Coaxial tube structure

Abstract

The invention provides a coaxial tube structure, relates to the technical field of coaxial jet flow, and aims to solve the technical problem of non-uniform mixing of coaxial jet flow in the prior art under the condition that a relatively high flow speed is not suitable to be adopted. A coaxial pipe structure comprises an external pipeline and an internal pipeline, a cavity is formed in the external pipeline, the internal pipeline is arranged in the cavity and is coaxial with the external pipeline, an annular first flow channel is formed between the outer wall of the internal pipeline and the inner wall of the external pipeline, and a second flow channel is formed in the internal pipeline. A spiral structure is arranged on the inner wall of the external pipeline or the inner wall of the internal pipeline, so that the first flow channel or the second flow channel is spiral, the first flow channel communicates with a first feeding port, the second flow channel communicates with a second feeding port, the tail end of the first flow channel communicates with the tail end of the second flow channel in the cavity, and a material contact area is formed at the communicating position of the first flow channel and the second flow channel; and a discharge hole communicated with the material contact area is formed in the external pipeline.

Description

Technical Field

[0001] The invention relates to the technical field of coaxial jets, in particular to a coaxial tube structure. Background Art

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

[0003] Coaxial jets mainly rely on the shear caused by the velocity difference between the outer ring and the inner tube to quickly mix the center flow with the outer flow. However, in some chemical applications, due to certain reasons, such as low kinetic rate and crystallization behavior being easily affected by high-intensity turbulence characteristics, it is not suitable to use a higher flow rate. Therefore, under this condition, the inner and outer flows do not have a large flow rate and flow rate difference, resulting in uneven mixing. Summary of the invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a coaxial tube structure to solve the technical problem of uneven mixing of coaxial jets in the prior art when a higher flow rate is not suitable.

[0005] In order to solve the above technical problems, the present invention provides a coaxial tube structure, including an external pipeline and an internal pipeline, a cavity is provided in the external pipeline, the internal pipeline is arranged in the cavity and is coaxially arranged with the external pipeline, a first annular flow channel is formed between the outer wall of the internal pipeline and the inner wall of the external pipeline, a second flow channel is provided in the internal pipeline, the inner wall of the external pipeline or the inner wall of the internal pipeline is provided with a spiral structure so that the first flow channel or the second flow channel is spiral, the first flow channel is connected to a first feed port, the second flow channel is connected to a second feed port, the end of the first flow channel is connected to the end of the second flow channel in the cavity and a material contact area is formed at the connection between the first flow channel and the second flow channel, and a discharge port connected to the material contact area is provided on the external pipeline.

[0006] After adopting the above structure, a coaxial tube structure of the present invention has the following advantages: a vortex is introduced through a spiral first flow channel or a second flow channel, and a strong vortex flow will generate radial and axial pressure gradients, thereby generating an internal or external annular recirculation zone and enhancing the mixing efficiency. Therefore, mixing does not rely on a large internal and external momentum difference, and the fluid can be mixed evenly even in an application background where a higher flow rate is not suitable, making the application of coaxial jets more extensive; the present invention can be used in a reactor or in a feed structure of a production device.

[0007] As an improvement, the spiral structure is composed of a non-circular contour rotated and stretched along the axial direction, and the non-circular contour is formed by connecting multiple identical arcs end to end. The arc is one of a circular arc, an elliptical arc, a spline curve, a conic curve and a parabola, and the number of arc segments ranges from 3 to 6. With this structure, one of a circular arc, an elliptical arc, a spline curve, a conic curve and a parabola is selected to form the non-circular contour of the spiral structure, further enhancing the mixing effect.

[0008] As an improvement, the arc is an ellipse and the number of arc segments is N, the major axis radius and the minor axis radius of the ellipse are b and a respectively, the b / a range is 0.5-1.2, the first and last connection points of the N ellipse segments are located on a circle with a radius of R2, and the farthest distance from the center of the circle with a radius of R2 to the ellipse is R3=a+R2cos(π / N), b=R2sin(π / N); this structure is used to further enhance the mixing effect.

[0009] As an improvement, the length of the internal pipeline is H, the value range of H / (2R3) is 5-50, and the spiral period P of the spiral structure is 1-10; using 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, a second feed port connected to the first end of the second flow channel is provided at one end of the external pipeline, a discharge port is provided at the other end of the external pipeline, a protrusion is provided on the side wall of the external pipeline, and a first feed port connected to the first end of the first flow channel is provided on the protrusion.

[0011] As an improvement, the inner wall of the inner pipeline is provided with a spiral structure so that the second flow channel is spiral. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural schematic diagram of the present invention.

[0013] Figure 2a It is a schematic diagram of a non-circular contour composed of three elliptical lines in the present invention.

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

[0015] Figure 2c It is a schematic diagram of a non-circular profile composed of three conic sections in the present invention.

[0016] Figure 2d It is a schematic diagram of a non-circular contour composed of four elliptical lines in the present invention.

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

[0018] Figure 2f It is a schematic diagram of a non-circular profile composed of four conic sections in the present invention.

[0019] Figure 3a This is a velocity cloud diagram of the CFD simulation of the coaxial tube structure in Example 1 of the present invention.

[0020] Figure 3b Velocity contour diagram of CFD simulation of coaxial transmission without internal piping.

[0021] Figure 4a This is a cloud diagram of the turbulence dissipation rate of the coaxial tube structure in Example 1 of the present invention through CFD simulation.

[0022] Figure 4b This is a turbulent dissipation rate cloud diagram of the CFD simulation of the coaxial device without internal piping.

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

[0024] Figure 6a This is a velocity cloud diagram of CFD simulation at the cross section where z is 80 mm in Example 1 of the present invention.

[0025] Figure 6b The velocity contour diagram of the CFD simulation at the cross section of the coaxial device with z of 80 mm without internal piping.

[0026] Figure 7a This is a cloud diagram of the turbulent dissipation rate of the CFD simulation at the cross section where z is 80 mm in the first embodiment of the present invention.

[0027] Figure 7b This is the turbulent dissipation rate cloud diagram of the CFD simulation at the cross section of the coaxial device with z of 80 mm without internal piping.

[0028] Figure 8a 1 is a cloud diagram of turbulent dissipation rate at different cross sections simulated by CFD in Example 1 of the present invention.

[0029] Figure 8b The turbulent dissipation rate cloud diagram of CFD simulation at different cross sections of the coaxial device without internal pipes.

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

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

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

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

[0034] Fig.11a It is a schematic diagram of the longitudinal section of the internal pipeline with a spiral period of 1 in the present invention.

[0035] Fig.11b It is a schematic diagram of the longitudinal section of the internal pipeline with a spiral period of 2 in the present invention.

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

[0037] Fig.12 It is a cross-sectional schematic diagram of the second embodiment of the present invention.

[0038] Fig.13 It is a cross-sectional schematic diagram of embodiment 3 of the present invention.

[0039] Figure numerals: 1. External pipeline; 2. Internal pipeline; 3. First flow channel; 4. Second flow channel; 5. First feed port; 6. Second feed port; 7. Material contact area; 8. Discharge port; 9. Protrusion. DETAILED DESCRIPTION

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

[0041] Embodiment 1: like Figure 1 As shown, in this embodiment, a coaxial tube structure is provided, including an external pipeline 1 and an internal pipeline 2, a cavity is provided in the external pipeline 1, the internal pipeline 2 is arranged in the cavity and is coaxially arranged with the external pipeline 1, a first annular flow channel 3 is formed between the outer wall of the internal pipeline 2 and the inner wall of the external pipeline 1, a second flow channel 4 is provided in the internal pipeline 2, and a spiral structure is provided on the inner wall of the external pipeline 1 or the inner wall of the internal pipeline 2 so that the first flow channel 3 or the second flow channel 4 is spiral. In this embodiment, the inner wall of the internal pipeline 2 is provided with a spiral structure so that the second flow channel 4 is spiral; the first flow channel 3 is connected to a first feed port 5, and the second flow channel 4 is connected to a second feed port 6, the end of the first flow channel 3 is connected to the end of the second flow channel 4 in the cavity and a material contact area 7 is formed at the connection between the first flow channel 3 and the second flow channel 4, and a discharge port 8 connected to the material contact area 7 is provided on the external pipeline 1.

[0042] Specifically, if Figure 1As shown, the external pipeline 1 and the internal pipeline 2 are both arranged horizontally, the first flow channel 3 and the second flow channel 4 are both arranged in the horizontal direction, and the cavity is also arranged coaxially with the external pipeline 1, and the internal pipeline 2 is integrally formed in the external pipeline 1, wherein the left end of the internal pipeline 2 is integrally formed with the external pipeline 1, and one end of the external pipeline 1 is provided with a second feed port 6 connected to the head end of the second flow channel 4, that is, the second feed port 6 is arranged at the left end of the external pipeline 1, the second flow channel 4 runs through the left and right ends of the internal pipeline 2, and the left end of the second flow channel 4 is connected to the second feed port 6, and the other end of the external pipeline 1 is provided with a discharge port 8, and the discharge port 8 is formed by the cavity running through the right end of the external pipeline 1, a protrusion 9 is provided on the side wall of the external pipeline 1, and a first feed port 5 connected to the head end of the first flow channel 3 is provided on the protrusion 9, and the right end of the second flow channel 4 is connected to the right end of the first flow channel 3 in the material contact area 7, and the material contact area 7 is the cavity part of the right part of the second flow channel 4.

[0043] The present invention introduces a vortex through the spiral second flow channel 4. The strong vortex flow will generate radial and axial pressure gradients, thereby generating an internal annular recirculation zone to enhance the mixing efficiency. Therefore, it is not necessary to rely on a large external (annular) and internal (center) momentum difference for mixing. The internal pipeline 2 is used to guide the fluid to rotate tangentially. The tangential vortex in the internal pipeline 2 and the axial flow in the annular gap are sheared violently, so that the fluid can be mixed evenly even in the application background where a higher flow rate is not suitable, making the application of coaxial jets more extensive. The present invention can be applied to the feeding mechanism of a reactor or a production device.

[0044] The spiral structure is formed by rotating and stretching a non-circular profile in an axial direction. The non-circular profile is formed by connecting multiple identical arcs end to end. The arc is one of a circular arc, an elliptical arc, a spline curve, a conic curve and a parabola, and the number of arc segments ranges from 3 to 6. Figure 2a to Figure 2f Six different non-circular profile structures are shown.

[0045] The coaxial tube structure of the present invention is simulated below. Both materials are fed at a flow rate of 12L / min. The average flow velocity in the second flow channel 4 of the internal pipe 2 is 2.13m / s, and the average velocity in the first flow channel 3 is 1.46m / s. In addition, for comparison, the internal pipe 2 is changed into a round pipe for comparison, and the cross-sectional area of ​​the flow channel is kept equal. The velocity cloud diagram is as follows: Figure 3a and Figure 3b As shown, Figure 3a and Figure 3b The black frame area shows the contact area of ​​the two materials. It can be seen that the red high-speed area in the internal pipeline 2 reactor is larger, while the medium-speed (green area) area in the circular tube reaction is larger. On the other hand, the high-speed red area of ​​the internal pipeline 2 after the two streams of materials contact continues for a long distance, while the speed in the circular tube decreases rapidly after a certain distance.

[0046] like Figure 4a and Figure 4b It is a cloud diagram of turbulence dissipation rate. The turbulence dissipation rate is related to the micro-mixing efficiency. The larger the turbulence dissipation rate, the higher the micro-mixing efficiency. It can be seen that the turbulence dissipation rate of the reactor with internal pipeline 2 in the contact area of ​​the two streams of materials is significantly greater than that of the circular tube, indicating that the reactor using internal pipeline 2 can significantly enhance the micro-mixing between materials.

[0047] In addition, if Figure 5 As shown, select Figure 1 The cross sections at z=80mm and z=110mm in the z-axis direction are shown to more specifically show the effect of the internal pipeline 2 on the flow. z=80mm is located before the mixing of the two materials, close to the material contact area 7, and z=110mm is the mixing area after the two materials come into contact.

[0048] like Figure 6a and Figure 6b As shown in the figure, since the cross-sectional areas of the inner and outer flow channels of the two structures are consistent, their average velocities are equal. It can be seen from the figure that the velocity distribution of the reactor using internal pipe 2 and the reactor using round pipe at z=80mm is very similar. However, Figure 7a and Figure 7b It shows that the distribution of turbulence dissipation rate in the reactors of the two structures is completely different. The area of ​​high turbulence dissipation zone in the reactor of internal pipeline 2 is significantly larger than that of the circular tube structure.

[0049] further, Figure 8a and Figure 8b The cloud diagrams of turbulence dissipation rate of the two reactors at two cross sections at z=80mm and z=110mm are shown respectively. It can be seen from the figure that the turbulence dissipation rate of the reactor with internal pipe 2 at z=110mm is very large, especially the area between the central area and the annular area has a high dissipation rate (red area), which shows that the microscopic mixing efficiency of the reactor with internal pipe 2 is higher.

[0050] The arc is an ellipse and the number of arc segments is N. The major axis radius and the minor axis radius of the ellipse are b and a respectively, and the range of b / a is 0.5-1.2. The first and last connection points of the N ellipse segments are located on a circle with a radius of R2. The farthest distance from the center of the circle with a radius of R2 to the ellipse is R3=a+R2cos(π / N), b=R2sin(π / N). The length of the internal pipeline (2) is H, and the value range of H / (2R3) is 5-50. The spiral period P of the spiral structure is in the range of 1-10. It should be noted that although the major axis radius and the minor axis radius of the ellipse are defined in the present invention, it does not mean that the major axis radius b must be 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.

[0051] like Figure 9a and Figure 9b The cross-sectional and longitudinal section diagrams of the internal pipeline 2 corresponding to the non-circular contour composed of three elliptical lines are shown. The outer diameter of the internal pipeline 2 is D1. The three elliptical lines are Arc1, Arc2 and Arc3. Each elliptical line corresponds to 120° of a circle with a radius of R2. R3=a+R2cos(π / 3), b=R2sin(π / 3), H is 10, and the spiral period P=3. Fig.10a and Fig.10b , when N is 4, R3=a+R2cos(π / 4), b=R2sin(π / 4), H is still 10, and the spiral period P is 2; Figures 11a to 11c The longitudinal cross-sectional diagrams of the internal pipeline 2 with different spiral periods are shown respectively. Fig.11a The spiral period in is 1, corresponding to a rotation angle of 360°. Fig.11b The spiral period in is 2, corresponding to a rotation angle of 720°. Fig.11c The spiral period in is 3, corresponding to a rotation angle of 1080°.

[0052] Embodiment 2: like Fig.12 As shown, another coaxial tube structure is provided in this embodiment. 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 period in the axial direction is z=20 mm.

[0053] Embodiment three: like Fig.13 As shown, another coaxial tube structure is provided in this embodiment. 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 period in the axial direction is z=20 mm.

[0054] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above three embodiments, and all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present invention.

Claims

1. A coaxial tube structure, characterized in that: The invention comprises an external pipeline (1) and an internal pipeline (2), wherein the external pipeline (1) is provided with a cavity, the internal pipeline (2) is arranged in the cavity and is coaxially arranged with the external pipeline (1), an annular first flow channel (3) is formed between the outer wall of the internal pipeline (2) and the inner wall of the external pipeline (1), a second flow channel (4) is provided in the internal pipeline (2), the inner wall of the external pipeline (1) or the inner wall of the internal pipeline (2) is provided with a spiral structure so that the first flow channel (3) or the second flow channel (4) is spiral-shaped, the first flow channel (3) is connected to a first feed port (5), the second flow channel (4) is connected to a second feed port (6), the end of the first flow channel (3) and the end of the second flow channel (4) are connected in the cavity, and a material contact area (7) is formed at the connection point between the first flow channel (3) and the second flow channel (4), and the external pipeline (1) is provided with a discharge port (8) connected to the material contact area (7).

2. The coaxial tube structure according to claim 1, characterized in that: The spiral structure is formed by a non-circular contour being rotated and stretched in the axial direction, and the non-circular contour is formed by connecting multiple identical arcs end to end. The arc is one of a circular arc, an elliptical arc, a spline curve, a conic curve and a parabola, and the number of arc segments ranges from 3 to 6.

3. The coaxial tube structure according to claim 2, characterized in that: The arc is an ellipse and the number of arc segments is N. The major axis radius and the minor axis radius of the ellipse are b and a respectively, and the range of b / a is 0.5-1.

2. The first and last connection points of the N segments of the ellipse are located on a circle with a radius of R2, and the farthest distance from the center of the circle with a radius of R2 to the ellipse is R3=a+R2cos(π / N), and b=R2sin(π / N).

4. The coaxial tube structure according to claim 3, characterized in that: The length of the internal pipeline (2) is H, the value range of H / (2R3) is 5-50, and the spiral period P of the spiral structure is in the range of 1-10.

5. The coaxial tube structure according to claim 1, characterized in that: The internal pipeline (2) is integrally formed in the external pipeline (1); one end of the external pipeline (1) is provided with the second feed port (6) connected to the head end of the second flow channel (4); the other end of the external pipeline (1) is provided with the discharge port (8); a protrusion (9) is provided on the side wall of the external pipeline (1); and the first feed port (5) connected to the head end of the first flow channel (3) is provided on the protrusion (9).

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

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