Self-inspiration obliquely-sectioned venturi type stirring paddle

Abstract

The invention discloses a self-inspiration inclined section type venturi stirring paddle which comprises a hollow main shaft, a plurality of venturi tubular paddle blades are annularly arrayed on the outer wall of a gas cavity at the bottom of the hollow main shaft, each venturi tubular paddle blade sequentially comprises a contraction section, a throat part and a diffusion section in the fluid direction, an inclined section is formed in the pipe wall of each contraction section, and the inner wall of each contraction section is provided with a gas inlet. The oblique section cutting plane extends to the upstream of the throat part from the inlet end face of the contraction section, and a mounting included angle is formed between the axis of the Venturi tubular paddle and the axis of the hollow main shaft. Under the flow guide effect of the inclined section cutting plane, liquid is efficiently entrained and sucked into the contraction section; in the throat area, external air is continuously sucked in through the connecting pipe and is instantly sheared into fine and dense bubble groups by the high-speed liquid flow; meanwhile, due to the existence of the fixed mounting included angle, the gas-liquid mixture sprayed out of the diffusion section presents an obvious inclined jet flow form, and the gas-liquid mixture flows downwards and radially in a combined manner under the leading action of the gas-liquid mixture, so that a bubble group is effectively conveyed to the lower part and the peripheral area of the kettle body.

Description

TECHNICAL FIELD

[0001] The present application relates to a Venturi type stirring paddle, in particular to a self-suction air inclined profile Venturi type stirring paddle. BACKGROUND

[0002] In the industries of chemical, pharmaceutical, environmental protection and biological fermentation, etc. with gas-liquid two-phase reaction as the core, high-performance gas phase dispersion is the key to determine the reaction rate, selectivity and energy consumption. The traditional stirring combined with external air blowing system can realize gas dispersion, but has inherent shortcomings such as complex system and high energy consumption. The self-suction air type stirring paddle as a kind of high-efficiency process intensification equipment integrates gas delivery and dispersion functions in a single rotating part. It automatically sucks gas phase working medium into the liquid phase and realizes in-situ shear dispersion through the local negative pressure generated by the impeller rotation. This design eliminates the complex external gas compression and distribution system, significantly simplifies the process, and has higher energy utilization efficiency because the energy is directly used to generate negative pressure and disperse bubbles, especially suitable for occasions that need to strictly control sterile environment, prevent gas leakage or carry out intermittent pressurization reaction.

[0003] The traditional self-suction air type stirring paddle relies on high rotation speed to generate sufficient negative pressure to suck in gas. This means that in order to realize self-suction function, most of the input power is used to maintain the rotation speed to overcome the static pressure, rather than directly used for effective fluid shear and bubble dispersion. And the bubbles generated by self-suction are difficult to be evenly distributed in the tank, often need to install additional stirring paddles on the shaft to improve the gas-liquid mixing performance in the tank.

[0004] When the fluid flows through the converging section of the Venturi tube, according to the principle of continuity, its flow rate increases; according to Bernoulli's principle, the increase of fluid kinetic energy causes its static pressure to drop to the lowest at the narrowest throat, forming a local negative pressure area significantly lower than the ambient air pressure. If the low pressure area is connected to the external gas source through an independent pipeline, the external gas will be automatically sucked into the main fluid under the driving of pressure difference, thereby realizing the self-suction air process without external mechanical pressurization.

[0005] In the Venturi structure, when the fluid passes through the contraction section, the rapid increase of kinetic energy leads to a significant decrease of static pressure in the center area of the throat, forming a local strong negative pressure area. If the low pressure area is connected with the outside gas through the hollow shaft, the gas is continuously sucked into the throat under the driving of strong pressure difference, and is immediately sheared and broken into bubbles by the surrounding high-speed liquid flow, thereby realizing self-suction and dispersion of the gas. As disclosed in a Venturi type stirring paddle structure in patent CN223393307U, the structure includes a support shaft, a communication pipe, a containing cavity and other components, and self-suction gas is generated through the pressure difference generated by the Venturi structure. Although this structure can improve the gas-liquid mass transfer performance in the kettle, it is limited by the structure of the contraction section, and cannot guarantee the maximum liquid flow and the maximum gas-liquid shearing force. In addition, in the rotating process, the bubble wake vortex generated by the diffusion section of the previous paddle will affect the liquid flow into the contraction section of the next paddle, and the wake effect acting on the paddle will also significantly increase the overall power consumption. SUMMARY

[0006] The purpose of the present application is to provide a self-suction gas inclined section type Venturi stirring paddle, which can greatly increase the liquid flow into the contraction section, improve the pressure difference, enhance the gas suction efficiency, and significantly reduce the flow resistance of the fluid around the paddle. By installing the paddle at a certain angle, the paddle structure has a certain axial dispersion function, further improving the dispersion performance and energy utilization efficiency.

[0007] Technical scheme: The present application comprises a hollow main shaft, a plurality of Venturi tube-shaped paddles are arranged in an annular array on the outer wall of the gas chamber at the bottom of the hollow main shaft, the Venturi tube-shaped paddles sequentially comprise a contraction section, a throat and a diffusion section along the fluid direction, an inclined section surface is formed on the pipe wall of the contraction section, the inclined section surface extends from the inlet end surface of the contraction section to the upstream of the throat, and an installation angle is formed between the axis of the Venturi tube-shaped paddle and the axis of the hollow main shaft.

[0008] The installation angle γ is in the range of 45° to 135°, so that the outlet direction of the Venturi tube-shaped paddle is inclined downward, guiding the bubbles to diffuse to the lower part of the kettle body, and prolonging the residence time of the bubbles in the liquid phase.

[0009] The ratio d / D of the inner diameter d of the throat to the inner diameter D of the starting end of the contraction section is in the range of 1:1.5 to 1:10, so as to ensure that a significant Venturi effect is generated.

[0010] The number n of the Venturi tube-shaped paddles is greater than or equal to 2.

[0011] The inclined section surface is a plane or a curved surface.

[0012] The angle β formed by the inclined section surface and the axis of the Venturi tube-shaped paddle is in the range of 30° to 90°, so as to widen the liquid inlet range, reduce the flow resistance, and increase the liquid mass passing through the throat per unit time through the asymmetric inlet design.

[0013] The open part of the Venturi tube-shaped paddle is welded on the outer wall of the gas chamber through a connecting pipe, without a curved connecting pipeline, thereby reducing the number of parts and potential failure points, and improving structural stability and sealing performance.

[0014] The plurality of Venturi tube-shaped paddles are arranged in at least one layer along the hollow main shaft in the axial direction.

[0015] The hollow main shaft is provided with a ventilation hole at the top, and the ventilation hole is communicated with the gas chamber to provide a channel for gas suction.

[0016] A gas-liquid mixing and stirring method, comprising the following steps:

[0017] The stirring paddle is installed in the stirring kettle, the Venturi tube-shaped paddle is arranged at a preset height from the kettle bottom, and the stirring kettle is filled with liquid-phase medium to be mixed;

[0018] The stirring paddle is started, the hollow main shaft drives the Venturi tube-shaped paddle to rotate, the inclined cross section of the converging section cuts and guides the fluid in front of the side to enter the inside of the paddle;

[0019] The fluid flow increases in speed when passing through the converging section, a local negative pressure is formed at the throat, and external gas is sucked into the throat through the ventilation hole of the hollow main shaft, the gas chamber, and shearing mixing with the high-speed liquid flow to form a bubble group;

[0020] The gas-liquid mixture is discharged through the diffusion section and diffused to the lower part of the kettle body under the action of the installed angle, so that the gas-liquid mixture is uniformly mixed in the whole kettle.

[0021] Advantages: the present application has the following advantages:

[0022] (1) Under the flow guiding effect of the inclined cross section, the liquid is efficiently sucked into the converging section; in the throat area, the external gas is continuously sucked in through the connecting pipe and is instantaneously sheared and broken into a fine bubble group by the high-speed liquid flow; at the same time, due to the existence of the fixed installation angle, the gas-liquid mixture ejected from the diffusion section presents an obvious inclined jet shape, the dominant downward and radial compound flow effectively transports the bubble group to the lower part and the peripheral area of the kettle body, and forms a macroscopic circulation in the whole kettle, and no obvious dead zone or accumulation is observed, and the bubbles are uniformly distributed in the kettle. The synergistic enhancement of local and global turbulence means that the micro-mixing intensity in the whole kettle is improved as a whole;

[0023] (2) The complex support pipe and mounting seat structure are cancelled, the paddle and the main shaft are directly welded, the number of parts and potential failure points are greatly reduced, the structure is more solid and reliable, and the manufacturing and maintenance are easy;

[0024] (3) The self-suction inclined profile Venturi type stirring paddle of the present application realizes performance improvement through geometric structure optimization instead of simply relying on increasing rotating speed or power. Compared with the traditional self-suction stirring paddle and the traditional Venturi structure stirring paddle, under the same energy consumption, the self-suction inclined profile Venturi type stirring paddle can obtain better mixing and dispersion effect and has higher energy utilization efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a structure schematic diagram of the self-suction inclined profile Venturi type stirring paddle of the present application;

[0026] Figure 2 is a sectional view of the paddle blade area in Example 1;

[0027] Figure 3 is a time-averaged velocity vector diagram in Example 1;

[0028] Figure 4 is a structure schematic diagram of the paddle blade in Example 2;

[0029] Figure 5 is a time-averaged velocity vector diagram in Example 2;

[0030] Figure 6 is a turbulent kinetic energy cloud chart of the traditional Venturi type stirring paddle and Examples 1 and 2;

[0031] Figure 7 is a paddle blade model diagram of Example 3;

[0032] Figure 8 is a paddle blade air suction process diagram actually photographed in Example 3. DETAILED DESCRIPTION

[0033] The present application will be further described below in combination with the drawings.

[0034] Example 1

[0035] As shown in Figure 1 and Figure 2 , the self-suction inclined profile Venturi type stirring paddle of the present embodiment comprises a hollow main shaft 2, the bottom of the hollow main shaft 2 is connected with a gas cavity 3, the top of the hollow main shaft 2 is provided with a gas passage 1, and the gas passage 1 is communicated with the gas cavity 3. The outer wall of the gas cavity 3 is annularly arrayed with a plurality of Venturi tube type paddle blades 4, and the plurality of Venturi tube type paddle blades 4 can also be provided in multiple layers along the axial direction of the hollow main shaft 2. The opening part of each Venturi tube type paddle blade 4 is welded on the outer wall of the gas cavity 3 through a connecting pipe 8 to form an integrated rigid structure.

[0036] The Venturi tube-shaped blade 4 includes, in sequence along the fluid direction, a converging section 6, a throat section 5, and a diffusing section 7. The ratio d / D of the inner diameter d of the throat section 5 to the inner diameter D of the starting end of the converging section 6 is between 1:1.5 and 1:10, so as to ensure that a significant Venturi effect is generated. An inclined cut surface is formed on the pipe wall of the converging section 6, and the inclined cut surface extends from the inlet end surface of the converging section 6 to the upstream of the throat section 5. The inclined cut surface, like an efficient guide vane, can significantly increase the liquid inlet amount. According to Bernoulli's principle, a larger flow rate through the fixed cross section of the throat section will generate a higher flow velocity and a lower static pressure, thereby greatly enhancing the gas entraining power and the initial shear intensity, improving the gas absorption rate and generating finer initial gas bubbles.

[0037] An optimized static installation angle γ between the axis of the Venturi tube-shaped blade 4 and the axis of the hollow main shaft 2 is formed, that is, the installation angle γ between the blade axis and the stirring shaft axis. The existence of the installation angle γ makes the discharged gas-liquid mixture have optimal radial and axial velocity components, forms a strong composite circulating flow field in the tank, ensures that the fine gas bubbles are quickly transported and uniformly dispersed to each area of the tank, and effectively eliminates the mixing dead zone. The installation angle γ is in the range of 45° to 135°, and preferably in the range of 90° to 120°, that is, the outlet direction of the blade is slightly inclined downward, which helps to guide the generated bubble group to the lower part of the tank body, overcomes the tendency of the bubbles to quickly float upward due to buoyancy, prolongs the residence time and movement path of the bubbles in the liquid phase, and thereby enhances the mass transfer process.

[0038] The number n of the Venturi tube-shaped blades 4 is greater than or equal to 2, and for a conventional stirring tank, the number n is preferably in the range of 2 to 6. In the embodiment, three Venturi tube-shaped blades 4 are provided. The inclined cut surface can be a plane or a curved surface, and the angle β formed between the inclined cut surface and the axis of the Venturi tube-shaped blade 4 is in the range of 30° to 90°, and preferably in the range of 45° to 75°.

[0039] In order to evaluate the comprehensive performance of the present application, the computational fluid dynamics (CFD) numerical simulation method is used for research. The SST k-ω model is used for simulation, and the Euler-Euler multiphase flow model is used to capture the gas-liquid two-phase interface and the bubble size distribution. The number of grids is determined according to the grid independence analysis, and the Sliding Mesh method is used to process the rotation of the stirring blade. The second-order implicit method is used for time discretization, and the second-order upwind format is used for the discretization of the convection term. The calculation convergence is determined by monitoring the residual changes of the pressure, velocity, and gas holdup at key positions such as the gas suction port and the monitoring points in the tank. Generally, when the residual is less than 10⁻ 6 ⁻ , it is considered that the calculation has reached a steady state. The simulation results can be used for quantitative analysis of the tank flow field distribution, the gas absorption rate, the gas holdup distribution in the tank, the bubble size distribution, and the power consumption of the present application, and compared with those of the traditional stirring blade.

[0040] The experiment employed high-speed photography to visualize the gas-liquid two-phase flow field within a transparent stirred tank. A stirrer was installed inside a cylindrical transparent tank with a square jacket. Water was circulated within the jacket to eliminate the influence of refractive index, and a trace amount of dye was dissolved in the water to enhance the contrast between the liquid phase and the bubbles. While the stirrer rotated at a set speed, a high-frame-rate high-speed camera, combined with a high-intensity continuous light source or pulsed backlight, was used to capture high-speed frontal images of key areas, including the inlet section, throat, and diffuser section, which contain a beveled cross-section. This method directly demonstrates the synergistic effect of the beveled cross-section and fixed tilt angle in enhancing gas entrainment, improving initial bubble quality, and optimizing the overall flow field within the tank.

[0041] In this embodiment, the stirred tank has a diameter of 400mm, four 40mm wide baffles are evenly distributed on the wall, the water level is 400mm high, and the inclined Venturi-type stirring paddle is 100mm from the bottom of the tank. Figure 1 As shown, the diameter of the obliquely shaped Venturi blade is 240 mm, the diameter at the inlet of the contraction section is 70 mm, the throat diameter is 20 mm, and the diameter at the outlet of the diffuser section is 35 mm. The oblique section is a plane with an included angle β of 60°. The included angle α between the connecting pipe and the axis is 90°, and the installation angle γ is 90°. The outer diameter of the air chamber is 50 mm, the height is 20 mm, and the thickness is 10 mm. The outer diameter of the hollow main shaft is 30 mm, and the inner diameter is 20 mm. A vent hole 1 with a diameter of 10 mm is provided at the top. The stirring speed is set to 480 rpm, and the number of calculated grids is 200W. Figure 3 This is a velocity vector distribution diagram inside the vessel in Example 1. It can be seen that when the tilt angle γ = 90°, the obliquely shaped Venturi impeller exhibits a very obvious radial effect. The fluid forms relatively regular vortex circulations on both the upper and lower sides of the impeller. The oblique cut increases the liquid intake, thereby increasing the throat pressure difference. This causes the gas to be subjected to higher velocities and shear rates at the throat, resulting in the violent shearing and fragmentation of the intake gas column, directly generating a cluster of microbubbles with smaller average size and more concentrated distribution. The stirring power obtained through finite element simulation in Example 1 is 1.85 kW.

[0042] Example 2:

[0043] Figure 4 , Figure 5respectively are the stirrer configuration diagram and the velocity vector diagram in Example 2. The diameter of the stirred tank in this example is 400 mm, the wall surface is uniformly distributed with four baffles with a width of 40 mm, the liquid level of water is 400 mm, and the inclined section type Venturi type stirring paddle is 100 mm away from the tank bottom. The diameter of the inclined section type Venturi type paddle is 240 mm, the diameter at the inlet of the contraction section is 70 mm, the throat diameter is 20 mm, the diameter at the outlet of the diffusion section is 35 mm, the inclined section is a plane, the included angle β is 60°, the included angle α between the connecting pipe and the axis is 90°, and the installation included angle γ is 75°. The gas chamber has an outer diameter of 50 mm, a height of 20 mm, and a thickness of 10 mm; the hollow shaft has an outer diameter of 30 mm and an inner diameter of 20 mm; and a ventilation hole with a diameter of 10 mm is provided at the top. The stirring speed is set to 480 rpm, and the number of calculated grids is 200w. Figure 5 is the velocity vector distribution diagram in the tank in Example 2. It can be seen that when the inclination angle γ = 75°, compared with the velocity vector distribution in Example 1, after tilting the tubular paddle by a certain angle, the flow field distribution in the tank is obviously more turbulent, the formation of large circulation vortices is reduced, local mixing is more conducive to being promoted, and the residence time of gas bubbles in the tank is increased. At the same time, in Example 2, the stirring power obtained by finite element calculation under this calculation condition is 1.78 kw. The structure in Example 2 consumes less power at the same speed and has better mixing effect and gas-liquid mass transfer effect.

[0044] Figure 6 The turbulent kinetic energy distribution of the traditional Venturi stirring paddle and Examples 1 and 2 under the same working condition is compared. By comparing and analyzing the turbulent kinetic energy cloud diagram obtained by CFD numerical simulation, the structural advantages of the present application can be clearly revealed. Compared with the traditional axisymmetric Venturi stirring paddle without an inclined section, the stirring paddle of the present application exhibits significant turbulent intensity in the throat region. The numerical value of the turbulent kinetic energy in this region is higher, and the range of high turbulent kinetic energy is wider. It is directly proved that the inclined section can increase the fluid shear, effectively excite more intense and extensive turbulent fluctuations in the throat of the Venturi structure, and create superior conditions for efficient gas suction and initial fragmentation. After installing the inclined section combined with the optimized fixed inclination angle, the distribution of the turbulent kinetic energy near the paddle is optimized. The CFD results show that the high turbulent kinetic energy region is no longer limited to the vicinity of the throat, but significantly expands along the liquid discharge direction of the paddle in a larger paddle action area. This synergistic enhancement of local and global turbulence means that the microscopic mixing intensity in the whole tank is improved as a whole, which explains the excellent performance of the present application in terms of shortening the mixing time, improving the uniformity of bubble dispersion, and strengthening the mass transfer rate.

[0045] Example 3:

[0046] Figure 7 , Figure 8respectively are the model diagram and the actual picture of the air suction process in example 3. The diameter of the stirred tank in the embodiment is 200 mm, four baffles with a width of 20 mm are uniformly distributed on the wall surface, the liquid level of water is 300 mm, and the distance between the Venturi type stirring paddle and the tank bottom is 100 mm. As shown in the figure, Figure 6 the diameter of the Venturi type paddle is 100 mm, the inner diameter at the inlet of the contraction section is 30 mm, the throat diameter is 10 mm, the diameter at the outlet of the diffusion section is 25 mm, and the wall thickness of the tubular paddle is 2 mm. No inclined section is arranged, the angle between the connecting pipe and the axis is alpha=90 DEG, and the installation angle is gamma=75 DEG. The outer diameter of the gas chamber is 30 mm, the height is 14 mm, and the wall thickness of the gas chamber is 3 mm; the outer diameter of the hollow shaft is 16 mm, and the inner diameter is 14 mm; a ventilation hole with a diameter of 6 mm is arranged at the top. Figure 6 the model diagram of the paddle in example 3. Figure 7 The air suction, air exhaust and bubble dispersion process of the inclined Venturi type paddle are photographed by using a high-speed camera. With the gradual increase of the rotating speed, it can be obviously observed that the bubbles are continuously discharged from the diffusion section in the tank. By directly analyzing the continuous frame image sequence, it can be clearly observed that under the guide action of the inclined section, the liquid is efficiently sucked into the contraction section; in the throat region, the external gas is continuously sucked in through the connecting pipe and is instantaneously sheared and broken into fine bubble groups by the high-speed liquid flow; at the same time, due to the existence of the fixed installation angle, the gas-liquid mixture ejected from the diffusion section presents an obvious inclined jet shape, the dominant downward and radial compound flow effectively transports the bubble groups to the lower part and the peripheral region of the tank body, forms a macroscopic circulation in the whole tank range, and no obvious dead zone or accumulation is observed, and the bubbles are uniformly distributed in the tank.

[0047] The inclined section Venturi type paddle provided by the application can greatly improve the liquid inlet amount of the contraction section, improve the pressure difference at the throat, and further improve the gas-liquid mass transfer efficiency and the reaction rate. By adjusting the angle between the axis of the inclined section Venturi type stirring paddle and the horizontal plane, the influence of the wake of the previous paddle on the next paddle is eliminated, the resistance generated when the paddle rotates is reduced, and the power consumption is reduced. Further, the existence of the installation angle makes the distribution of the bubbles in the tank more uniform in the axial direction, greatly improves the mixing effect and the mass transfer rate of the stirring. At the same time, the paddle is directly welded with the gas chamber and the hollow shaft through the connecting pipe, which is easy to process and has a stable structure, and the manufacturing cost is reduced.

Claims

1. A self-aspirating, obliquely slanted Venturi-type stirring impeller, characterized in that, The device includes a hollow main shaft. The outer wall of the gas chamber at the bottom of the hollow main shaft is arranged in a ring with multiple Venturi tube blades. The Venturi tube blades include a constriction section, a throat, and a diffuser section in sequence along the fluid direction. The wall of the constriction section has an oblique section, which extends from the inlet end face of the constriction section to the upstream of the throat. The axis of the Venturi tube blades and the axis of the hollow main shaft are provided with an installation angle.

2. The self-aspirating, obliquely shaped Venturi-type stirring impeller according to claim 1, characterized in that, The installation angle γ is in the range of 45° to 135°.

3. The self-aspirating, obliquely shaped Venturi-type stirring impeller according to claim 1, characterized in that, The ratio of the inner diameter d of the throat to the inner diameter D of the starting end of the contraction section, d / D, is between 1:1.5 and 1:

10.

4. The self-aspirating, obliquely shaped Venturi-type stirring impeller according to claim 1, characterized in that, The number of Venturi tubular blades n≥2.

5. The self-priming, obliquely shaped Venturi-type stirring impeller according to claim 1, characterized in that, The oblique cutting surface can be a plane or a curved surface.

6. The self-aspirating, obliquely shaped Venturi-type stirring impeller according to claim 1 or 5, characterized in that, The angle β formed by the oblique section and the axis of the Venturi tube blade is between 30° and 90°.

7. The self-aspirating, obliquely shaped Venturi-type stirring impeller according to claim 1, characterized in that, The opening portion of the Venturi tubular blade is welded to the outer wall of the gas chamber via a connecting pipe.

8. The self-priming, obliquely shaped Venturi-type stirring impeller according to claim 1, characterized in that, Multiple Venturi tubular blades are arranged in at least one layer along the hollow main shaft.

9. The self-priming, obliquely shaped Venturi-type stirring impeller according to claim 1, characterized in that, The hollow spindle has a vent hole at the top, which is connected to the gas chamber.

10. A gas-liquid mixing and stirring method, characterized in that, The method of using the self-aspirating, angled Venturi-type impeller according to any one of claims 1-9 includes the following steps: Install the agitator inside the mixing vessel, so that the venturi tube blades are at a preset height from the bottom of the vessel, and fill the mixing vessel with the liquid phase medium to be mixed. When the agitator is started, the hollow main shaft drives the venturi tube blades to rotate, and the oblique section of the contraction section cuts and guides the fluid from the side front into the interior of the blades. When the fluid flows through the contraction section, the flow velocity increases, creating a local negative pressure in the throat. External gas is drawn into the throat through the vent holes and gas chambers of the hollow main shaft, where it is sheared and mixed with the high-speed liquid flow to form a group of bubbles. The gas-liquid mixture is discharged through the diffuser section and diffuses towards the lower part of the vessel under the action of the installation angle, so as to achieve uniform gas-liquid mixing throughout the vessel.

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