【作者】 段岩峰；

【导师】 于达仁； 杨金福；

【作者基本信息】 哈尔滨工业大学 ， 动力机械及工程， 2010， 博士

【摘要】 随着电力工业的发展,许多大中型汽轮发电机组也参与到调峰中来,而且峰谷差最大能达到50%,很多机组在采用喷嘴调节(局部进汽)进行调峰变负荷的过程中,在中间负荷区发生了一种轴系故障,主要现象为高压转子各轴承处瓦温升高、振动增大等;还有不少机组在单阀向顺序阀切换的过程中,因振动超标而不得不中断,无法投运顺序阀控制。这些故障的产生机制不明确,也没有有效的处理方法,一直困扰着发电企业。为了保证安全生产,这些机组不得不采用节流调节(全周进汽),给电厂带来很大的经济损失。因此,对上述故障开展诊断研究,寻找故障原因和发生机理,并提出有效的解决方案,对完善电站汽轮机故障诊断理论体系,提高电站运行的安全性和经济性,具有重要的理论和实践价值。本文针对电站汽轮机局部进汽工况下发生的高压转子-轴承系统故障和阀门切换过程振动故障,开展一系列故障诊断、机理分析、数值模拟、过程仿真和实验研究工作,进而研究相应的解决方案。本文主要研究工作包括以下几个方面:首先,分析了某型200MW和600MW机组在局部进汽工况下的轴系故障(简称配汽故障),对其典型故障特征进行了总结,然后选取其中具有代表性的200MW机组案例进行诊断。为了获取充分的故障特征信息,提出了基于动态时间规整技术(DTW)的快速关联分析算法,在DAS系统大量测点中自动搜索故障相关信号。基于相关信号和先验知识进行推理诊断,发现故障与局部进汽产生的作用于调节级动叶片的不对称汽流力(简称配汽力)之间的联系。通过调节级变工况热力计算,建立了该200MW机组的配汽力模型,分析了变负荷工况下配汽力与故障特征之间的相关性,推断配汽力为故障原因。其次,对某型200MW机组的高中压转子-轴承系统进行非线性动力学建模,然后基于该模型和配汽力模型,采用带阻尼Newmark方法开展了配汽力作用下轴系运动行为的数值模拟研究,分析了变负荷过程配汽力对轴心位置、轴承载荷、轴系稳定性、振动等特性的影响规律。通过在该机组上开展的现场实验,根据配汽力作用下轴系状态实际变化验证数值模拟结果。研究结果揭示了配汽力对轴心位置、瓦温和轴振的影响机理,证实了故障诊断结论。针对稳定性好、水平方向油膜刚度大的可倾瓦轴承支撑轴系也开展了实验研究,结果表明配汽力对可倾瓦轴承的影响规律和程度与椭圆瓦轴承基本相同。第三,在阀门管理设计中考虑配汽力约束,对最小进汽度50%的喷嘴调节方案进行了数值模拟研究,从经济和安全两个角度综合分析了对角进汽相对于顺序进汽和双对角进汽的优势,并通过实验研究揭示了各种对角进汽方案对轴心位置、瓦温和轴振的影响规律。通过现场实验探讨了利用阀门管理控制配汽力的可行性及必要性,以达到消除配汽故障、调整轴承载荷或提高轴系稳定性的目的。分析了1000MW超超临界机组现有阀门管理方案因最小进汽度为75%而导致的效率损失,提出了配汽力扰动能力的衡量指标,并采用该指标论证了应用最小进汽度50%喷嘴调节的安全裕度小,进而设计了一种可减小配汽力的偏对角进汽阀门管理,可提高1000MW超超临界机组的安全性。分析了季节变化对空冷机组阀门节流损失的影响,设计了可组合多个三阀点的阀门管理方案,分别对应不同季节工况,在保证安全的基础上提高了经济效率。最后,针对阀门切换过程轴振异常变化问题开展了诊断工作,分析出问题原因在于阀门晃动产生的汽流力瞬态冲击,然后通过数值模拟研究了汽流力瞬态冲击对转子振动的影响。分析出阀门晃动原因在于阀门管理整体流量特性与实际情况不匹配,建立了阀位控制回路模型,分别进行了阀门管理流量特性准确与不准确情况下的阀门切换过程仿真研究,验证了这一分析结论。提出了基于运行数据的阀门管理整体流量特性辨识方法,并在工程实践中准确地辨识并修正了阀门管理流量特性,有效地解决了阀门切换过程的轴振异常问题。更多还原

【Abstract】 With the development of power industry, many large and medium turbo-generatorsparticipate in power dispatching, and the biggest difference between peak and valley ofload can reach 50%. A type of rotor-bearing system fault occured at some units whichare in the use of nozzle control (under partial admission) to regulate load when operate atintermediate-load, suffered by bearing pad temperature rise and shaft vibration increases.Some other units have to interrupt valve switching process due to excessive shaft vibrationwhen switch from single valve mode to sequential valve mode, thus can not operate underpartial admission. Mechanism of the fault is not clear, and there is no effective solutionto it. To ensure safety, these units have to use throttle control (under full admission),lead to a great deal of economic loss. Therefore, diagnostic studies of the fault to find thecause and the mechanism, and effective solutions, have important theoretical and practicalvalues to improve fault diagnosis theory and to enhance operation safety and efficiency ofpower plant.In this paper, to deal with faults occur in high-pressure rotor-bearing system andduring valve switching process when units operate under partial admission, we carry outa series of fault diagnosis, mechanism analysis, numerical simulation, process simulationand experimental research, and study the corresponding solutions. This paper mainlyincludes the following:Firstly, a type of rotor-bearing system faults occurred at a 200MW unit and a600MW unit under partial admission (partial admission fault for short) is analyzed, sum-mary their typical fault features, and then select the case of 200MW unit to diagnose. Inorder to obtain sufficient fault information, an algorithm based on dynamic time warpingtechnique (DTW) is proposed for fast correlation analysis. It can be used to search forfault-related signals automatically among a large number of signals in the DAS system.Based on the fault-related signals, fault cause is inferred to be asymmetric steam ?owforces (partial arc steam force for short) acting on governing stage rotor blades gener-ated by partial admission. The model of partial arc steam force with variable load of the200MW unit is established by thermal calculation of governing stage. Correlations be-tween partial arc steam force and fault features are analyzed and the inference result is confirmed that the fault is caused by partial arc steam force.Secondly, nonlinear dynamic modeling of the high and medium pressure rotor-bearing system of the 200MW unit is performed. Based on the model of the unit andpartial arc steam force, numerical simulation research on rotor-bearing system dynamicbehavior under the action of the partial arc steam force is carried out with damped new-mark method, to investigate the variation of shaft centerline position, bearing load, rotor-bearing system stability and vibration characteristics with different load. The results ofnumerical simulation are verified by the actual variation of rotor-bearing system underthe action of partial arc steam force through a field experiment. The research reveal themechanism how partial arc steam force in?uences shaft centerline position, bearing padtemperature and shaft vibration, confirm the diagnosis conclusion. For rotor-tilting-pad-bearing system whose stability and horizontal stiffness are higher than rotor-oval-pad-bearing system, an experiment is carried out and illustrate that the impact extent on bothof them are similar.Thirdly, partial arc steam force is considered as an restriction in valve managementprogram design. All 50% minimum admission nozzle control programs are studied withnumerical simulation. The advantage of diagonal admission compared to sequential ad-mission and double-diagonal admission is comprehensively analyzed when consideringpartial arc steam force and throttle loss. The law that diagonal admission in?uences shaftcenterline position, bearing pad temperature and shaft vibration is revealed through exper-imental studies. The feasibility and necessity of controlling partial arc steam force withvalve management are investigated through field experiments, to achieve the purpose ofeliminating partial admission fault, regulating bearing load or increase rotor-bearing sys-tem stability. The loss of efficiency of 1000MW ultra-supercritical unit which use 75%minimum admission in valve management is analyzed. Two indicators are proposed tomeasure the disturbance capacity of partial arc steam force, and are utilized to demon-strate the feasibility of the application of 50% minimum admission nozzle control. Valvemanagement based on a beveled diagonal admission structure is designed to reduce partialarc steam force and can improve the safety of 1000MW ultra-supercritical units. Throttleloss of air-cooling unit in?uenced by seasonal change is analyzed. A multi three-valve-point valve management program is designed to improve the efficiency of air-cooling unitcorresponding to different seasonal conditions as well as ensure safety. Finally, diagnosis is performed for abnormal shaft vibration during valve switch-ing. The cause is analyzed to be the transient impact of steam forces generated by valveshaking, and then the response of steam forces transient impact on the rotor is studied bynumerical simulation. A valve position control loop model is established for the simu-lation of valve switching, and the cause of valve shaking is inferred to be that the valvemanagement ?ow characteristics do not match the actual condition. A method to identifyvalve management ?ow characteristics based on operation data is proposed. By applyingthe method to practice, the characteristics are accurately identified and corrected, and theabnormal shaft vibration during valve switching is effectively solved.更多还原