Fractal porous orifice plate flowmeter design method and fractal porous orifice plate flowmeter
By using the fractal multi-hole orifice plate flowmeter design method, the problems of large pressure loss and poor adaptability of traditional orifice plate flowmeters are solved, and pressure loss is reduced and pressure differential is increased, pressure recovery speed is accelerated, and the metering performance of the flowmeter is improved.
Patent Information
- Application Number
- CN202511954176.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-02-13
AI Technical Summary
Traditional orifice plate flow meters have limitations such as high pressure loss, low range ratio, and poor adaptability to flow conditions, which affect measurement accuracy and increase system energy consumption.
A fractal orifice plate flowmeter design method is adopted. By designing fractal strategy parameters and fractal primitives, a fractal orifice plate unit with strict self-similarity characteristics is formed, and then the whole is shrunk to construct a fractal orifice plate flowmeter.
It reduces pressure loss by 5.27% to 10%, increases differential pressure, and has a significantly faster pressure recovery speed than traditional configurations, thus improving metering performance.
Smart Images
Figure CN121521212A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fractal orifice plate design technology, specifically to a design method for fractal multi-hole orifice plate flow meters and a fractal multi-hole orifice plate flow meter. Background Technology
[0002] Flow measurement plays a vital role in scientific research and industrial production, serving as a key link in optimizing energy utilization, ensuring process stability, and guaranteeing product quality. Orifice plate flow meters, as a common type of differential pressure flow meter, have long been widely used due to their simple structure, low cost, and high measurement accuracy.
[0003] However, with the continuous advancement of industrial technology and the increasing demands for measurement accuracy, some inherent limitations of traditional orifice plate flow meters have gradually become apparent. These limitations include significant pressure loss, limited measurement accuracy across a wide flow range, and poor adaptability to upstream fluid flow conditions (laminar, turbulent, etc.). These problems not only affect measurement accuracy but also increase system energy consumption and operating costs, prompting researchers to continuously explore innovative design concepts and technical methods. In 2004, NASA proposed the concept of multi-orifice plates, which has made significant progress in terms of measurement accuracy and applicability. The emergence of multi-orifice plate flow meters has, to some extent, improved upon the shortcomings of single-orifice plates, such as significant pressure loss, low rangeability, and sensitivity to upstream disturbances. Traditional multi-orifice plates can provide effective flow mixing to reduce pressure loss, but they cannot provide a sufficiently large pressure drop to meet the needs of flow measurement. Summary of the Invention
[0004] To address the shortcomings of existing technologies, this invention provides a design method and a fractal multi-hole orifice plate flowmeter, which can effectively solve the above-mentioned problems.
[0005] The technical solution adopted in this invention is as follows:
[0006] This invention provides a design method for a fractal porous plate flow meter, comprising:
[0007] Step S1, given the fractal strategy parameters: first contraction ratio Second contraction ratio Elementary radiation dimension The equivalent diameter ratio β of the orifice plate flowmeter to be designed and the pipe diameter D of the pipe used to install the orifice plate flowmeter are required.
[0008] Step S2: Design the basic fractal primitives based on the fractal strategy parameters and the fractal strategy.
[0009] Based on the fractal strategy parameters, the diameter d0 of the circular boundary of the basic fractal primitive is determined, and the circular boundary S0 of the basic fractal primitive is designed accordingly.
[0010] Using the center of the circular boundary S0 of the basic fractal element as the center, arrange the circle with a diameter d1 = The basic main throttling orifice of d0;
[0011] In the annular region between the circular boundary S0 of the basic fractal element and the boundary of the basic main throttling circular hole, the following elements are arranged symmetrically at the center. Diameter d2 = The basic auxiliary throttling orifice of d1; Each basic auxiliary throttling circular hole is internally tangent to the circular boundary S0 of the basic fractal element, thereby designing the centrally symmetrical basic fractal element.
[0012] Step S3: Based on the fractal strategy parameters and the basic fractal unit, a fractal strategy is adopted to design the fractal perforated plate unit. The design method is as follows:
[0013] Design a first-order fractal element: Using the center of the basic main throttling orifice as the center, arrange elements with a diameter d. 11 = The primary main throttling orifice of d1 is arranged symmetrically in a centrally symmetrical manner in the annular region between the boundary of the basic main throttling orifice and the boundary of the primary main throttling orifice. A diameter d 12 = d 11 The primary auxiliary throttling orifice; Each primary auxiliary throttling orifice is internally tangent to the circular boundary of the primary throttling orifice, and, The orientation of each primary auxiliary throttling orifice relative to the primary main throttling orifice is... Each basic auxiliary throttling orifice is positioned in the same direction as the basic main throttling orifice, thus creating a centrally symmetrical first-order fractal element.
[0014] Design of Second-Level Fractal Elements: For each of the basic auxiliary throttling orifices, a second-level fractal element is obtained through uniform fractal design. The fractal method is as follows: taking the center position of the basic auxiliary throttling orifice as the center, arrange elements with a diameter d. 21 = The secondary main throttling orifice of d2 is arranged symmetrically in a centrally symmetrical manner in the annular region between the boundary of the basic auxiliary throttling orifice and the boundary of the secondary main throttling orifice. A diameter d 22 = d 21 Secondary auxiliary throttling orifice; Each of the secondary auxiliary throttling orifices is internally tangent to the circular boundary of the basic auxiliary throttling orifice, and, The orientation of each secondary auxiliary throttling orifice relative to the secondary main throttling orifice is... Each basic auxiliary throttling orifice is positioned in the same direction as the basic main throttling orifice, thus designing a centrally symmetric second-order fractal element.
[0015] Two secondary fractal primitives and one primary fractal primitive are used to form a fractal perforated plate unit;
[0016] Step S4: Determine the shrinkage ratio of the fractal orifice plate unit based on the pipe diameter D and the equivalent diameter ratio β; shrink the fractal orifice plate unit as a whole based on the shrinkage ratio, and concentrically design it in a circular orifice plate with a diameter of D according to the parameters of the shrunken fractal orifice plate unit to obtain the designed fractal multi-hole orifice plate flow meter.
[0017] Furthermore, in designing the first shrinkage ratio Second shrinkage ratio When the following constraints are satisfied:
[0018] (1)
[0019] Where: D s It is a fractal dimension.
[0020] Furthermore, using formula (2), the diameter d0 of the circular boundary of the basic fractal element is calculated:
[0021] (2).
[0022] Furthermore, the equivalent diameter ratio β = the area of all throttling orifices of the fractal porous plate flowmeter / the area of the fractal porous plate.
[0023] Furthermore, for the designed fractal orifice plate flowmeter, the contraction diameter D is defined. c This is used to characterize the degree of centripetal convergence of the throttling orifice:
[0024] (3)
[0025] Where: N is the total number of throttling orifices; R i It is the distance from the center of the i-th throttling orifice to the center of the orifice plate.
[0026] The present invention also provides a fractal orifice plate flow meter, which is designed using the aforementioned fractal orifice plate flow meter design method.
[0027] Furthermore, the fractal porous plate flowmeter has strict self-similarity characteristics.
[0028] The fractal porous orifice plate flowmeter design method and the fractal porous orifice plate flowmeter provided by this invention have the following advantages:
[0029] This invention introduces fractal theory to establish a design method for fractal orifice plate flowmeters, breaking through the limitations of conventional orifice layouts. It designs a fractal orifice plate flowmeter with strict self-similarity characteristics. This fractal orifice plate has advantages over traditional orifice plates in terms of pressure loss and pressure recovery. Compared to single-orifice plates, its pressure loss ratio is reduced by 5.27%, and compared to other orifice plates, the pressure loss ratio can be reduced by 5%-10%. This superior metering characteristic benefits from the local fusion and joint development of small-scale jets. The local fusion region induces a negative pressure peak, and the local joint region enables this negative pressure peak to recover rapidly, with a recovery speed significantly faster than traditional configurations. Attached Figure Description
[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 A flowchart illustrating the design method of the fractal porous plate flowmeter provided by the present invention;
[0032] Figure 2 This is a schematic diagram of the fractal strategy designed for this invention;
[0033] Figure 3 This is a schematic diagram of the fractal perforated plate unit designed according to the present invention;
[0034] Figure 4 To Figure 3 The effect of shrinking each fractal perforated plate unit as a whole;
[0035] Figure 5 This is a model diagram of the fractal porous plate finally prepared according to the present invention;
[0036] Figure 6 Structural diagrams of three conventional perforated plate structures used for comparison;
[0037] Figure 7 The metering characteristics of orifice plates with different configurations are shown in the diagram.
[0038] Figure 8 This is a diagram showing the pressure drop ratios of orifice plates with different configurations. Detailed Implementation
[0039] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.
[0040] This invention introduces fractal theory to establish a design method for fractal multi-hole plate flowmeters, breaking through the limitations of conventional multi-hole layouts and designing a fractal multi-hole plate flowmeter with strict self-similarity characteristics.
[0041] like Figure 1 As shown, the present invention provides a design method for a fractal porous orifice plate flow meter, comprising:
[0042] Step S1, given the fractal strategy parameters: first contraction ratio Second contraction ratio Elementary radiation dimension The equivalent diameter ratio β of the orifice plate flowmeter to be designed and the pipe diameter D of the pipe used to install the orifice plate flowmeter are required; where, the equivalent diameter ratio β = the area of all throttling orifices of the fractal orifice plate flowmeter / the area of the fractal orifice plate.
[0043] Designing the first shrinkage ratio Second shrinkage ratio When the following constraints are satisfied:
[0044] (1)
[0045] Where: D s It is a fractal dimension.
[0046] Step S2: Design the basic fractal primitives based on the fractal strategy parameters and the fractal strategy.
[0047] Based on the fractal strategy parameters, the diameter d0 of the circular boundary of the basic fractal element is determined, and the circular boundary S0 of the basic fractal element is designed accordingly; specifically, the diameter d0 of the circular boundary of the basic fractal element is calculated using formula (2):
[0048] (2).
[0049] Using the center of the circular boundary S0 of the basic fractal element as the center, arrange the circle with a diameter d1 = The basic main throttling orifice of d0;
[0050] In the annular region between the circular boundary S0 of the basic fractal element and the boundary of the basic main throttling circular hole, the following elements are arranged symmetrically at the center. Diameter d2 = The basic auxiliary throttling orifice of d1; Each basic auxiliary throttling circular hole is internally tangent to the circular boundary S0 of the basic fractal element, thereby designing the centrally symmetrical basic fractal element.
[0051] Step S3: Based on the fractal strategy parameters and the basic fractal unit, a fractal strategy is adopted to design the fractal perforated plate unit. The design method is as follows:
[0052] Design a first-order fractal element: Using the center of the basic main throttling orifice as the center, arrange elements with a diameter d. 11 = The primary main throttling orifice of d1 is arranged symmetrically in a centrally symmetrical manner in the annular region between the boundary of the basic main throttling orifice and the boundary of the primary main throttling orifice. A diameter d 12 = d 11 The primary auxiliary throttling orifice; Each primary auxiliary throttling orifice is internally tangent to the circular boundary of the primary throttling orifice, and, The orientation of each primary auxiliary throttling orifice relative to the primary main throttling orifice is... Each basic auxiliary throttling orifice is positioned in the same direction as the basic main throttling orifice, thus creating a centrally symmetrical first-order fractal element.
[0053] Design of Second-Level Fractal Elements: For each of the basic auxiliary throttling orifices, a second-level fractal element is obtained through uniform fractal design. The fractal method is as follows: taking the center position of the basic auxiliary throttling orifice as the center, arrange elements with a diameter d. 21 = The secondary main throttling orifice of d2 is arranged symmetrically in a centrally symmetrical manner in the annular region between the boundary of the basic auxiliary throttling orifice and the boundary of the secondary main throttling orifice. A diameter d 22 = d 21 Secondary auxiliary throttling orifice; Each of the secondary auxiliary throttling orifices is internally tangent to the circular boundary of the basic auxiliary throttling orifice, and, The orientation of each secondary auxiliary throttling orifice relative to the secondary main throttling orifice is... Each basic auxiliary throttling orifice is positioned in the same direction as the basic main throttling orifice, thus designing a centrally symmetric second-order fractal element.
[0054] Two secondary fractal primitives and one primary fractal primitive are used to form a fractal perforated plate unit;
[0055] Step S4: Determine the shrinkage ratio of the fractal orifice plate unit based on the pipe diameter D and the equivalent diameter ratio β; shrink the fractal orifice plate unit as a whole based on the shrinkage ratio, and concentrically design it in a circular orifice plate with a diameter of D according to the parameters of the shrunken fractal orifice plate unit to obtain the designed fractal multi-hole orifice plate flow meter.
[0056] For the designed fractal multi-orifice plate flowmeter, define the contraction diameter D. c This is used to characterize the degree of centripetal convergence of the throttling orifice:
[0057] (3)
[0058] Where: N is the total number of throttling orifices; R i It is the distance from the center of the i-th throttling orifice to the center of the orifice plate.
[0059] The present invention also provides a fractal orifice plate flow meter, which is designed using the above-described fractal orifice plate flow meter design method, and the fractal orifice plate flow meter has strict self-similarity characteristics.
[0060] The following is an example:
[0061] In terms of the dimension of elementary radiation The first contraction ratio is 4. =0.5, second shrinkage ratio For example, =0.4 Figure 2 The fractal strategy designed for this invention.
[0062] Figure 2 a represents the basic fractal element designed using step S2 of this invention. The basic fractal element has one basic main throttling circular hole and four basic auxiliary throttling circular holes; the diameter d0 of the circular boundary of the basic fractal element is 1, and the diameter d1 of the basic main throttling circular hole is... d0=0.5; Diameter d2 of the basic auxiliary throttling orifice= d1=0.2.
[0063] Figure 2 b is a schematic diagram of the intermediate process of the fractal perforated plate unit designed using step S3 of the present invention; Figure 2 c is a schematic diagram of the fractal perforated plate unit designed using step S3 of the present invention. Figure 2 In b, there is one first-level fractal element and four second-level fractal elements; each fractal element has one main throttling orifice and four auxiliary throttling orifices, and the diameter of each throttling orifice is designed proportionally, and the size is determined according to the fractal strategy of the present invention.
[0064] When the elementary radiation dimension When the values are 4, 5, 6, and 7 respectively, the design method of this invention is used to design the following: Figure 3 The four configurations of fractal perforated plate units are a, b, c, and d.
[0065] After designing the fractal orifice plate unit, the fractal orifice plate unit is shrunk as a whole using the method in step S4 of this invention to obtain the designed fractal multi-orifice plate flowmeter. For example... Figure 4As shown, this is for an equivalent diameter ratio of β=0.4, a pipe diameter of D=114.3mm, and an orifice plate thickness of 3mm. Figure 3 The image shows the effect obtained after the overall shrinkage of each fractal perforated plate unit. (Example:) Figure 5 The image shown is a model of the final fractal porous plate, with its elementary radiation dimension. They are 4, 5, 6 and 7 respectively.
[0066] In contrast, traditional perforated plate structures, such as Figure 6 As shown, the equivalent diameter ratio is β=0.4, the pipe diameter is D=114.3mm, and the orifice plate thickness is 3mm.
[0067] Figure 6 The three traditional perforated plate structures are referred to as SHOP, MHOP, and FOP-G1, respectively. Figure 5 The four perforated plate structures designed in this invention are respectively named FOP-G2_5, FOP-G2_6, FOP-G2_7, and FOP-G2_9; the main structural parameters of these seven perforated plate configurations are shown in Table 1:
[0068] Table 1: Main Structural Parameters of Seven Perforated Plate Configurations
[0069]
[0070] Performance testing was conducted on the above seven orifice plate configurations to test the orifice plate metrology characteristics:
[0071] Specifically, for orifice plate flow meters, three parameters are generally used to evaluate their metering characteristics: pressure loss, differential pressure, and pressure recovery rate. It is generally believed that orifice plate flow meters with lower pressure loss, higher differential pressure, and faster pressure recovery rate have better metering performance. Lower pressure loss means less energy loss as the fluid flows through the orifice plate, which plays an important role in reducing energy consumption and saving operating costs. A higher differential pressure indicates a wider measurement range for the orifice plate flow meter, allowing it to obtain differential pressure values that meet the transmitter's lower measurement limit even at lower flow rates, significantly improving the flow meter's testing accuracy. A fast pressure recovery rate means that the downstream flow can quickly return to uniformity, thereby reducing the length of the downstream straight pipe section and lowering installation costs.
[0072] Numerical simulation is a mature and convenient method for studying the metrological performance of orifice plate flowmeters. This invention verifies the metrological performance of a novel fractal porous orifice plate through numerical simulation. The numerical simulation setup is as follows: the unsteady Reynolds-averaged (URANS) equations are solved using the finite volume method, and the closed control equations of the SST k-ω turbulence model are introduced. Inviscid and viscous fluxes are discretized using AUSM and a second-order central scheme, respectively. In the unsteady solution process, a dual-time-progression method is used to solve the control equations, and a multi-step Runge-Kutta scheme is employed for pseudo-time iteration. The convergence criteria are continuity and momentum equation residuals <10. −6 The time step is set to 0.001 seconds. The orifice plate and pipe wall are set to no-slip wall conditions, the inlet is a velocity boundary condition, and the outlet is a pressure outlet condition. The Reynolds number based on the pipe inner diameter is Re = 55800, and the fluid medium is water.
[0073] Pressure loss, also known as permanent pressure loss, refers to the difference between the pressure before and after the orifice plate when it is fully recovered, as shown in equation (4); pressure difference refers to the pressure difference before and after the orifice plate, as shown in equation (5).
[0074] (4)
[0075] (5)
[0076] In the formula, Δπ is the pressure loss, and P o It is the pressure on the orifice wall far in front of the orifice plate, P r It is the orifice wall pressure after the orifice plate has fully recovered; ΔP is the pressure difference, P u It is the pressure on the orifice wall at a certain point upstream of the orifice plate, P d P is the pressure on the orifice wall at a certain point downstream of the orifice plate. u and P d The pressure tap location depends on the actual situation; here, we choose the flange pressure tap, i.e., P. u The position is x = -25.4 mm, P d The position is x=25.4mm.
[0077] Metering characteristics of orifice plates with different configurations, such as Figure 7 As shown. Figure 7 (a) shows the axial wall pressure distribution; Figure 7 (b) is a graph showing the relationship between pressure loss and pressure difference.
[0078] For orifice plates with different configurations, the pressure loss varies significantly: the No.1 (SHOP) orifice plate has the largest pressure loss, followed by the No.2 (MHOP) and No.3 (FOP-G1) orifice plates. The pressure loss of No.4 to No.7 is less than that of No.1 to No.3, and the larger the similarity dimension, the smaller the pressure loss. Figure 7As shown in (a). It is noteworthy that the negative pressure peak value after the No.4 (FOP-G2_5) orifice plate ( Figure 7 (a) is significantly larger than the other six orifice plate configurations, allowing it to achieve a pressure drop comparable to that of annular and radial orifice plates while having a smaller pressure drop. The current consensus on pressure drop is that it gradually decreases as the number of openings increases. In this invention, the FOP-G2_9 configuration has the most openings (81), and therefore has the smallest pressure drop.
[0079] From the perspective of pressure drop ratio (Δπ / ΔP), the pressure drop ratio of the FOP-G2_5 orifice plate is significantly lower than that of other configurations, such as... Figure 7 As shown in (b), the functional relationship between the pressure loss ratio and the equivalent diameter ratio of a single-hole plate is shown in equation (6).
[0080] (6)
[0081] In the formula, β is the equivalent diameter ratio of the orifice plate.
[0082] like Figure 8 The figure shows the pressure drop ratios for orifice plates with different configurations. Figure 8 The dashed line in the middle represents the international standard for the pressure drop ratio of a single-hole orifice plate, as shown in Equation (6), also known as the theoretical curve or the "empirical curve." The blue shaded area in the lower left of the theoretical curve represents the region with theoretically small pressure drop and large pressure difference, which is also the design region that researchers have been pursuing. The pressure drop ratio curve of a single-hole orifice plate shown in Equation (6) is more like an "ideal boundary." The pursuit of the metrological characteristics of small pressure drop and large pressure difference is essentially a breakthrough or expansion of the ideal boundary. Currently, most porous orifice plates fall within the elliptical shaded area. This region only achieves the single objective of small pressure drop or large pressure difference. Compared with single-hole orifice plates, it does not show the comprehensive performance advantage of small pressure drop and large pressure difference. At present, few studies have been able to break through the "ideal boundary" of the pressure drop ratio of single-hole orifice plates. Encouragingly, the second-generation fractal orifice plate FOP-G2_5 designed in this invention achieves both small pressure drop and large pressure difference. Compared with the ideal boundary of a single-hole orifice plate, the pressure drop ratio is reduced by 5.27% (under the same β conditions). It is evident that the present invention breaks through the ideal boundary of the single-hole plate pressure loss ratio described by equation (6), and the author believes that this breakthrough is very important for the field of metrology.
[0083] Furthermore, the pressure recovery rates of annular porous plates and second-generation fractal porous plates are significantly faster than those of single-hole plates and radial porous plates, such as... Figure 7As shown in (a), the pressure recovery curves of No.1 (SHOP), No.2 (MHOP), and No.3 (FOP-G1) show the same pressure recovery pattern, except that the porous plate recovers faster. However, the pressure recovery pattern of the FOP-G2 series (No.4~No.7) orifice plates is divided into a rapid recovery stage and a slow recovery stage, which is significantly different from the other three configurations. This is caused by the increased flow mixing due to the multi-scale jet.
[0084] As can be seen, compared with traditional orifice plate configurations, the novel second-generation fractal orifice plate configuration proposed in this invention is significantly more effective in reducing pressure loss. A comprehensive comparison of pressure loss, differential pressure, and pressure recovery rate shows that the FOP-G2_5 orifice plate configuration exhibits significantly superior metering characteristics compared to other configurations.
[0085] This invention presents a novel fractal orifice plate flow meter. This fractal orifice plate exhibits advantages over traditional orifice plates in terms of pressure loss and pressure recovery. Compared to single-orifice plates, its pressure loss ratio is reduced by 5.27%, and compared to other multi-orifice plates, the pressure loss ratio can be reduced by 5%-10%. This superior metering characteristic benefits from the local fusion and joint development of small-scale jets. The local fusion region induces a negative pressure peak, and the local joint region enables the rapid recovery of this negative pressure peak, with a recovery speed significantly faster than that of traditional configurations.
[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A design method for a fractal multi-hole orifice plate flowmeter, characterized in that, include: Step S1, given the fractal strategy parameters: first contraction ratio Second contraction ratio Elementary radiation dimension The equivalent diameter ratio β of the orifice plate flowmeter to be designed and the pipe diameter D of the pipe used to install the orifice plate flowmeter are required. Step S2: Design the basic fractal primitives based on the fractal strategy parameters and the fractal strategy. Based on the fractal strategy parameters, the diameter d0 of the circular boundary of the basic fractal primitive is determined, and the circular boundary S0 of the basic fractal primitive is designed accordingly. Using the center of the circular boundary S0 of the basic fractal element as the center, arrange the circle with a diameter d1 = The basic main throttling orifice of d0; In the annular region between the circular boundary S0 of the basic fractal element and the boundary of the basic main throttling circular hole, the following elements are arranged symmetrically at the center. Diameter d2 = The basic auxiliary throttling orifice of d1; Each basic auxiliary throttling circular hole is internally tangent to the circular boundary S0 of the basic fractal element, thereby designing the centrally symmetrical basic fractal element. Step S3: Based on the fractal strategy parameters and the basic fractal unit, a fractal strategy is adopted to design the fractal perforated plate unit. The design method is as follows: Design a first-order fractal element: Using the center of the basic main throttling orifice as the center, arrange elements with a diameter d. 11 = The primary main throttling orifice of d1 is arranged symmetrically in a centrally symmetrical manner within the annular region between the boundary of the basic main throttling orifice and the boundary of the primary main throttling orifice. A diameter d 12 = d 11 The primary auxiliary throttling orifice; Each primary auxiliary throttling orifice is internally tangent to the circular boundary of the primary throttling orifice, and, The orientation of each primary auxiliary throttling orifice relative to the primary main throttling orifice is... Each basic auxiliary throttling orifice is positioned in the same direction as the basic main throttling orifice, thus creating a centrally symmetrical first-order fractal element. Design of Second-Level Fractal Elements: For each of the basic auxiliary throttling orifices, a second-level fractal element is obtained through uniform fractal design. The fractal method is as follows: taking the center position of the basic auxiliary throttling orifice as the center, arrange elements with a diameter d. 21 = The secondary main throttling orifice of d2 is arranged symmetrically in a centrally symmetrical manner in the annular region between the boundary of the basic auxiliary throttling orifice and the boundary of the secondary main throttling orifice. A diameter d 22 = d 21 Secondary auxiliary throttling orifice; Each of the secondary auxiliary throttling orifices is internally tangent to the circular boundary of the basic auxiliary throttling orifice, and, The orientation of each secondary auxiliary throttling orifice relative to the secondary main throttling orifice is... Each basic auxiliary throttling orifice is positioned in the same direction as the basic main throttling orifice, thus designing a centrally symmetric second-order fractal element. Two secondary fractal primitives and one primary fractal primitive are used to form a fractal perforated plate unit; Step S4: Determine the shrinkage ratio of the fractal orifice plate unit based on the pipe diameter D and the equivalent diameter ratio β; shrink the fractal orifice plate unit as a whole based on the shrinkage ratio, and concentrically design it in a circular orifice plate with a diameter of D according to the parameters of the shrunken fractal orifice plate unit to obtain the designed fractal multi-hole orifice plate flow meter.
2. The design method for a fractal porous orifice plate flowmeter according to claim 1, characterized in that, Designing the first shrinkage ratio Second shrinkage ratio When the following constraints are satisfied: （1） Where: D s It is a fractal dimension.
3. The design method for a fractal multi-hole orifice plate flowmeter according to claim 1, characterized in that, Using formula (2), the diameter d0 of the circular boundary of the basic fractal element is calculated: （2）。 4. The design method of a fractal multi-hole plate flowmeter according to claim 1, characterized in that, The equivalent diameter ratio β = the area of all throttling orifices of the fractal porous orifice flowmeter / the area of the fractal porous orifice plate.
5. The design method for a fractal porous orifice plate flowmeter according to claim 1, characterized in that, For the designed fractal multi-orifice plate flowmeter, the contraction diameter D is defined. c This is used to characterize the degree of centripetal convergence of the throttling orifice: （3） Where: N is the total number of throttling orifices; R i It is the distance from the center of the i-th throttling orifice to the center of the orifice plate.
6. A fractal porous orifice plate flow meter, characterized in that, The flow meter was designed using the fractal porous orifice plate design method described in any one of claims 1 to 5.
7. A fractal porous orifice plate flow meter according to claim 6, characterized in that, The fractal orifice plate flowmeter has strict self-similarity characteristics.