A coaxial tube structure

Abstract

The application provides a coaxial pipe structure, relates to the coaxial jet flow technical field, and aims at solving the technical problem of uneven mixing of the coaxial jet flow in the prior art under the condition that a high flow rate is not suitable. The coaxial pipe structure comprises an outer pipe and an inner pipe, the outer pipe is internally provided with a cavity, the inner pipe is arranged in the cavity and coaxially arranged with the outer pipe, an annular first flow channel is formed between the outer wall of the inner pipe and the inner wall of the outer pipe, the inner pipe is internally provided with a second flow channel, the inner wall of the outer pipe or the inner wall of the inner pipe is provided with a spiral structure so that the first flow channel or the second flow channel is spiral-shaped, the first flow channel is communicated with a first feeding port, the second flow channel is communicated with a second feeding port, the end of the first flow channel and the end of the second flow channel are communicated in the cavity, and a material contact area is formed at the communication position of the first flow channel and the second flow channel, and a discharging port communicated with the material contact area is arranged on the outer pipe.

Description

Technical Field

[0001] This invention relates to the field of coaxial jet technology, specifically to a coaxial tube structure. Background Technology

[0002] In chemical reaction applications, the turbulent mixing of two coaxial flows is used in many engineering devices, such as industrial burners, injectors, and jet pumps, and this coaxial turbulent mixing is crucial to the efficiency of these devices. In the upstream region, the flow comprises two cores generated by the pipe and the annular flow, as well as a mixing region between the two flows.

[0003] Coaxial jet mixing primarily relies on the shearing effect caused by the velocity difference between the fluids in the outer ring and the inner tube to rapidly mix the central and outer flows. However, in some chemical applications, due to factors such as low kinetic rates and the susceptibility of crystallization behavior to high-intensity turbulence, high flow velocities are unsuitable. Therefore, under these conditions, the inner and outer flows lack significant velocities and a sufficient velocity difference, resulting in inhomogeneous mixing. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a coaxial tube structure to solve the technical problem of uneven mixing in coaxial jets when high flow rates are not suitable.

[0005] To solve the above-mentioned technical problems, the present invention provides a coaxial tube structure, including an external pipe and an internal pipe. The external pipe has a cavity, and the internal pipe is located in the cavity and coaxially arranged with the external pipe. An annular first flow channel is formed between the outer wall of the internal pipe and the inner wall of the external pipe. A second flow channel is provided in the internal pipe. The inner wall of the external pipe or the inner wall of the internal pipe has a spiral structure, making the first flow channel or the second flow channel spiral. The first flow channel is connected to a first inlet, and the second flow channel is connected to a second inlet. The ends of the first flow channel and the second flow channel are connected in the cavity, and the connection between the first flow channel and the second flow channel forms a material contact area. The external pipe has an outlet that is connected to the material contact area.

[0006] With the above structure, the coaxial tube structure of the present invention has the following advantages: vortices are introduced through the spiral first or second flow channel, and the strong vortex flow generates radial and axial pressure gradients, thereby creating internal or external annular recirculation zones and enhancing mixing efficiency. Therefore, mixing can be achieved without relying on a large internal and external momentum difference, and even in applications where high flow rates are not suitable, the fluid can be mixed uniformly, making the application of coaxial jets more widespread. The present invention can be applied in reactors or in the feed structure of production equipment.

[0007] As an improvement, the spiral structure is formed by rotating and stretching a non-circular contour along the axial direction. The non-circular contour is formed by connecting multiple identical arcs end to end. The arcs are one of the following: circular arcs, elliptical arcs, spline curves, conic sections, and parabolas, and the number of arc segments ranges from 3 to 6. By adopting this structure, the non-circular contour of the spiral structure is formed by selecting one of the following: circular arcs, elliptical arcs, spline curves, conic sections, and parabolas, which further enhances the blending effect.

[0008] As an improvement, the arc is an ellipse with N segments. The major axis radius and minor axis radius of the ellipse are b and a, respectively, with b / a ranging from 0.5 to 1.2. The connection point between the beginning and end of the N ellipse segments is located on a circle with radius R2. The farthest distance from the center of the circle with radius R2 to the ellipse is R3 = a + R2cos(π / N) and b = R2sin(π / N). This structure further enhances the mixing effect.

[0009] As an improvement, the internal pipeline length is H, the value of H / (2R3) ranges from 5 to 50, and the spiral period P of the spiral structure ranges from 1 to 10. By adopting this structure, the length of the internal pipeline and the spiral period are optimized to further enhance the mixing effect.

[0010] As an improvement, the internal pipeline is integrally formed inside the external pipeline. One end of the external pipeline is provided with a second inlet that communicates with the first end of the second flow channel, and the other end of the external pipeline is provided with a discharge port. A protrusion is provided on the side wall of the external pipeline, and a first inlet that communicates with the first end of the first flow channel is provided on the protrusion.

[0011] As an improvement, the inner wall of the internal pipe is provided with a spiral structure, making the second flow channel spiral-shaped. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the present invention.

[0013] Figure 2a This is a schematic diagram of the non-circular outline composed of three elliptical lines in this invention.

[0014] Figure 2b This is a schematic diagram of a non-circular contour composed of three spline curves in this invention.

[0015] Figure 2c This is a schematic diagram of the non-circular contour composed of three conic curves in this invention.

[0016] Figure 2d This is a schematic diagram of the non-circular outline composed of four elliptical lines in this invention.

[0017] Figure 2e This is a schematic diagram of a non-circular contour composed of four spline curves in this invention.

[0018] Figure 2f This is a schematic diagram of the non-circular contour composed of four conic curves in this invention.

[0019] Figure 3a This is a velocity contour plot of the coaxial tube structure in Embodiment 1 of the present invention, obtained through CFD simulation.

[0020] Figure 3b The velocity contour plot is from a CFD simulation of a coaxial cable without internal piping.

[0021] Figure 4a This is a cloud map of the turbulent dissipation rate from a CFD simulation of the coaxial tube structure in Embodiment 1 of the present invention.

[0022] Figure 4b The turbulent dissipation rate contour plot is obtained from a CFD simulation of a coaxial cable without internal piping.

[0023] Figure 5 The positions of the cross sections at z=80mm and 110mm in Embodiment 1 of the present invention on the coaxial tube structure.

[0024] Figure 6a This is a velocity contour plot of a cross section with z = 80 mm in Embodiment 1 of the present invention, simulated by CFD.

[0025] Figure 6b The velocity contour plot is a CFD simulation of a coaxial cable with a cross-section of z = 80 mm without internal piping.

[0026] Figure 7a This is a cloud map of turbulent dissipation rate simulated by CFD at a cross section with z = 80 mm in Embodiment 1 of the present invention.

[0027] Figure 7b The turbulent dissipation rate contour plot is obtained from a CFD simulation of a coaxial device with a cross-section of z = 80 mm without internal piping.

[0028] Figure 8a This is a cloud map of turbulent dissipation rate at different cross sections in Embodiment 1 of the present invention, obtained from CFD simulation.

[0029] Figure 8b The image shows the turbulent dissipation rate contour plots at different cross-sections of a coaxial cable without internal piping, obtained from CFD simulations.

[0030] Figure 9a This is a schematic diagram of the internal pipeline cross-section corresponding to the non-circular contour composed of three elliptical lines in this invention.

[0031] Figure 9b This is a schematic diagram of the longitudinal section of the internal pipeline corresponding to the non-circular contour composed of three elliptical lines in this invention.

[0032] Figure 10aThis is a schematic diagram of the cross-section of the internal pipeline corresponding to the non-circular contour composed of four elliptical lines in this invention.

[0033] Figure 10b This is a schematic diagram of the longitudinal section of the internal pipeline corresponding to the non-circular contour composed of four elliptical lines in this invention.

[0034] Figure 11a This is a schematic diagram of the longitudinal section of the internal pipeline with a spiral period of 1 in this invention.

[0035] Figure 11b This is a schematic diagram of the longitudinal section of the internal pipeline with a spiral period of 2 in this invention.

[0036] Figure 11c This is a schematic diagram of the longitudinal section of the internal pipeline with a spiral period of 3 in this invention.

[0037] Figure 12 This is a cross-sectional schematic diagram of Embodiment 2 of the present invention.

[0038] Figure 13 This is a cross-sectional schematic diagram of Embodiment 3 of the present invention.

[0039] Reference numerals in the attached diagram: 1. External pipeline; 2. Internal pipeline; 3. First flow channel; 4. Second flow channel; 5. First feed inlet; 6. Second feed inlet; 7. Material contact area; 8. Discharge outlet; 9. Protrusion. Detailed Implementation

[0040] The coaxial tube structure of the present invention will be described in detail below with reference to the accompanying drawings.

[0041] Example 1:

[0042] like Figure 1 As shown in the figure, this embodiment provides a coaxial tube structure, including an external pipe 1 and an internal pipe 2. The external pipe 1 has a cavity, and the internal pipe 2 is located in the cavity and coaxially arranged with the external pipe 1. An annular first flow channel 3 is formed between the outer wall of the internal pipe 2 and the inner wall of the external pipe 1. A second flow channel 4 is provided in the internal pipe 2. The inner wall of the external pipe 1 or the inner wall of the internal pipe 2 has a spiral structure, so that the first flow channel 3 or the second flow channel 4 is spiral. In this embodiment, the inner wall of the internal pipe 2 has a spiral structure, so that the second flow channel 4 is spiral. The first flow channel 3 is connected to a first feed inlet 5, and the second flow channel 4 is connected to a second feed inlet 6. The end of the first flow channel 3 and the end of the second flow channel 4 are connected in the cavity, and the connection between the first flow channel 3 and the second flow channel 4 forms a material contact area 7. The external pipe 1 is provided with a discharge port 8 that is connected to the material contact area 7.

[0043] Specifically, such as Figure 1As shown, both the external pipe 1 and the internal pipe 2 are horizontally arranged. The first flow channel 3 and the second flow channel 4 are both arranged in the horizontal direction, and the cavity is also coaxially arranged with the external pipe 1. The internal pipe 2 is integrally formed inside the external pipe 1. The left end of the internal pipe 2 is integrally formed with the external pipe 1. One end of the external pipe 1 is provided with a second inlet 6 that communicates with the first end of the second flow channel 4. That is, the second inlet 6 is located at the left end of the external pipe 1. The second flow channel 4 passes through both ends of the internal pipe 2. The left end of the second flow channel 4 communicates with the second inlet 6. The other end of the external pipe 1 is provided with an outlet 8. The outlet 8 is formed by the cavity passing through the right end of the external pipe 1. The side wall of the external pipe 1 is provided with a protrusion 9. The protrusion 9 is provided with a first inlet 5 that communicates with the first end of the first flow channel 3. The right end of the second flow channel 4 communicates with the right end of the first flow channel 3 in the material contact area 7. The material contact area 7 is the cavity part of the right side of the second flow channel 4.

[0044] This invention introduces vortices through a spiral-shaped second flow channel 4. The strong vortex flow generates radial and axial pressure gradients, creating an internal annular recirculation zone that enhances mixing efficiency. Therefore, mixing can be achieved without relying on a large momentum difference between the outer (annular) and inner (center) sides. The internal pipe 2 guides the flow, causing the fluid to rotate tangentially on its own. The tangential vortex in the internal pipe 2 and the axial flow in the annular gap undergo intense shearing, ensuring uniform mixing even in applications where high flow rates are unsuitable. This broadens the application of coaxial jets. This invention can be applied to the feeding mechanisms of reactors or production equipment.

[0045] The spiral structure is formed by rotating and stretching a non-circular contour along the axial direction. The non-circular contour is formed by connecting multiple identical arc segments end-to-end. These arcs can be circular arcs, elliptical arcs, spline curves, conics, or parabolas, and the number of arc segments ranges from 3 to 6. Figures 2a to 2f Six different non-circular contour structures are shown.

[0046] The coaxial tube structure of this invention is simulated below. Both materials are fed at a flow rate of 12 L / min. The average flow velocity in the second channel 4 of the internal pipe 2 is 2.13 m / s, and the average velocity in the first channel 3 is 1.46 m / s. Furthermore, for comparison, the internal pipe 2 is replaced with a circular pipe, while maintaining the same cross-sectional area. The velocity contour plot is shown below. Figure 3a and Figure 3b As shown, Figure 3a and Figure 3b The area within the black box shows the contact zone between the two materials. It can be seen that the red high-speed zone in reactor 2 (internal pipe) is larger, while the medium-speed zone (green zone) in the circular tube reactor is larger. On the other hand, the high-speed red zone in internal pipe 2 extends for a longer distance after the two materials come into contact, while the velocity in the circular tube decreases rapidly after a certain distance.

[0047] like Figure 4a and Figure 4b The image shows the turbulent dissipation rate cloud map. The turbulent dissipation rate is related to the micro-mixing efficiency. The higher the turbulent dissipation rate, the higher the micro-mixing efficiency. It can be seen that the turbulent dissipation rate of the reactor with internal pipe 2 in the contact zone of the two materials is significantly greater than that of the circular pipe, indicating that the reactor with internal pipe 2 can significantly enhance the micro-mixing between materials.

[0048] In addition, such as Figure 5 As shown, select Figure 1 The cross-sections at z=80mm and z=110mm along the z-axis are shown in more detail to illustrate the influence of the internal pipe 2 on the flow. z=80mm is located before the two materials are mixed, close to the material contact area 7, and z=110mm is the mixing area after the two materials come into contact.

[0049] like Figure 6a and Figure 6b As shown, because the cross-sectional areas of the inner and outer channels are consistent in both structures, their average velocities are equal. It can be seen from the figure that the velocity distribution at z=80mm is very similar between the reactor using internal pipe 2 and the reactor using a circular pipe. However, Figure 7a and Figure 7b The results show that the turbulent dissipation rate distributions in the two reactor structures are quite different, with the area of ​​the high turbulent dissipation zone in the reactor with internal pipe 2 being significantly larger than that in the circular pipe structure.

[0050] further, Figure 8a and Figure 8b The figures show the turbulent dissipation rate contour maps of the two reactors at two cross-sections at z=80mm and z=110mm, respectively. It can be seen from the figures that the reactor with internal piping 2 has a very high turbulent dissipation rate at z=110mm, especially in the area between the central region and the annular region (red area), indicating that the reactor with internal piping 2 has a higher micro-mixing efficiency.

[0051] The arc is an ellipse with N segments. The major axis radius and minor axis radius of the ellipse are b and a, respectively, with b / a ranging from 0.5 to 1.2. The connection point of the N segments of the ellipse is located on a circle with radius R2. The farthest distance from the center of the circle with radius R2 to the ellipse is R3 = a + R2cos(π / N) and b = R2sin(π / N). The length of the internal pipe (2) is H, with H / (2R3) ranging from 5 to 50. The spiral period P of the spiral structure ranges from 1 to 10. It should be noted that although the major axis radius and minor axis radius of the ellipse are defined in this invention, it does not mean that the major axis radius b is necessarily longer than the minor axis radius a. The so-called major axis and minor axis are only used to distinguish the two different axes of the ellipse.

[0052] like Figure 9a and Figure 9b The diagram shows the cross-sectional and longitudinal sections of the internal pipe 2, which is a non-circular profile composed of three elliptical lines. The outer diameter of the internal pipe 2 is D1. The three elliptical lines are Arc1, Arc2, and Arc3, each corresponding to 120° of a circle with radius R2. R3 = a + R2cos(π / 3), b = R2sin(π / 3), H is taken as 10, and the spiral period P = 3. For example... Figure 10a and Figure 10b When N is 4, R3 = a + R2cos(π / 4), b = R2sin(π / 4), H remains 10, and the spiral period P is 2; For example... Figures 11a to 11c Schematic diagrams of longitudinal sections of internal pipes 2 with different helical periods are shown respectively. Figure 11a The spiral period in the diagram is 1, corresponding to a rotation angle of 360°. Figure 11b The spiral period is 2, corresponding to a rotation angle of 720°. Figure 11c The spiral period is 3, corresponding to a rotation angle of 1080°.

[0053] Example 2:

[0054] like Figure 12 As shown, this embodiment provides another coaxial tube structure. In this embodiment, the outer wall radius of the inner pipe 2 is 2.5 mm, the inner wall radius of the outer pipe 1 is 3.1 mm, the cross-sectional area of ​​the first flow channel 3 is 10.6 mm², the cross-sectional area of ​​the second flow channel 4 is 10.6 mm², and the length of the unit rotation cycle in the axial direction is z = 20 mm.

[0055] Example 3:

[0056] like Figure 13 As shown, this embodiment provides another coaxial tube structure. In this embodiment, the outer wall radius of the inner pipe 2 is 2.5 mm, the inner wall radius of the outer pipe 1 is 3.05 mm, the cross-sectional area of ​​the first flow channel 3 is 9.6 mm², the cross-sectional area of ​​the second flow channel 4 is 9.2 mm², and the length of the unit rotation cycle in the axial direction is z = 20 mm.

[0057] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above three embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A coaxial tube structure, characterized in that, The system includes an external pipeline (1) and an internal pipeline (2). The external pipeline (1) has a cavity. The internal pipeline (2) is located in the cavity and is coaxially arranged with the external pipeline (1). The outer wall of the internal pipeline (2) and the inner wall of the external pipeline (1) form an annular first flow channel (3). The internal pipeline (2) has a second flow channel (4). The inner wall of the external pipeline (1) or the inner wall of the internal pipeline (2) has a spiral structure so that the first flow channel (3) or the second flow channel (4) is spiral. The first flow channel (3) is connected to a first feed inlet (5). The second flow channel (4) is connected to a second feed inlet (6). The end of the first flow channel (3) and the end of the second flow channel (4) are connected in the cavity, and the connection between the first flow channel (3) and the second flow channel (4) forms a material contact area (7). The external pipeline (1) has a discharge port (8) connected to the material contact area (7). The spiral structure is formed by rotating and stretching a non-circular contour along the axial direction. The non-circular contour is formed by connecting multiple identical arc segments end to end, and the number of arc segments ranges from 3 to 6. The arc is an ellipse with N segments. The major axis radius and minor axis radius of the ellipse are b and a, respectively, with b / a ranging from 0.5 to 1.

2. The connection point between the beginning and end of the N segments of the ellipse is located on a circle with radius R2. The farthest distance from the center of the circle with radius R2 to the ellipse is R3 = a + R2cos(π / N) and b = R2sin(π / N).

2. The coaxial tube structure according to claim 1, characterized in that, The length of the internal pipeline (2) is H, the value of H / (2R3) is 5-50, and the spiral period P of the spiral structure is 1-10.

3. The coaxial tube structure according to claim 1, characterized in that, The internal pipeline (2) is integrally formed inside the external pipeline (1). One end of the external pipeline (1) is provided with a second inlet (6) that communicates with the first end of the second flow channel (4). The other end of the external pipeline (1) is provided with the outlet (8). The side wall of the external pipeline (1) is provided with a protrusion (9). The protrusion (9) is provided with a first inlet (5) that communicates with the first end of the first flow channel (3).

4. The coaxial tube structure according to claim 1, characterized in that, The inner wall of the internal pipe (2) is provided with the spiral structure, so that the second flow channel (4) is spiral.

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