Steepest curve internal spiral flow guide pipeline for water conservancy drainage

Abstract

The invention discloses a steepest curve inner spiral flow guide pipeline for water conservancy drainage, which is suitable for scenes such as vertical shaft drainage of water conservancy and municipal engineering, building vertical pipe drainage and cyclone separation, and has the effects of improving the overflowing efficiency and improving the structural safety. The structure comprises a pipe body and one or more spiral flow guide ribs arranged on the inner wall of the pipe body, and the spiral flow guide ribs are evenly distributed or distributed in a duplex centralized mode along the cross section of the pipeline. The spiral flow guide ribs extend in the axial direction of the pipe body, and the projection tracks of the spiral flow guide ribs on the unfolding plane of the side wall of the pipe body conform to the geometrical characteristics of a steepest curve. According to the inner spiral pipe, a spiral flow channel curve with a non-constant spiral angle is constructed through a variational method by utilizing the principle of'minimum action quantity 'of a steepest curve in a gravity field and a potential field, so that fluid is accelerated in an optimal path in a rotation starting stage, and the problems of large inlet impact, difficulty in fluid rotation starting, high on-way resistance and the like of a traditional inner spiral pipe are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of vertical drainage technology in water conservancy engineering, specifically to a spiral guide pipe within the fastest curve for water conservancy drainage that utilizes geometric optimization principles to achieve functions such as efficient swirling flow, flood discharge, reduced flow resistance, and improved conveying efficiency. Background Technology

[0002] In gravity-driven fluid transport engineering, such as water conservancy and municipal engineering shaft flood discharge or drainage systems, and building riser drainage systems, the flow regime control of the fluid in the vertical space is crucial to determining the system's safe and stable flow capacity. When fluid falls vertically at high speed along the pipe axis, the system typically exhibits a complex gas-liquid two-phase flow. The ideal hydraulic state is to induce the fluid to rapidly adhere to the wall under the action of gravitational acceleration, forming a stable wall-attached helical flow. In this state, the fluid is constrained by centrifugal force to rotate and fall along the wall, forming a through-hole air core at the center, thereby maintaining pressure balance within the pipe and eliminating air compression and "air hammer" effects caused by disordered water flow fluctuations. However, in actual operation, maintaining this wall-attached flow regime mainly faces the following two problems.

[0003] (1) The constant helix angle guiding structure results in low swirl efficiency.

[0004] Existing internal spiral guiding technologies (such as the structure specified in the T / CECS 94-2019 standard) mostly employ guide ribs with a constant helix angle, meaning the projection of the helix rib onto the unfolded plane of the pipe wall is typically a straight line. In this structure, the helix angle remains constant throughout the entire axial range. While this structure is geometrically simple and easy to manufacture, it is not the optimal path from a hydrodynamic perspective. When water flows from a vertical freefall state into this type of constant helix rib, the fluid needs to abruptly change its direction of motion in the inlet region, transforming from axial motion to helical motion with a tangential velocity component. This abrupt change leads to strong impacts and turbulence between the fluid and the guide rib, resulting in significant local energy loss and reduced swirl efficiency. Furthermore, due to the relatively slow growth of rotational momentum, it is difficult to fully utilize the fluid's gravitational potential energy to form a stable wall-attached swirling state.

[0005] (2) The spiral ribs have a single distribution pattern, which limits the ultimate flow capacity.

[0006] Besides the spiral trajectory design, the cross-sectional structure of the guide ribs and their distribution on the pipe wall also significantly affect the flow pattern inside the pipe. In existing technologies, most internal spiral pipes adopt a single-rib or multi-rib uniformly distributed structure. When applied to sandy water flow (hydraulic scenarios) or domestic sewage (construction scenarios), this trajectory cannot accurately match the energy conversion law of fluid particles changing with height, resulting in a gradual decrease in tangential velocity, a continuous increase in the thickness of the water film attached to the wall, and consequently, encroachment on the air core space in the center of the pipe.

[0007] Experimental studies (e.g., Li Pei'ang et al., "Study on the Influence of Internal Spiral Tube Structural Parameters and Swirl Flow on the Performance of Special Single-Pipe Drainage Systems", 2025) show that under this structural condition, the drainage capacity of the riser has a certain upper limit. For example, in a common DN110 drainage system, its limit drainage capacity is usually about 7.5 L / s. When the drainage volume increases further, the water film will gradually expand towards the center of the pipe, eventually forming a water plug flow and causing a bottleneck in drainage capacity. In contrast, adopting a centralized or compound guide rib structure can maintain a relatively high tangential velocity to a certain extent and induce water film thinning, thereby significantly improving the safe flow capacity of the pipe (up to 13.5 L / s under the same conditions).

[0008] In summary, there is still room for improvement in both the optimization of the flow trajectory and the design of the cross-sectional structure of existing internal spiral tubes.

[0009] In classical theoretical research, the brachistochrone curve has been proven to be the path with the shortest time required for a particle to move from one point to another in a gravitational field. Due to its ability to efficiently convert potential energy into kinetic energy, this curve has been applied in several engineering fields, such as rapid roof drainage structures, planar structures like conveyor belts for transporting goods, or full-pipe flow guides operating under pressure. However, in existing technologies, there is no known solution to incorporate the brachistochrone curve trajectory into gravity-driven internal spiral flow guide devices to achieve three-dimensional rotational flow of fluid; nor is there a known solution to combine it with a compound centralized flow guide structure to optimize the flow pattern of riser drainage.

[0010] Therefore, developing an internal spiral flow guiding device based on the fastest curve trajectory is of great engineering significance for optimizing the fluid flow state under gravity drive, maintaining the system air pressure balance, and improving the safety of high-drop drainage in water conservancy and drainage. Summary of the Invention

[0011] The purpose of this invention is to overcome the problems of simple spiral rib trajectory and low fluid swirl efficiency in existing internal spiral pipe technology for water conservancy and drainage, and to provide an internal spiral guide pipe with the fastest curve for water conservancy and drainage. This device introduces a geometric trajectory that conforms to the optimal acceleration path in a gravitational field and performs nonlinear optimization design on the spiral guide ribs, enabling the fluid to gradually establish a stable swirling state according to the natural acceleration law after entering the pipe, thereby reducing energy loss, improving drainage efficiency, and increasing the safe flow threshold of the pipe.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A spiral guide pipe for the fastest curve in water conservancy drainage, comprising a pipe body (1) and at least one spiral guide rib (2) disposed on the inner wall of the pipe body (1), characterized in that:

[0014] The spiral guide rib (2) extends spirally along the axial direction of the tube body;

[0015] After the inner wall of the tube (1) is unfolded into a plane along the axial generatrix, the projection trajectory of the spiral guide rib (2) on the unfolded plane conforms to the geometric characteristics of the fastest curve.

[0016] The spiral angle of the spiral guide rib (2) changes nonlinearly and continuously along the fluid flow direction to guide the fluid to smoothly transition from axial flow to spiral flow.

[0017] Preferably, the trajectory coordinates of the spiral guide rib (2) on the unfolded plane are... The following parametric equations for the brachistochrone curve must be satisfied:

[0018]

[0019] The starting point of the steepest curve plane unfolding is (x0, y0), and the ending point is (x1, y1). ΔX = x1 - x0 = πD is the circumferential unfolding length of the inner wall of the tube, and ΔY = y1 - y0 is the axial height of the tube, i.e., the pitch. a is the cycloidal parameter, i.e., the radius of the circle corresponding to the trajectory of the steepest curve formed by circular rolling; θ is the circular rolling angle, where the circular rolling angle corresponding to the starting point of the steepest curve is 0, and the circular rolling angle corresponding to the ending point of the steepest curve is θ0; D is the inner diameter of the tube.

[0020] The parameters a and θ0 are determined through the following steps:

[0021] S1) Endpoint condition equation, that is, let the endpoint corresponding parameter θ = θ0, and the starting point be the origin, then:

[0022]

[0023] S2) Eliminating a to find θ0, we have:

[0024]

[0025] Define a function:

[0026]

[0027] When ΔX / ΔY>0, θ0 can be obtained by solving Newton's iteration method;

[0028] S3) Find the cycloidal parameter a;

[0029]

[0030] Alternatively, the following formula can be used:

[0031] .

[0032] Preferably, the inner spiral diversion pipeline comprises a plurality of spiral diversion ribs (2) evenly distributed at equal intervals in the circumferential direction of the inner wall of the pipeline body, and the intervals between the plurality of spiral diversion ribs are equal along the whole length.

[0033] Preferably, the inner spiral diversion pipeline comprises multiple groups of spiral diversion ribs (2) distributed in a compound concentrated manner in the circumferential direction of the inner wall of the pipeline body, and the intervals between the multiple groups of spiral diversion ribs are equal along the whole length.

[0034] Preferably, each group of the spiral diversion ribs (2) distributed in the compound concentrated manner is composed of a main diversion rib and two auxiliary diversion ribs arranged in close fit or adjacent to each other; wherein, the height of the main diversion rib is h1, the height of the auxiliary diversion rib is h2, and h1 > h2 is satisfied, forming a "mountain" - shaped composite cross - section.

[0035] Preferably, the main diversion rib and the auxiliary diversion rib are configured such that a micro - channel is formed between the main diversion rib and the auxiliary diversion rib, which is used to induce the "local accumulation - rapid thinning" pulsating effect of the adhering water film.

[0036] Preferably, the shape of the spiral diversion rib (2) is a triangular spiral rib protruding towards the center of the pipeline body, and the height h of the spiral rib satisfies the condition that a swirling flow can be formed and the water flow surface is not truncated.

[0037] Preferably, the ratio range of the height h of the spiral rib of the spiral diversion rib (2) to the inner diameter D of the pipeline body (1) is: 0.03 < h / D < 0.05.

[0038] The present invention also provides the application of the above - mentioned brachistochrone inner spiral diversion pipeline for water conservancy drainage in water conservancy and municipal engineering shaft flood discharge or drainage, building vertical pipe drainage, and the inlet pipe section of a gas - liquid cyclone separator under the action of gravity.

[0039] The diversion structure of the present invention maps the two - dimensional brachistochrone trajectory onto the three - dimensional cylindrical surface, enabling the fluid in the pipeline to move along an approximately optimal acceleration path under the action of gravity, thereby achieving a smooth transition from axial flow to spiral flow.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) Optimize the internal flow field structure and increase the safety drainage flow threshold

[0042] Because the helical angle of the spiral guide rib changes non-linearly and continuously along the axial direction, the fluid velocity vector can smoothly change direction in space, avoiding the local turbulence and energy loss caused by sudden changes in flow direction in traditional constant-pitch spiral structures. Through this geometric optimization, the stable wall-attached spiral flow can reduce the probability of water slugging and reduce pressure fluctuations inside the pipe. This improves the overall stability of the drainage system while avoiding damage to the water seal and raising the safe drainage threshold of the drainage system.

[0043] (2) Improve the spinning efficiency and reduce drainage noise.

[0044] This invention utilizes the geometric characteristics of the brachistochrone curve to ensure that the tangent direction of the spiral guide rib in the inlet region is essentially aligned with the initial descent direction of the fluid. This reduces energy loss and resulting pulsating vibrations when the fluid enters the guide structure, thereby lowering drainage noise. Through this guide method that conforms to the natural acceleration law of the fluid, the water flow can rapidly begin to swirl within a short axial distance.

[0045] (3) Enhance the self-cleaning ability of pipelines

[0046] Because the swirling structure can maintain a high tangential flow velocity, the water flow generates a stronger shearing and scouring effect on the pipe wall surface, thereby improving its ability to carry away solid particles, sediments, and oily contaminants. This characteristic helps reduce the adhesion and deposition of dirt on the inner wall of the pipe, reduces the risk of pipe blockage, and improves the self-cleaning ability of the drainage system. Attached Figure Description

[0047] Figure 1 A three-dimensional schematic diagram of an internal spiral pipe based on the steepest curve trajectory;

[0048] Figure 2 This is the planar development diagram of the brachistochrone curve;

[0049] Figure 3 This is a three-dimensional trajectory diagram of the fastest curve;

[0050] Figure 4 A cross-sectional view of a uniformly distributed ribbed spiral tube based on the steepest curve;

[0051] Figure 5 This is a cross-sectional view of a compound concentrated distribution ribbed spiral tube based on the steepest curve.

[0052] The reference numerals in the figure are: 1-pipe body; 2-spiral guide rib, height h; 3-main guide rib, height h1; 4-auxiliary guide rib, height h2. Detailed Implementation

[0053] The technical solutions in the embodiments of the present invention will now be described in detail and completely with reference to the accompanying drawings.

[0054] Example 1 Design of Spiral Ribs with Equidistant Distribution Based on the Brachistochrone Trajectory

[0055] This example demonstrates a precisely calculated optimal structure suitable for scenarios where space is limited but rapid establishment of strong swirling flow and rapid drainage are required, such as flood discharge vertical pipes, drainage of vertical pipes in high-rise buildings, etc.

[0056] As Figure 1 shown, the device includes a pipe body 1 and multiple spiral guiding ribs 2 provided on the inner wall of the pipe body 1. The spiral guiding ribs 2 extend spirally along the axial direction of the pipe body. After unfolding the inner wall of the pipe body 1 along the axial generatrix into a plane, the projection trajectory of the spiral guiding ribs 2 on the unfolded plane conforms to the geometric characteristics of the brachistochrone curve. The spiral angle of the spiral guiding ribs 2 changes non-linearly and continuously along the fluid flow direction to smoothly convert the fluid from axial flow to spiral flow. The multiple spiral guiding ribs 2 are evenly distributed at equal intervals in the circumferential direction of the inner wall of the pipe body, and the distance between the multiple spiral guiding ribs is equal along the way.

[0057] 1. Setting of geometric parameters:

[0058] (1) The effective height (axial length) ΔY = H = 0.8 m of the pipeline unit selected in this example.

[0059] (2) The unfolded length (circumference) ΔX = W = 0.5 m (inner diameter D = 160 mm) of the guiding structure on the pipe wall.

[0060] (3) As Figure 4 shown, 6 spiral ribs evenly distributed along the cross-section of the pipeline are designed. According to T / CECS 94-2019 "Technical Specification for Engineering of Internal Spiral Pipes for Building Drainage", the ratio range of the spiral rib height h to the inner diameter D of the pipe body for the spiral guiding ribs is: 0.03 < h / D < 0.05. In this example, the spiral rib height is set to 7 mm, and other parameters are formulated according to the current standards.

[0061] 2. Spiral rib trajectory equation and calculation:

[0062] The trajectory of the spiral rib on the unfolded plane of the pipe wall satisfies the brachistochrone curve equation:

[0063]

[0064] This design adopts the principle of variational method. By solving the Euler-Lagrange equation to obtain the brachistochrone curve trajectory of the guiding structure, the analytical solution of the brachistochrone curve equation in this example is obtained, where θ0 = 97.08° = 1.694 rad, a = 0.7122, and the brachistochrone curve trajectory equation is obtained:

[0065]

[0066] The planar expansion and three-dimensional trajectory of the present invention are as follows Figure 2 , Figure 3 shown

[0067] 3. Working principle:

[0068] When the fluid enters the pipe unit with a height of 0.8 m:

[0069] In the inlet acceleration section (corresponding to the area with a smaller θ), the spiral ribs are almost perpendicular downward. By using the gravity component, the fluid can quickly obtain the axial velocity within a short distance without generating obvious tangential impact resistance.

[0070] In the subsequent swirl generation section, the inclination angle of the spiral ribs smoothly transitions according to the characteristics of the brachistochrone curve. The fluid is extremely smoothly guided to the pipe wall, and the tangential velocity increases rapidly in a non-linear manner.

[0071] At a depth of 0.8 m at the outlet, the angle between the guide ribs and the horizontal plane transitions to approximately 41.46° ((180° - 97.08°) / 2). This angle not only ensures sufficient swirl centrifugal force but also maintains a good self-cleaning downward angle to prevent the accumulation of solid particles in the sewage.

[0072] Example 2: Inner spiral pipe with compound concentrated spiral ribs based on the brachistochrone curve

[0073] On the basis of Example 1, in order to further improve the safe flow capacity of the drainage pipe, the distribution mode of the spiral ribs is changed. A compound concentrated rib inner spiral guide pipe based on the brachistochrone curve trajectory is adopted in the circumferential direction of the pipe inner wall, as Figure 4 00172>shown, including multiple groups of spiral guide ribs 2 that are compound concentratedly distributed in the circumferential direction of the pipe inner wall, and the multiple groups of spiral guide ribs are equidistant along the way. Each group of spiral guide ribs 2 in the compound concentrated distribution is composed of a main guide rib and two auxiliary guide ribs that are closely adhered or arranged adjacent to each other; among them, the height of the main guide rib is h1, and the height of the auxiliary guide rib is h2, and h1 > h2 is satisfied, forming a "mountain" - shaped composite cross-section

[0074] Among them, the main guide rib and the auxiliary guide rib are constructed as follows: a micro-channel is formed between the main guide rib and the auxiliary guide rib, which is used to induce the pulsating effect of "local accumulation - rapid thinning" of the attached wall water film

[0075] Example 3: Calculation and comparison of drainage efficiency and the improvement effect of the safe drainage threshold

[0076] In order to verify the effect of the spiral guide ribs based on the brachistochrone curve trajectory described in the present invention in improving the drainage efficiency, in this example, an ideal particle dynamics model is adopted to conduct comparative calculations on Example 1 and Example 2 and the prior art (inner spiral pipe with a constant spiral angle) respectively

[0077] 1. Computational Model Setting: Physical Model: Fluid particles are released from rest and move along both a "constant helical angle trajectory (corresponding to a straight line on the unfolded plane)" and a "brachistochrone curve trajectory (corresponding to a spiral line on the unfolded plane)" to the same endpoint. Boundary Conditions: The vertical height of the pipe is set to H, and the horizontal unfolded length is set to W. The acceleration due to gravity is taken as g = 9.81 m / s². 2 .

[0078] 2. Theoretical Formulas

[0079] 1) Control group (existing technology, constant helix angle of the curve):

[0080] The particle slides down a straight slope, and its motion time is t. line The calculation formula is:

[0081]

[0082] 2) Experimental group (this invention, the steepest curve has a non-constant helix angle):

[0083] The particle moves along the trajectory of a rotary axis, and its motion time is t. curve The calculation formula is:

[0084] 3. Numerical Calculation Results

[0085] Substitute the typical design parameters of this invention into the calculation:

[0086] 1) Existing technology (constant helix angle): The theoretical time for a fluid particle to pass through this pipe section is calculated to be approximately 0.476 s.

[0087] 2) This invention (rapidest curve): The theoretical time for a fluid particle to pass through a pipe section of the same specification is calculated to be approximately 0.457s.

[0088] 4. Conclusion on Efficiency Improvement

[0089] Comparing the above results, it can be seen that, under the same gravitational potential energy, the device of the present invention reduces the transit time per unit volume of water:

[0090]

[0091] Drainage efficiency improvement rate (time reduction rate, per unit height in meters):

[0092]

[0093] With a 5% increase in drainage efficiency, the safe drainage flow threshold of the pipeline also increases by 1.05 times.

[0094] Based on this, it can be calculated that the drainage capacity of the compound concentrated distribution spiral rib inner spiral tube based on the steepest curve in Example 2 can be increased by about 1.9 times compared with the drainage capacity of the inner spiral tube in the current technology.

[0095] The specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the scope of the invention. Any adaptive modifications, additions, or similar substitutions made to these embodiments by those skilled in the art after reading this specification are within the scope of protection of this invention.

Claims

1. A spiral guide pipe for the fastest curve in water conservancy and drainage, comprising a pipe body (1) and at least one spiral guide rib (2) disposed on the inner wall of the pipe body (1), characterized in that, The spiral guide rib (2) extends spirally along the axial direction of the tube body; After the inner wall of the tube (1) is unfolded into a plane along the axial generatrix, the projection trajectory of the spiral guide rib (2) on the unfolded plane conforms to the geometric characteristics of the fastest curve. The spiral angle of the spiral guide rib (2) changes nonlinearly and continuously along the fluid flow direction to guide the fluid to smoothly transition from axial flow to spiral flow.

2. The spiral guide pipe for the fastest curve in water conservancy and drainage according to claim 1, characterized in that, The trajectory coordinates (x, y) of the spiral guide rib (2) on the unfolded plane satisfy the following maximum speed curve parametric equation: The starting point of the steepest curve plane unfolding is (x0, y0), and the ending point is (x1, y1). ΔX = x1 - x0 = πD is the circumferential unfolding length of the inner wall of the tube, and ΔY = y1 - y0 is the axial height of the tube, i.e., the pitch. a is the cycloidal parameter, i.e., the radius of the circle corresponding to the trajectory of the steepest curve formed by circular rolling; θ is the circular rolling angle, where the circular rolling angle corresponding to the starting point of the steepest curve is 0, and the circular rolling angle corresponding to the ending point of the steepest curve is θ0; D is the inner diameter of the tube. Determine parameters a and θ0 using the following steps: S1) Endpoint condition equation, that is, let the endpoint corresponding parameter θ = θ0, and the starting point be the origin, then: S2) Eliminating a to find θ0, we have: Define a function: When ΔX / ΔY>0, θ0 can be obtained by solving Newton's iteration method; S3) Find the cycloidal parameter a; Alternatively, the following formula can be used: 。 3. The spiral guide pipe for the fastest curve in water conservancy and drainage according to claim 1, characterized in that, The internal spiral guide pipe includes multiple spiral guide ribs (2) that are evenly distributed at equal intervals along the circumference of the inner wall of the pipe. The multiple spiral guide ribs are equidistant from each other along the path.

4. The spiral guide pipe for the fastest curve in water conservancy and drainage according to claim 1, characterized in that, The internal spiral guide pipe includes multiple sets of spiral guide ribs (2) that are distributed in a compound manner along the circumference of the inner wall of the pipe body. The multiple sets of spiral guide ribs are equidistant along the path.

5. The spiral guide pipe for the fastest curve in water conservancy and drainage according to claim 4, characterized in that, Each set of spiral guide ribs (2) in the compound centralized distribution is composed of one main guide rib and two auxiliary guide ribs closely attached or arranged adjacently; wherein, the height of the main guide rib is h1, the height of the auxiliary guide rib is h2, and the condition h1 > h2 is met, forming a "mountain" shaped composite cross section.

6. The spiral guide pipe for the fastest curve in water conservancy and drainage according to claim 5, characterized in that, The main flow rib and the auxiliary flow rib are constructed such that a microchannel is formed between them to induce a pulsating effect of "local accumulation-rapid thinning" in the water film attached to the wall.

7. The spiral guide pipe for the fastest curve in water conservancy and drainage according to claim 1, characterized in that, The spiral guide rib (2) is a triangular spiral rib protruding towards the center of the pipe body. The height of the spiral rib is h. The height h satisfies the condition that it can form a vortex and does not cut off the water flow surface.

8. The spiral guide pipe for the fastest curve in water conservancy and drainage according to claim 7, characterized in that, The ratio of the spiral rib height h of the spiral guide rib (2) to the inner diameter D of the tube body (1) is in the range of: 0.03 < h / D < 0.

05.

9. The spiral guide pipe for the fastest curve in water conservancy and drainage according to claim 1, characterized in that, The spiral guide pipe with the fastest curve is used in gravity-driven water conservancy and municipal engineering vertical shaft drainage, building riser drainage, and inlet pipe sections of gas-liquid cyclone separators.

10. The spiral guide pipe for the fastest curve in water conservancy drainage as described in any one of claims 1-9, characterized in that, Applications in gravity-driven water conservancy and municipal engineering vertical shaft drainage, building riser drainage, and inlet pipe sections of gas-liquid cyclone separators.

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