输气站场离心式压缩机叶轮开裂成因分析

Cause analysis of cracking in an impeller of centrifugal compressor at gas transmission station

  • 摘要: 随着天然气管道向高压力、大流量方向发展,输气站场离心式压缩机的运行压力和负荷不断增加,结构振动和疲劳断裂等问题更加突出,威胁站场安全运行。针对某站场压缩机三级叶轮局部开裂问题,提出一种理论建模-数值仿真- 实验测试耦合分析思路,并通过流-固耦合研究探讨了叶轮断裂机理。首先,分析叶轮气动载荷变化规律;其次,通过静力学实验测定叶轮材料强度;然后,基于运行工况构建有限元模型,求解叶轮振动特性;最后,结合动、静强度分析,开展静强度校核及流-固耦合共振风险评估,揭示叶轮开裂机理。研究结果表明,在运行过程中,事故叶轮进口叶片根部最大应力值达到538 MPa,低于实验测得叶轮材料的屈服强度841 MPa和抗拉强度914 MPa,叶轮气流脉动频率与结构第6~8阶固有频率高度重合。叶轮静强度满足要求,局部开裂由于气流脉动载荷频率接近叶轮固有频率,从而引发共振造成疲劳破坏所致。研究成果可为输气站场压缩机运行安全及叶轮结构优化提供理论依据和实践指导。

     

    Abstract: The ongoing development of natural gas pipelines towards elevated pressures and accelerated flow rates increases operating pressures and loads on centrifugal compressors at gas transmission stations. Consequently, challenges such as structural vibration and fatigue fractures become more prominent, threatening the safe operation of these stations. This paper presents an analytical approach that combines theoretical modeling, numerical simulation, and experimental testing through a case analysis focusing on local cracking in a three-stage impeller of a compressor at a station. It also explores the mechanisms behind impeller fractures through fluid-solid coupling research. First, an analysis was conducted to investigate the patterns of aerodynamic load changes on the impeller. Secondly, static experiments were performed to determine the material strength of the impeller. A finite element model was then established based on the operating conditions to identify the vibration characteristics of the impeller through a solving process. Finally, alongside dynamic and static strength analyses, a static strength check and evaluation of fluid-solid coupling resonance risks were conducted to reveal the cracking mechanism of the impeller. The maximum stress observed at the root of the inlet blades of the faulty impeller reached 538 MPa during operation, which was lower than the tensile strength and yield strength of the impeller material, measured at 914 MPa and 841 MPa in the experiments, respectively. The pulsation frequency of the airflow across the impeller closely coincided with the natural frequencies of the structure in the sixth to eighth orders. These results indicated that the impeller' s static strength met the requirements, and the local cracking was related to the frequency of pulsating loads caused by airflow that approached the natural frequencies of the impeller. Thus, fatigue damage caused by resonance is identified as the underlying cause. The research findings provide a theoretical basis and practical guidance for the safe operation of compressors at gas transmission stations and for the structural optimization of impellers.

     

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