Natural gas transportation pipeline drag reduction structure with flow direction-spanwise discontinuous semicircular micro grooves

Abstract

The utility model provides a natural gas transportation pipeline drag reduction structure with flow direction-spanwise discontinuous semicircular micro grooves, and belongs to the field of energy conservation and drag reduction. The problem that certain limitation still exists in micro-groove resistance reduction research in the field of natural gas pipeline conveying is solved. A plurality of semicircular micro-grooves are uniformly distributed on the inner wall of the pipeline, and the micro-grooves are intermittently and periodically arranged in the flowing direction of natural gas and the direction perpendicular to the flowing direction; the inlet end and the outlet end of each micro groove are provided with smooth transition sections with the inclination angle of 45 degrees + / -5 degrees; the spanwise width of the micro-grooves is 0.0012-0.0013 times of the diameter of the pipeline, the flow direction discontinuous length of the micro-grooves is 0.011-0.012 times of the diameter of the pipeline, and the spanwise discontinuous length of the micro-grooves is 0.4-0.6 times of the spanwise width of the micro-grooves. The device is mainly used in the field of natural gas long-distance pipeline transportation.

Description

Technical Field

[0001] This utility model belongs to the field of energy saving and drag reduction, and in particular relates to a drag reduction structure for natural gas transmission pipelines with flow-stretching discontinuous semi-circular microgrooves. Background Technology

[0002] During long-distance natural gas pipeline transportation, the frictional resistance between the pipe wall and the fluid leads to significant mechanical energy loss. This not only greatly increases transportation costs but also easily causes safety hazards such as pipeline vibration and pressure fluctuations. Statistics show that approximately 30%-40% of the energy consumption in natural gas transportation originates from the frictional resistance of the turbulent boundary layer. Therefore, reducing wall resistance through structural optimization has become a key issue for energy conservation and emission reduction in the industry. In recent years, biomimetic microgroove drag reduction technology has become a research hotspot in the field of pipeline drag reduction due to its inherent advantage of requiring no external energy input.

[0003] In existing technologies, the exploration of the drag reduction mechanism of microgrooves mainly relies on two methods: experimental research and numerical simulation. Regarding experimental research, Nitschke P et al. in 1983 conducted experiments on airflow within a circular pipe with circular groove peaks and flat groove valleys, discovering that when the dimensionless groove width s... + The drag reduction effect is achieved when the temperature is between 8 and 23°C; Lee SJ et al. used synchronous smoke line technology to conduct flow field analysis on the turbulent boundary layer of the semi-circular microgroove surface, and obtained the results at s + At a velocity of 25.2, because the large longitudinal vortex is larger than the microgroove spacing, most flow-directing vortices remain on the microgrooves, resulting in relatively calm flow within the microgroove valleys and reduced drag. Wang Jinjun et al. conducted a series of experiments on the wall turbulent boundary layer structure characteristics of flow-directing grooves: they designed three different sizes of V-shaped grooves for smooth flat plates and carried out drag reduction experiments, comparing turbulence intensity and drag characteristics, finding that the local drag of the V-shaped groove structure can be reduced by as much as 13%-26%.

[0004] To further explore the drag reduction mechanism of microgrooves, in the field of numerical simulation, Launder BE et al. conducted numerical studies on microgrooves at different Reynolds numbers, finding that when the Reynolds number is less than 15000, the drag reduction effect is relatively sensitive to the Reynolds number. Peet et al. used LES to numerically simulate sinusoidal flow-oriented microgrooves with triangular cross-sections, obtaining a drag reduction effect of over 50%. Ahn, Klumpp, and other scholars revealed the control law of square, semi-circular, and triangular grooves on near-wall vortex structures through large eddy simulation.

[0005] However, current technology still has significant limitations: First, existing experimental and numerical studies are mostly focused on small-diameter (<100mm) conditions, lacking adaptability verification for industrial-grade gas pipelines (such as DN400 and above); second, the design of microgrooves suffers from a lack of simplification, with traditional continuous grooves, while possessing some drag reduction capability, failing to effectively suppress both flow-direction and spanwise vortices, especially exhibiting drag reduction rate fluctuations over a wide Reynolds number range; third, most studies focus on the isolated optimization of groove geometry parameters, lacking a systematic exploration of groove arrangement methods, making it difficult to further improve turbulence disturbance suppression. These shortcomings restrict the large-scale application of microgrooving drag reduction technology in long-distance natural gas pipelines, necessitating breakthroughs in structural innovation and flow field control mechanisms. Utility Model Content

[0006] In view of this, the present invention aims to propose a drag reduction structure for natural gas transmission pipelines with discontinuous semi-circular microgrooves in the flow direction and span direction, so as to solve the problem that there are still certain limitations in the research on microgroove drag reduction in the field of natural gas pipeline transportation.

[0007] To achieve the above objectives, this utility model adopts the following technical solution: a drag-reducing structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and spanwise direction, the drag-reducing structure comprising:

[0008] The inner wall of the pipeline is uniformly distributed with multiple semi-circular microgrooves, which are intermittently and periodically arranged along the natural gas flow direction and perpendicular to the flow direction.

[0009] Each microgroove has a smooth transition section with an inclination angle of 45°±5° at both the inlet and outlet ends.

[0010] The spanwise width of the microgroove is 0.0012 to 0.0013 times the pipe diameter, the flow discontinuity length is 0.011 to 0.012 times the pipe diameter, and the spanwise discontinuity length is 0.4 to 0.6 times the spanwise width.

[0011] Furthermore, a preferred embodiment is proposed, wherein the spanwise width of the microgroove is 0.54~0.55mm, the flow discontinuity length is 4.72~4.74mm, and the spanwise discontinuity length is 0.27~0.28mm.

[0012] Furthermore, a preferred embodiment is proposed, wherein the ratio of the depth to the spanwise width of the microgroove is 0.5 to 0.7.

[0013] Furthermore, a preferred embodiment is proposed in which the microgrooves are distributed on the inner wall of the pipe in a rotating array manner, and the spacing angle between adjacent microgrooves in the spanwise direction is 24°.

[0014] Furthermore, a preferred embodiment is proposed, wherein the Reynolds number of the microgrooves is in the range of 1.30 × 10⁻⁶. 5 ~6.54×10 5 .

[0015] Furthermore, a preferred embodiment is proposed, wherein the inner diameter of the pipe is 426 mm, and the ratio of the spanwise width of the microgroove to the pipe diameter is 1:800~1:780.

[0016] Furthermore, a preferred embodiment is proposed, wherein the spanwise arrangement density of the microgrooves is 15 to 18 microgrooves evenly distributed within each 24° arc.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] 1. This utility model proposes a drag-reducing structure for natural gas transmission pipelines with discontinuous semi-circular microgrooves in the flow-stretcher direction. Compared to traditional continuous microgrooves (such as V-shaped or triangular ones) which are only effective in specific Reynolds number ranges (such as Re < 15000), this utility model, through its discontinuous semi-circular microgrooves in the flow-stretcher direction, achieves drag reduction even at Re = 1.30 × 10⁻⁶. 5 ~6.54×10 5 Stable drag reduction is achieved within the range (5m / s~25m / s flow velocity), especially when Re=2.60×10 5 The drag reduction rate reached 18.08% (see Table 1), breaking through the technical bottleneck of traditional structures being sensitive to Reynolds number.

[0019] 2. This utility model proposes a combined design based on a semi-circular geometric configuration and a 45° smooth transition section. The microgrooves form a dual suppression effect in the near-wall region. By suppressing the generation and expansion of flow vortices along the flow direction, the longitudinal turbulence intensity is reduced; by hindering the migration of spanwise vortices in the spanwise direction, the transverse velocity fluctuations are reduced. Through numerical simulation verification, this structure pushes the high-turbulence disturbance zone away from the pipe wall, making the boundary layer velocity distribution closer to the laminar state and significantly reducing the wall shear stress.

[0020] 3. This utility model adopts a rotating array arrangement (24° spanning interval) and standardized dimensional parameters (0.54072mm spanning width, 4.72964mm flow discontinuity) to ensure the feasibility of processing microgrooves on the inner wall of industrial-grade large-diameter pipes (such as 426mm).

[0021] 4. The drag-reduction structure proposed in this invention has significant energy-saving and consumption-reducing effects. Taking a flow velocity of 25 m / s as an example, the microgroove structure reduces the pipe resistance from 0.00455 N on a smooth wall to 0.004537 N (drag reduction rate of approximately 0.29%). Combined with the kilometer-scale extension characteristics of long-distance pipelines, the cumulative energy-saving benefits are significant. Compared with the V-shaped grooves and sinusoidal grooves in small-diameter pipes in the prior art, this invention achieves balanced drag reduction under large-diameter and wide flow velocity ranges. It is mainly used in the field of long-distance natural gas pipeline transportation. Attached Figure Description

[0022] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0023] Figure 1 This is a schematic diagram of the flow-stretching discontinuous microgroove structure described in this utility model;

[0024] Figure 2 The overall shape of the lower wall surface of the pipe described in this utility model;

[0025] Figure 3 This is a schematic diagram of the drag reduction structure of this utility model, wherein, Figure 3 (a) is a schematic diagram of the flow direction dimensions of a single microgroove structure. Figure 3 (b) is a schematic diagram of the spanwise dimensions of a single microgroove, where S represents the width of the microgroove and L represents the depth of the microgroove.

[0026] Figure 4 This is a schematic diagram showing the drag reduction rate under various operating conditions described in this utility model;

[0027] Figure 5 This is a schematic diagram of the average velocity distribution of the smooth pipe with a flow direction of 10m / s as described in this utility model. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0029] Implementation Method 1: The drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow-stretcher direction described in this implementation method includes:

[0030] The inner wall of the pipeline is uniformly distributed with multiple semi-circular microgrooves, which are intermittently and periodically arranged along the natural gas flow direction and perpendicular to the flow direction.

[0031] Each microgroove has a smooth transition section with an inclination angle of 45°±5° at both the inlet and outlet ends.

[0032] The spanwise width of the microgroove is 0.0012 to 0.0013 times the pipe diameter, the flow discontinuity length is 0.011 to 0.012 times the pipe diameter, and the spanwise discontinuity length is 0.4 to 0.6 times the spanwise width.

[0033] The structure described in this embodiment significantly reduces frictional resistance between the fluid and the pipe wall by uniformly distributing multiple semi-circular microgrooves on the inner wall. This intermittent, periodic arrangement of the microgrooves optimizes the fluid flow path, reducing turbulence generation and energy loss. Each microgroove has a smooth transition section with an inclination angle of 45°±5° at both its inlet and outlet ends, avoiding abrupt fluid changes and reducing energy loss during flow. This design allows natural gas to flow more smoothly within the pipe, further reducing flow resistance. The design of the discontinuous lengths in the flow direction and spanwise direction of the microgrooves ensures that the structure is periodically arranged not only in the natural gas flow direction but also intermittently perpendicular to the flow direction. This design can adapt to gas flow requirements under different flow velocities and flow regimes, optimizing the pipe's flow performance.

[0034] The dimensions of the microgrooves (spanning width, flow discontinuity length, and spanning discontinuity length) are precisely designed in proportion to the pipe diameter. The spanning width is 0.0012 to 0.0013 times the pipe diameter, the flow discontinuity length is 0.011 to 0.012 times the pipe diameter, and the spanning discontinuity length is 0.4 to 0.6 times the spanning width. This dimensional design ensures effective drag reduction while guaranteeing the stability of the drag-reducing structure and the reliability of long-term operation.

[0035] Implementation Method 2: This implementation method further defines the drag reduction structure of a natural gas transmission pipeline with flow-spreading discontinuous semi-circular microgrooves as described in Implementation Method 1. The spread width of the microgrooves is 0.54~0.55mm, the flow discontinuity length is 4.72~4.74mm, and the spread discontinuity length is 0.27~0.28mm.

[0036] In this embodiment, the spanwise width of the microgrooves is further defined (0.54~0.55 mm). The microgrooves on the inner wall of the pipe can optimize the contact area between the fluid and the pipe to a large extent. Appropriately increasing the spanwise width of the microgrooves helps to enhance the distribution and flow stability of the fluid, thereby reducing local turbulence and uneven flow, and further reducing the flow resistance inside the pipe.

[0037] Adjustments to the flow-direction discontinuity length (4.72~4.74 mm) and spanwise discontinuity length (0.27~0.28 mm) optimized the discontinuous arrangement of the microgrooves. This fine-tuning of the flow-direction and spanwise discontinuity lengths made the microgroove design more consistent with fluid dynamics principles, effectively suppressing turbulence generation and reducing energy loss at different flow velocities, thus achieving better drag reduction. The design of the spanwise discontinuity length also optimized fluid distribution along the pipe, improving flow stability.

[0038] Implementation Method 3: This implementation method further defines the drag reduction structure of a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction as described in Implementation Method 1. The ratio of the depth to the span direction width of the microgrooves is 0.5 to 0.7.

[0039] In this embodiment, the semi-circular microgroove design effectively breaks the laminar flow state of the fluid inside the pipe, promoting turbulent mixing and thus reducing flow resistance within the pipe. Furthermore, by controlling the ratio of the microgroove's depth to its spanwise width within the range of 0.5 to 0.7, the fluid's movement path can be optimized to some extent, further improving flow efficiency and reducing pressure drop.

[0040] Implementation Method 4: This implementation method further defines the drag reduction structure of a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction as described in Implementation Method 1. The microgrooves are distributed on the inner wall of the pipeline in a rotating array manner, and the spacing angle between adjacent microgrooves in the span direction is 24°.

[0041] The rotating array distribution ensures that the fluid is affected by different microstructures at different locations. With adjacent microgrooves spaced at 24° intervals, this layout creates a regular, uniformly distributed structure within the pipe, preventing localized flow instability and reducing energy loss. Compared to a single linear arrangement of microstructures, the rotating array design achieves smoother and more uniform fluid guidance, thus enhancing the overall drag reduction capability of the pipe.

[0042] Implementation Method 5: This implementation method further defines the drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow-stretcher direction described in Implementation Method 1. The Reynolds number of the microgrooves is in the range of 1.30 × 10⁻⁶. 5 ~6.54×10 5 .

[0043] Implementation Method Six: This implementation method further defines the drag reduction structure of a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction as described in Implementation Method One. The inner diameter of the pipeline is 426 mm, and the ratio of the span direction width of the microgrooves to the pipeline diameter is 1:800~1:780.

[0044] Implementation Method Seven: This implementation method further defines the drag reduction structure of a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction as described in Implementation Method One. The span direction arrangement density of the microgrooves is 15 to 18 microgrooves evenly distributed within each 24° arc.

[0045] Implementation Method 8, see below Figures 1 to 5 This embodiment describes a specific example of a drag-reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow-stretcher direction, as described in Embodiment 1. It also serves to explain Embodiments 2 through 7. Specifically:

[0046] This embodiment proposes a novel semi-circular structure for pipe inner wall drag reduction microgrooves. The unique flow-direction and spanwise discontinuous microgroove layout optimizes near-wall flow characteristics. Based on computational fluid dynamics, this embodiment also utilizes the Fluent numerical simulation platform to analyze drag reduction performance under different flow velocities. The results show that this novel groove structure effectively reduces wall friction resistance, significantly improving drag reduction efficiency and range compared to traditional structures. This provides an innovative solution for energy saving and consumption reduction in long-distance natural gas transportation. Specifically:

[0047] In this embodiment, the size of a single microgroove is as follows: Figure 1 As shown, a circular tube with a diameter of 426 mm is used as the simulation object. To minimize the increase in resistance caused by abrupt structural changes during the flow of methane gas within the tube, instead of simply vertically excavating each microgroove inlet and outlet, a 45° inclination angle is added to allow for a smooth transition, with a flow discontinuity of 4.72964 mm. In the spanwise direction, the width of a single microgroove remains constant at 0.54072 mm, and the spanwise groove discontinuity L is set to 0.27036 mm. The overall effect of the lower wall of the microgrooved circular tube is shown below. Figure 2 As shown, the dimensions of the drag reduction structure are as follows: Figure 3 As shown.

[0048] In actual modeling, drawing the entire circular pipe would result in an excessive number of mesh nodes and high computational resource consumption. Therefore, when using Designmodeler, a flow length of 100mm, a normal height of 213mm (radius), and a span of 24° were used to generate a local computational domain model, representing 1 / 15 of a circular arc. Due to the large number and small size of the microgrooves, overall modeling and meshing were difficult. Therefore, it was chosen to first draw a single discontinuous microgroove structure model, and then obtain a circular pipe with longitudinal grooves covering its entire bottom through rotation and arraying.

[0049] In the actual verification, the structured mesh was generated using Icem mesh generation software. To ensure the accuracy of data comparison, the flow direction of the smooth / groove model was uniformly set to 120 nodes, and the height of the first layer mesh was 3.3e-5m from the wall.

[0050] Large eddy simulation (LES) was performed on smooth-walled pipes and semi-circular microgrooved pipes with flow-stretcher discontinuities. The resistance was calculated and compared with and without the microgrooving structure by monitoring the weighted average of the flow velocity and wall shear stress. The results are shown in the table below. The Reynolds number is... , For wall shear stress, For the wall area, As resistance, For drag reduction ratio, the calculation formula is ( (A positive value indicates drag reduction, while a negative value indicates drag increase). The drag reduction structure is shown in the table below.

[0051] Table 1. Drag reduction effect of flow-width-span discontinuous semi-circular microgrooves under various operating conditions.

[0052]

[0053] Continued table

[0054]

[0055] As shown in Table 1, the discontinuous microgroove structure exhibits good performance when the incoming flow velocity is between 5 m / s and 25 m / s (corresponding to Re = 1.30 × 10⁻⁶). 5 ~6.54 × 10 5 At Re = 2.60 × 10⁻⁶, it exhibits drag reduction, and at Re = 2.60 × 10⁻⁶, it exhibits drag reduction. 5 At this point, the drag reduction effect reaches its maximum value of 18.08%, and the overall drag reduction rate changes with the Reynolds number as follows: Figure 4 As shown.

[0056] Figure 5 This is a schematic diagram of the average velocity distribution of a smooth pipe with a flow rate of 10 m / s, where y + u is the dimensionless height of the wall. + As the velocity is dimensionless, it can be seen that the results calculated by LES (solid line) and the experimental data (dashed line) fit well, proving the accuracy of the LES calculation results. At the same time, when the incoming flow velocity is 10 m / s, the theoretical value of the shear stress on the smooth pipe wall is 0.11698 (Pa), and the LES simulation value is 0.11721 (Pa), with an error of 0.196%, which is within the acceptable range.

[0057] The specific embodiments of this utility model disclosed above are merely illustrative of the present utility model. These specific embodiments do not exhaustively describe all details, nor do they limit the utility model to only the described embodiments. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this utility model, thereby enabling those skilled in the art to better understand and utilize it.

Claims

1. A drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow-stretcher direction, characterized in that, The drag reduction structure includes: The inner wall of the pipeline is uniformly distributed with multiple semi-circular microgrooves, which are intermittently and periodically arranged along the natural gas flow direction and perpendicular to the flow direction. Each microgroove has a smooth transition section with an inclination angle of 45°±5° at both the inlet and outlet ends. The spanwise width of the microgroove is 0.0012 to 0.0013 times the pipe diameter, the flow discontinuity length is 0.011 to 0.012 times the pipe diameter, and the spanwise discontinuity length is 0.4 to 0.6 times the spanwise width.

2. The drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction as described in claim 1, characterized in that, The microgrooves have a spanwise width of 0.54–0.55 mm, a flow discontinuity length of 4.72–4.74 mm, and a spanwise discontinuity length of 0.27–0.28 mm.

3. The drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction as described in claim 1, characterized in that, The ratio of the depth to the spanwise width of the microgroove is 0.5 to 0.

7.

4. The drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction as described in claim 1, characterized in that, The microgrooves are distributed on the inner wall of the pipe in a rotating array manner, with the spacing angle between adjacent microgrooves in the spanwise direction being 24°.

5. The drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction according to claim 1, characterized in that, The Reynolds number of the microgrooves ranges from 1.30 × 10⁻⁶. 5 ~6.54×10 5 .

6. The drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and spanwise direction as described in claim 1, characterized in that, The inner diameter of the pipe is 426 mm, and the ratio of the spanwise width of the microgroove to the pipe diameter is 1:800 to 1:

780.

7. The drag reduction structure for a natural gas transmission pipeline with discontinuous semi-circular microgrooves in the flow direction and span direction according to claim 1, characterized in that, The microgrooves are arranged in a spanwise density of 15 to 18 microgrooves evenly distributed within each 24° arc.

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