Venturi device based on vortex analysis and optimization design method

Abstract

The invention discloses a venturi device based on vortex analysis and an optimization design method.The venturi device comprises a water inlet pipe, a contraction pipe, a fertilizer mixing cavity, a diffusion pipe and a water outlet pipe which are sequentially arranged in the main flow direction, an absorption pipe is obliquely arranged at the top of the fertilizer mixing cavity, the diffusion pipe is of a symmetrically-distributed double-arc-shaped structure and diffuses along an arc, and the contraction pipe is connected with the water outlet pipe; flow deflectors are symmetrically mounted in the diffusion pipe, and the fertilizer mixing cavity, the diffusion pipe and the water outlet pipe are coaxially arranged. The venturi device provided by the invention can effectively prevent liquid in the water outlet pipe from flowing back through the cooperation of the double-arc-shaped diffusion pipe, the flow deflector and the inclined absorption pipe, reduces the possibility that vortexes develop towards the fertilizer mixing cavity, protects the stability of a throat negative pressure area, and improves the throat negative pressure utilization efficiency; the fertilizer mixing cavity, the diffusion pipe and the water outlet pipe are coaxially arranged, so that liquid in the shrinkage pipe and the absorption pipe can be effectively prevented from generating deflection flow after being mixed in the fertilizer mixing cavity, cavitation caused by deflection flow and the vortex area and strength are reduced, and the mixed liquid is uniformly diffused.

Description

Technical Field

[0001] The invention relates to a Venturi device and an optimization design method, and in particular to a Venturi device and an optimization design method based on vortex analysis. Background Art

[0002] Under the background of modern agricultural development and high-standard farmland construction, the promotion and application of water-fertilizer integration technology is conducive to saving water and fertilizer and improving the efficiency of water and fertilizer utilization. Water-fertilizer mixing equipment is the carrier for realizing water-fertilizer integration technology. Its structural form and parameters have an important influence on its vortex characteristics and working performance, which in turn can affect the irrigation quality. The Venturi device has a simple structure, low cost, and is easy to use, and is widely used. However, the existing Venturi device has problems such as small fertilizer absorption and large head loss. Reasonable analysis methods and structural design schemes are conducive to improving the working performance of the Venturi device.

[0003] In order to improve the working performance of the Venturi device, a large number of studies have focused on optimizing design methods and innovative designs of structural forms and structural parameters, which can effectively improve the working performance of the Venturi device. For example, the invention patents "A Venturi Fertilizer Optimization Design Method Based on AI Algorithm and Working Requirements" (CN109863868B) and "Structural Optimization Method of Venturi Fertilizer" (CN102630426A) use AI technology combined with computational fluid dynamics software such as Fluent to interact, and propose an optimization design method for the structural parameters of the Venturi device, realizing design automation.

[0004] Existing studies have shown that laminar mixing in vortices can produce large head losses. However, existing studies rarely analyze the response relationship between the structural characteristics, vortex characteristics, and working performance of the Venturi device. The influence of vortex characteristics (vortex size and position) on working performance is still unclear. Summary of the invention

[0005] Purpose of the invention: The purpose of the invention is to propose a Venturi device and an optimization design method based on vortex analysis to improve the working performance of the Venturi device.

[0006] Technical solution: The present invention includes an inlet pipe, a contraction pipe, a fertilizer mixing chamber, a diffusion pipe and a water outlet pipe which are sequentially arranged along the mainstream direction. An absorption pipe is inclined at the top of the fertilizer mixing chamber. The diffusion pipe adopts a symmetrically distributed double-arc structure and diffuses along the arc. Guide plates are symmetrically installed inside the diffusion pipe. The fertilizer mixing chamber, the diffusion pipe and the water outlet pipe are coaxially arranged.

[0007] The arc radius of the diffuser is between 240 and 290 mm, which is conducive to the stable flow of the fluid and can effectively increase the distance from the boundary of the vortex in the diffuser section to the mixing chamber, thereby reducing the influence of the vortex on the negative pressure utilization rate of the mixing chamber, improving the negative pressure utilization efficiency of the mixing chamber, and reducing the probability of vortex generation.

[0008] The spacing between the small ends of the diffusion tubes is equal to the diameter of the fertilizer mixing chamber, and the spacing between the large ends of the diffusion tubes is equal to the diameter of the water outlet pipe.

[0009] The guide plate is installed at 3 / 4 to 3 / 5 of the inside of the diffuser, and the installation angle of the guide plate is 4° to 8°. The guide plate can guide the flow direction of the mixed liquid in the diffuser, prevent the formation of large vortices in the diffuser, reduce the area and intensity of the vortex, and thus reduce the local head loss caused by the large vortex; at the same time, it can prevent the liquid in the outlet pipe from flowing back to a certain extent, invading the negative pressure area of ​​the throat, and improving the negative pressure utilization efficiency.

[0010] The water inlet pipe, the contraction pipe and the fertilizer mixing chamber are connected in sequence, and the bottom projections are arranged flush, which is beneficial to reducing the change in the flow direction of the mainstream fluid before entering the fertilizer mixing chamber, and further beneficial to reducing the head loss.

[0011] The shrink tube shrinks on one side, and the shrink tube angle range is about 40°. A reasonable shrink angle can reduce the head loss along the way and control the local head loss.

[0012] The large end of the shrinkable tube has a diameter equal to that of the water inlet pipe, and the small end of the shrinkable tube has a diameter equal to that of the fertilizer mixing chamber.

[0013] The diameter of the fertilizer mixing chamber is 6-8 mm, which is beneficial to improving the utilization efficiency of the negative pressure of the fertilizer mixing chamber.

[0014] The installation angle of the absorption tube is greater than 90°, which reduces the angle at which the liquid in the absorption tube enters the fertilizer mixing chamber, reduces the change in direction of the fluid, and is beneficial to reducing local head loss.

[0015] An optimization design method for a Venturi structure comprises the following steps:

[0016] Display the flow field of the Venturi device, including pressure distribution cloud map, velocity distribution cloud map, turbulent kinetic energy distribution cloud map, etc.;

[0017] Analyze the response relationship between the flow field distribution characteristics of the Venturi device and the working performance and the vortex characteristics: establish a mathematical model of the vortex characteristics, working performance, structural form and structural parameters of the Venturi device, and analyze the response relationship between the vortex characteristics and working performance and the key structural parameters of the Venturi device;

[0018] A structural optimization design scheme is proposed: according to the vortex position and characteristics in the Venturi device, the contraction section is designed as a single-side contraction, the diffusion section is designed as a double-arc structure, and a guide vane is installed in the diffusion section to establish the above-mentioned Venturi device model;

[0019] Compare the flow field distribution characteristics and working performance of the Venturi device before and after optimization, and compare the analysis results with the analysis results of the previous Venturi device to analyze the differences in vortex characteristics and working performance;

[0020] If the vortex is reduced, moves away from the throat or disappears, and the working performance is improved, the structural parameters of the Venturi device are output, otherwise the structure is optimized again until the requirements are met.

[0021] Beneficial effects: The present invention has the following advantages:

[0022] (1) The coaxial arrangement of the fertilizer mixing chamber, the diffusion tube and the water outlet pipe can effectively prevent the liquid in the contraction tube and the absorption tube from flowing obliquely after mixing in the fertilizer mixing chamber, thereby reducing the cavitation and vortex area and intensity caused by the oblique flow; making the mixed liquid diffuse evenly, reducing the head loss caused by the spinning vortex in the diffusion section and improving the phenomenon of uneven mixing of water and fertilizer;

[0023] (2) The diffuser adopts a symmetrically distributed double-arc structure, which is conducive to the stable flow of the fluid and can effectively increase the distance from the boundary of the vortex in the diffuser section to the mixing chamber, thereby reducing the influence of the vortex on the utilization rate of the negative pressure of the mixing chamber, improving the utilization efficiency of the negative pressure of the mixing chamber, and reducing the probability of vortex generation;

[0024] (3) The guide vane can guide the flow direction of the mixed liquid in the diffuser, prevent the formation of large vortices in the diffuser, reduce the vortex area and intensity, and thus reduce the local head loss caused by the large vortex; at the same time, it can prevent the liquid in the outlet pipe from flowing back to a certain extent, invading the throat negative pressure area, and improving the negative pressure utilization efficiency;

[0025] (4) The setting of the absorption tube greater than 90° reduces the angle of the liquid in the absorption tube entering the mixing chamber, reduces the change of direction of the fluid, reduces the mixing and friction between the flow layers, and thus helps to reduce the local head loss;

[0026] (5) The coordination of the double arc diffuser, guide plate, and oblique absorption tube can effectively prevent the backflow of liquid in the outlet pipe, reduce the possibility of the vortex developing into the mixing chamber, protect the stability of the throat negative pressure area, and improve the utilization efficiency of the throat negative pressure. It can effectively reduce the vortex area by more than 28.41% and the vortex intensity by more than 6.64%;

[0027] (6) The water inlet pipe, the contraction pipe, and the mixing chamber of the venturi device provided by the present invention are arranged flush with each other in horizontal projection, which is beneficial to reducing the angle of change of the mainstream flow direction and further beneficial to reducing the head loss;

[0028] (7) By establishing a mathematical model of the response relationship between the structural form, parameter range, vortex characteristics, and working performance, the influence of the vortex characteristics on the working performance of the Venturi device was determined. With the goal of reducing or eliminating the vortex influence and improving the working performance of the Venturi device, the optimal structural form and output parameters were obtained through optimization analysis. Compared with the existing optimization design method, from the perspective of vortex influence analysis, an effective structural design scheme for reducing the vortex influence was provided, which can effectively reduce the vortex area and improve the working performance of the Venturi device by more than 18.75%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of the Venturi device of the present invention;

[0030] Figure 2 It is a vortex analysis (flow velocity streamline) diagram of the Venturi device of the present invention;

[0031] Figure 3 is a flow chart of the present invention;

[0032] Figure 4 This is a working performance comparison chart. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings.

[0034] like Figure 1 and Figure 2 As shown, the Venturi device based on vortex analysis of the present invention comprises an inlet pipe 1, a contraction pipe 2, a fertilizer mixing chamber 3, a diffuser 4 and an outlet pipe 6 arranged in sequence along the mainstream direction. The inlet pipe 1, the contraction pipe 2 and the fertilizer mixing chamber 3 are connected in sequence, and the bottom projection is arranged flush, which is conducive to reducing the change of the flow direction of the fluid before the mainstream enters the fertilizer mixing chamber 3, and further helps to reduce the head loss. The contraction pipe 2 only contracts along a straight line on one side, and the angle range of the contraction pipe 2 is about 40°. A reasonable contraction angle can reduce the head loss along the way and control the local head loss; the large end of the contraction pipe 2 is equal to the diameter of the water inlet pipe 1, and the small end of the contraction pipe 2 is equal to the diameter of the fertilizer mixing chamber 3. The diameter of the fertilizer mixing chamber 3 is 6-8mm, which is conducive to improving the negative pressure utilization efficiency of the fertilizer mixing chamber 3. The top of the fertilizer mixing chamber 3 is inclined with an absorption pipe 7, and the installation angle of the absorption pipe 7 is greater than 90°, which reduces the angle of the liquid in the absorption pipe 7 entering the fertilizer mixing chamber 3, reduces the change of direction of the fluid, and thus helps to reduce the local head loss.

[0035] The outlet of the mixing chamber 3 is connected to the diffuser 4, and the outlet of the diffuser 4 is connected to the water outlet pipe 6, wherein the diffuser 4 adopts a symmetrically distributed double-arc structure and diffuses along the arc with an arc radius of 240 to 290 mm, which is conducive to the stable flow of the fluid and can effectively increase the distance from the boundary of the vortex in the diffusion section to the mixing chamber, thereby reducing the influence of the vortex on the negative pressure utilization rate of the mixing chamber, improving the negative pressure utilization efficiency of the mixing chamber, and reducing the probability of vortex generation; the spacing between the small ends of the diffuser 4 is equal to the diameter of the mixing chamber 3, and the spacing between the large ends of the diffuser 4 is equal to the diameter of the water outlet pipe 6.

[0036] The fertilizer mixing chamber 3, the diffusion tube 4 and the water outlet pipe 6 are arranged coaxially, which can effectively prevent the liquid in the contraction tube and the absorption tube from generating skewed flow after mixing in the fertilizer mixing chamber, thereby reducing the cavitation and vortex area and intensity caused by the skewed flow; making the mixed liquid diffuse evenly, reducing the head loss caused by the spinning vortex in the diffusion section and improving the phenomenon of uneven mixing of water and fertilizer.

[0037] An upper guide vane 5-1 and a lower guide vane 5-2 are symmetrically installed at 3 / 4 to 3 / 5 inside the diffuser 4. The guide vanes can be produced by 3D printing or integrating with the venturi device through a specific mold. The installation angle of the guide vanes is 4° to 8°. The guide vanes can guide the flow direction of the mixed liquid in the diffuser 4, prevent the formation of a large vortex in the diffuser 4, reduce the vortex area and intensity, and thereby reduce the local head loss caused by the large vortex; at the same time, it can prevent the liquid in the outlet pipe 6 from flowing back to a certain extent, intruding the throat negative pressure area, and improving the negative pressure utilization efficiency.

[0038] The venturi device provided by the present invention can effectively prevent the backflow of liquid in the water outlet pipe and reduce the possibility of the vortex developing into the mixing chamber through the cooperation of the double arc diffuser, the guide plate and the oblique absorption tube, protect the stability of the throat negative pressure area, and improve the utilization efficiency of the throat negative pressure, wherein the vortex area can be effectively reduced by more than 28.41% and the vortex intensity can be reduced by more than 6.64%.

[0039] The present invention establishes a mathematical model of the response relationship between the structural form, parameter range, vortex characteristics, and working performance, and determines the influence of vortex characteristics on the working performance of the Venturi device. With the goal of reducing or eliminating the vortex influence and improving the working performance of the Venturi device, the optimal structural form and output parameters are obtained through optimization analysis. Compared with the existing optimization design method, from the analysis of vortex influence, an effective structural design scheme for reducing the vortex influence is provided, which can effectively reduce the vortex area and improve the working performance of the Venturi device by more than 18.75%. Figure 4 shown.

[0040] like Figure 3 As shown, the optimization design method of the Venturi device based on vortex analysis of the present invention can effectively reduce or eliminate the vortex effect of the Venturi device and improve its working performance, and specifically includes the following steps:

[0041] S1. The flow field display of the Venturi device is realized by means of flow field visualization technology; the flow field display includes pressure distribution cloud map, velocity distribution cloud map, turbulent kinetic energy distribution cloud map, etc.

[0042] S2. Analyze the response relationship between the flow field distribution characteristics and working performance of the Venturi device and the vortex characteristics; specifically: establish a mathematical model of the vortex characteristics, working performance, structural form, and structural parameters of the Venturi device, and analyze the response relationship between the vortex characteristics and working performance and the key structural parameters of the Venturi device (contraction tube angle, diffusion tube curvature, mixing tube diameter, absorption tube direction, guide vane position and angle);

[0043] The vortex characteristics include: vortex intensity, vortex area, distance between the vortex and the mixing chamber, vortex center position, etc., among which the vortex area, distance between the vortex and the mixing chamber, and vortex center position can be observed through numerical simulation or particle imaging, and the vortex intensity can be calculated using the existing vortex intensity calculation formula;

[0044] Working performance includes: fertilizer absorption flow, fertilizer absorption efficiency, head loss and other conventional performance indicators;

[0045] The structural forms include: symmetrical, asymmetrical, arc-shaped structures, etc. The structural parameters include: Figure 1 Structural parameters marked in ;

[0046] The mathematical model can be established using related technologies such as nonlinear regression or structural equation modeling. The model is mainly used to show whether there is correlation between vortex characteristics, working performance, structural parameters, and structural forms, the size of the correlation, the size of the influence, and other relationships.

[0047] S3. Propose a structural optimization design plan: According to the vortex position and characteristics in the Venturi device, the contraction section is designed to be single-sided contraction, the diffusion section is designed to be a double-arc structure, and two guide vanes are installed in the diffusion section to establish a new Venturi device model;

[0048] S4, comparing the flow field distribution characteristics and working performance of the Venturi device before and after optimization, comparing the analysis results in S4 with the analysis results in S2, and analyzing the vortex characteristics and working performance differences;

[0049] S5, judgment: if the vortex is reduced, away from the throat or the vortex disappears (the flow state of the Venturi device is more stable), and the working performance is improved, then enter S6; otherwise, repeat S3 to S5 until entering S6;

[0050] S6. Output the structural parameters of the Venturi device, including the contraction tube angle, the diffusion tube curvature, the fertilizer mixing tube diameter, the absorption tube direction, the diffusion tube curvature, etc., and output the response relationship between the structural parameters and the vortex characteristics and working performance of the Venturi device.

[0051] Taking the Venturi device with D1=D2=25mm as an example, a 3D model is established, and the distribution of cloud maps such as pressure, flow velocity streamlines, and turbulent kinetic energy is analyzed by means of numerical simulation or particle imaging technology; the flow field distribution characteristics of the Venturi device and the response relationship of the working performance to the vortex characteristics are analyzed, and a mathematical model of the vortex characteristics, working performance, structural form, and structural parameters of the Venturi device is established, and the response relationship between the vortex characteristics and working performance and the key structural parameters of the Venturi device is analyzed; the key structural parameters include the contraction tube angle α, which is selected to be about 40° , the curvature of the diffuser R = 240 ~ 290mm, the diameter of the fertilizer mixing chamber d = 6 ~ 8mm, the direction of the absorption tube β>90°, the position of the guide plate is 3 / 4 of the diffuser, and the angle is 4° ~ 8°; the relationship between the vortex characteristics and the working performance is analyzed by correlation, and the flow field comparison and working performance comparison can be directly carried out; the flow field comparison mainly compares the flow velocity streamline cloud map to observe whether there is a vortex, the size of the vortex, whether the vortex is far away from the fertilizer mixing chamber, etc.; the working performance comparison mainly compares the parameters such as fertilizer absorption flow rate, fertilizer absorption efficiency, and fertilizer mixing concentration under the same working conditions.

Claims

1. A Venturi device based on vortex analysis, characterized in that: It includes an inlet pipe, a contraction pipe, a fertilizer mixing chamber, a diffusion pipe and a water outlet pipe which are arranged in sequence along the mainstream direction. An absorption pipe is inclined on the top of the fertilizer mixing chamber. The diffusion pipe adopts a symmetrically distributed double-arc structure and diffuses along the arc. Guide plates are symmetrically installed inside the diffusion pipe. The fertilizer mixing chamber, the diffusion pipe and the water outlet pipe are arranged on the same axis.

2. A Venturi device based on vortex analysis according to claim 1, characterized in that: The arc radius of the diffusion tube is between 240 and 290 mm.

3. A Venturi device based on vortex analysis according to claim 1 or 2, characterized in that: The spacing between the small ends of the diffusion tubes is equal to the diameter of the fertilizer mixing chamber, and the spacing between the large ends of the diffusion tubes is equal to the diameter of the water outlet pipe.

4. A Venturi device based on vortex analysis according to claim 1, characterized in that: The guide vane is installed at 3 / 4 to 3 / 5 of the inside of the diffuser, and the installation angle of the guide vane is 4° to 8°.

5. A Venturi device based on vortex analysis according to claim 1, characterized in that: The water inlet pipe, the contraction pipe and the fertilizer mixing chamber are connected in sequence, and the bottom projections are arranged flush.

6. A Venturi device based on vortex analysis according to claim 1 or 5, characterized in that: The shrink tube shrinks on one side, and the shrink tube angle range is about 40°.

7. A Venturi device based on vortex analysis according to claim 6, characterized in that: The large end of the shrinkable tube has a diameter equal to that of the water inlet pipe, and the small end of the shrinkable tube has a diameter equal to that of the fertilizer mixing chamber.

8. A Venturi device based on vortex analysis according to claim 5, characterized in that: The diameter of the fertilizer mixing cavity is 6-8 mm.

9. A Venturi device based on vortex analysis according to claim 1, characterized in that: The installation angle of the absorber tube is greater than 90°.

10. An optimization design method for a Venturi structure according to any one of claims 1 to 9, comprising the following steps: Conduct flow field demonstration on the Venturi device; Analyze the response relationship between the flow field distribution characteristics of the Venturi device and the working performance and the vortex characteristics: establish a mathematical model of the vortex characteristics, working performance, structural form and structural parameters of the Venturi device, and analyze the response relationship between the vortex characteristics and working performance and the key structural parameters of the Venturi device; A structural optimization design scheme is proposed: according to the vortex position and characteristics in the Venturi device, the contraction section is designed as a single-side contraction, the diffusion section is designed as a double-arc structure, and a guide vane is installed in the diffusion section to establish the above-mentioned Venturi device model; Compare the flow field distribution characteristics and working performance of the Venturi device before and after optimization, and compare the analysis results with the analysis results of the previous Venturi device to analyze the differences in vortex characteristics and working performance; If the vortex is reduced, moves away from the throat or disappears, and the working performance is improved, the structural parameters of the Venturi device are output, otherwise the structure is optimized again until the requirements are met.

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