A pull-ring paddle mixing device with a ring-shaped induction structure and a mixing method thereof

Abstract

The invention provides a pull ring paddle stirring device with ring induction structure. The device uses the pressure difference effect and edge shedding vortex mechanism of the inside and outside of the ring body to actively intervene in the wake flow pattern of the paddle by setting a ring induction structure at the end of the paddle arm, so as to make the area around the paddle and between adjacent paddles produce a composite vortex structure with highly irregular shape, thereby significantly expanding the spatial distribution range of the high-turbulent energy area. The ring induction structure generates an additional axial component during rotation, inducing the formation of a bottom vortex structure at the bottom of the stirring tank, driving the fluid at the tank bottom to move upward, effectively improving the low flow rate problem at the bottom of the traditional paddle, enhancing the exchange between fluids at different axial heights, and helping to suppress the deposition of solid particles and improve the suspension uniformity of the liquid-solid system.

Description

Technical Field

[0001] This invention relates to the field of stirred reactor calculation, and in particular to a ring-shaped paddle stirring and mixing device with an annular induction structure. Background Technology

[0002] Mechanically stirred reactors are among the most widely used mixing equipment in process industries such as chemical, metallurgical, pharmaceutical, food, and materials processing. Their core component is the stirring impeller, which applies shear and pressure to the fluid within the tank through rotational motion, driving the fluid to circulate and achieve uniform mixing, enhanced heat transfer, and promoted mass transfer. Based on the different flow patterns generated, traditional stirring impellers are mainly divided into two categories: axial flow and radial flow. Axial flow impellers primarily generate axial circulating flow and are suitable for large-scale mixing of low-viscosity systems; radial flow impellers primarily generate radial jets and have strong local shearing capabilities, often used in systems requiring strong dispersion. In addition, near-wall impellers such as anchor impellers and ribbon impellers are mainly designed for high-viscosity systems, achieving fluid renewal through near-wall scraping motion. All of these impeller types have extensive engineering applications and mature design specifications under their respective applicable conditions.

[0003] In recent years, researchers have further improved the mixing performance of agitators by modifying impeller geometry and developing novel composite impeller structures. Meanwhile, advancements in computational fluid dynamics have provided powerful tools for the refined analysis of stirred flow fields, enabling research on impeller structure optimization to be conducted at a more systematic level. However, existing agitation technologies still have several shortcomings that have not yet been effectively addressed:

[0004] A. Traditional impellers tend to establish a relatively stable macroscopic circulation flow pattern in the tank during rotation. While this stable flow pattern is beneficial for overall convective mixing, it also creates flow dead zones in local areas. In particular, the fluid renewal rate is significantly lower in the corners of the mixing tank and in areas outside the impeller coverage, resulting in uneven local mixing.

[0005] B. In the bottom region of the stirred tank, the axial flow intensity induced by traditional impellers usually decreases rapidly with the increase of distance from the impeller. The flow velocity near the bottom of the tank is low, which easily causes solid particles to deposit and the fluid at the bottom to stagnate for a long time, which significantly restricts the suspension uniformity of the liquid-solid system.

[0006] C. Existing blade structures do not adequately utilize the blade wake region. The blade tip is the region with the largest velocity gradient and the highest turbulence intensity, which has the potential to generate complex vortex structures. However, the wake vortex of traditional blades dissipates rapidly after leaving the blade, failing to effectively enhance fluid disturbance over a larger area, resulting in limited micro-mixing efficiency.

[0007] D. Existing research on structural improvements to impellers mostly focuses on adjusting the overall size of the impeller blades, installation angle, or multi-stage combination methods. There is insufficient attention to the targeted design of local structures at the blade tip, and there is a lack of effective technical solutions to actively control the wake structure by changing the end geometry.

[0008] Therefore, it is necessary to actively intervene in the blade wake morphology by specifically designing the blade tip structure. Summary of the Invention

[0009] The purpose of this invention is to provide a ring-shaped paddle stirring and mixing device with an annular induction structure to solve the problems existing in the prior art.

[0010] The technical solution adopted to achieve the purpose of this invention is as follows: a ring-shaped paddle mixing device with an annular induction structure includes a mixing tank, a drive mechanism, a stirring shaft, and at least one set of ring-shaped paddles mounted on the stirring shaft. The drive motor drives the ring-shaped paddles to rotate through the stirring shaft, thereby forming a circulating flow within the mixing tank.

[0011] The ring-shaped impeller includes a central hub and at least two blade arms extending radially from the central hub. An annular induction structure is provided at the end of each blade arm. The annular induction structure is a ring-shaped body. The cross-sectional profile of the annular body forms a closed curve or a non-closed curve with an opening. As the impeller rotates, the annular induction structure alters the impeller wake structure and generates complex vortices in the fluid to enhance fluid mixing.

[0012] Furthermore, the cross-sectional profile of the annular guiding structure is any one of the following: circular, elliptical, polygonal, C-shaped, U-shaped, notched ring, spiral open ring, or irregular closed curve, or a combination of the above shapes. The notched ring is detachably connected to the blade arm end in a snap-fit ​​manner. The annular guiding structures at the ends of different blade arms in the same device can adopt the same or different profile shapes.

[0013] Furthermore, the diameter of the circumscribed circle of the annular induction structure is 0.1 to 0.5 times the diameter of the blade.

[0014] Furthermore, there is an installation angle between the annular induction structure and the plane of the blade arm. The installation angle ranges from 5° to 60°.

[0015] Furthermore, the annular guiding structure is connected to the end of the blade arm in a fixed, detachable, or hinged adjustable manner.

[0016] Furthermore, the material of the annular induction structure can be any one of rigid material, elastic material, or flexible material.

[0017] Furthermore, the pull ring impeller is configured as a multi-stage impeller structure with two or more stages along the stirring shaft axial direction. The number of impeller arms, the shape of the annular induction structure, or the installation angle of adjacent two-stage impellers may be the same or different.

[0018] Furthermore, one or more baffles are provided in the stirring tank to suppress the overall rotating flow and enhance local turbulent disturbances.

[0019] Furthermore, it also includes a torque sensor, a torque acquisition unit, and a data processing terminal. The torque sensor is mounted on the stirring shaft and is used to collect torque signals during the rotation of the impeller blades. The torque acquisition unit is electrically connected to the torque sensor and transmits the signals to the data processing terminal.

[0020] This invention also discloses a fluid mixing method, employing the aforementioned apparatus to mix liquid-liquid, liquid-solid, or gas-liquid multiphase systems. A ring-shaped induced structure generates a complex vortex in the impeller wake region. Utilizing the complex vortex and the bottom vortex induced at the bottom of the stirred tank, axial circulation and interface renewal of the fluid are enhanced, thereby shortening the mixing time and improving mixing uniformity.

[0021] The technical effects of this invention are beyond doubt:

[0022] A. By setting an annular induced structure at the end of the blade arm, the pressure difference effect between the inner and outer sides of the annular body and the edge shedding vortex mechanism are used to actively intervene in the blade wake morphology, so that a highly irregular composite vortex structure is generated around the blade and between adjacent blades, which significantly expands the spatial distribution range of the high turbulent kinetic energy region.

[0023] B. The annular induced structure generates an additional axial component during rotation, inducing a bottom vortex structure at the bottom of the mixing tank, driving the fluid in the bottom area of ​​the tank to move upward, effectively improving the problem of low flow velocity at the bottom of traditional impellers, enhancing the exchange between fluids at different axial heights, helping to suppress solid particle deposition and improve the suspension uniformity of the liquid-solid system.

[0024] C. The introduction of the annular induced structure causes the fluid to generate more complex velocity gradients in the radial and axial directions, as well as in the tangential and circumferential directions. The multi-directional enhanced flow changes help to break up fluid stratification, promote the fragmentation of fluid micro-clusters and the renewal of interfaces, thereby improving micro-mixing efficiency and shortening the mixing time required for the system to reach a homogeneous state.

[0025] D. The annular induction structure can be directly installed at the end of existing impeller arms in a modular manner, without requiring modification to the stirring shaft, drive mechanism, or main body of the stirring tank. It is suitable for the design and integration of new devices, as well as for low-cost retrofitting and upgrading of existing equipment. The shape, size, and installation angle of the annular structure can be flexibly adjusted according to specific working conditions, exhibiting strong engineering adaptability. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a ring-type paddle mixing device.

[0027] Figure 2 This is a schematic diagram of the ring-shaped blade structure.

[0028] Figure 3 This is a schematic diagram of the cross-sectional profile of the annular induced structure;

[0029] Figure 4 This is a schematic diagram of a multi-stage blade structure;

[0030] Figure 5 This is a schematic diagram of the working annular induction structure at the end of the pull ring blade; Figure 5 'a' represents a 3D streamline tracing view; Figure 5 b is a cloud map showing the distribution of turbulent kinetic energy;

[0031] Figure 6 A comparison chart of the mixing performance of a pull-ring impeller and a regular agitator; Figure 6 a is a comparison chart of pressure fluctuation amplitude attenuation curves; Figure 6 b is a comparison chart of the time to reach the stable pressure state; Figure 6 c is a comparison chart of experimental mixing times;

[0032] Figure 7 A schematic diagram comparing the flow field characteristics of a slanted blade propeller and a ring propeller; Figure 7 a is a schematic diagram of the three-dimensional flow field and the characteristic diagram of the circulating flow field in the inclined blade impeller agitator; Figure 7 b is a schematic diagram of the three-dimensional flow field of the ring-type impeller agitator and a characteristic diagram of the secondary vortex flow field induced by the annular structure.

[0033] In the figure: 1. Stirring tank; 2. Drive mechanism; 3. Stirring shaft; 4. Pull ring blade; 401. Central hub; 402. Blade arm; 403. Annular induction structure; 5. Torque sensor; 6. Torque acquisition device; 7. Data processing terminal. Detailed Implementation

[0034] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0035] Example 1:

[0036] See Figure 1 and Figure 2This embodiment provides a ring-shaped paddle mixing device with an annular induction structure, including a mixing tank 1, a drive mechanism 2, a stirring shaft 3, and at least one set of ring-shaped paddles 4 mounted on the stirring shaft 3. The drive motor 2 drives the ring-shaped paddles 4 to rotate through the stirring shaft 3, thereby forming a circulating flow in the mixing tank 1.

[0037] The ring-shaped blade 4 includes a central hub 401 and at least two blade arms 402 extending radially from the central hub 401. An annular induction structure 403 is provided at the end of each blade arm 402. The annular induction structure 403 forms a closed or partially closed annulus. When the blade rotates, the annular induction structure 403 alters the blade wake structure and generates a complex vortex in the fluid to enhance fluid mixing.

[0038] Example 2:

[0039] The main content of this embodiment is the same as that of Embodiment 1, wherein, see [link / reference]. Figure 3 The cross-sectional profile of the annular induction structure 403 is any one of the following: circular, elliptical, polygonal, C-shaped, U-shaped, notched ring, spiral open ring, or irregular closed curve, or a combination of the above shapes. The annular induction structures at the ends of different blade arms in the same device can adopt the same or different profile shapes. Using annular induction structures with different profile shapes in the same device allows each blade arm to generate wake vortex structures of different shapes during rotation, thereby breaking the symmetrical flow field distribution within the mixing tank and avoiding local flow cancellation and ineffective energy consumption caused by highly symmetrical flow fields. For the notched ring type annular induction structure, its opening can be designed with a snap-fit ​​connection to achieve quick installation and disassembly with the blade arm end, facilitating flexible replacement of induction structures of different shapes according to working conditions and improving the engineering applicability of the device.

[0040] Example 3:

[0041] This embodiment is similar in main content to Embodiment 1 or 2, wherein the circumscribed circle diameter of the annular guiding structure 403 is 0.1 to 0.5 times the blade diameter. In this embodiment, the circumscribed circle diameter is used as the unified dimensional characterization benchmark for the annular guiding structure. Regardless of whether the outline shape of the annular guiding structure is circular, elliptical, polygonal, or other irregular, all its endpoints are inscribed within the same circumscribed circle; that is, each shape is drawn inside this circumscribed circle, and the endpoints coincide on the same circle. Using the circumscribed circle diameter as a unified benchmark facilitates dimensional comparison and engineering design selection between annular guiding structures of different shapes, while also ensuring the consistency of the radial dimensions of each end guiding structure when multiple blade arms are combined.

[0042] Example 4:

[0043] The main content of this embodiment is the same as any one of embodiments 1 to 3, wherein there is an installation angle between the annular guiding structure 403 and the plane of the blade arm 402. The installation angle ranges from 5° to 60°.

[0044] Example 5:

[0045] The main content of this embodiment is the same as any one of embodiments 1 to 4, wherein the annular guiding structure 403 is connected to the end of the blade arm 402 in a fixed, detachable or hinged adjustable manner.

[0046] Example 6:

[0047] The main content of this embodiment is the same as any one of embodiments 1 to 5, wherein the material of the annular induction structure 403 is stainless steel 304 or 316 stainless steel.

[0048] Example 7:

[0049] This embodiment is similar in content to any one of embodiments 1 to 6, wherein the ring-shaped impeller 4 is configured as a multi-stage impeller structure with two or more stages along the stirring shaft 3. The number of impeller arms, the shape of the annular induction structure, or the installation angle of adjacent impeller stages may be the same or different. On the same stage of the impeller, the deviation angle (installation angle) of annular induction structures of the same shape should be consistent to ensure flow field symmetry. Annular induction structures of different shapes can have different deviation angles because the shape itself already causes differences in the flow field. Furthermore, the selection of the installation angle is also related to the rotational speed; the optimal installation angle will differ depending on the rotational speed.

[0050] Example 8:

[0051] The main content of this embodiment is the same as any one of the embodiments in embodiment 7, wherein, see [link to embodiment 7]. Figure 4 In this embodiment, the ring-pulling blade 4 is arranged in five stages along the axial direction of the stirring shaft 3, from top to bottom: elliptical ring-pulling blade, rectangular ring-pulling blade, square ring-pulling blade, circular ring-pulling blade, and triangular ring-pulling blade. Each stage of blade is fixedly installed on the stirring shaft 2 by a bushing 1. Each stage of blade includes two symmetrically arranged blade arms, and each blade arm end is equipped with an annular induction structure of a corresponding shape for that stage.

[0052] The five-stage impeller blades are evenly distributed axially. The axial spacing between adjacent stages is determined by dividing the effective liquid level in the mixing tank equally to ensure that the action area of ​​each stage of the impeller basically covers the entire liquid column height in the tank axially, avoiding axial mixing blind zones. The blade arms of each stage of the impeller are staggered at a certain angle in the circumferential direction, so that the wake regions of the blades at different height levels are complementary in the circumferential direction, further improving the spatial uniformity of the flow field.

[0053] The different shapes of the various levels of annular induced structures result in variations in the wake vortex structures and local shear characteristics they generate: elliptical rings exhibit directional shear characteristics in the direction of rotation; rectangular and square rings produce strong local turbulent separation at their corners; circular rings generate axisymmetric vortex structures; and triangular rings, due to their maximum curvature at their corners, exhibit the strongest edge shedding vortex effect. The five levels of annular induced structures of different shapes are sequentially superimposed axially, resulting in diverse composite vortex morphologies at each height level. The superposition and interference of these vortex structures further enriches the turbulent structure of the entire channel flow field, helping to break up stable macroscopic circulation patterns and eliminate local flow dead zones.

[0054] This embodiment is applicable to liquid-liquid multiphase systems and liquid-solid suspension systems that require high mixing uniformity, and is especially suitable for stirring conditions with high effective liquid level and high axial mixing resistance.

[0055] Example 9:

[0056] The main content of this embodiment is the same as any one of embodiments 1 to 8, wherein one or more baffles are provided in the stirring tank 1 to suppress the overall rotating flow and enhance the local turbulent disturbance.

[0057] Example 10:

[0058] This embodiment is similar in main content to any one of embodiments 1 to 9, and further includes a torque sensor 5, a torque acquisition device 6, and a data processing terminal 7. The torque sensor 5 is mounted on the stirring shaft 3 and is used to collect torque signals during the rotation of the impeller. The torque acquisition device 6 is electrically connected to the torque sensor 5 and transmits the signals to the data processing terminal 7.

[0059] Example 11:

[0060] This embodiment provides a fluid mixing method, employing the apparatus described in any one of Embodiments 1 to 10 to mix liquid-liquid, liquid-solid, or gas-liquid multiphase systems. The annular induction structure 403 generates a composite vortex in the impeller wake region. Utilizing the composite vortex and the bottom vortex induced at the bottom of the mixing tank, axial circulation and interface renewal of the fluid are enhanced, thereby shortening the mixing time and improving mixing uniformity.

[0061] See Figure 5 To verify the technical effectiveness of this embodiment, computational fluid dynamics (CFD) was used to numerically simulate the flow field structure inside the stirred tank, and the simulation was compared with that of a traditional impeller. Figure 5As shown in the three-dimensional streamline tracing view, under the operating conditions of the ring impeller, the streamlines within the stirred tank exhibit a significant composite flow pattern coupled with helical upward movement and radial diffusion. Notably, a distinct concentric helical streamline structure can be observed at the bottom of the stirred tank, indicating that the ring impeller induces a stable bottom vortex. The presence of this bottom vortex drives the stagnant fluid at the bottom to continuously rise, effectively connecting with the circulating flow in the upper and middle sections, thereby eliminating the low-speed stagnation zone commonly found at the bottom of the tank under traditional impeller operation. Figure 5 As shown in the turbulent kinetic energy distribution cloud map (b), using normalized turbulent kinetic energy as the characterizing quantity, the high turbulent kinetic energy region within the ring-type impeller agitator is not only concentrated near the impeller blades but also extends significantly towards the agitator wall and bottom. A large area of ​​medium-to-high turbulent kinetic energy distribution exists between adjacent impeller stages, indicating that the ring structure induces highly irregular composite vortex structures between adjacent blades, effectively compensating for the low turbulence intensity between traditional multi-stage impellers. Simultaneously, the turbulent kinetic energy level near the agitator wall is significantly higher than that of traditional impellers, indicating that the radial disturbance range of the fluid by the ring-type impeller is significantly expanded.

[0062] The simulation results show that the introduction of the pull ring structure, without changing the main structure of the mixing tank and the drive system, achieves an overall improvement in the turbulence intensity of the flow field throughout the entire tank by actively controlling the blade wake morphology. The effect is particularly significant in strengthening the bottom vortex and forming the composite vortex structure between adjacent blades, thereby effectively shortening the mixing time and improving the mixing uniformity.

[0063] Example 12:

[0064] The main content of this embodiment is the same as any one of embodiments 1 to 11. See also... Figure 6 To further verify the mixing performance of the ring-pulling impeller in high-viscosity systems, numerical simulations and experimental comparisons were conducted on the mixing processes of ordinary stirring impellers and ring-pulling impellers under the same high-viscosity single-phase materials and operating conditions.

[0065] Under the same high-viscosity single-phase material and operating conditions, the mixing processes of a conventional agitator and a ring-pulling impeller were compared. Simulation monitoring results show that, using the stabilization of pressure fluctuations at monitoring points during mixing as the criterion for a stable mixing state, the ring-pulling impeller exhibits a faster rate of pressure fluctuation amplitude decay than the conventional agitator, reaching a stable pressure state at approximately 15,000 calculation steps; the conventional agitator reaches a stable pressure state at approximately 20,000 calculation steps. These results indicate that the ring-pulling impeller can more quickly reduce localized pressure fluctuations in high-viscosity systems, leading to earlier stabilization of the material flow.

[0066] A comparative experiment was conducted on mixing time under the same material system and stirring conditions. The results showed that a conventional agitator required 60 minutes to reach the target mixing state, while a ring-pulling agitator required 45 minutes to reach the same or similar target mixing state. Compared to a conventional agitator, the ring-pulling agitator can shorten the mixing time by approximately 15 minutes. This indicates that the ring-pulling agitator can improve material turnover and mixing efficiency, and shorten the time required to reach a stable mixing state in high-viscosity systems.

[0067] Example 13:

[0068] The main content of this embodiment is the same as any one of embodiments 1 to 12. See also... Figure 7 This embodiment compares the effects of a conventional blade PBT and a ring-type impeller in laminar mixing of high-viscosity systems. The conventional blade PBT primarily relies on inclined blades to drive basic circulation within the channel, achieving overall material circulation, but its local fluid renewal and tensile / shear effects are relatively limited. In contrast, the ring-type impeller features a ring structure at the blade tip, inducing secondary eddies during rotation, enhancing local tensile, shear, and interfacial renewal effects, allowing high-viscosity materials to achieve more thorough disturbance and circulation exchange in laminar flow. Therefore, under conditions requiring similar mixing performance, the ring-type impeller requires a shorter mixing time and is suitable for high-viscosity systems where high mixing efficiency and local renewal capabilities are required.

Claims

1. A ring-shaped paddle mixing device with an annular induction structure, characterized in that: It includes a stirring tank (1), a drive mechanism (2), a stirring shaft (3), and at least one set of ring blades (4) mounted on the stirring shaft (3); the drive motor (2) drives the ring blades (4) to rotate through the stirring shaft (3), thereby forming a circulating flow in the stirring tank (1); The ring-shaped blade (4) includes a central hub (401) and at least two blade arms (402) extending radially from the central hub (401); the ends of the blade arms (402) are provided with annular induction structures (403); the annular induction structure (403) is an annular body; the cross-sectional profile of the annular body forms a closed curve or a non-closed curve with an opening; when the blade rotates, the annular induction structure (403) changes the blade wake structure and generates a composite vortex in the fluid to enhance fluid mixing.

2. The ring-shaped paddle mixing device with an annular induction structure according to claim 1, characterized in that: The cross-sectional profile of the annular guiding structure (403) is any one of the following: circular, elliptical, polygonal, C-shaped, U-shaped, notched ring, spiral open ring, or irregular closed curve, or a combination of the above shapes; wherein the notched ring is detachably connected to the end of the blade arm in the form of a snap fastener; the annular guiding structures at the ends of different blade arms in the same device may adopt the same or different profile shapes.

3. The ring-shaped paddle mixing device with an annular induction structure according to claim 1, characterized in that: The outer diameter of the annular induction structure (403) is 0.1 to 0.5 times the diameter of the blade.

4. The ring-shaped paddle mixing device with an annular induction structure according to claim 1, characterized in that: There is an installation angle between the annular induction structure (403) and the plane of the blade arm (402); the installation angle ranges from 5° to 60°.

5. The ring-shaped paddle mixing device with an annular induction structure according to claim 1, characterized in that: The annular induction structure (403) is connected to the end of the blade arm (402) in a fixed, detachable or hinged adjustable manner.

6. The ring-shaped paddle mixing device with an annular induction structure according to claim 1, characterized in that: The material of the annular induction structure (403) can be any one of rigid material, elastic material or flexible material.

7. A ring-shaped paddle mixing device with an annular induction structure according to claim 1, characterized in that: The pull ring blade (4) is configured as a multi-stage blade structure with two or more stages along the stirring shaft (3); the number of blade arms, the shape of the annular induction structure, or the installation angle of adjacent blade stages are the same or different.

8. The ring-shaped paddle mixing device with an annular induction structure according to claim 1, characterized in that: One or more baffles are provided in the stirring tank (1) to suppress the overall rotating flow and enhance the local turbulent disturbance.

9. A ring-shaped paddle mixing device with an annular induction structure according to claim 1, characterized in that: It also includes a torque sensor (5), a torque acquisition device (6), and a data processing terminal (7); the torque sensor (5) is installed on the stirring shaft (3) and is used to collect torque signals during the rotation of the blades; the torque acquisition device (6) is electrically connected to the torque sensor (5) and transmits the signal to the data processing terminal (7).

10. A fluid mixing method, characterized in that, The apparatus described in any one of claims 1 to 9 is used to mix liquid-liquid, liquid-solid, or gas-liquid multiphase systems; the annular induced structure (403) generates a composite vortex in the blade wake region; the composite vortex and the bottom vortex induced at the bottom of the mixing tank are used to enhance the axial circulation and interface renewal of the fluid, thereby shortening the mixing time and improving the mixing uniformity.

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