含内腐蚀缺陷高强钢输气管道剩余强度的评估方法研究

发布时间：2018-01-16 02:21

本文关键词：含内腐蚀缺陷高强钢输气管道剩余强度的评估方法研究　出处：《北京交通大学》2015年博士论文　论文类型：学位论文

【摘要】：高强钢输气管道因具备耐腐蚀、大口径、及耐高压等特点,将逐步取代现有的普通钢级管道,成为承担全球天然气输送的主力管道。正因为高强钢输气管道大口径、高压输送以及薄壁的特点,当管道出现内部腐蚀缺陷时其较之普通钢级管道将面临更严峻的挑战,严重时甚至造成泄漏爆炸等灾难性事故。当前对于高强钢管道腐蚀模型及剩余强度评价的研究开展仍较片面,没有考虑管道在输运过程中内部流体的影响,缺乏针对高强钢长输输气管道重点位置的内腐蚀缺陷强度评价方法。因此考虑高强钢管道运营过程中输运气体流场对内腐蚀模型的影响,引入流固耦合下高强钢管道产生内腐蚀缺陷后的强度分析,对于高强钢输气管道剩余强度与运营状态的快速评估具有重大意义。论文以现有的建立较完善的管道内腐蚀模型及管道剩余强度评价方法为依托,探讨了天然气流场对于管道内腐蚀及内腐蚀缺陷评价的影响,将理论分析、模型实验、数值模拟与现场数据相结合,提供了一种比较快速、全面的高强钢输气管道内腐蚀速率模型及含内腐蚀缺陷高强钢输气管道剩余强度评价方法。首先,根据雷诺数相似性设计了高强钢试片冲刷试验平台,并进行了高强钢试片X80的冲刷磨损试验,得到了高强钢试片在不同冲刷角度下的磨损结果,分析了流场变化对高强钢冲刷形貌的影响；同时基于颗粒动力学采用有限元方法引入双流体模型对试验进行了仿真计算,分析了高强钢试片冲刷过程中对其冲刷影响较大的流体参数,在模拟计算的流场参数分布(速度与湍动能)与试验中的高强钢冲刷缺陷形状相似。然后,进行了高强钢X70与X80试件成分、屈服强度及抗拉强度的测定与含半椭圆缺陷下的X90试件的拉伸试验,试验得到缺陷深度的变化对于其屈服强度时最大拉力的影响较大,而在本实验范围内(15mm-55mm)缺陷长度的变化对于拉伸试件屈服强度处的最大拉力影响基本不变；在与有限元计算的对比分析中得到了拉伸试件的缺陷位置存在的一定局部范围内的应力集中现象。圆滑过渡后半椭圆缺陷表面应力状态比之圆滑过渡前缺陷更能精确、有效地反映拉伸样件的破坏失效状态。在管道内湍流可压缩流体方程的基础上,进行了不同倾角下高强钢输气管道内部流场参数分析,推导了长输管道的压降公式并在De waard腐蚀模型的基础上,完成了高强钢输气管道内腐蚀速率随流场参数变化公式。得到管道高程的起伏会造成管道内压的变化,而管道内CO2分压则成为影响管道沿程平均内腐蚀率高低的最重要参数之一；在引入的流场参数中,输运气体速度与湍流动能数值变化可代替倾角变化描述对高强钢输气管道沿程平均内腐蚀率的影响,根据修正后的公式预测出的管道重点位置处内腐蚀形貌大致呈半椭圆片状分布。同时,针对含半椭圆缺陷的X70高强钢直管道建立了三维有限元模型,模拟了流固耦合下管道内流场参数及应力的变化。得到相对于纯内压作用下管道,流场的存在会增高管道内壁缺陷处的应力值：在10MPa的操作压力下,半椭圆缺陷深度对于管道内壁最大应力分布影响最大,缺陷长度在超过100mm时管道内壁应力值变化范围不大,而缺陷宽度的变化对于管道内壁面应力值的影响很小；对于X70管线钢,超过其壁厚50%以上的缺陷深度会对管道的失效压力造成恶劣的影响。而对于含双椭圆缺陷高强钢管道,双缺陷处最大等效应力随双缺陷间距离呈反比变化；当双缺陷间距离超过一定长度时,可忽略双缺陷间应力的交互影响。最后,根据不同缺陷参数对高强钢输气管道的应力影响,采用Marquardt方法进行数据的分段拟合,并提出了流固耦合下的管道失效压力模型,在与纯压力载荷下的爆管实验参数的对比下,提出管道失效压力模型,其预测结果分布稳定。同时基于论文提出的高强钢输气管道内腐蚀速率分析,以流固耦合下的含内腐蚀缺陷高强钢输气管道失效压力为评定准则,提出了流固高强钢输气管道剩余寿命预测模型,可对长输管道的重点位置进行针对性分析。在含流体参数的高强钢输气管道内腐蚀速率分析与流固耦合下含内腐蚀缺陷高强钢管道破坏失效压力分析的基础上,提出了含内腐蚀缺陷高强钢输气管道剩余强度的评价方法,可对高强钢输气管道进行重点检测位置的划分、管道产生内腐蚀缺陷后的强度校核计算以及管道的再评估间隔预测,为保证高强钢输气管道的可靠运行提供理论基础。论文形成了一套进行在役高强钢输气管道内腐蚀缺陷强度评价的较为完整的评价体系,使对在役高强钢输气管道内腐蚀缺陷评价更为快速精准,可为高强钢输气管道的安全运营提供技术支撑。
[Abstract]:High strength steel pipeline with corrosion resistance, large diameter and high pressure resistance, etc., will gradually replace the existing ordinary steel pipes, bear the brunt of global natural gas pipeline as transportation. Because of high strength steel gas pipelines of large diameter, thin wall and high pressure conveying characteristics, when the pipeline internal corrosion defects compared with ordinary steel pipe will face more severe challenges, even when serious leaks caused by explosion accidents. The research on high strength steel pipe corrosion model and residual strength evaluation carried out is still relatively one-sided, without considering the influence in the pipeline transport of fluid in the process, in view of the lack of corrosion defect strength evaluation method of transmission the key position of high strength steel gas pipeline of long distance transport. Considering the gas flow field in the process of pipeline operation in high strength steel corrosion effect on the internal model, introducing the fluid solid coupling under high strength steel pipes produced in The strength analysis of corrosion defects is of great significance for the rapid assessment of the residual strength and operation state of high strength steel gas transmission pipeline.
Based on the residual strength evaluation method of the existing pipeline established a model based on the internal corrosion and pipeline, discusses the influence of gas flow and for internal corrosion defects in pipeline corrosion evaluation, theoretical analysis, model experiment, numerical simulation and field data binding phase, provides a fast, comprehensive high strength steel within the gas pipeline corrosion rate and corrosion defect model with high strength steel pipeline residual strength evaluation method of gas pipeline.
First of all, according to the Reynolds number similarity design of high strength steel specimen erosion test platform, test and erosion wear of high strength steel specimens of X80, the wear test results of high strength steel specimens at different erosion angle, analyzed the influence of flow change on erosion morphology of high strength steel; and the particle dynamics with finite element method the two fluid model of test is simulated based on the analysis of the impact of fluid parameters on the large scour erosion process in high strength steel plate, the flow field distribution in the simulation (velocity and turbulent kinetic energy) and high strength steel shape defects similar erosion test.
Then, the high strength steel X70 and X80 specimens, the yield strength and tensile strength and determination of the defects with semi elliptical X90 under test tensile test pieces, obtained defect depth test changes for the yield strength when the influence of maximum force is large, and in this experimental range (15mm-55mm) changes the defect length the maximum tensile yield strength tensile specimens at the same; in contrast analysis and finite element calculation by the tensile stress concentration phenomenon of certain local defect position in the second half. Smooth elliptic surface defects shall be smooth and stress than before the transition defects more accurately and effectively. The tensile samples reflect failure failure state.
Based in the pipe turbulent compressible fluid equations, the different angle analysis of internal flow field parameters of gas pipeline under high strength steel, deduced the formula of pressure drop of pipeline based on De waard corrosion model, completed the transmission of high strength steel corrosion rate of gas pipeline with the flow field parameters obtained pipeline formula. The elevation fluctuation can cause changes in pipeline pressure, has become one of the influences of corrosion along the average rate in the most important parameters in pipeline CO2 pressure; in the flow field parameter is introduced in numerical transport velocity and turbulent kinetic energy of gas can replace the angle change description of high strength steel gas pipeline along the average corrosion rate in the process, according to the corrosion morphology of pipeline key position correction formula to predict the roughly half elliptical distribution.
At the same time, a three-dimensional finite element model is established for containing semi elliptical defects of X70 high strength steel straight pipe, simulated flow solid coupling flow field parameters of pipeline and stress. Compared to pure pressure inside the pipeline, the flow stress value will increase the pipeline inner wall defects: in the operating pressure of 10MPa under the semi elliptical defect depth for pipe wall maximum stress distribution of the maximum length of the defect in more than 100mm pipe wall stress variation range is not big, but also affected the pipeline wall defect width for stress value is very small; for X70 pipeline steel, more than the wall thickness of more than 50% of the depth of defect will cause bad influence on pipe failure pressure. For high strength steel pipe with double elliptical defect, two defects maximum equivalent stress with two defects is inversely proportional to the distance between the change of distance between the two defects; when more than a certain length of time The interaction of stress between two defects can be ignored.
Finally, according to the influence of different parameters on the stress defects of high strength steel gas pipeline, Marquardt method was used for fitting data, and put forward the failure pressure model of pipeline coupling under flow, and in the pure pressure loading tube explosion experimental parameters contrast, proposed pipeline failure pressure model, the prediction results of distribution stability analysis. The corrosion rate of gas pipeline in high strength steel and the thesis based on the transmission, to flow with internal corrosion defects in solid coupling under high strength steel gas pipeline failure pressure as the criterion of assessment, put forward the high strength steel transmission fluid solid gas pipeline residual life prediction model, but for the analysis of key position of long distance pipeline.
In high strength steel containing fluid parameters transmission gas pipeline corrosion rate and flow solid coupling analysis with internal corrosion defects of high strength steel pipeline failure based on the analysis of failure pressure, put forward the evaluation method with the internal corrosion defects of high strength steel pipeline residual strength of the gas pipeline, the high strength steel pipeline Road Division focuses on the detection of position then, evaluate the pipeline internal corrosion defects produced after the strength calculation and pipeline interval prediction, in order to provide theoretical basis for reliable operation of high strength steel gas pipeline.
A complete evaluation system for evaluating the strength of in-service high-strength steel gas pipeline corrosion defects is formed, which makes the evaluation of corrosion defects in service high strength steel gas pipelines faster and more precise, and provides technical support for the safe operation of high strength steel gas transmission pipelines.

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE973;TG142.1

【参考文献】