;

[0017] Figure 4 It is a curve diagram of the mixing efficiency of the present application changing with the side-center distance;

[0018] Figure 5 It is a curve diagram of the mixing efficiency of the present application changing with the characteristic length;

[0019] Figure 6 It is a diagram of the fluid velocity distribution in the micro-mixer when Re=1, 10, 30, and 90 of the present application;

[0020] Figure 7 It is a diagram of the concentration distribution in the micro-mixer when Re=1, 10, 30, and 90 of the present application;

[0021] Figure 8 It is a curve diagram of the relationship between the mixing efficiency of the micro-mixer and different Re of the present application.

[0022] In the figure: 1, first channel entrance; 2, front mixing cavity; 3, left upper cavity; 4, right upper cavity; 5, focusing channel; 6, first Luoluo triangle obstacle; 7, first rectangular obstacle; 8, contraction channel; 9, channel exit; 10, second channel entrance; 11, left lower cavity; 12, mixing unit; 13, right lower cavity; 14, second Luoluo triangle obstacle; 15, second rectangular obstacle; 16, equilateral triangle; 17, circular arc. DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, 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 therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" are only for the purpose of description and cannot be understood as indicating or implying the importance of the opposite.

[0024] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] Example 1

[0026] As Figures 1 to 8The application discloses a Luoluo triangle baffle structure passive micro-mixer, which adopts the technical scheme and comprises a channel, wherein a first channel inlet 1, a second channel inlet 10, a channel outlet 9, a contraction channel 8, a front mixing cavity 2 and a mixing unit 12 are arranged in the channel; the first channel inlet 1 and the second channel inlet 10 are arranged in the channel from left to right; the front mixing cavity 2 is arranged between the first channel inlet 1 and the second channel inlet 10; the mixing unit 12 is arranged beside the channel outlet 9; the mixing unit 12 is connected with the front mixing cavity 2; a plurality of groups of rectangular obstacles are arranged in the mixing unit 12; the rectangular obstacles further comprise a first rectangular obstacle 7 and a second rectangular obstacle 15; the first rectangular obstacle 7 and the second rectangular obstacle 15 are arranged on the inner top surface and the inner bottom surface of the mixing unit 12 respectively, and a focusing channel 5 is formed between the first rectangular obstacle 7 and the second rectangular obstacle 15; the rectangular obstacles divide the mixing unit 12 into a plurality of cavities; Luoluo triangle obstacles are arranged between the rectangular obstacles; the Luoluo triangle obstacles are arranged in multiple groups and diagonally, and divide the mixing unit 12 into a left upper cavity 3, a right upper cavity 4, a left lower cavity 11 and a right lower cavity 13; the left upper cavity 3, the right upper cavity 4, the left lower cavity 11 and the right lower cavity 13 are communicated with the focusing channel 5; two different component fluids flow into the mixer from the first channel inlet and the second channel inlet, flow into the front mixing cavity after meeting at the middle position of the channel, gather at the focusing channel through the Luoluo triangle obstacles, then may form a jet phenomenon through the focusing channel, and at the same time, a secondary flow is generated, convection diffusion becomes dominant, and the mixing of solute particles is promoted.

[0027] As a preferred technical scheme of the application, the channel is T-shaped, and the first channel inlet 1, the second channel inlet 10 and the front mixing cavity 2 are arranged at an angle of 90 degrees.

[0028] As a preferred technical scheme of the application, the first rectangular obstacle 7 and the second rectangular obstacle 15 are arranged in a staggered mode, so that the fluid is accelerated under the condition of sudden change of cross-sectional area.

[0029] As a preferred technical scheme of the application, the Luoluo triangle obstacles comprise a first Luoluo triangle obstacle 6 and a second Luoluo triangle obstacle 14, and the first Luoluo triangle obstacle 6 and the second Luoluo triangle obstacle 14 are arranged diagonally, so that two groups of different component fluids walk along three paths and finally meet at the focusing channel.

[0030] As a preferred technical scheme of the present application, the LuGre triangle obstacle comprises an equilateral triangle 16 and a circular arc 17, the LuGre triangle obstacle is formed by a circle with the center at the vertex of the equilateral triangle 16 and the radius equal to the length of the three segments of the circular arc 17.

[0031] As a preferred technical scheme of the present application, the LuGre triangle obstacle and the mixing unit 12 form a contraction channel 8, the contraction channel 8 is in communication with the left upper cavity 3, the right upper cavity 4, the left lower cavity 11 and the right lower cavity 13.

[0032] The working principle of the present application: COMSOL Multiphysics 5.5 software is used to carry out finite element simulation on the above-mentioned micro-mixer, two physical field interfaces of fluid velocity analysis and dilute substance concentration analysis are set in the simulation analysis, water is selected as the material in the model, the inlet boundary is laminar flow, the outlet pressure condition is backflow inhibition and the value is 0, the wall boundary condition is no slip, three-dimensional Navier-Stokes control equation is used, the inlet concentration of the channel inlet 1 and 2 is set to 0 mol / m3 and 1 mol / m3 respectively; the fluid density p is 998 kg / m3, the dynamic viscosity m is 0.97*10-3 Pa·s, and the sample diffusion coefficient is 3.23*10-10 m2 / s.

[0033] Figure 3 The mixing efficiency and pressure change curve of the micro-mixer are shown in the figure, and the mixing efficiency is the highest when a=0°, and the mixing effect of the micro-mixer is not as good as the former when a is 30°, 60° and 90°. This is because when the fluid passes through the LuGre triangle obstacle with a=0°, the cross-sectional area of the micro-channel is more sharply contracted than the other three cases, resulting in a greater change in the flow direction of the fluid working medium, a significant secondary flow phenomenon, and an increased contact area between the two component solute particles. In addition, when the fluid passes through the narrow contraction channel 8 formed by a pair of LuGre triangles, the fluid is extruded and the molecular diffusion distance is reduced. Since the arc segment of the narrow contraction channel 8 formed when a=0° is longer, the mixing time of the fluid in the process is prolonged, which promotes the mixing of the fluid. At the same time, the speed of the fluid increases when passing through the narrow contraction channel 8, forming a jet effect at the outlet, and the cross-sectional area of the channel is suddenly expanded due to the LuGre triangle obstacle, which is beneficial to the formation of vortex flow after a pair of LuGre triangle obstacles, causing the flow lines in the cavity to be severely distorted, improving the uniformity of the components, so a=0° is the best choice when designing the micro-mixer.

[0034] Figure 4The figure shows the mixing efficiency and pressure change curve of the Louver triangle obstacle with edge-center distance l3=l5=225, 250, 275 μm when the Reynolds number Re is 0.1-90 under the characteristic length l=400 μm and the direction angle α=60°. It can be seen from the figure that the fluid disturbance is stronger with the decrease of the edge-center distance, and the distance from the micro-mixer boundary is only 25 μm when l3=l5=225 μm. Considering the limitation of the micro-fabrication process precision, in order to prevent the increase of processing difficulty and the high manufacturing cost, the micro-mixer is preferably designed with l3=l5=250 μm.

[0035] Figure 5 The figure is the mixing efficiency change curve of the micro-mixer when the Reynolds number Re=0.1-90 under the direction angle α=60° and the edge-center distance l3=l5=250 μm and the characteristic length l is 325, 350, 375, 400 μm respectively. It can be seen from the figure that the change of the characteristic length has little effect on the promotion of fluid mixing degree, and the mixing efficiency gradually increases with the increase of the characteristic length l. This is because the increase of the characteristic length l leads to the decrease of the distance between the Louver triangle obstacles and the distance from the boundary, and the decrease of the cross-sectional size leads to the more severe compression of the fluid, the increase of the jet effect, and the provision of conditions for the development of vortex. At the same time, the increase of the characteristic length leads to the growth of the arc segment of the narrow and long contraction channel 8 formed between the two obstacles, which reflects that the fluid can diffuse more fully between the arc segments, further promotes the mixing between different components, and improves the mixing uniformity. It can be seen from the pressure drop loss analysis in the figure that the increase of the characteristic length leads to the increase of the pressure drop loss of the micro-mixer, and the phenomenon of hindering the movement of the fluid is more obvious. The micro-mixer is preferably designed with l=400 μm.

[0036] It can be known from the analysis of the influence of the Louver triangle obstacle on the mixing effect of the T-shaped micro-mixer that it is difficult to obtain high mixing efficiency with a single structure. In order to obtain a micro-mixer with higher mixing efficiency, a rectangular obstacle with vortex structure characteristics is now added to the structure, the length w1 and the width d of the baffle are 350 μm and 100 μm respectively, the direction angle α=0°, the characteristic length l=400 μm, and the edge-center distance l3=l5=250 μm, Figure 6 The figure is the fluid velocity distribution in the Louver triangle micro-mixer with the baffle when the Reynolds number Re=1, 10, 30, 90, and the velocity vector diagram on the A section which is 1550 μm away from the left end surface of the micro-mixer, Figure 7 The figure is the concentration distribution diagram of the micro-mixer when Re=1, 10, 30, 90, Figure 6It can be seen that after the fluid flows into the mixing unit 12, the main channel is subjected to the action of the rectangular barrier and the Loukoss triangular barrier, and the cross-sectional size is subjected to severe contraction and expansion, which disturbs the flow direction of the fluid in the horizontal plane; the contraction of the cross-sectional size leads to rapid increase of the flow rate, and the cavities behind the rectangular barrier and in front of the narrow gap between the two Loukoss triangular barriers form expansion vortices, and the velocity of the fluid in the x-axis direction appears negative value, i.e. backflow, and the mixing effect is enhanced; in addition, the fluid converges with the fluid in the right upper cavity 4 through the gap between the two Loukoss triangular barriers, and it can be found in the figure that the flow lines of the two branches cross, which is because the fluid is subjected to vertical pressure under the influence of the baffle, causing secondary flow, and under the action of centrifugal force, a dean vortex is formed on the y-z section of the right upper cavity 4, and a pair of directionally symmetric vortices are formed on the section, which further increases the disturbance to the fluid; it can be seen from Figure 7 c that when Re=30, the fluid is disturbed by the expansion vortex and the dean vortex, and after passing through the third mixing unit 12, the mixing is basically completed.

[0037] Figure 8 For the working condition of direction angle α=0°, characteristic length l=400μm, and edge-to-center distance l3=l5=250μm, the relationship between the Reynolds number Re and the mixing efficiency of the micro-mixer is shown in the figure. When Re is in the range of 0.1-1, the mixing efficiency decreases with the increase of Re, because the fluid in the laminar state relies on molecular diffusion for mixing, and as the flow rate increases, the diffusion time of the fluid in the micro-channel decreases; when Re is in the range of 1-10, due to the gradual generation of vortex flow in the channel, the influence of molecular diffusion on fluid mixing gradually decreases, and the convection diffusion gradually becomes significant, leading to rapid increase of the mixing efficiency; when 10≤Re≤90, as the flow rate increases, the vortex flow gradually develops and grows, and at the same time, new vortex centers are formed, and the convection effect continues to be enhanced. In the range of 0.1≤Re≤90, the mixing efficiency of the micro-mixer is greater than 90%, and when Re=90, the mixing efficiency reaches 96.58%, and the fluid is completely mixed. At this time, the pressure drop loss of the micro-mixer with baffle is 28.5kPa.

[0038] The mechanical connection involved in the present application is a common means adopted by those skilled in the art, and can be obtained through limited experiments, and belongs to the public knowledge.

[0039] The components not described in detail in the present application are prior art.

[0040] Although the specific embodiments of the present application have been described in detail above, the present application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application, and modifications or deformations without creative labor are still within the protection scope of the present application.

Claims

1. A Lurox triangular baffle structure passive micro mixer, comprising a channel, wherein a first channel inlet (1), a second channel inlet (10), a channel outlet (9), a contraction channel (8), a front mixing chamber (2), and a mixing unit (12) are provided in the channel, wherein the first channel inlet (1), the second channel inlet (10), and the channel outlet (9) are provided in the channel from left to right, a front mixing chamber (2) is provided between the first channel inlet (1) and the second channel inlet (10), the mixing unit (12) is provided next to the channel outlet (9), and the mixing unit (12) is connected to the front mixing chamber (2), characterized in that: The mixing unit (12) is provided with a plurality of groups of rectangular obstacles, and the rectangular obstacles further include a first rectangular obstacle (7) and a second rectangular obstacle (15). The first rectangular obstacle (7) and the second rectangular obstacle (15) are respectively provided on the inner top surface and the inner bottom surface of the mixing unit (12), and a focusing channel (5) is formed between the first rectangular obstacle (7) and the second rectangular obstacle (15); the rectangular obstacles divide the mixing unit (12) into a plurality of cavities, and Luluox triangular obstacles are provided between the rectangular obstacles. The Luluox triangular obstacles are provided in a plurality of groups and are diagonally arranged, and divide the mixing unit (12) into an upper left cavity (3), an upper right cavity (4), a lower left cavity (11), and a lower right cavity (13). The upper left cavity (3), the upper right cavity (4), the lower left cavity (11), and the lower right cavity (13) are interconnected with the focusing channel (5).

2. The Lurox triangular baffle passive micromixer according to claim 1, characterized in that: The channel is T-shaped, and the first channel inlet (1), the second channel inlet (10) and the front mixing chamber (2) form an angle of 90°.

3. The Lurox triangular baffle passive micromixer according to claim 1, characterized in that: The first rectangular obstacle (7) and the second rectangular obstacle (15) are arranged in a staggered manner.

4. The Lurox triangular baffle passive micromixer according to claim 1, characterized in that: The Ruroux triangular obstacle comprises a first Ruroux triangular obstacle (6) and a second Ruroux triangular obstacle (14), wherein the first Ruroux triangular obstacle (6) and the second Ruroux triangular obstacle (14) are arranged diagonally.

5. A Lurox triangular baffle structure passive micro-mixer according to claim 4, wherein the Lurox triangular obstacle comprises an equilateral triangle (16) and an arc (17), and the Lurox triangular obstacle is formed by three segments of the arc (17) with the center at the vertex of the equilateral triangle (16) and the radius equal to the side of the equilateral triangle (16).

6. The Lurox triangular baffle passive micromixer according to claim 1, characterized in that: A contraction channel (8) is formed between the Lurocks triangle obstacle and the mixing unit (12), and the contraction channel (8) is interconnected with the upper left chamber (3), the upper right chamber (4), the lower left chamber (11), and the lower right chamber (13).

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