A method, system and storage medium for optimizing the design of a venturi contraction under free stream conditions

Abstract

The application discloses a method and system for optimizing design of a contraction section of a Venturi tube under free flow conditions and a storage medium, and belongs to the technical field of fluid machinery and stirring equipment. The technical problem to be solved is to accurately solve the hydraulic performance of the contraction section of the Venturi tube under free flow conditions, to establish a functional relationship between the acceleration ratio and the contraction ratio and to solve the optimal contraction ratio. The technical scheme is characterized in that the range of the inlet diameter of the Venturi tube is determined; a fluid calculation domain model is established, in which the inside outlet and the outside outlet of the Venturi tube are respectively set as independent pressure outlet boundaries; CFD numerical simulation is performed on the contraction section of the Venturi tube under different contraction ratios based on the fluid calculation domain model, inlet flow velocity and throat flow velocity data are obtained; the inlet deceleration ratio K1 and the pipe acceleration ratio K2 are calculated, and a functional relationship formula in which K1 and K2 change with the contraction ratio is obtained through regression analysis fitting; and the best contraction ratio under the target condition is solved according to the functional relationship formula, and size parameters are output.

Description

Technical Field

[0001] This invention relates to the field of fluid machinery and mixing equipment design technology, specifically to an optimized design method, system, and storage medium for the contraction section of a Venturi tube under free flow conditions. Background Technology

[0002] Stirring paddles are essential equipment widely used in industries such as chemical engineering and bioengineering. They provide mixing capabilities for two-phase or multi-phase materials, such as liquid-solid mixing, gas-liquid mixing, and gas-liquid-solid mixing, thereby improving chemical reaction rates and reactant utilization. In gas-liquid two-phase mixing and contact reactions, self-priming stirring paddles are widely used in fermentation, hydrogenation, oxidation, amination, and alkylation processes in industries such as food, pharmaceuticals, petroleum, and biochemistry due to their advantages including simple and reliable structure, no need for additional gas delivery equipment, low power consumption per unit volume, and high gas utilization.

[0003] The Venturi effect refers to the phenomenon that the flow velocity of a fluid increases and the static pressure decreases as it flows through the constricted section of a pipe. Based on Bernoulli's principle, as the fluid velocity increases, the pressure near it decreases, creating a local negative pressure zone. Utilizing this effect, Venturi tubes can be used as stirring components in self-priming stirring devices. By accelerating the fluid in the constricted section and generating negative pressure in the throat, gas is ejected, achieving efficient gas-liquid mixing.

[0004] In existing research, Venturi tubes, when used as hydraulic components, are primarily applied under pipe flow conditions, where the fluid is completely confined by the pipe wall. In this case, the velocity of the fluid after acceleration through the contraction section can be directly derived using the continuity equation, which can then be used for the specific dimensional design of the Venturi jet mixer. Traditional Venturi jet mixer design theories, such as Sokolov's theory, are all based on these conditions.

[0005] However, in Venturi-type self-priming mixers and other similar Venturi-type hydraulic devices, the Venturi tube rotates with the main shaft, and its inlet and outlet are completely exposed to the fluid medium. In this case, the Venturi tube can be approximated as operating under free-flow conditions. Under free-flow conditions, the fluids inside and outside the Venturi tube combine to satisfy the continuity equation: the uniform inflow slows down at the inlet section of the Venturi tube, with only a portion of the fluid flowing into the tube, while the rest flows around the outside of the tube; subsequently, the fluid flowing into the tube first accelerates through the contraction section, then slows down through the expansion section, and finally merges with the fluid outside the tube. This flow mechanism is completely different from the direct acceleration of fluid under pipe flow conditions; therefore, traditional design theories cannot be directly applied to the design of Venturi jet mixers under free-flow conditions.

[0006] A review of existing research data reveals that there is currently no detailed study on the flow characteristics of Venturi tubes under free-flow conditions. Although other hydraulic components with similar structures and flow characteristics include the duct of a hydrofoil-type propeller, whose airfoil profile can also be considered as a contraction section, their structural proportions differ significantly, and their functional roles are completely different: the Venturi tube's main function is to generate sufficient pressure differential in the contraction section to induce a second fluid, while the duct's main function is to rectify the flow and provide a uniform and stable inflow for the propeller.

[0007] Chinese patent document CN102630426B discloses a structural optimization method for a venturi fertilizer applicator. By combining CFD numerical simulation with orthogonal experimental design, the seven structural parameters of the fertilizer applicator are optimized with fertilizer absorption efficiency as the evaluation index. This method can shorten the development cycle and improve fertilizer absorption performance. However, this method is for venturi tubes under pipe flow conditions and cannot be applied to the flow characteristic analysis and optimization design of the contraction section of venturi tubes under free flow conditions.

[0008] Chinese patent document CN115043458A discloses a Venturi cavitation test system and its operation method. By setting a turbine section before the inlet of the Venturi tube and using a horn-shaped diffuser wall, the cavitation efficiency can be improved and the wall cavitation erosion can be reduced. However, the system also operates in an annular flow channel composed of closed pipes, which is a pipe flow condition. Moreover, its purpose is to generate cavitation effect for water treatment. It does not involve the research method of the hydraulic performance of the Venturi tube contraction section under free flow conditions or the establishment of the corresponding functional relationship. Summary of the Invention

[0009] The purpose of this invention is to provide:

[0010] An optimization design method, system, and storage medium for the contraction section of a Venturi tube under free-flow conditions, and related technologies, to solve technical problems such as accurately solving the hydraulic performance of the contraction section of a Venturi tube under free-flow conditions, establishing the functional relationship between the acceleration ratio and the contraction ratio, and solving for the optimal contraction ratio, or a combination thereof.

[0011] Terminology Explanation:

[0012] Unless otherwise defined, all technical terms in this document have the same meanings as commonly understood by one of ordinary skill in the art to which the subject matter of the claims pertains. Unless otherwise stated, all patents, patent inventions, and publications cited in this document are incorporated herein by reference in their entirety. If multiple definitions exist for terms in this document, the definitions in this chapter shall prevail.

[0013] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0014] Unless specifically defined herein, the use of all commercially available products herein employs standard techniques. For example, it may be carried out using the manufacturer's instructions for use with the kit, or in accordance with methods known in the art or the description of this invention. The techniques and methods described herein can generally be implemented according to conventional methods well known in the art, based on the descriptions in the various summary and more specific documents cited and discussed in this specification.

[0015] The term "Venturi" as used in this article refers to the Venturi self-priming impeller principle, which incorporates the Venturi tube structure as part of the impeller, in which the gas ejection branch is connected to the hollow main shaft. The main shaft drives the Venturi tube to rotate, and the liquid flows into the Venturi tube with the rotation of the impeller blades. After being accelerated through the contraction section, it is then ejected through the nozzle, forming a local negative pressure zone, thereby achieving gas intake.

[0016] The term "free flow condition" used in this article, in English, refers to the following: In fluid mechanics, free flow condition usually means that equipment (such as propellers, hydraulic machinery, etc.) is exposed to a uniform flow and there are no external boundary disturbances such as closed pipes or containers (similar terms: open channel flow, unpressurized flow); In contrast, pipe flow condition: the fluid is completely confined within a pipe, which is also the conventional operating condition of venturi tubes (applied to jet mixers, etc.).

[0017] According to experiments and CFD, under free flow conditions, because the Venturi inlet contraction section is a pipe with a gradually decreasing flow area, the fluid will decelerate at the Venturi inlet section and then accelerate through the contraction pipe, which is different from the direct acceleration under pipe flow conditions. From the perspective of the continuity equation, under free flow conditions, the fluid inside and outside the Venturi tube jointly satisfy the continuity equation, while under pipe flow conditions, only the fluid inside the pipe satisfies the continuity equation.

[0018] In summary, the flow conditions in the contraction section of a Venturi tube under free flow conditions are completely different from those under pipe flow conditions. Traditional design methods (such as Sokolov et al.) cannot be directly used to design Venturi jet mixers. The design methods need to be modified to take into account the working characteristics of the contraction section of the Venturi tube under free flow conditions. That is, the flow performance of the Venturi tube inlet and the contraction section under free flow conditions needs to be determined first.

[0019] In a first aspect, the present invention provides: an optimized design method for the contraction section of a Venturi tube under free-flow conditions, comprising the following steps:

[0020] S1: Determine the range of Venturi tube inlet diameters and select several inlet diameter values ​​based on the inflow velocity conditions in the application scenario;

[0021] S2: Establish a fluid computational domain model for solving the performance of the constriction section of a Venturi tube under free flow conditions. In the fluid computational domain model, the inner outlet and the outer outlet of the Venturi tube are set as independent pressure outlet boundaries.

[0022] S3: Based on the fluid computational domain model, perform CFD numerical simulation on the contraction section of the Venturi tube under different contraction ratios to obtain inlet velocity and throat velocity data;

[0023] S4: Based on the inlet velocity and throat velocity data, calculate the inlet deceleration ratio K1 and the in-pipe acceleration ratio K2, and obtain the functional relationships between K1 and K2 as a function of the contraction ratio S through regression analysis;

[0024] S5: Solve for the optimal shrinkage ratio under the target conditions based on the aforementioned functional relationship, and output the corresponding Venturi tube shrinkage section size parameters.

[0025] Further: In S2, the boundary conditions of the fluid computational domain model are set as follows: the upstream boundary is the velocity inlet boundary, and the distance between it and the venturi tube contraction section is not less than 5D; the left and right sides and the upper and lower sides are symmetry plane boundaries, and the distance between them and the venturi tube contraction section is not less than 5D; in the downstream boundary, the distance between the pressure outlet inside the venturi tube and the contraction section is not less than 16D, and the distance between the pressure outlet outside the venturi tube and the contraction section is not less than 10D; where D is the venturi tube inlet diameter.

[0026] Furthermore, S3 also includes performing CFD numerical simulations on the venturi tube contraction sections under different contraction section lengths, different incoming flow velocities, and different inlet diameters to obtain inlet flow velocity, throat flow velocity, and resistance data under each parameter condition.

[0027] Further: In S4, the inlet deceleration ratio K1 is defined as the ratio of the inlet flow velocity to the incoming flow velocity, the pipe acceleration ratio K2 is defined as the ratio of the throat flow velocity to the inlet flow velocity, and the final acceleration ratio K is defined as the product of the inlet deceleration ratio K1 and the pipe acceleration ratio K2.

[0028] Furthermore, the functional relationship is in the form of K = a·ln(S) + b, where a and b are regression coefficients, S is the shrinkage ratio, and for any liquid property, b should approach 1.

[0029] It should be noted that, under ideal conditions, when S=1, the Venturi tube does not affect the fluid, and K=1 at this time; substituting back into the formula, it can be deduced that for liquids of arbitrary density and viscosity, b in the formula should approach 1.

[0030] Furthermore: when the fluid medium is a liquid with a specific gravity close to 1 and a viscosity close to 1 cP, the functional relationship is:

[0031] K1 = -0.41118ln(S) + 0.98013;

[0032] K2 = 1.28895ln(S) + 0.98817;

[0033] The final speedup ratio K = -0.53008[ln(S)]² + 0.85702ln(S) + 0.96853;

[0034] The functional relationship is applicable within the range of 1 ≤ S ≤ 6.

[0035] Furthermore, in step S5, when the target condition is the maximum final acceleration ratio, the extreme value of the functional relationship of the final acceleration ratio K can be obtained. When the fluid medium is a liquid with a specific gravity close to 1 and a viscosity close to 1 cP, the optimal contraction ratio S = 2.24553 can be obtained, and the corresponding maximum final acceleration ratio Kmax = 1.315.

[0036] Furthermore: in S3, resistance data under various parameter conditions is also acquired; in S4, the energy consumption of the Venturi tube is calculated, which is the product of resistance and incoming flow velocity; in S5, the optimal contraction ratio is solved based on the multi-objective optimization conditions of final acceleration ratio and energy consumption.

[0037] Furthermore, in S3, the acceleration ratio performance of the venturi tube's contraction section reaches its optimal level when the length of the contraction section is equal to the throat diameter.

[0038] Furthermore, the optimal shrinkage ratio and the corresponding final acceleration ratio obtained in S5 are used to replace the acceleration ratio parameter in the traditional Venturi jet mixer design theory, and then the remaining dimensional parameters of the Venturi jet mixer are designed.

[0039] Secondly, an optimized design system for the contraction section of a Venturi tube under free-flow conditions includes:

[0040] The parameter determination module is used to determine the range of Venturi tube inlet diameters and select several inlet diameter values ​​based on the incoming flow velocity conditions in the application scenario.

[0041] The computational domain modeling module is used to establish a fluid computational domain model for solving the performance of the constriction section of a Venturi tube under free flow conditions. In the fluid computational domain model, the inner outlet and the outer outlet of the Venturi tube are set as independent pressure outlet boundaries.

[0042] The CFD simulation module is used to perform numerical simulations of the contraction section of a Venturi tube under different contraction ratios based on the fluid computational domain model, and to obtain inlet velocity and throat velocity data.

[0043] The data processing module is used to calculate the inlet deceleration ratio K1 and the in-pipe acceleration ratio K2 based on the inlet flow velocity and throat flow velocity data, and to obtain the functional relationships between K1 and K2 as a function of the contraction ratio S through regression analysis.

[0044] The optimization solution module is used to solve for the optimal shrinkage ratio under the target conditions based on the functional relationship, and output the corresponding Venturi tube shrinkage section size parameters.

[0045] Thirdly, an electronic device includes:

[0046] processor;

[0047] A memory that stores computer-executable instructions;

[0048] When the computer-executable instructions are executed by the processor, the processor performs the above-described optimization design method for the contraction section of a Venturi tube under free-flow conditions.

[0049] Fourthly, a computer-readable storage medium stores computer-executable instructions that, when executed by a processor, implement the aforementioned optimized design method for the contraction section of a Venturi tube under free-flow conditions.

[0050] The present invention has at least the following beneficial effects:

[0051] 1. This invention addresses the special working condition of free flow, which has not been extensively studied before. By designing a fluid computational domain model with independent pressure outlets inside and outside the pipe, it eliminates the interference of upstream and downstream fluids and can accurately solve the hydraulic performance of the contraction section of the Venturi tube independently, filling the gap in the study of Venturi tube flow characteristics under free flow conditions.

[0052] 2. This invention establishes a logarithmic function relationship between the inlet deceleration ratio K1 and the in-pipe acceleration ratio K2 and the contraction ratio S through CFD simulation and regression analysis, and gives specific formulas for water and similar common liquids. This relationship can directly replace the acceleration ratio parameter in the traditional design theory, and expand the application scope of the Venturi jet mixer design method from closed pipe flow conditions to open free flow conditions.

[0053] 3. This invention provides clear values ​​for the optimal shrinkage ratio and maximum acceleration ratio, and can optimize solutions for single or multiple objectives such as maximum acceleration ratio and minimum energy consumption. It provides a theoretical basis and calculation tools for the engineering design of Venturi-type self-priming stirring devices and similar hydraulic equipment, shortening the product development cycle and reducing the testing cost. Attached Figure Description

[0054] Figure 1 The flowchart illustrates an optimized design method for the contraction section of a Venturi tube under free-flow conditions, as provided by this invention.

[0055] Figure 2 The diagram shows the structure of an optimized design system for the contraction section of a Venturi tube under free-flow conditions, as provided by this invention.

[0056] Figure 3 This is a schematic diagram of the fluid computation domain model for CFD numerical simulation of the venturi tube contraction section provided in this embodiment.

[0057] Figure 4 This is a schematic diagram of the boundary conditions for the CFD numerical simulation fluid computation domain model of the venturi tube contraction section provided in this embodiment.

[0058] Figure 5 This is a schematic diagram of the process flow for an optimized design method of the contraction section of a Venturi tube under free-flow conditions provided in this embodiment.

[0059] Figure 6 This is a schematic diagram showing the calculation results of an optimized design method for the contraction section of a Venturi tube under free-flow conditions provided in this embodiment. Detailed Implementation

[0060] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0061] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0062] Example 1

[0063] This invention provides an optimized design method for the contraction section of a Venturi tube under free-flow conditions, applicable to situations where both the inner and outer walls of the Venturi tube are exposed to open, uniform flow. Under free-flow conditions, the uniform flow decelerates at the inlet section of the Venturi tube, with only a portion of the fluid flowing into the tube and accelerating through the contraction section, while the remaining fluid flows around the outside of the tube. This is completely different from the direct acceleration of fluid under pipe flow conditions. This method combines CFD numerical simulation and regression analysis to establish a functional relationship between the hydraulic performance of the contraction section and the contraction ratio, thereby solving for the optimal contraction ratio.

[0064] This method includes the following steps: S1, determining the inlet diameter range of the Venturi tube, and selecting several inlet diameter values ​​based on the incoming flow velocity conditions in the application scenario; S2, establishing a fluid computational domain model for solving the performance of the Venturi tube contraction section under free flow conditions, with the inner and outer outlets of the Venturi tube set as independent pressure outlet boundaries in the fluid computational domain model; S3, performing CFD numerical simulations on the Venturi tube contraction section under different contraction ratios based on the fluid computational domain model to obtain inlet and throat velocity data; S4, calculating the inlet deceleration ratio K1 and the inlet acceleration ratio K2 based on the inlet and throat velocity data, and fitting the functional relationships of K1 and K2 with the contraction ratio S through regression analysis; S5, solving for the optimal contraction ratio under the target conditions based on the functional relationships, and outputting the corresponding Venturi tube contraction section size parameters.

[0065] In step S1, the inlet diameter directly affects the flow rate and ejection volume entering the venturi tube. Empirically, the inlet diameter is selected within the range of 0.5% to 2% of the incoming flow velocity. Under an incoming flow velocity of 8 m / s, five diameters—30 mm, 60 mm, 80 mm, 120 mm, and 160 mm—can be selected for analysis.

[0066] In step S2, the core of the fluid computational domain model is to set independent pressure outlets inside and outside the pipe to prevent the outer fluid from squeezing or sucking the inner fluid, thereby solving the performance of the contraction section separately.

[0067] The functional relationship established through regression analysis in step S4 can be used to replace the acceleration ratio parameter in the traditional Venturi jet mixer design theory, and combined with Sokolov theory to complete the overall design.

[0068] In one specific embodiment of this example, the boundary conditions of the fluid computational domain model in step S2 are set as follows: the upstream boundary is the velocity inlet boundary, and the distance between it and the venturi tube contraction section is not less than 5D; the left and right sides and the upper and lower boundaries are symmetry plane boundaries, and the distance between them and the venturi tube contraction section is not less than 5D; in the downstream boundary, the distance between the inner pressure outlet of the venturi tube and the contraction section is not less than 16D, and the distance between the outer pressure outlet and the contraction section is not less than 10D, where D is the venturi tube inlet diameter. Maintaining a certain distance upstream and around the perimeter ensures uniform incoming flow and prevents the fluid around the outside of the tube from being disturbed, while setting a sufficiently long distance downstream ensures sufficient flow development and avoids pressure abrupt changes affecting the calculation results.

[0069] In one specific embodiment of this example, step S3 further includes performing CFD numerical simulations on the venturi tube contraction sections under different contraction section lengths, different incoming flow velocities, and different inlet diameters to obtain inlet flow velocity, throat flow velocity, and resistance data under each parameter condition. Multi-parameter simulation allows for a comprehensive analysis of the influence of various factors on the performance of the contraction section.

[0070] In one specific embodiment of this example, in step S4, the inlet deceleration ratio K1 is defined as the ratio of the inlet flow velocity to the incoming flow velocity, the pipe acceleration ratio K2 is defined as the ratio of the throat flow velocity to the inlet flow velocity, and the final acceleration ratio K is defined as the product of K1 and K2, that is, K = K1 × K2 = throat flow velocity / incoming flow velocity.

[0071] In one specific embodiment of this example, the functional relationship is in the form of K = a·ln(S) + b, where a and b are regression coefficients, and S is the contraction ratio, i.e., the area ratio of the venturi inlet to the throat. When the contraction ratio S = 1, there is no contraction, the contraction section has almost no effect on the fluid, and both the deceleration ratio and the acceleration ratio are 1, so b approaches 1.

[0072] In one specific embodiment of this example, when the fluid medium is a liquid with a specific gravity close to 1 and a viscosity close to 1 cP, the functional relationship is: K1 = -0.41118ln(S) + 0.98013, K2 = 1.28895ln(S) + 0.98817, and the final acceleration ratio K = -0.53008[ln(S)]² + 0.85702ln(S) + 0.96853. The above relationship has good accuracy within the range of 1 ≤ S ≤ 6. This relationship was obtained through extensive CFD iterative calculations and is not an obvious result.

[0073] In one specific embodiment of this example, when the target condition is the maximum final acceleration ratio, the final acceleration ratio K is a quadratic function of ln(S). Finding its extreme value yields a maximum value Kmax = 1.315, which is reached when ln(S) = 0.80886, i.e., S = 2.24553. That is, when the venturi tube operates under free-flow conditions and the fluid is water at normal temperature and pressure, the final acceleration ratio reaches its maximum when the contraction ratio is 2.24553.

[0074] In one specific embodiment of this example, step S3 further acquires resistance data under various parameter conditions, step S4 further calculates the venturi tube energy consumption, which is the product of resistance and incoming flow velocity, and step S5 solves for the optimal contraction ratio based on the multi-objective optimization conditions of the final acceleration ratio and energy consumption. Multi-objective optimization can achieve a balance between acceleration performance and energy consumption.

[0075] In one specific embodiment of this example, in step S3, the acceleration ratio performance of the venturi tube's contraction section reaches its optimal level when the length of the contraction section is equal to the throat diameter.

[0076] In one specific embodiment of this example, the optimal contraction ratio and the corresponding final acceleration ratio obtained in step S5 are used to replace the acceleration ratio parameter in the traditional Venturi jet mixer design theory, and then the remaining dimensional parameters of the Venturi jet mixer are designed, thereby extending the applicability of the traditional design method from pipe flow conditions to free flow conditions.

[0077] Example 2

[0078] This invention also provides an optimization design system for the contraction section of a Venturi tube under free-flow conditions, including a parameter determination module, a computational domain modeling module, a CFD simulation module, a data processing module, and an optimization solution module. The parameter determination module determines the inlet diameter range and selects the inlet diameter value based on the incoming flow velocity conditions. The computational domain modeling module establishes a fluid computational domain model, where the inner and outer outlets of the Venturi tube are set as independent pressure outlet boundaries. The CFD simulation module performs numerical simulations to obtain flow velocity data for different contraction ratios. The data processing module calculates K1 and K2 and fits the functional relationship. The optimization solution module solves for the optimal contraction ratio and outputs the dimensional parameters. These modules work collaboratively to automate the execution of the above method.

[0079] Example 3

[0080] The present invention also provides an electronic device, including a processor and a memory, wherein the memory stores computer-executable instructions, and when the computer-executable instructions are executed by the processor, the processor executes the above-described optimization design method.

[0081] Example 4

[0082] The present invention also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described optimized design method.

[0083] Example 5

[0084] This embodiment provides an optimized design method for the contraction section of a Venturi tube; in particular, the method is applicable to Venturi tubes operating under free-flow conditions, i.e., both the inner and outer walls of the Venturi tube are placed in an open, uniform inflow.

[0085] The basic process of this method is as follows:

[0086] 1. Determining the Venturi tube inlet diameter range: Under free flow conditions, the size of the Venturi tube inlet diameter directly affects the flow rate entering the Venturi tube, and thus affects the ejection volume of the jet mixer; for the Venturi-type self-priming agitator described in CN119034568A, it also directly affects the power consumption of the agitator; currently, there is no discussion or optimal solution for the selection of the inlet diameter, and it needs to be selected based on the conditions and constraints such as the incoming flow velocity in the application scenario; (according to experience, the inlet diameter (m) is in the range of about 0.5% to 2% of the incoming flow velocity (m / s); in the case of this invention patent, under the condition of an incoming flow velocity of 8m / s, five diameters of 30mm, 60mm, 80mm, 120mm and 160mm are selected for discussion and explanation;

[0087] 2. CFD Numerical Simulation Analysis: CFD numerical simulation analysis is a common method for solving hydraulic mechanical properties. Its basic steps and principles are common methods in this field and are therefore not included in the scope of this invention. This invention aims to protect the special fluid computational domain model used in CFD numerical simulation to separately solve the hydraulic performance of the venturi constriction section under free flow conditions, such as... Figures 3-4 As shown;

[0088] To solve the performance of the venturi tube's contraction section independently, the interference from upstream and downstream fluids must be eliminated. In the special fluid computational domain model provided in this invention: the upstream boundary is the velocity inlet boundary, with a distance ≥5D from the venturi tube's contraction section (D represents the venturi tube inlet diameter), and the velocity value is set to the free flow velocity; the left and right sides, and the upper and lower sides are symmetry plane boundaries, with a distance ≥5D from the venturi tube's contraction section; the downstream boundary is the pressure outlet boundary, with independent pressure outlets distributed inside and outside the venturi tube, with distances ≥10D and ≥16D from the venturi tube's contraction section, respectively, and the outlet value is 0 Pa gauge pressure.

[0089] Reasons: Maintaining a certain distance upstream and to the top, bottom, left, and right sides ensures uniform inflow and prevents interference with the fluid flowing around the outside of the Venturi tube; the reason for separating the downstream side is to prevent the pressure of the fluid outside the Venturi tube outlet from squeezing or sucking the fluid inside, interfering with the calculation results of the upstream contraction section; setting a sufficiently long distance (≥16D) on the inner downstream side ensures sufficient development of fluid flow and avoids the influence of sudden pressure changes on the calculation results;

[0090] Based on the aforementioned CFD numerical simulation method provided by this invention, the hydraulic performance of the venturi tube contraction section under different contraction section lengths, different inflow velocities, different inlet diameters, and different contraction ratios can be simulated and calculated. The calculation results can be filled into a data table for later use (wherein, the contraction ratio refers to the area ratio of the venturi tube inlet to the throat).

[0091] 3. Data processing and solving the functional relationship: The calculation results obtained in the previous steps are processed and analyzed using regression analysis; the functional relationship between the deceleration ratio at the venturi inlet and the acceleration ratio in the venturi constriction section and the venturi constriction ratio is solved.

[0092] Wherein, the definition is:

[0093] Inlet reduction ratio K1 = Inlet flow velocity / Incoming flow velocity;

[0094] Intra-pipe acceleration ratio K2 = throat velocity / inlet velocity;

[0095] Final acceleration ratio K = throat velocity / incoming flow velocity = inlet deceleration ratio K1 × inlet acceleration ratio K2;

[0096] Venturi tube energy consumption (W) = resistance (N) × inflow velocity (m / s);

[0097] The data processing results can be entered into a data table for use:

[0098] like Figure 5 As shown, the specific steps are as follows:

[0099] ① Based on the results in Table 1, determine whether the length of the contraction section affects the acceleration ratio performance of the venturi contraction section, and select the optimal length (in the later embodiments, the calculation results show that the acceleration ratio performance reaches its optimal level when the length of the contraction section = the throat (nozzle) diameter).

[0100] ② Based on the results in Table 2, determine whether the magnitude of the incoming flow velocity affects the acceleration ratio performance of the venturi tube contraction section (in the later embodiments, the results show that there is basically no effect).

[0101] ③ Based on Tables 3 and 4, summarize the results of each calculation point onto the same chart, analyze the curve trend, select an appropriate function for regression analysis, and fit the functional relationship; In this invention, the functional forms of the inlet deceleration ratio K1 and the pipe acceleration ratio K2 with the contraction ratio S are both chosen as K=a·ln(S)+b, and b≈1 (this is because when the contraction ratio S=1, that is, when there is no contraction, the contraction section has almost no effect on the fluid, and the deceleration ratio and acceleration ratio are both 1);

[0102] For common liquids with fluid properties similar to water (specific gravity close to 1, viscosity close to 1 cP), this invention directly provides and claims the following functional relationship: (This relationship is obtained through the aforementioned complex iterative calculations and is not an obvious result) (Experimental verification shows that this relationship has good accuracy in the range of 1≤S≤6).

[0103] K1= -0.41118 ln(S) + 0.98013;

[0104] K2= 1.28895 ln(S) + 0.98817;

[0105] The final acceleration ratio K = K1 × K2 = -0.53008[ln(S)]^2 + 0.85702 ln(S) + 0.96853;

[0106] In particular, for fluids with densities and viscosities that differ significantly from water, the aforementioned process can also yield corresponding functional relationship results.

[0107] 4. Solving for the optimal shrinkage ratio under multiple objectives: Based on the relationship between the final acceleration ratio, energy consumption, pressure drop and other indicators of the Venturi tube and the shrinkage ratio, the optimal shrinkage ratio of the Venturi tube under different single objectives or multiple objectives is solved, thereby achieving the performance optimization design under specific objectives or multiple objectives.

[0108] With a single objective—maximum final acceleration ratio power:

[0109] According to the aforementioned formula, the final acceleration ratio is a quadratic equation in ln(S), and its maximum value Kmax=1.315 can be solved. It is reached when ln(S)=0.80886, that is, when S=2.24553.

[0110] That is, when the Venturi tube is operating under free flow conditions and the fluid is water at normal temperature and pressure, its final acceleration ratio K reaches its maximum when the contraction ratio S is 2.24553, and the maximum final acceleration ratio Kmax = 1.315.

[0111] 5. Output the optimal structure: Through the aforementioned specific steps, the optimal size and optimal performance of the Venturi tube contraction section under one or more objectives can be obtained.

[0112] The final acceleration ratio of the Venturi tube obtained by solving step 4 above can be used to replace the acceleration ratio in a traditional Venturi jet mixer, and then the remaining dimensional parameters of the Venturi jet mixer can be designed using traditional design theory formulas.

[0113] Take water at normal temperature and pressure—the most common fluid medium—as an example:

[0114] Table 1. Analysis of the shape of the contraction segment curve

[0115]

[0116] Table 2 Incoming Flow Velocity Analysis

[0117]

[0118] Table 3 Inlet Diameter Analysis

[0119]

[0120] Table 4 Shrinkage Ratio Analysis

[0121]

[0122] Table 5 Data Processing

[0123]

[0124] ① According to the results in Tables 1 and 5, the calculation results show that the acceleration ratio performance is optimal when the length of the contraction section equals the diameter of the throat (nozzle).

[0125] ② According to the results in Tables 2 and 5, the calculation results show that the magnitude of the incoming flow velocity has basically no effect on the acceleration ratio performance of the venturi tube contraction section;

[0126] ③ Based on the results in Tables 3, 4, and 5, summarize the calculation points as follows: Figure 6 As shown:

[0127] Based on the calculation results, fit and solve the functional relationship:

[0128] K1= -0.41118 ln(S) + 0.98013;

[0129] K2= 1.28895 ln(S) + 0.98817;

[0130] The final acceleration ratio K = K1 × K2 = -0.53008[ln(S)]^2 + 0.85702 ln(S) + 0.96853;

[0131] ④ Final acceleration ratio optimization: The final acceleration ratio is a quadratic equation in ln(S), and its maximum value Kmax=1.315 can be solved. It is reached when ln(S)=0.80886, that is, when S=2.24553. That is, when the Venturi tube is working under free flow conditions and the fluid is water at normal temperature and pressure, its final acceleration ratio K reaches its maximum when the contraction ratio S is 2.24553, and the maximum final acceleration ratio Kmax=1.315.

[0132] Verification of technical effectiveness and / or analysis of technical problem solving

[0133] The key to this invention lies in the research and discussion of the hydraulic performance of a Venturi tube under free-flow conditions, a special working condition that has not been previously considered or studied in depth. The main aspects are as follows:

[0134] 1. The method described in the invention for optimizing the design of the contraction section of a Venturi tube under free flow conditions through CFD simulation experiments and numerical analysis, which employs a special fluid computational domain model.

[0135] 2. For water and similar substances (specific gravity close to 1, viscosity close to 1 cP), a common fluid medium in daily life and engineering applications, this invention provides the formula and functional relationship of the Venturi tube contraction section changing with the contraction ratio, as well as the expression for the optimal contraction ratio and maximum acceleration performance.

[0136] The optimization design method provided by this invention can yield a functional relationship between the hydraulic performance and the contraction ratio of the venturi tube contraction section under free flow conditions, thereby obtaining the theoretically optimal inflow performance of the contraction section shape and contraction ratio. Based on the method of this invention, the application scope of traditional design methods for venturi jet mixers (such as Sokolov's theory) can be expanded and improved (from closed pipe flow to open free flow), perfecting the design theory and method, and obtaining the theoretically optimal comprehensive performance of the venturi jet mixer structural parameters under various applicable environments and objectives.

[0137] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. An optimized design method for the contraction section of a Venturi tube under free-flow conditions, characterized in that, Includes the following steps: S1: Determine the range of Venturi tube inlet diameters and select several inlet diameter values ​​based on the inflow velocity conditions in the application scenario; S2: Establish a fluid computational domain model for solving the performance of the Venturi tube contraction section under free flow conditions. In the fluid computational domain model, the inner and outer outlets of the Venturi tube are set as independent pressure outlet boundaries. The boundary conditions of the fluid computational domain model are set as follows: the upstream boundary is a velocity inlet boundary, and the distance between it and the Venturi tube contraction section is not less than 5D; the left and right sides and the upper and lower boundaries are symmetry plane boundaries, and the distance between them and the Venturi tube contraction section is not less than 5D; in the downstream boundary, the distance between the inner pressure outlet of the Venturi tube and the contraction section is not less than 16D, and the distance between the outer pressure outlet of the Venturi tube and the contraction section is not less than 10D; where D is the inlet diameter of the Venturi tube. S3: Based on the fluid computational domain model, perform CFD numerical simulation on the contraction section of the Venturi tube under different contraction ratios to obtain inlet velocity and throat velocity data; S4: Based on the inlet velocity and throat velocity data, calculate the inlet deceleration ratio K1 and the in-pipe acceleration ratio K2, and obtain the functional relationships between K1 and K2 as a function of the contraction ratio S through regression analysis; S5: Solve for the optimal shrinkage ratio under the target conditions based on the aforementioned functional relationship, and output the corresponding Venturi tube shrinkage section size parameters.

2. The optimized design method for the contraction section of a Venturi tube under free-flow conditions according to claim 1, characterized in that, S3 also includes performing CFD numerical simulations on the venturi tube contraction sections under different contraction section lengths, different incoming flow velocities, and different inlet diameters to obtain inlet flow velocity, throat flow velocity, and resistance data under each parameter condition.

3. The optimized design method for the contraction section of a Venturi tube under free-flow conditions according to claim 1, characterized in that, In S4, the inlet deceleration ratio K1 is defined as the ratio of the inlet flow velocity to the incoming flow velocity, the pipe acceleration ratio K2 is defined as the ratio of the throat flow velocity to the inlet flow velocity, and the final acceleration ratio K is defined as the product of the inlet deceleration ratio K1 and the pipe acceleration ratio K2. The functional relationship is in the form of K=a·ln(S)+b, where a and b are regression coefficients, S is the contraction ratio, and for any liquid, b should approach 1.

4. The optimized design method for the contraction section of a Venturi tube under free-flow conditions according to claim 3, characterized in that, When the fluid medium is a liquid with a specific gravity close to 1 and a viscosity close to 1 cP, the functional relationship is: K1 = -0.41118ln(S) + 0.98013; K2 = 1.28895ln(S) + 0.98817; The final speedup ratio K = -0.53008[ln(S)]² + 0.85702ln(S) + 0.96853; The functional relationship is applicable within the range of 1 ≤ S ≤ 6.

5. The optimized design method for the contraction section of a Venturi tube under free-flow conditions according to claim 4, characterized in that, In S5, when the target condition is the maximum final acceleration ratio, for a fluid medium that is a liquid with a specific gravity close to 1 and a viscosity close to 1 cP, the extreme value of the functional relationship of the final acceleration ratio K is obtained, and the optimal contraction ratio S = 2.24553 is obtained, corresponding to the maximum final acceleration ratio Kmax = 1.

315.

6. The optimized design method for the contraction section of a Venturi tube under free-flow conditions according to claim 1, characterized in that, In step S3, resistance data under various parameter conditions is also acquired. In step S4, the energy consumption of the Venturi tube is calculated. The energy consumption of the Venturi tube is the product of the resistance and the incoming flow velocity. In step S5, the optimal contraction ratio is solved based on the multi-objective optimization conditions of the final acceleration ratio and energy consumption.

7. The optimized design method for the contraction section of a Venturi tube under free-flow conditions according to claim 1, characterized in that, In S3, the acceleration ratio performance of the venturi tube's contraction section reaches its optimal level when the length of the contraction section is equal to the throat diameter.

8. An optimized design system for the contraction section of a Venturi tube under free-flow conditions, characterized in that, An optimization design method for the contraction section of a Venturi tube under free-flow conditions as described in any one of claims 1-7, comprising: The parameter determination module is used to determine the range of Venturi tube inlet diameters and select several inlet diameter values ​​based on the incoming flow velocity conditions in the application scenario. The computational domain modeling module is used to establish a fluid computational domain model for solving the performance of the constriction section of a Venturi tube under free flow conditions. In the fluid computational domain model, the inner outlet and the outer outlet of the Venturi tube are set as independent pressure outlet boundaries. The CFD simulation module is used to perform numerical simulations of the contraction section of a Venturi tube under different contraction ratios based on the fluid computational domain model, and to obtain inlet velocity and throat velocity data. The data processing module is used to calculate the inlet deceleration ratio K1 and the in-pipe acceleration ratio K2 based on the inlet flow velocity and throat flow velocity data, and to obtain the functional relationships between K1 and K2 as a function of the contraction ratio S through regression analysis. The optimization solution module is used to solve for the optimal shrinkage ratio under the target conditions based on the functional relationship, and output the corresponding Venturi tube shrinkage section size parameters.

9. A computer-readable storage medium, characterized in that, The storage medium stores computer-executable instructions, which, when executed by a processor, implement the optimized design method for the contraction section of a Venturi tube under free-flow conditions as described in any one of claims 1 to 7.

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