考虑管道失效概率与管网水力特征的环状高压燃气管网供气可靠性评价方法研究

As an important part of the city lifeline engineering, and also a municipal public infrastructure, a high pressure gas pipeline network is the city’s gas supply aorta. Its reliable work is related to the whole city’s normal gas supply and social public security. Considering existing researches mainly focus on safety analysis of pipeline itself but not pay enough attention to its influence on the whole city’s gas supply, this project will take into account both the pipeline structure failure and the network hydraulic characteristics to evaluate the whole gas supply capacity of the network. It includes three main contents: (1) Making full use of the reliability analysis methods in field of long distance pipeline as well as the outstanding achievements in field of pipeline safety assessment, the failure model of high pressure gas pipelines is established, and its failure probability is analyzed; (2) Through numerical and experimental simulation of the hydraulic operation states under different fault conditions, the hydraulic characteristics of several circular networks are analyzed to explore the influence of different position pipeline failure on the reduction of gas supply; (3) Based on the above two achievements, the quantitative characterization of the network’s whole gas supply capacity is researched, and then the method of gas supply reliability evaluation of the network is proposed from the viewpoint of system reliability. The purpose of the research is to achieve the quantitative analysis and evaluation of the network’s whole gas supply capacity. Consequently, the weakness of the network can be tracked, and also some measures can be provided to ensure its supply reliability, from the perspective of planning design, operation maintenance, contingency planning and so on.

作为城市生命线工程和市政基础设施之一的高压燃气管网，是城市燃气供应的主动脉，其可靠工作关系到整个城市的正常能源供应和社会公共安全。本项目针对现有相关研究侧重管道本身安全性分析而较少关注其对管网整体供气影响的现状，尝试综合考虑管道结构失效和管网水力特征两方面，研究环状管网整体供气能力的评价方法。具体包括：1.借鉴长输油气管线常用的可靠性分析方法，针对城市高压燃气管道特点建立失效模型，研究其失效概率；2.在对不同故障状态下管网水力工况进行数值和实验模拟基础上，深入分析环状管网水力特征，揭示不同位置管道失效对管网减供气量的影响规律；3.综合以上两方面成果，对管网的整体供气能力进行量化表征，进而从系统可靠性角度提出管网供气可靠性的评价方法。研究目的在于对规划或在役管网的整体供气能力进行定量分析评价，以期找出影响供气的薄弱环节，从管网规划、运行维护、应急预案制定等视角提供保障供气可靠性的思路或措施。

管网供气可靠性是评价燃气管网供气功能的一个综合评价标准，可依据此评价结果，从管道结构和管网水力工况两个方面来改善管网设计方案或完善已建成系统，保证城市燃气的可靠供应和公共安全。为此，本项目主要进行了三个方面的研究：（1）通过对高压燃气管道的现有失效水平、失效原因等调研统计，得出近年来国内外燃气管道失效率的变化范围，指出第三方破坏、腐蚀、施工/材料缺陷是影响燃气管道失效的三个主要因素，并基于结构可靠性理论建立失效模型，研究了埋地高压燃气管道失效概率的确定方法，指出了城市埋地高压燃气管道在运行之初，单是力学因素很难致使其失效，在运行后期，影响其失效概率的主要参数是腐蚀指数、腐蚀乘子和工作压力；（2）通过对环状燃气管网故障工况下水力特征的理论分析、数值仿真和实验模拟，揭示了不同位置管道失效对环状管网各节点压力、流量的影响规律，说明了故障工况下的流量计算需要考虑节点流量和节点压力的动态变化关系，并分析论证了采用节点法编制水力计算程序是一种确定环状高压燃气管网故障工况下实际节点流量的可行方法；（3）综合管道失效概率和管网水力特征两方面因素对环状燃气管网的整体供气能力进行量化表征，提出了一种针对城市环状燃气管网供气可靠性的分析评价方法，并基于失效概率的研究成果分析了管道失效率的计算方法，得出了管道失效率“浴盆曲线”，利用管网水力特征的研究成果解决了故障工况下管网减供气量的确定这一瓶颈，使管网供气可靠性评价方法更具合理性和可操作性。通过本课题的研究，可使燃气相关单位从规划建设层面着手进行管网宏观优化；从管理维护层面，可使燃气供应企业参考管网中不同管道对管网整体供气能力“贡献率”的相对大小，找出影响管网供气的薄弱环节，进而采取有差别的管道运行、监控及管网维修改造方案，达到降低管网运行维护代价，改善管网供气能力的目的。