Static mixer with bionic starfish type inlet structure and mixing method thereof

Abstract

The invention provides a static mixer with a bionic starfish type inlet structure and a mixing method thereof. The static mixer comprises a shell, a cavity is formed in the shell, one end of the shell is provided with an air inlet communicating with one end of the cavity, and the other end of the shell is provided with an air outlet communicating with the other end of the cavity; an air inlet pipe set is arranged at the end, close to the air inlet, of the shell and comprises a center air inlet pipe extending in the axial direction and five peripheral air inlet pipes evenly distributed in the circumferential direction of the center air inlet pipe. The central air inlet pipe and the peripheral air inlet pipe form a bionic starfish type inlet structure for simulating a central disc and a radiation wrist structure of starfish; a plurality of spiral pieces arranged in the axial direction of the cavity are arranged in the cavity, and the arrangement angles of the adjacent spiral pieces are different. By means of the bionic starfish type inlet structure design, hydrogen is evenly dispersed to the whole mixing area, the mixing uniformity of natural gas and hydrogen is effectively improved, and meanwhile the risk of hydrogen embrittlement is delayed.

Description

Technical Field

[0001] This invention belongs to the field of natural gas hydrogen blending technology, specifically relating to a static mixer with a biomimetic starfish-shaped inlet structure and its mixing method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Hydrogen blending technology for natural gas refers to the addition of a certain proportion of hydrogen to existing natural gas pipeline networks. This technology can reduce the cost of hydrogen transportation, improve the combustion efficiency of natural gas, and reduce carbon emissions, making it an important way to promote the large-scale utilization of hydrogen energy.

[0004] The technical challenges posed by differences in gas properties during the transportation of natural gas blended with hydrogen cannot be ignored. Since hydrogen's density is only 1 / 8 that of natural gas, and the two gases have significantly different viscosity coefficients, these differences make the mixed gas highly susceptible to stratification during pipeline transportation. Especially under low flow rate conditions, hydrogen in horizontal pipelines will rise rapidly due to buoyancy, resulting in uneven distribution of the mixed gas components along the pipeline cross-section. This uneven mixing not only affects the operational stability of the terminal combustion equipment but may also pose safety hazards due to excessively high local hydrogen concentrations.

[0005] While traditional static mixers avoid the energy consumption of mechanical stirring, achieving thorough mixing often requires multiple mixing stages, leading to a significant increase in system pressure drop. During long-distance transport, additional compressor power is needed to compensate for pressure losses, resulting in persistently high overall energy consumption. Particularly under high-pressure gas transport conditions, the complex flow channel structure within the mixer generates turbulent dissipation and localized resistance losses, further reducing system energy efficiency and directly impacting the economic feasibility of hydrogen blending technology.

[0006] Furthermore, hydrogen embrittlement risk is one of the core bottlenecks restricting the large-scale application of natural gas hydrogen blending technology. For example... Figure 1 As shown, existing mixers generally employ a simple single-pipe hydrogen injection structure. This design has significant hydrodynamic defects: hydrogen struggles to achieve rapid and uniform diffusion in the main flow channel, easily leading to hydrogen enrichment zones near the mixer wall and in downstream localized areas. This uneven mixing significantly increases the risk of hydrogen embrittlement in the pipe material. Particularly under high-pressure transport conditions, the localized increase in hydrogen partial pressure exacerbates the penetration of hydrogen atoms into the metal lattice, drastically increasing the material's hydrogen embrittlement sensitivity and posing a serious threat to the long-term safe operation of the pipeline system. Summary of the Invention

[0007] The static mixer with the bionic starfish type inlet structure and the mixing method thereof are provided to solve the above problems.

[0008] According to some embodiments, the present application adopts the technical scheme as follows: The static mixer with the bionic starfish type inlet structure comprises a shell, a cavity is arranged in the shell, an air inlet is arranged at one end of the shell and communicates with one end of the cavity, and an air outlet is arranged at the other end of the shell and communicates with the other end of the cavity. An air inlet pipe group is arranged at one end of the shell close to the air inlet, the air inlet pipe group comprises one axially extending central air inlet pipe and five peripheral air inlet pipes which are uniformly distributed in the circumferential direction of the central air inlet pipe, and the central air inlet pipe and the peripheral air inlet pipes form a bionic starfish type inlet structure simulating the central disc and the radial arm structure of a starfish. A plurality of helical blades are arranged in the cavity in the axial direction of the cavity, and the arrangement angles of adjacent helical blades are different.

[0009] As an optional implementation, the air inlet is used to transport natural gas, and the air inlet pipe group is used to transport hydrogen.

[0010] As an optional implementation, the central air inlet pipe and the peripheral air inlet pipes each comprise two parts which are perpendicular to each other, the first part is perpendicular to the axis of the cavity and penetrates the wall of the cavity, the second part is parallel to the axis of the cavity, and the extension length of the second part of the central air inlet pipe in the cavity is greater than the extension length of the second part of the peripheral air inlet pipes in the cavity. That is, the extension direction of the central air inlet pipe is consistent with the extension direction of the cavity, so that the entering path of a part of hydrogen is inconsistent with the entering path of other hydrogen and the entering path of natural gas, and the hydrogen is better diffused and mixed, and the thickness characteristics of the central disc of a starfish are simulated based on the bionics principle to optimize the air flow distribution.

[0011] As an optional implementation, the cavity is in a circular tube structure. Such a design can make the gas more smoothly diffuse in the cavity.

[0012] As an optional implementation, the extension length of the second part of the central air inlet pipe in the cavity is greater than or equal to the diameter of the cavity.

[0013] As an optional implementation, the diameter of the central air inlet pipe is the same as the diameter of each peripheral air inlet pipe, the radial spacing between each peripheral air inlet pipe and the central air inlet pipe is the same, and the central included angle between adjacent peripheral air inlet pipes is 72°.

[0014] As an alternative embodiment, the helical fins include four, and the adjacent helical fins have opposite rotation directions.

[0015] As an alternative embodiment, the outer ends of the helical fins are in contact with the inner wall of the shell.

[0016] As an alternative embodiment, the mixing elements composed of the helical fins are arranged in the middle of the cavity, and the gas inlet groups are arranged in the front of the cavity, and there is a gap between the two. Such a design can better give the natural gas and hydrogen mixing space.

[0017] Based on the mixing method of the static mixer, the method comprises the following steps: The natural gas is pressurized to a set value, and the hydrogen is pressurized to a set value; The natural gas is input into the cavity of the shell through the gas inlet at a preset flow rate, and the hydrogen is input into the cavity of the shell through the gas inlet group at a flow rate matched with the flow rate of the natural gas; wherein, when the flow rate of the natural gas is greater than the flow rate of the hydrogen, the mapping is set in advance; The natural gas and the hydrogen are mixed by the helical mixing elements in the shell; The mixed gas is discharged through the gas outlet.

[0018] Compared with the prior art, the beneficial effects of the present application are: The gas inlet group of the present application adopts a bionics design, which is composed of a central gas inlet pipe and five peripheral gas inlet pipes uniformly distributed in the circumference, simulating the structure of the central disc and radial arm of a starfish. This layout can uniformly spray hydrogen to various positions in the mixing area, avoiding local over-concentration or under-concentration, and significantly improving the mixing uniformity of natural gas and hydrogen.

[0019] The bionic starfish type inlet structure design of the present application uniformly distributes the gas inlets in the circumference, so that the hydrogen jet flow and the natural gas main flow form a cooperative flow, effectively inhibiting local vortex flow and flow separation phenomenon, and significantly improving the flow field uniformity. This optimized design can smoothly reduce the flow resistance, reduce the system energy consumption, and improve the overall energy efficiency performance.

[0020] In the traditional design, the insufficient penetration depth of the hydrogen pipe may cause high-concentration hydrogen to gather near the pipe wall, accelerating the hydrogen embrittlement phenomenon of the metal material. The gas inlet group of the present application has a reasonable spray angle and distribution depth, so that the hydrogen rapidly diffuses to the center of the mixing area, avoiding high hydrogen concentration near the pipe wall, thereby effectively delaying the occurrence of hydrogen embrittlement and improving the service life and safety of the equipment.

[0021] The application utilizes the mixed element to construct the periodically changed flow field, so that the gas experiences repeated shearing and recombination process, the alternately arranged spiral structure forms complex three-dimensional turbulent flow in the flow channel, the mass exchange between the gases is enhanced, and the flow separation phenomenon is avoided; the design effectively promotes the mutual penetration between the gas microgroups through the regular change of the flow field direction, realizes the sufficient mixing of the natural gas and the hydrogen, and keeps the flow channel unobstructed.

[0022] In order to make the above-mentioned purpose, characteristics and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described below, and the accompanying drawings are used for detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0023] The drawings for constituting a part of the specification of the present application are used to provide further understanding of the present application, the schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application.

[0024] Figure 1 It is a structural schematic view of a conventional static mixer; Figure 2 It is a structural schematic view of the present application; Figure 3 It is a three-view of the structure of the present application; Figure 4 It is a schematic view of the bionic starfish inlet structure of the present application; Figure 5 It is a three-view of the bionic starfish inlet structure of the present application; Figure 6 It is a structural schematic view of the mixed element of the present application; Figure 7 It is a three-view of the structure of the mixed element of the present application; Figure 8 It is an outlet hydrogen molar concentration distribution nephogram of the conventional static mixer when the natural gas inlet flow rate is 5m / s; Figure 9 It is an outlet hydrogen molar concentration distribution nephogram of the bionic starfish inlet structure static mixer of the present application when the methane inlet flow rate is 5m / s; Figure 10 It is an outlet hydrogen molar concentration distribution nephogram of the conventional static mixer when the natural gas inlet flow rate is 10m / s; Figure 11 It is an outlet hydrogen molar concentration distribution nephogram of the bionic starfish inlet structure static mixer of the present application when the methane inlet flow rate is 10m / s; Figure 12 It is an outlet hydrogen molar concentration distribution nephogram of the conventional static mixer when the natural gas inlet flow rate is 15m / s; Figure 13This is a cloud map showing the molar concentration distribution of hydrogen at the outlet of the biomimetic starfish-shaped inlet static mixer of the present invention when the methane inlet flow rate is 15 m / s. In the diagram, 1. housing, 2. air inlet, 3. air outlet, 4. air inlet pipe assembly, 4-1. central air inlet pipe, 4-2. peripheral air inlet pipe, 5. mixing element, 6. spiral vane. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0029] Example 1 A static mixer with a biomimetic starfish-shaped inlet structure, such as Figure 2 As shown, it includes: a shell 1, which adopts a sealed design and forms a closed cavity inside. One end of the shell is provided with an air inlet 2 communicating with the cavity, and the other end is provided with an air outlet 3 communicating with the cavity; an air inlet pipe group 4, which consists of a central air inlet pipe 4-1 extending axially and five peripheral air inlet pipes 4-2 evenly distributed circumferentially, respectively simulating the central disk and radial arm structure of a starfish. This biomimetic layout can evenly distribute hydrogen in the mixing area; and a mixing element 5, which is set in the mixing cavity of the shell 1 and consists of four axially arranged spiral blades 6.

[0030] The gas inlet pipe group 4 is designed by bionics, which is composed of a central gas inlet pipe 4-1 and five peripheral gas inlet pipes 4-2 evenly distributed in the circumference, simulating the structure of the central disc and radial arm of a starfish. The structure realizes the coordinated injection of the central axial gas flow and the peripheral radial gas flow, so that the hydrogen gas is uniformly distributed in three-dimensional space when entering the mixing chamber, effectively avoiding the phenomenon of hydrogen gas gathering along the pipe wall when injected by a traditional single pipe. The central gas inlet pipe forms a stable axial hydrogen gas jet, and the peripheral gas inlet pipes produce uniform circumferential hydrogen gas distribution, which forms a multi-directional three-dimensional intersection with the axially input natural gas main flow, realizing good initial dispersion before contacting the spiral mixing element. The design effectively reduces the possibility of excessively high local hydrogen concentration, delays the hydrogen embrittlement phenomenon while improving the mixing uniformity, and improves the overall flow field distribution, thereby reducing the flow resistance.

[0031] The mixing element 5 is composed of two left-handed spiral blades 6 and two right-handed spiral blades 6 arranged alternately, which produces continuous flow field disturbance by alternating the rotation direction. The left-handed spiral blade 6 forms a specific rotational flow field along the spiral axis direction, and the right-handed spiral blade 6 produces a flow effect in the opposite direction. The periodically changing flow field makes the gas experience repeated shearing and recombination processes. The alternating spiral structure forms complex three-dimensional turbulent flow in the flow channel, enhancing the mass exchange between the gases while avoiding flow separation. The design effectively promotes the mutual penetration between the gas clusters by the regular change of the flow direction, realizing the sufficient mixing of natural gas and hydrogen while keeping the flow channel unobstructed.

[0032] In an embodiment of the present application, the shell 1 is in a circular tube structure. The central gas inlet pipe axis of the gas inlet pipe group 4 is perpendicular to the axis of the shell 1. The natural gas is input through the gas inlet 2 at one end of the shell 1, and the hydrogen gas is injected through the gas inlet pipe group 4 in the bionic starfish structure. The two gases are mixed in the shell 1 and then output through the gas outlet 3 at the other end. The innovative design of multi-channel coordinated injection realizes efficient mixing and can adapt to different flow or medium requirements, ensuring the stability of the mixing performance. In this embodiment, as shown in Figure 3 , the length A of the shell 1 is 3276 mm, and the diameter B is 273 mm.

[0033] In an embodiment of the present application, as shown in Figure 4 , the gas inlet pipe group 4 is composed of one central gas inlet pipe 4-1 extending in the axial direction and five peripheral gas inlet pipes 4-2 evenly distributed in the circumference, respectively simulating the central disc and radial arm structure of a starfish. This bionic layout can uniformly distribute hydrogen gas in the mixing area. The axial length of the central gas inlet pipe 4-1 is greater than that of the peripheral gas inlet pipe 4-2. This design is based on the principle of bionics, simulating the thickness characteristics of the central disc of a starfish, and optimizing the gas flow distribution. In this embodiment, preferably, as shown in Figure 5As shown, the axial length C of the central inlet pipe 4-1 is 273 mm, and the diameter D is 27.3 mm; the axial length E of the five peripheral inlet pipes 4-2 is 200 mm, and the diameter is the same as that of the central inlet pipe; the radial distance F between each peripheral inlet pipe and the central inlet pipe is 100 mm, and the central angle M between adjacent peripheral inlet pipes is 72°.

[0034] In one embodiment of the present application, as shown in Figure 6 、 Figure 7 The mixing element 5 is arranged in the mixing cavity of the housing 1 and is composed of four axially arranged helical blades 6, including two left-handed helical blades 6 and two right-handed helical blades 6, and the rotation directions of adjacent helical blades 6 are opposite. The outer end of the helical blade 6 is in contact with the inner wall of the housing 1. The helical blade 6 is bent from X70 round steel or X80 round steel. In this embodiment, preferably, the length G of the mixing element 5 is 1092 mm, the length H of the helical blade 6 is 273 mm, and the thickness I is 4 mm; the axial distance J from the junction of the inlet pipe group 4 and the housing 1 to the gas inlet 2 is 546 mm, and the axial distance K from the mixing element 5 to the gas inlet 2 is 1092 mm.

[0035] A mixing method using a static mixer with a bionic starfish type inlet structure, comprising the following steps: S1. Gas parameter setting: The natural gas is pressurized to 4.0 MPa, and the hydrogen gas is pressurized to 4.0 MPa; the volume flow ratio of the natural gas to the hydrogen gas is set to 4:1; S2. Graded gas injection: The natural gas is input into the cavity of the housing through the gas inlet 2 at a flow rate selected from any one of 5 m / s, 10 m / s and 15 m / s; The hydrogen gas is input into the cavity of the housing through the inlet pipe group 4 at a corresponding flow rate selected from any one of 20.83 m / s, 41.67 m / s and 62.5 m / s; S3. Mixing treatment: The natural gas and the hydrogen gas are mixed by the helical mixing element 5 in the housing 1; S4. Mixing treatment: The uniformly mixed gas is discharged through the gas outlet 3.

[0036] Of course, the specific numerical values in the above embodiments are preferred examples, and those skilled in the art can adjust or change them according to the situation.

[0037] The computational fluid dynamics software Fluent is used to simulate the two models, and the mixing uniformity at the gas outlet of the static mixer is calculated.

[0038] To quantitatively evaluate the performance of the mixer, the coefficient of variation (COV) is selected as the key evaluation index. The coefficient is defined as the ratio of the standard deviation to the average value of the volume fraction of the gas component, and its value is inversely proportional to the mixing uniformity, i.e. the lower the coefficient value, the better the mixing effect. This evaluation method has clear physical meaning and good engineering applicability.

[0039] As shown in Figure 8 , Figure 10 and Figure 12 , the test of the conventional static mixer under the conditions of natural gas inlet flow rates of 5 m / s, 10 m / s and 15 m / s shows that when the traditional single-pipe injection method is used, the uniformity of the hydrogen molar concentration distribution at the outlet cross section is poor, and the coefficient of variation reaches 5.79%, 5.84% and 6.05% respectively, which cannot meet the strict requirements of industrial applications for mixing uniformity. In addition, there is a significant near-wall hydrogen concentration enrichment phenomenon in the flow field, which may lead to hydrogen embrittlement of the mixer wall material, affecting the safety and service life of the equipment.

[0040] As shown in Figure 9 , Figure 11 and Figure 13 , the static mixer with the bionic starfish type inlet structure proposed by the present application has a coefficient of variation of hydrogen concentration distribution at the outlet of 1.24%, 1.79% and 2.02% respectively under the conditions of natural gas inlet flow rates of 5 m / s, 10 m / s and 15 m / s, which is significantly improved compared with the traditional structure and meets the requirements of industrial mixing uniformity. This innovative design significantly improves the near-wall hydrogen enrichment phenomenon in conventional mixers, effectively reduces the risk of excessive local hydrogen concentration, thereby greatly reducing the possibility of material hydrogen embrittlement and improving the safety performance and service life of the equipment.

[0041] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art without creative labor within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A static mixer in the form of a biomimetic sea star inlet structure, characterized in that The shell is internally provided with a cavity, one end of the shell is provided with an air inlet communicating with one end of the cavity, and the other end is provided with an air outlet communicating with the other end of the cavity. The shell is provided with an air inlet pipe group near the air inlet end, the air inlet pipe group comprises an axially extending central air inlet pipe and five peripheral air inlet pipes uniformly distributed around the central air inlet pipe, and the central air inlet pipe and the peripheral air inlet pipes form a bionic starfish type inlet structure simulating the central disc and radial arm structure of a starfish. The cavity is provided with a plurality of helical blades arranged axially in the cavity, and the adjacent helical blades are arranged at different angles.

2. A static mixer of the biomimetic starfish inlet configuration of claim 1, characterized in that, The air inlet is used for conveying natural gas, and the air inlet pipe group is used for conveying hydrogen.

3. A static mixer of the biomimetic starfish inlet configuration of claim 1, characterized in that, The central air inlet pipe and the peripheral air inlet pipe each comprise two parts perpendicular to each other, the first part is perpendicular to the axis of the cavity and penetrates the wall of the cavity, and the second part is parallel to the axis of the cavity, and the extension length of the second part of the central air inlet pipe in the cavity is greater than that of the second part of the peripheral air inlet pipe in the cavity.

4. A static mixer of the biomimetic starfish inlet configuration of claim 1, characterized in that, The cavity is a circular tube structure.

5. A static mixer of the biomimetic starfish inlet configuration of claim 1, characterized in that, The extension length of the second part of the central air inlet pipe in the cavity is greater than or equal to the diameter of the cavity.

6. A static mixer of the biomimetic starfish inlet configuration of claim 1, characterized in that, The diameter of the central air inlet pipe is the same as that of each peripheral air inlet pipe, the radial spacing between each peripheral air inlet pipe and the central air inlet pipe is the same, and the central included angle between adjacent peripheral air inlet pipes is 72°.

7. A static mixer of the biomimetic starfish inlet configuration of claim 1, characterized in that, The helical blades include four, and the rotation directions of adjacent helical blades are opposite.

8. A static mixer of the biomimetic starfish inlet configuration of claim 1, characterized in that, The outer end of the helical blade is in contact with the inner wall of the shell.

9. A static mixer of the biomimetic starfish inlet configuration of claim 1, characterized in that, The mixing element composed of the helical blades is arranged in the middle part of the cavity, and the air inlet pipe group is arranged in the front part of the cavity, and there is a gap between the two.

10. Mixing method based on the static mixer according to any one of claims 1 to 9, characterized in that, The steps include: The natural gas is pressurized to a set value, and the hydrogen is pressurized to a set value; The gas injection is graded: the natural gas is input into the cavity of the shell through the air inlet at a preset flow rate, the hydrogen is input into the cavity of the shell through the air inlet pipe group at a flow rate matched with the flow rate of the natural gas, and the ratio of the flow rate of the natural gas to the flow rate of the hydrogen is set in advance; The natural gas and hydrogen are mixed by the helical mixing element in the shell; The mixed gas is discharged through the air outlet.

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