大型空冷结构振动疲劳可靠性分析理论与设计方法研究

Air-cooling power plants have overriding advantages in water saving, and conform to the mandatory provisions of Chinese industry policy and the planning of thermal power plants. The air-cooling technique is therefore rapidly developing and shows a good prospect. As air-cooling units bacome larger, the structural fatigue and damage due to the unbalanced vibration of fans evidently arise. Taking such a critical problem into acount, principles of developing fatigue load spectrum, cumulative fatigue damage analysis and design methods for air-cooling structures will be carried out by in-situ survey, theoretical analysis and numerical simulation. In details, a random disturbing force model of fans will be established in terms of recorded vibration responses of air-cooling structures. Rainflow counting method would be employed to determine mean and range of fatigue stresses, probability distribution and corresponding parameters will also be evaluated. Furthermore, probability density evolution of nonlinear cumulative fatigue damage and its reliablity will be analyzed, which provide theoretical basis for the researches on the fatigue design method of air-cooling structures based on linear fatigue damage cumulation rule and nominal stress concepts. The findings of this proposal are expected to broaden subjects of study on fatigue load spectrum and enrich methods of fatigue reliability analysis, supplement design factors of air-cooling structures and promote reliable operation of air-cooling power plants as well.

直接空冷工艺具有显著的节水效率，符合国家产业政策和行业规划导向。因此，近年来得到了快速发展，且进一步应用前景广阔。本课题针对空冷机组大型化过程中风机运行引起的结构振动及疲劳损伤问题，采用现场调查、理论分析及数值模拟的方法开展空冷结构疲劳载荷谱编制原则、累积疲劳损伤分析及工程设计方法研究。基于实测空冷结构振动响应建立随机风机扰力模型，通过雨流计数法确定空冷结构疲劳应力均值及幅值的样本值，并对其进行分布特性及参数估计研究。进而，考虑变频风机扰力加载次序的影响，实现非线性累积疲劳损伤概率密度演化及其可靠度分析，为基于线性累积损伤法则和名义应力的空冷结构疲劳设计方法研究提供理论基础和技术手段。研究成果对拓展疲劳载荷谱研究对象、丰富疲劳可靠度分析方法具有重要的理论意义，对完善空冷结构设计内容、保障空冷机组可靠运行具有重要的工程价值。

直接空冷工艺具有显著的节水效率，符合国家产业政策和行业规划导向，近年来得到了快速发展，且进一步应用前景广阔。针对空冷机组大型化过程中风机运行引起的结构振动及疲劳损伤问题，基于实测空冷结构振动响应建立了随机风机扰力模型，考虑变频风机扰力加载次序的影响，通过雨流计数法和线性损伤累积准则预测了空冷风机桥架的疲劳寿命。进而，发展了基于概率密度演化理论的疲劳可靠度分析方法，开展了空冷风机桥架疲劳热点预实验研究，初步明确了其微动磨损失效的物理过程。研究成果对疲劳可靠度分析方法具有重要的理论意义，对完善空冷结构设计内容、保障空冷机组可靠运行具有重要的工程价值，为进一步开展微动疲劳可靠性分析奠定了基础。