直接空冷结构风机致振研究

发布时间：2018-04-14 12:19

本文选题：空冷桥架 + 随机振动　；参考：《西安建筑科技大学》2015年硕士论文

【摘要】：空冷系统具有明显的环境效益,广泛用于我国富煤缺水的北方地区。空冷结构的安全性直接影响到火电厂正常运行,以往研究主要集中在整体结构遭受风荷载、地震作用等方面,关于风机运转致振问题研究尚显不足。空冷桥架和风机系统属于耦合体系,风机运转必然引起桥架结构振动,尤其在空冷结构长期工作状态下风机运转产生的扰力将使桥架结构出现疲劳破坏。本文以现场实测空冷结构桥架振动结果为基础,建立桥架上风机扰力荷载模型。在扰力荷载作用下进行空冷结构随机振动响应分析,最后定量评价桥架结构在服役期内风机扰力影响下的可靠性。(1)本文首先阐述了空冷结构在我国发展的必然趋势,系统总结了空冷结构目前的研究现状,分别从频域和时域角度介绍荷载识别方法。围绕空冷结构风机桥架现场实测振动呈现随机特性,论述有关随机过程的基本概念,窄带随机过程的统计特性以及结构随机振动的计算分析方法。(2)针对不同转速下现场实测的直接空冷系统风机桥架振动速度响应,分别在时域和频域对振动响应进行分析,传统简谐扰力荷载作用下的振动响应不能反映实测结果中幅度和相位缓慢变化的窄带随机特性。本文以实测振动响应为基础,建立基于载波理论的风机随机扰力模型,并以振动响应的功率谱为目标,识别扰力模型参数,结果表明建立的扰力模型能够很好地反映桥架振动的随机性。(3)根据结构动力学理论的振型叠加法,动力反应数值分析方法中的中心差分原理,推导已知桥架结构振动响应,反分析求解桥架上风机扰力的计算方法。基于实测各工况桥架结构振动输出响应,结合有限元模态分析结果,采用反演方法识别风机扰力,并在频域和时域内对比验证反分析结果的可靠性。结果表明识别的等效扰力荷载模型能够反映实际不同工作条件下风机运行对支撑桥架的影响。(4)建立实际空冷结构有限元模型,以谐波叠加法生成目标功率谱下的风机扰力时程样本,计算扰力荷载作用下空冷结构随机振动响应,并对计算结果进行分析。提取多组风机扰力荷载作用下桥架随机振动的应力结果,采用雨流计数程序对其应力幅进行统计,计算桥架危险点在不同服役期内的疲劳累积损伤,给出相应服役期内结构不发生疲劳失效的可靠度。
[Abstract]:Air-cooling system has obvious environmental benefits and is widely used in the north of China, which is rich in coal and short of water.The safety of air-cooled structures has a direct impact on the normal operation of thermal power plants. Previous studies focused on wind load and seismic action on the whole structure.The air-cooled bridge frame and fan system belong to the coupling system, the fan operation will inevitably cause the bridge structure vibration, especially under the air-cooled structure long-term operation disturbance force will cause fatigue damage to the bridge frame structure.Based on the measured results of vibration of air-cooled structure bridge, the model of disturbance load of fan on bridge frame is established in this paper.The random vibration response analysis of air-cooled structure under disturbance load is carried out. Finally, the reliability of bridge frame structure under the influence of blower disturbance force during service period is quantitatively evaluated.) in this paper, the inevitable development trend of air-cooled structure in China is first expounded.The present research status of air-cooled structures is summarized systematically, and load identification methods are introduced from frequency domain and time domain respectively.Based on the random characteristics of field measured vibration of air-cooled structure fan bridge frame, the basic concepts of stochastic process are discussed.Statistical characteristics of narrow Band Stochastic process and calculation and Analysis method of structural Random Vibration. (2) aiming at the vibration velocity response of fan bridge of direct air-cooled system measured at different rotational speeds, the vibration response is analyzed in time domain and frequency domain, respectively.The vibration response under the traditional harmonic disturbance force can not reflect the narrow band random characteristic of the amplitude and phase in the measured results.Based on the measured vibration response, a random disturbance model of fan based on carrier theory is established in this paper. The parameters of the disturbance model are identified by taking the power spectrum of the vibration response as the target.The results show that the disturbance force model can well reflect the randomness of bridge vibration. According to the vibration superposition method of structural dynamics theory and the central difference principle in the numerical analysis method of dynamic response, the known vibration response of bridge frame structure is deduced.The calculation method for calculating the disturbance force of the blower on the bridge frame by inverse analysis.Based on the measured vibration output response of the bridge structure under different operating conditions, combined with the modal analysis results of finite element method, the inverse method is used to identify the disturbance force of the fan, and the reliability of the back-analysis results is verified by comparing the results in frequency domain with that in time domain.The results show that the identified equivalent disturbance load model can reflect the influence of fan operation on the supporting bridge under different actual working conditions.The harmonic superposition method is used to generate the time history samples of the disturbance force of the fan under the target power spectrum. The random vibration response of air-cooled structure under the disturbing force load is calculated, and the calculated results are analyzed.The stress results of random vibration of the bridge frame under the disturbance force load of many sets of fans were extracted. The stress amplitude of the bridge was counted by the rain flow counting program, and the fatigue cumulative damage of the dangerous point of the bridge in different service periods was calculated.The reliability of structure without fatigue failure during the corresponding service period is given.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU311.3

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