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CN-121997623-A - Design method of steel sleeve crack stopper for dense-phase carbon dioxide pipeline

CN121997623ACN 121997623 ACN121997623 ACN 121997623ACN-121997623-A

Abstract

The invention discloses a design method of a steel sleeve crack stopper for a dense-phase carbon dioxide pipeline, which comprises the following steps of S1, selecting a sample steel pipe, determining steady-state expansion speed of cracks in the steel pipe, S2, establishing a finite element model, simulating the geometric dimension of a real pipeline, dividing the pipeline, adopting a cohesive force unit for a crack expansion path, S3, calculating saturated pressure of a carbon dioxide component, applying the pressure to the tip of the crack, S4, determining cohesive force parameters, taking the cohesive force parameters as finite element model parameters, S5, determining pressure distribution of the crack after entering the crack stopper, S6, establishing a non-contact algorithm, evaluating constraint force of the crack stopper on crack expansion through an algorithm, S7, obtaining steady-state expansion speed of the crack, and completing the design of the steel sleeve crack stopper. The design method of the steel sleeve crack stopper for the dense-phase carbon dioxide pipeline solves the problem that the dense-phase carbon dioxide pipeline with small caliber of OD508 and below cannot be timely crack-stopped after being cracked.

Inventors

  • LI HE
  • Gao Xiongxiong
  • REN JUNJIE

Assignees

  • 中国石油天然气集团有限公司
  • 中国石油集团工程材料研究院有限公司

Dates

Publication Date
20260508
Application Date
20241108

Claims (8)

  1. 1. The design method of the steel sleeve crack stopper for the dense-phase carbon dioxide pipeline is characterized by comprising the following steps of: S1, selecting a sample steel pipe, and determining the steady-state expansion speed of cracks in the sample steel pipe through a DWTT experiment; s2, establishing a finite element model, namely simulating the geometric dimension of a real pipeline, dividing the pipeline by adopting a shell unit, and adopting a cohesive force unit for a crack propagation path; S3, calculating the saturation pressure of the carbon dioxide component, and applying the pressure to the tip of the crack; s4, performing three-dimensional dynamic elastoplastic finite element analysis by using a general program, determining cohesive force parameters, and taking the cohesive force parameters as finite element model parameters; S5, determining pressure distribution of cracks after entering the crack stopper; S6, establishing a non-contact algorithm, and evaluating the constraint force of the crack stopper on crack propagation through the algorithm; and S7, equivalent constraint force to externally applied stress to obtain crack propagation speed, and finishing the design of the steel sleeve crack stopper.
  2. 2. The method for designing a steel sleeve crack stopper for a dense phase carbon dioxide pipeline according to claim 1, wherein the specific process of S1 is as follows: S1.1, selecting a steel pipe, carrying out a DWTT experiment, collecting load-displacement and load-time curves of a hammer head, and carrying out high-speed shooting; S1.2, determining the linear section time t 1 and t 2 of the steel pipe, determining the crack propagation distance d of the time t 1 ～t 2 by high-speed shooting, and calculating the crack steady-state propagation speed v in the steel pipe according to the formula (1); v=d/(t 2 -t 1 ) (1)。
  3. 3. The method for designing a steel sleeve crack stopper for dense phase carbon dioxide pipelines according to claim 1, wherein in S2, modeling is performed by simulating real pipeline geometry using ABAQUS software, in a grid module, pipelines are divided by adopting shell units, the refinement degree of the shell units is increased in a region close to an upper bus, crack propagation is applied to the region, the average side length of the shell units is 100mm-10mm, the code of the finite element model uses explicit integral algorithm code based on a central difference method, and the crack propagation path adopts cohesive units, and the size of the cohesive units is smaller than 2mm.
  4. 4. The method for designing a steel sleeve crack stopper for a dense phase carbon dioxide pipe as claimed in claim 1, wherein the calculating the saturation pressure of the carbon dioxide component in S3 is specifically calculating the saturation pressure of the carbon dioxide component by applying GERG' S08 equation of state.
  5. 5. The design method for the steel sleeve crack stopper for the dense-phase carbon dioxide pipeline according to claim 1, wherein the specific process of the step S4 is that an ABAQUS software Explicit solver module is selected for three-dimensional dynamic elastoplasticity finite element analysis by a general program, saturation pressure is applied to the tip of a crack, cohesive force unit parameters are continuously adjusted, crack steady-state expansion speed under the pressure of the pointed tip of the crack is calculated, the crack steady-state expansion speed is compared with the crack steady-state expansion speed obtained in the step S1 until the crack steady-state expansion speed is equal to the crack steady-state expansion speed obtained in the step S1, and the cohesive force unit parameters at the moment are selected as finite element model parameters; the cohesive force unit adopts a bilinear traction force-separation amount curve, and cohesive energy is calculated according to a formula (2); Wherein G is cohesive energy, sigma m is the maximum traction force when a cohesive unit is damaged, delta c is critical separation quantity, sigma m ＝2.8σ y ;σ y is the yield strength of the steel pipe, and the initial slope of the cohesive unit is 100 times of the elastic modulus of the steel pipe, namely K=210×10 11 .
  6. 6. The design method of the steel sleeve crack stopper for the dense-phase carbon dioxide pipeline according to claim 1, wherein in the step S5, the pressure distribution of the crack entering the crack stopper is divided into three areas, namely a crack front pressure area, a crack tip pressure distribution area, a crack stopper edge-to-crack tip pressure distribution area, a crack front pressure area, a crack tip pressure distribution area and a crack tip pressure distribution area; the pressure distribution in the first area is calculated by using a shock tube model and a GERG state equation; the pressure distribution in the second area is calculated by adopting the formula (3); P 2 ＝0.8 P s +0.002222222X (3); Wherein, P 2 is the pressure of the second region, X is the distance between the rear end of the crack and the crack tip; The pressure distribution in the third region is calculated by adopting the formula (4); Wherein, when θ <5, c=0.0408θ+0.4867, n= -0.314lnθ+2.7489, c1= -0.0197θ+0.0367, when 5< θ <90, c=0.0058θ+0.5931, n=0.0103θ+1.9522, c1=0, when 90< θ <180, c=1.0, n=1.0, c1=0.
  7. 7. The method for designing a steel sleeve crack stopper for a dense phase carbon dioxide pipeline according to claim 1, wherein the specific process of S6 is as follows: S6.1, calculating the annular total length Lp of the outer surface of the deformed pipeline after the crack is directly extracted and enters a stable expansion stage before the crack stopper through a finite element model, wherein the annular total length Lp is the sum of the deformed length of the steel pipe and the crack opening amount COD; s6.2, calculating equivalent circumferential strain delta e according to formula (5); Wherein, delta e is equivalent circumferential strain, sigma up is steel pipe tensile strength, sigma ua is crack stopper tensile strength, t p is steel pipe wall thickness, t α is crack stopper wall thickness, L p is annular total length of the outer surface of the deformed pipeline, and L A is annular length of the crack stopper; s6.3, calculating corresponding annular stress t through stress corresponding to equivalent strain in a true stress-strain curve of the crack stopper; S6.4, for each cell, applying a tensile stress t to the edges of the cell, i.e. the edges aligned with the longitudinal cell direction, which are bisectors of the angle existing between the cell under consideration and the circumferentially adjacent cells, calculating an equivalent pressure p according to equation (6) by vector sum of the virtual forces F resulting from the tensile stress calculation; Wherein, A is the unit area and F is the virtual force.
  8. 8. The design method of the steel sleeve crack stopper for the dense-phase carbon dioxide pipeline according to claim 1, wherein the specific process of the S7 is that the constraint of the steel sleeve crack stopper on a steel pipe is equivalent to externally applied stress p, the steady-state crack expansion speed is calculated through a finite element model, and when the steady-state crack expansion speed is 0 in the action range of the crack stopper, the design of the steel sleeve crack stopper is completed.

Description

Design method of steel sleeve crack stopper for dense-phase carbon dioxide pipeline Technical Field The invention belongs to the technical field of fracture control of carbon dioxide conveying pipelines, and particularly relates to a design method of a steel sleeve crack stopper for a dense-phase carbon dioxide pipeline. Background It has been proposed in China to achieve carbon peak before 2030 and carbon neutralization before 2060. To achieve this goal, at least tens of millions of tons of carbon dioxide are sequestered each year, and pipeline transportation by dense-phase carbon dioxide is a necessary way. Compared with natural gas, dense-phase carbon dioxide has a long decompression wave platform (saturation pressure), so that the pressure at the tip of a crack cannot be released, and the crack is easy to propagate for a long time to cause huge loss of personnel and property. Once the dense-phase carbon dioxide pipeline is cracked, the high-pressure gas in the pipeline cannot be immediately emptied, and a pressure reducing wave is generated from the breaking point to two sides and propagates to the far end. Because the gas decompression wave speed is lower than the steady-state expansion speed of the crack, the crack tip can keep a continuous high-stress state, and the crack can also continuously expand at a high speed, so that the ductile crack of the gas transmission pipeline can be expanded in a long range. The long-range expansion of cracks in dense-phase carbon dioxide pipelines can cause huge disasters and losses, so that the pipelines must be ensured to be capable of timely crack arrest once cracked. The existing full-size blasting test results show that for a high design coefficient CO 2 pipeline, the crack is difficult to stop by means of self toughness, and the problem is a bottleneck problem which seriously threatens the pipeline safety and restricts the application of a carbon dioxide pipeline. Disclosure of Invention The invention aims to provide a design method of a steel sleeve crack stopper for a dense-phase carbon dioxide pipeline, which solves the problem that the dense-phase carbon dioxide pipeline with small caliber of OD508 and below cannot be timely crack-stopped after being cracked. The technical scheme adopted by the invention is that the design method of the steel sleeve crack stopper for the dense-phase carbon dioxide pipeline comprises the following steps: S1, selecting a sample steel pipe, and determining the steady-state expansion speed of cracks in the sample steel pipe through a DWTT experiment; s2, establishing a finite element model, namely simulating the geometric dimension of a real pipeline, dividing the pipeline by adopting a shell unit, and adopting a cohesive force unit for a crack propagation path; S3, calculating the saturation pressure of the carbon dioxide component, and applying the pressure to the tip of the crack; s4, performing three-dimensional dynamic elastoplastic finite element analysis by using a general program, determining cohesive force parameters, and taking the cohesive force parameters as finite element model parameters; S5, determining pressure distribution of cracks after entering the crack stopper; S6, establishing a non-contact algorithm, and evaluating the constraint force of the crack stopper on crack propagation through the algorithm; and S7, equivalent constraint force to externally applied stress to obtain crack propagation speed, and finishing the design of the steel sleeve crack stopper. The invention is also characterized in that: the specific process of S1 is as follows: S1.1, selecting a steel pipe, carrying out a DWTT experiment, collecting load-displacement and load-time curves of a hammer head, and carrying out high-speed shooting; S1.2, determining the linear section time t 1 and t 2 of the steel pipe, determining the crack propagation distance d of the time t 1～t2 by high-speed shooting, and calculating the crack steady-state propagation speed v in the steel pipe according to the formula (1); v=d/(t2-t1) (1)。 In S2, modeling is carried out by simulating the geometric dimension of a real pipeline by using ABAQUS software, in a grid module, dividing the pipeline by adopting shell units, increasing the refinement degree of the shell units in a region close to an upper bus, applying crack growth in the region, wherein the average side length of the shell units is 100mm-10mm, using an explicit integral algorithm code based on a central difference method by using a finite element model, and adopting a cohesive unit in a crack growth path, wherein the size of the cohesive unit is smaller than 2mm. And S3, calculating the saturation pressure of the carbon dioxide component, namely, calculating the saturation pressure of the carbon dioxide component by applying GERG' S08 state equation. The specific process of the S4 is that a general program selects an ABAQUS software Explicit solver module to carry out three-dimensional dynamic elasto