Orbital transfer rib type variable cross-section elbow for multiphase flow and design method

Abstract

The invention discloses an orbital transfer rib type variable cross-section elbow pipe for multiphase flow and a design method, and belongs to the field of pipeline transportation, the elbow pipe is composed of a first straight pipe section, a middle elbow pipe section and a second straight pipe section, and the inner wall of the first straight pipe section is provided with a plurality of first ribs distributed in the circumferential direction; a plurality of second ribs which are distributed in the circumferential direction are arranged on the inner wall of the middle bent pipe section; a plurality of third ribs corresponding to the first ribs in shape and position are arranged on the inner wall of the second straight pipe section and used for outflow of multiphase flow. The middle bent pipe section is divided into an outer pipe body and an inner pipe body of which the variable cross section is arranged in an inward shrinkage manner along the center line; the second ribs comprise shape follow-up ribs, ridge line ribs, side ribs and orbital transfer ribs located between the ridge line ribs and the side ribs and used for changing the circumferential direction. The variable cross-section design is coupled with the orbital transfer effect of the orbital transfer ribs, flow separation and secondary vortexes are reduced, vortexes on the pipe wall of the elbow part are also reduced, and the conveying efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the field of pipeline transportation, and relates to a variable cross-section erosion-proof diversion elbow, specifically to a variable-rail rib type variable cross-section elbow for multiphase flow and a design method thereof. Background Art

[0002] In the current process of oil and gas resource development, multiphase flow with solid particles carried in the transported fluid often causes serious erosion and wear to the transport pipe wall, and then leads to the occurrence of pipe wall erosion and damage. As an important connecting part of the transportation pipeline, elbows have a wide range of applications. However, due to the special structure of the elbow, the fluid motion in the internal flow field of the elbow is relatively complex. The fluid on the outer side of the pipeline is squeezed towards the inner side of the flow field by the action of the pipe wall and the centrifugal force. After the fluid on the inner side of the pipeline is affected by the fluid on the outer side, and with the influence of the adverse pressure gradient, a low-speed flow area is formed on the inner side of the pipeline, and unstable flows such as flow separation and secondary eddy currents occur. The solid particles carried by the fluid cause more serious erosion and wear to the pipe wall in such a flow field.

[0003] The utility model patent (CN203585670U) disclosed by Zhang Chengchun et al. from Jilin University proposed a bionic erosion-resistant pipeline elbow, which reduces erosion by evenly distributing bionic ribs with a semi-circular cross-section shape along the flow direction or perpendicular to the flow direction at the elbow. This patent constructs an air cushion effect at the wall surface through the bionic ribs to reduce the erosion of solid particles, and functionally slows down the direct erosion and wear of the multiphase flow on the wall surface. However, there are still unstable flows such as flow separation and secondary flow in the overall internal flow field of the elbow, and solid particles will cause erosion and wear over a longer scale in the unstable flow field, resulting in relatively large energy losses during the transportation of multiphase flow in the elbow.

[0004] The utility model patent (CN217762580U) disclosed by Liu Enbin, Huang Shen et al. from Southwest Petroleum University proposed a spiral pipe section pipeline structure for alleviating elbow erosion, which controls the flow field by arranging a spiral structure in the pipeline before entering the elbow, forms vortices to separate the particles, and thus reduces the maximum erosion rate of the elbow. Although this patent guides the overall internal flow field of the pipeline and reduces the erosion and wear during multiphase flow transportation, this kind of diversion directly changes the original motion state of the pipeline fluid, causing additional energy losses, and does not guide the elbow part. Although the maximum erosion rate is reduced, the efficiency of transporting fluid in the pipeline is also reduced at the same time.

[0005] Therefore, a large amount of relevant research still needs to be carried out on how to reduce energy losses during multiphase flow transportation and improve transportation efficiency. Summary of the Invention

[0006] The object of the present invention is to overcome the above-mentioned disadvantages of the prior art, and provide a variable-rail ribbed variable-section elbow for multiphase flow and its design method. The elbow can improve the complex flow field inside the elbow on the basis of the original anti-erosion for multiphase flow transportation, reduce the energy loss when transporting multiphase flow fluid by an ordinary elbow, reduce the length of unstable fluid flow, and thus shorten the erosion wear under a complex flow field.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a variable-rail ribbed variable-section elbow for multiphase flow, including a first straight pipe section, with a number of first ribs circumferentially distributed on the inner wall for the inflow of multiphase flow; an intermediate elbow section, with a number of second ribs circumferentially distributed on the inner wall for the turning of multiphase flow; and a second straight pipe section, with a number of third ribs whose shapes and positions correspond to those of the first ribs on the inner wall for the outflow of multiphase flow; wherein, the intermediate elbow section is a right-angle elbow, which is divided into an inner pipe body and an outer pipe body along the center line of the right-angle elbow, and the inner pipe body is arranged with a variable cross-section and inward contraction; the second ribs include conforming ribs located on the inner pipe body, a back ridge line rib located in the middle of the inner wall of the outer pipe body, side ribs located at the boundary line between the inner and outer pipe bodies, and variable-rail ribs located between the back ridge line rib and the side ribs and changing the circumferential orientation;

[0008] Further, a number of virtual rib positions corresponding to the first ribs are arranged on the inner wall of the right-angle elbow; Along the flow direction, the back ridge line rib, the conforming rib and the side rib all inherit from the corresponding virtual rib positions to the first ribs, and terminate at the corresponding third ribs; and the conforming rib changes conformingly when the inner pipe body has a variable cross-section and inward contraction; The variable-rail rib inherits from the corresponding virtual rib position to the first rib, changes the rail to an adjacent virtual rib position in the direction close to the back ridge line rib, and terminates at the corresponding third rib after adding a rib at the original virtual rib position.

[0009] Further, the variable-rail rib completes the rail change at the middle part of the intermediate elbow section.

[0010] Further, the number of variable-rail ribs on the outer pipe body is 2 - 8.

[0011] Further, the first ribs are circumferentially evenly distributed on the inner wall of the first straight pipe section.

[0012] Further, a smooth transition is adopted between the first rib and the inner wall of the first straight pipe section, and the protrusion of the first rib is smoothly arranged itself, so that the cross-sections of a number of first ribs are wavy, the middle part of the first rib is the wave crest, and the inner wall between two adjacent first ribs is the wave trough.

[0013] Further, when the inner tube body is provided with a variable cross-section and is retracted, the middle part of the inner tube body is symmetrically retracted. During the retraction, the wall thickness remains unchanged, and the height of the follow-shaped rib remains unchanged.

[0014] Further, the outer diameters of the first straight pipe section and the second straight pipe section are the same, and the diameter is denoted as D. Then the wall thickness of the first straight pipe section and the second straight pipe section is D / 20 - D / 13, and the protruding height of the first rib is D / 12 - D / 8.

[0015] Further, the center line turning radius of the middle elbow section is D. After the outer tube body turns, it axially extends a certain distance for the inner tube body to contract. The inner tube body is smoothly connected to the first straight pipe section and then undergoes contraction and deformation.

[0016] On the other hand, the present invention provides a design method for a variable-rail rib type variable cross-section elbow for multiphase flow, including the following steps: Divide the elbow into a first straight pipe section, a middle elbow section, and a second straight pipe section; On the inner walls of the first straight pipe section and the second straight pipe section, arrange a number of circumferentially distributed first ribs and third ribs respectively, and the orientations of the first ribs and the third ribs are correspondingly distributed; Set the middle elbow section as a right-angle elbow, and set a number of virtual rib positions corresponding to the first ribs in the right-angle elbow; Divide the right-angle elbow along its center line into an inner tube body and an outer tube body; On the virtual rib positions in the middle of the inner wall of the outer tube body, arrange back ridge line ribs, on the virtual rib positions at the junction line of the inner and outer tube bodies, arrange side ribs, and supplement candidate ribs at the virtual rib positions of the inner tube body; Set variable-rail ribs between the back ridge line ribs and the side ribs on the corresponding side. The variable-rail ribs start to inherit from the corresponding first ribs at the virtual rib positions. After the variable-rail is completed in the direction close to the back ridge line ribs, new ribs are added at the original virtual ribs. After the variable-rail of the variable-rail ribs, the new ribs and the variable-rail ribs extend along the virtual rib positions and terminate at the corresponding third ribs; Perform variable cross-section contraction on the inner tube body. During the variable cross-section contraction process, the candidate ribs change in shape to obtain follow-shaped ribs.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a variable-rail rib type variable cross-section elbow applied to multiphase flow transportation in view of the severe erosion and wear of solid particles at the elbow part during the oil and gas transportation process and the major defect of the long-term existence of an unstable flow field brought by the elbow structure widely used at the present stage.

[0018] Based on the law of fluid flow in the elbow part of the bent pipe, the present invention designs a variable cross-section pipe wall and variable track ribs respectively. The variable cross-section section is a variable cross-section pipe wall with a variable cross-section shrinkage curve structure. This design fully conforms to the characteristic that the fluid in the inner arc flows outward due to the inertial action of the multiphase fluid, that is, the fluid does not flow completely along the inner arc of the original pipe wall but gradually changes from flowing along the original direction to flowing inward along the inner arc. There is a large consumption of momentum and energy in this process. The present invention designs a variable cross-section pipe wall along the fluid movement trajectory according to the actual flow process of the fluid through the inner arc of the bent pipe, so that the fluid flows along the inner wall of the variable cross-section. The overall pipeline at the variable cross-section structure is a gradually expanding structure, thus avoiding a large loss of momentum and kinetic energy. In addition, the dual design of the rib structure on the inner wall of the inner arc of the bent pipe and the variable cross-section pipe wall has a more favorable fluid taming effect on the fluid flowing through the inner wall of the bent pipe, reducing the occurrence of flow separation phenomenon, and at the same time reducing the bubbles generated by fluid separation, and reducing the wall vibration caused by the bubble rupture in the ordinary bent pipe and the resulting structural vibration and noise. In addition, through the variable cross-section pipe wall with a variable cross-section shrinkage curve structure, the cross-sectional area of the elbow part is appropriately reduced, so that the flow velocity is increased compared with that of the ordinary elbow, avoiding the situation that the pipeline flow velocity is reduced in the prior art in order to prevent erosion, ensuring the original conveying efficiency of the pipeline, and having strong practicability.

[0019] Secondly, on the outer arc side of the elbow, the fluid is extruded outward due to centrifugal force, resulting in an increase in the outer side flow velocity (according to Bernoulli's principle, the pressure decreases), while the inner side flow velocity decreases, forming an adverse pressure gradient. When the adverse pressure gradient is large enough, the boundary layer separates, generating eddies and recirculation zones. According to the original motion characteristics of the fluid on the outer arc side of the pipeline, the present invention designs variable track ribs. On the one hand, through the gradually offset track design, the fluid is forced to concentrate on the dorsal ridge rib (the central axis on the outer arc side), increasing the momentum of the fluid on the outer arc side and delaying the boundary layer separation; thus realizing flow guiding and momentum redistribution. On the other hand, the convex structure of the ribs disturbs the flow field, enhances turbulent mixing, increases the kinetic energy of the fluid in the boundary layer, and delays the formation of the separation point, thereby obtaining a turbulent enhancement effect.

[0020] In addition, in the bent pipe, the centrifugal force causes the high-speed mainstream to shift outward, while the fluid near the wall surface has a lower velocity due to viscous action, forming a transverse pressure gradient, which drives the generation of secondary eddies. The secondary eddies bring the high-speed fluid from the pipe center to the outer arc side and the low-speed fluid from the wall surface back to the inner arc side, exacerbating energy loss and particle erosion.

[0021] The variable track ribs provided by the present invention have the following functions: 1. Weakening the secondary eddy current: Weakening the lateral pressure gradient, suppressing the lateral migration of the fluid at the pipe wall, and restricting the development space of the secondary eddy current. At the same time, the dynamic offset path of the variable-rail ribs destroys the stability of the secondary eddy current core, causing its energy to rapidly decay through turbulent dissipation. The protruding structure of the variable-rail ribs disturbs the flow field, breaking large-scale vortices into small-scale vortices and reducing the interference of large-scale vortices on the main flow.

[0022] 2. Slowing down particle erosion: The variable-rail ribs change the streamline, reducing the lateral migration distance of the particles. The locally high-speed areas formed between the ribs accelerate the particles through the elbow, reducing the contact time with the pipe wall. Thus, the particle trajectory is optimized.

[0023] Through the above-mentioned orbital rib design, while planning the fluid motion, the present invention reduces the energy loss caused by unstable flow. The variable-rail ribs cooperate with the variable-section pipe wall constructed based on the variable-section contraction curve to straighten and guide the overall flow field of the elbow, reducing the generation of flow separation and secondary eddy currents, reducing the generation of vortices on the pipe wall of the elbow part, reducing the vibration of the elbow and the noise during transportation, and at the same time playing a role in quickly taming the original unstable fluid motion within a short distance, enabling the fluid to quickly tend to stable flow along the main flow direction in the straight pipe, so that the elbow achieves a very strong guiding effect within a short scale range. Cooperating with the internal ribs can reduce the erosion and wear caused by solid particles moving with the unstable fluid, and at the same time play the roles of erosion prevention and flow guiding, with versatility. The strong guiding effect can further reduce the erosion of the multiphase flow on the pipe wall. The invention realizes the stable flow of the multiphase flow from the triple action mechanisms of internal rib guiding, variable-section guiding, and variable-rail rib guiding, and with the erosion-resistant effect of the specially designed internal ribs, realizes an all-round multiphase flow elbow with functions of flow guiding, erosion resistance, vibration reduction, noise reduction, and high efficiency, having great market prospects. Brief Description of the Drawings

[0024] Figure 1 It is the overall external view of the variable-rail rib type variable-section elbow of the present invention.

[0025] Figure 2 It is the longitudinal sectional three-dimensional schematic diagram of the variable-rail rib type variable-section elbow of the present invention.

[0026] Figure 3 It is the schematic diagram of the variable-rail rib type variable-section elbow of the present invention cut along the turning direction.

[0027] Figure 4 It is the longitudinal sectional view schematic diagram of the variable-rail rib type variable-section elbow of the present invention.

[0028] Figure 5 It is Figure 4 the cross-section A-A in

[0029] Figure 6 It isFigure 4 Cross-section A1-A1

[0030] Figure 7 is Figure 4 Schematic diagram of the deformation of the conformal rib on the inner tube body in cross-section B-B

[0031] Figure 8 is Figure 4 Schematic diagram of the azimuth angle of the distribution of the conformal ribs in cross-section B-B

[0032] Figure 9 Schematic diagram of the principle of the variable track of the variable cross-section elbow with variable track ribs of the present invention

[0033] Figure 10 Scatter diagram of the variable cross-section contraction curve of the variable cross-section elbow with variable track ribs of the present invention

[0034] Among them, 1 - the first straight pipe section, 11 - the first rib, 2 - the middle elbow section, 210 - the inner tube body; 211 - conformal rib, 212 - variable cross-section contraction curve, 213 - origin of the coordinate system, 220 - outer tube body, 221 - turning part, 222 - straight pipe guiding part, 223 - axis line, 230 - the second rib, 231 - ridge line rib, 232 - side rib, 233 - variable track rib, 234 - virtual rib position, 3 - the second straight pipe section, 31 - the third rib. Specific embodiments

[0035] The following further describes in detail the embodiments of the present invention in conjunction with the drawings and examples. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0036] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Embodiment 1: Refer to Figures 1 to 3 , the present invention discloses a variable-rail ribbed variable-section elbow for multiphase flow, including a first straight pipe section 1, with a plurality of circumferentially distributed first ribs 11 provided on the inner wall for the inflow of multiphase flow; an intermediate elbow section 2, with a plurality of circumferentially distributed second ribs 230 provided on the inner wall for the turning of multiphase flow; and a second straight pipe section 3, with a plurality of third ribs 31 whose shapes and positions correspond to those of the first ribs 11 provided on the inner wall for the outflow of multiphase flow; wherein, the intermediate elbow section 2 is a right-angle elbow, and along the center line of the right-angle elbow, it is divided into an inner pipe body 210 and an outer pipe body 220, and the inner pipe body 210 is arranged with a variable cross-section and inward contraction; the second ribs 230 include a conforming rib 211 located on the inner pipe body 210, a back-ridge line rib 231 located at the middle part of the inner wall of the outer pipe body 220, a side rib 232 located at the junction line of the inner and outer pipe bodies, and a variable-rail rib 233 located between the back-ridge line rib 231 and the side rib 232 and changing the circumferential orientation.

[0039] The present invention decomposes the variable-rail ribbed variable-section elbow into a first straight pipe section 1, an intermediate elbow section 2, and a second straight pipe section 3; designs a variable-section pipe wall along the flow path of the fluid actually flowing through the inner arc surface of the elbow, enabling the fluid to flow along the inner wall of the variable section. At the maximum cross-section inward contraction of the inner pipe body 210, the outer pipe body 220 also completes the turning and guiding. The cross-section of the subsequent intermediate elbow section 2 is a gradually expanding structure, thereby avoiding large losses of momentum and kinetic energy; in addition, the double design of the conforming rib 211 and the variable-section pipe wall at the inner arc inner wall of the elbow has a more favorable fluid-taming effect on the fluid flowing through the inner wall of the elbow, reducing the occurrence of flow separation phenomena, and at the same time reducing the bubbles generated due to fluid separation, and reducing the wall vibration caused by the bubble rupture in the ordinary elbow and the resulting structural vibration and noise. Additionally, through the variable-section pipe wall constructed by the variable-section contraction curve 212, the cross-sectional area of the turning part 221 is appropriately reduced, resulting in an increase in the flow velocity compared to ordinary elbows, avoiding the situation in the prior art where the pipe flow velocity is reduced to prevent erosion, ensuring the original conveying efficiency of the pipeline, and having strong practicability.

[0040] Secondly, according to the original motion characteristics of the fluid on the outer arc side of the pipeline, while retaining the ridge line rib 231 and the side rib 232, a variable orbit rib 233 is designed on the inner wall of the outer pipe body 220 to guide the motion of the fluid in the elbow part, so that the fluid flows in the orbit constructed by the variable orbit rib (referred to as the variable orbit rib 233 for short), guiding the fluid to concentrate near the ridge line rib 231. While planning the fluid motion, the energy loss caused by unstable flow is reduced. The variable orbit rib cooperates with the variable cross-section pipe wall constructed based on the variable cross-section contraction curve 212 to comb and guide the overall flow field of the elbow, reducing the generation of flow separation and secondary eddies, reducing the generation of vortices on the pipe wall of the elbow part, reducing the vibration of the elbow and the noise during transportation, and at the same time playing the role of quickly taming the original unstable fluid motion within a short distance, enabling the fluid to more quickly tend to stable flow along the main flow direction in the straight pipe, so that the elbow realizes a very strong flow guiding effect within a short scale range. Cooperating with the action of the internal rib can reduce the erosion and wear caused by the movement of solid particles along with the unstable fluid, and at the same time play the role of anti-erosion and flow guiding, with multifunctionality. The strong flow guiding effect can further reduce the erosion of the pipe wall by the multiphase flow. The invention realizes the stable flow of the multiphase flow from the triple action mechanisms of internal rib flow guiding, variable cross-section flow guiding and variable orbit rib flow guiding, and cooperates with the anti-erosion effect of the specially designed internal rib to realize an all-round multiphase flow elbow with functions of flow guiding, anti-erosion, vibration reduction, noise reduction and high efficiency, which has great market prospects.

[0041] Exemplarily, as Figure 2 and 3 shown, a plurality of virtual rib positions 234 corresponding to the first rib 11 are arranged on the inner wall of the right-angle elbow; Along the flow direction, the ridge line rib 231, the conforming rib 211 and the side rib 232 all inherit from the first rib 11 at the corresponding virtual rib positions 234 and terminate at the corresponding third rib 31; and the conforming rib 211 changes conformingly when the inner pipe body 210 has a variable cross-section contraction; The variable orbit rib 233 inherits from the first rib 11 at the corresponding virtual rib positions 234, changes the orbit to the adjacent virtual rib positions 234 in the direction close to the ridge line rib 231, and terminates at the corresponding third rib 31 after adding ribs at the original virtual rib positions 234.

[0042] Exemplarily, as Figure 1 , 2 , 4 shown, the outer pipe body 220 includes a turning part 221 and a straight pipe guiding part 222. The turning part 221 is connected to the first straight pipe section 1, and the straight pipe guiding part 222 is connected to the second straight pipe section 3. The variable orbit rib 233 completes the orbit change at the middle part of the middle elbow section 2, that is, after the turning part 221.

[0043] The first rib strips 11 are circumferentially and uniformly distributed on the inner wall of the first straight pipe section 1. Correspondingly, the third rib strips 31 are circumferentially and uniformly distributed on the inner wall of the second straight pipe section 3. Uniform distribution is a preferred embodiment of the present invention, which can provide all-round flow guidance for the elbow pipe and prevent the occurrence of flow patterns with high energy losses such as eddies and turbulences at the pipe wall.

[0044] Exemplarily, as Figure 5 described, taking 12 first rib strips 11 uniformly distributed on the first straight pipe section 1 as an example, the included angle between two adjacent first rib strips 11 is 30°, and the third rib strips 31 adopt the same distribution; for the middle elbow pipe section 2, as Figure 2 、 6 、Figure 7 shows, the second rib strips 230 are distributed as follows: 5 follow-shaped rib strips 211 are distributed on the inner wall of the inner pipe body 210, 2 side rib strips 232 are distributed at the boundary line between the inner and outer pipe bodies, 1 backbone line rib strip 231 is distributed in the middle of the outer pipe body 220, 2 virtual rib strip positions 234 are distributed on each side of the backbone line rib strip 231, a track-changing rib strip 233 is arranged. At the turning part 221 of the outer pipe body 220, along the fluid flow direction, the track-changing rib strip 233 gradually changes its track from the virtual rib strip position 234 far from the backbone line rib strip 231 to the virtual rib strip position 234 close to the backbone line rib strip 231, and completes the track change at the junction of the turning part 221 and the straight pipe guiding part 222. In the straight pipe guiding part 222, the track-changing rib strip 233 continues to extend at the virtual rib strip position 234 close to the backbone line rib strip 231, and the second rib strip 230 is reset at the virtual rib strip position 234 that was originally far from the backbone line rib strip 231.

[0045] It should be noted that the first rib strips 11, the second rib strips 230, and the third rib strips 31 of the present invention have the same shape and size to achieve smooth butt joint transition. Among the second rib strips 230, the shapes and sizes of the side rib strips 232 and the backbone line rib strip 231 are inherited from the first rib strips 11 and remain unchanged. The follow-shaped rib strips 211 are inherited from the first rib strips 11 and may change partially during the process of the inner pipe body 210 shrinking with the variable cross-section, but the protruding height remains unchanged. When the track-changing rib strip 233 is inherited from the first rib strips 11 and changes its track, the cross-sectional shape will change similarly, but the height remains unchanged.

[0046] Exemplarily, as Figure 6 、 7As shown, when the inner tube body 210 is provided with a variable cross-section and is retracted, the middle part of the inner tube body 210 is symmetrically retracted. During the retraction, the wall thickness remains unchanged, and the height of the conforming rib 211 remains unchanged, so as to obtain the synergistic function of the variable cross-section setting and the conforming rib 211. This enables the present invention to plan the fluid movement while reducing the energy loss caused by unstable flow. The variable-rail rib cooperates with the variable-cross-section pipe wall constructed based on the variable-cross-section shrinkage curve to straighten and guide the overall flow field of the elbow, reducing the generation of flow separation and secondary eddies, reducing the generation of vortices on the pipe wall of the elbow part, reducing the vibration of the elbow and the noise during transportation, and at the same time playing the role of quickly taming the original unstable fluid movement within a short distance, making the fluid more quickly tend to stable flow along the mainstream direction in the straight pipe, so that the elbow realizes a very strong flow guiding effect within a short scale range.

[0047] Exemplarily, as Figure 5 shown, a smooth transition is adopted between the first rib 11 and the inner wall of the first straight pipe section 1. The protrusion of the first rib 11 is smoothly arranged itself, so that the cross-sections of the plurality of first ribs 11 are wavy. The middle part of the first rib 11 is the wave crest, and the inner wall between two adjacent first ribs 11 is the wave trough; through this setting, the flow guiding performance of the rib is improved, and the flow resistance is reduced.

[0048] It should be noted that although all the ribs and pipe walls of the present invention are separately arranged in terms of function, they can be manufactured in a split manner during the actual manufacturing process (for example, the manufactured ribs are assembled by welding or bonding) or integrally manufactured (for example, integrally manufactured by a milling process).

[0049] Exemplarily, as Figure 4 、 5 shown, the outer contour of the first straight pipe section 1 is denoted as D, the wall thickness of the first straight pipe section 1 is D / 20 - D / 13, and preferably D / 15 can be adopted. The turning radius of the axis line 223 of the right-angle elbow is D; taking 12 first ribs 11 as an example, the height of the first rib 11 is D / 10, the cross-sectional shape of the rib is symmetrically arranged with respect to a highest point, the curvature radius of the arc curve of the wave crest on one side is D / 5, the curvature center is concave outward from the pipe, and the corresponding included angle is 40°. The wave trough is also symmetrically arranged. The curvature radius of the arc curve of the wave trough on one side is D / 6, the included angle is 45°, the curvature center is concave inward from the pipe, and the wave crest and wave trough on one side can be mirrored along the radius of the first straight pipe section 1 as a complete rib curve. The minimum distance between the wave trough of the first rib 11 and the outer contour of the cross-section is denoted as the wall thickness of the first straight pipe section 1, which is D / 15; if the arc curve of the wave crest and the arc curve of the wave trough are just tangent, it is the optimal design state. If they are not tangent, a smooth curve or a spline curve is used for transition.

[0050] Next, taking 12 first ribs 11 as an example, the rail-changing method of the variable-rail rib 233 of the present invention will be described in detail, asFigure 2 , 3 As described above, the middle elbow section 2 is a right-angle elbow, and the inlet of the right-angle elbow inherits the wall characteristics of the first straight pipe section 1; the A1-A1 cross-section is the cross-sectional view at the inlet of the middle elbow section 2, which is provided with 12 virtual rib positions 234. Starting from the middle line of the outer surface of the inner pipe body 210, it is marked as azimuth angle 0°. Starting from the A1-A1 cross-section and counting clockwise, the two regions between azimuth angle 0° - 90° and azimuth angle 270° - 360° are the regions of the inner pipe body 210. One side rib 232 is provided at azimuth angles 90° and 270° respectively, a back ridge line rib 231 is provided at azimuth angle 180°, no rib is provided at azimuth angle 150°, a track-changing rib 233 is provided at azimuth angle 120°, and it starts to gradually change the track towards azimuth angle 150°, and completely changes the track to azimuth angle 150° at the end of the turning part 221 of the outer pipe body 220 (i.e., the B-B cross-section). After that, this track-changing rib 233 extends to the second straight pipe section 3 at azimuth angle 150°. A second rib 230 is reset at the 120° azimuth angle of the straight pipe guiding part 222 of the outer pipe body 220 and extends to the second straight pipe section 3. The structure characteristics of this second rib 230 are exactly the same as those of the first rib 11 and the third rib 31 at the 120° azimuth angle.

[0051] As Figure 4 , 6 , 7 shows, the variable cross-section shrinking mode of the inner pipe body 210 is as follows: At the A1-A1 cross-section, the wall boundaries of the inner pipe body 210 where it is connected to the first straight pipe section 1, the outer pipe body 220, and the second straight pipe section 3 are all smoothly transitioned. At the same time, the pipe wall in the central region of the inner pipe body 210 presents a three-dimensional shrinking curved surface guided by the variable cross-section shrinking curve 212. Within the same axial distance range of the inner pipe body 210 and the outer pipe body 220, the wall thickness is D / 15; referring to Figure 8 , the inner side of the pipe wall of the inner pipe body 210 inherits the rib characteristics of the first straight pipe section 1 along azimuth angles 0°, 30°, 60°, 300°, and 330° and extends along the same azimuth angles on the inner side of the three-dimensional shrinking curved surface pipe wall until the second straight pipe section 3.

[0052] Referring to Figure 4 , Figure 6 , Figure 10 , in the axially symmetric cross-section, with the outer end point of the radius at the 0° azimuth angle of the A1-A1 cross-section at the end of the first straight pipe section 1 as the coordinate origin 213, an X-Y coordinate system is constructed, where the positive direction of the x-axis is the direction pointing to the elbow outlet, and the positive direction of the y-axis is the direction pointing to the elbow inlet. The horizontal axial length of the variable cross-section shrinking curve 212 is , the vertical length is , and the characteristic point coordinates of the variable cross-section shrinking curve 212 are , X and Y are specifically described as in the following table:

[0053] The above data is fitted by polynomial to obtain the following curve function:

[0054] Reference Figure 4 , the cross-sectional profile of the inner pipe body 210 in the axial direction first changes from an arc state to a curve shape that contracts towards the center, and then gradually returns to the arc state. Among them, the curvature of the curve that contracts towards the center changes with the variable cross-section contraction curve 212, and the radius of curvature first becomes larger and then smaller. Reference Figure 7 , when reaching the maximum, the radius of curvature is 2D, and the corresponding opening angle is 24°. Reference Figure 8 , the trough parts of the ribs at 0°, 30°, 60°, 300°, and 330° arranged on the inner side of the inner pipe body 210 change with the variable cross-section contraction curve 212. Reference Figure 5 , Figure 7 , the radius of curvature of the trough curve changes in the range of D / 7.5~D / 6, and the opening angle changes in the range of 40°~50°, and the center of curvature of the curvature is concave towards the inside of the pipe.

[0055] The principle of the present invention for alleviating erosion and taming the flow field is briefly described as follows: Reference Figure 9 , based on the law of fluid flow in the elbow part of the elbow pipe, the present invention designs a variable cross-section pipe wall and variable-rail ribs respectively. Among them, the variable cross-section section is the variable cross-section pipe wall constructed by the variable cross-section contraction curve 212, so that the fluid flows along the inner wall of the variable cross-section. The overall pipe at the variable cross-section structure is a gradually expanding structure; in addition, the double design of the rib structure and the variable cross-section pipe wall at the inner arc inner wall of the elbow pipe has a more favorable fluid taming effect on the fluid flowing through the inner wall of the elbow pipe. In addition, the variable cross-section pipe wall constructed by the variable cross-section contraction curve 212 appropriately reduces the cross-sectional area of the elbow part, so that the flow rate is increased compared with that of a common elbow.

[0056] According to the original motion characteristics of the fluid on the outer arc side of the pipe, variable-rail ribs are designed to guide the motion of the fluid in the elbow part, so that the fluid flows in the track constructed by the variable-rail ribs. The variable-rail ribs cooperate with the variable cross-section pipe wall constructed based on the variable cross-section contraction curve 212 to sort and guide the overall flow field of the elbow, playing a role in quickly taming the original unstable fluid motion within a short distance, enabling the fluid to more quickly tend to stable flow along the main flow direction in the straight pipe, and enabling the elbow pipe to achieve a very strong flow guiding effect within a short scale range. Cooperating with the internal rib action can reduce the erosion and wear caused by the movement of solid particles along with the unstable fluid, and at the same time play the roles of anti-erosion and flow guiding, with versatility.

[0057] Embodiment 2: The present invention also provides a design method for a variable-rail rib type variable cross-section elbow for multiphase flow, comprising the following steps: Divide the elbow into a first straight pipe section 1, an intermediate elbow section 2, and a second straight pipe section 3; Arrange a number of circumferentially distributed first ribs 11 and third ribs 31 on the inner walls of the first straight pipe section 1 and the second straight pipe section 3 respectively, and the orientations of the first ribs 11 and the third ribs 31 are correspondingly distributed; Set the intermediate elbow section 2 as a right-angle elbow, and set a number of virtual rib positions 234 corresponding to the first ribs 11 inside the right-angle elbow; Divide it along the center line of the right-angle elbow into an inner pipe body 210 and an outer pipe body 220; Arrange a back ridge line rib 231 at the virtual rib position 234 in the middle of the inner wall of the outer pipe body 220, arrange side ribs 232 at the virtual rib position 234 at the junction line between the inner and outer pipe bodies, and supplement candidate ribs at the virtual rib position 234 of the inner pipe body 210; Set a variable-rail rib 233 between the back ridge line rib 231 and the side ribs 232 on the corresponding side. The variable-rail rib 233 inherits from the corresponding first rib 11 starting from the virtual rib position 234. After the variable-rail is completed in the direction close to the back ridge line rib 231, new ribs are added at the original virtual rib. After the variable-rail of the variable-rail rib 233, the new ribs extend along the virtual rib position 234 and terminate at the corresponding third rib 31; Perform variable cross-section internal contraction on the inner pipe body 210. During the variable cross-section internal contraction process, the candidate ribs change conformally to obtain conforming ribs 211.

[0058] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that various combinations, modifications or equivalent replacements of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and should all be covered within the scope of the claims of the present invention.

Claims

1. A variable-orbital rib type variable cross-section elbow for multiphase flow, characterized in that: Comprising A first straight pipe section, with several circumferentially distributed first ribs provided on the inner wall for the inflow of multiphase flow; An intermediate elbow section, with several circumferentially distributed second ribs provided on the inner wall for the turning of multiphase flow; and A second straight pipe section, with several third ribs provided on the inner wall, the shapes and positions of which correspond to those of the first ribs, for the outflow of multiphase flow; Among them, the intermediate elbow section is a right-angle elbow, which is divided into an inner pipe body and an outer pipe body along the center line of the right-angle elbow, and the inner pipe body is arranged with a variable cross-section in a shrinking manner; The second ribs include conforming ribs located in the inner pipe body, backbone line ribs located in the middle of the inner wall of the outer pipe body, side ribs located at the junction line between the inner and outer pipe bodies, and transition ribs located between the backbone line ribs and the side ribs for changing the circumferential orientation.

2. The variable-orbital ribbed variable cross-section elbow for multiphase flow according to claim 1, characterized in that: Several virtual rib positions corresponding to the first ribs are arranged on the inner wall of the right-angle elbow; Along the flow direction, the backbone line ribs, conforming ribs, and side ribs all inherit from the first ribs at the corresponding virtual rib positions and terminate at the corresponding third ribs; and the conforming ribs change conformingly when the inner pipe body shrinks with a variable cross-section; The transition ribs inherit from the first ribs at the corresponding virtual rib positions, change tracks to adjacent virtual rib positions in the direction close to the backbone line ribs, and terminate at the corresponding third ribs after adding ribs at the original virtual rib positions.

3. The variable-orbital rib type variable cross-section elbow for multiphase flow according to claim 2, characterized in that: The transition ribs complete the track change at the middle of the intermediate elbow section.

4. The variable-orbital rib type variable cross-section elbow for multiphase flow according to claim 3, wherein: There are 2 - 8 transition ribs on the outer pipe body.

5. The variable-orbital rib type variable cross-section elbow for multiphase flow according to claim 1, characterized in that: The first ribs are circumferentially uniformly distributed on the inner wall of the first straight pipe section.

6. The variable-orbital rib type variable cross-section elbow for multiphase flow according to claim 1, wherein: A smooth transition is adopted between the first ribs and the inner wall of the first straight pipe section, and the protrusions of the first ribs are smoothly arranged themselves, so that the cross-sections of the multiple first ribs are wavy, with the middle of the first ribs being the wave crest and the inner wall between two adjacent first ribs being the wave trough.

7. The variable-orbital rib type variable cross-section elbow for multiphase flow according to claim 4, characterized in that: When the inner pipe body is arranged with a variable cross-section in a shrinking manner, the middle part of the inner pipe body shrinks symmetrically. During the shrinking process, the wall thickness remains unchanged, and the height of the conforming ribs remains unchanged.

8. The variable-orbit ribbed variable cross-section elbow for multiphase flow according to claim 4, wherein: The outer diameters of the first straight pipe section and the second straight pipe section are the same, denoted as D. Then the wall thickness of the first straight pipe section and the second straight pipe section is D / 20 - D / 13, and the protruding height of the first ribs is D / 12 - D / 8.

9. The variable-orbital rib type variable cross-section elbow for multiphase flow according to claim 8, wherein: The center line turning radius of the intermediate elbow section is D. After the outer pipe body turns, it axially extends a certain distance for the inner pipe body to shrink, and the inner pipe body is smoothly connected to the first straight pipe section and then shrinks and deforms.

10. A design method for a variable-orbit ribbed variable cross-section elbow for multiphase flow, characterized in that, Including the following steps: Dividing the elbow into a first straight pipe section, an intermediate elbow section, and a second straight pipe section; Respectively arranging several circumferentially distributed first ribs and third ribs on the inner walls of the first straight pipe section and the second straight pipe section, and the first ribs and the third ribs are correspondingly distributed in terms of orientation; Setting the intermediate elbow section as a right-angle elbow and arranging several virtual rib positions corresponding to the first ribs inside the right-angle elbow; Dividing it into an inner pipe body and an outer pipe body along the center line of the right-angle elbow; Arranging backbone line ribs at the virtual rib positions in the middle of the inner wall of the outer pipe body, arranging side ribs at the virtual rib positions at the junction line between the inner and outer pipe bodies, and supplementing candidate ribs at the virtual rib positions of the inner pipe body; A rail-changing rib is provided between the backbone rib and the side rib on the corresponding side. The rail-changing rib starts inheriting from the corresponding first rib at the virtual rib position. After the rail-changing is completed in the direction close to the backbone rib, a new rib is added at the original virtual rib. After the rail-changing of the rail-changing rib, the new rib and the rail-changing rib extend along the virtual rib position and terminate at the corresponding third rib. The inner tube body is subjected to variable cross-section internal contraction. During the variable cross-section internal contraction process, the candidate rib changes conformally to obtain a conforming rib.

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