【作者】 安宏文；

【导师】 柳亦兵； 胡三高；

【作者基本信息】 华北电力大学 ， 动力机械及工程， 2014， 博士

【摘要】 随着我国经济的快速发展,用电负荷的峰谷差逐渐增大。近些年来,针对越来越高的节能环保要求,我国火力发电设备经过了上大压小的产业结构调整,投运了大量600MW及以上的大容量火电机组。我国新能源发电的快速发展,也对电网的负荷变化产生新影响。在这种背景下,参与调峰运行的火电机组容量不断增加,许多大容量火电机组也投入到调峰运行的行列,根据电网的负荷需求在较大范围内进行负荷调节。火电机组参与宽负荷范围调峰运行的关键问题是对电网负荷快速变化的适应性和低负荷下运行的稳定性。我国大容量火电机组通常以承担中问负荷为主进行设计,这类机组参与调峰运行,由于运行工况条件发生变化,出现较多极端运行工况,可能带来轴系结构热应力、变形、轴系振动和稳定性等方面的新问题,导致设备存在重大安全隐患。提高大容量火电机组在宽范围负荷快速变动条件下的运行安全性是发电行业急需解决的关键技术问题。大容量火电机组参与调峰所带来的运行安全稳定性问题在我国更加突出,原因是我国在机网两侧的条件与西方国家存在差异,而这方面尚缺少深入的研究。本文针对大容量火电机组的特殊性,以600MW汽轮发电机组为对象,在国家和企业科技项目的支持下,深入开展大范围变负荷运行条件下的机组轴系动态特性与稳定性、故障状态下的振动特性及故障特征提取方法等方面的研究,对于提高机组参与调峰运行的安全可靠性具有重要的科学和工程实际意义。论文的主要研究内容及成果如下：(1)600MW机组结构及运行特点分析。结合两个细则,分析了AGC运行方‘式对汽轮机寿命、材料及轴系振动特性的影响,对大容量火电机组振动监测保护系统(TSI系统和TDM系统)的技术现状进行综述；针对某600MW亚临界火电机组,利用实际运行数据分析了自动发电控制(AGC)运行方式下,机组负荷、主汽压力、主汽流量变化对于汽轮机轴系振动的扰动。从运行数据反映的长期趋势看,机组快速变化负荷对高中压缸两端轴承振动产生一定影响。从瞬态振动数据分析来看,负荷变化对振动信号波形、频谱构成影响不明显,没有改变高中压转子的振动状态。(2)轴系振动特性的计算分析。以国产典型600MW火电机组为对象,分别用传递矩阵法和有限元法对轴系弯振和扭振固有特性、快速变负荷状态下的轴系扭振响应特性、发电机两相短路故障下的轴系扭振响应特性进行了仿真计算和比较研究。分析结果表明,600MW机组的轴系扭振危险轴段均位于各转子之间的连接部位：在快速升降负荷时,轴系扭矩响应呈现衰减振荡特性,表明机组在快速升负荷时轴系处于稳定状态；两相短路故障的扭矩响应中,一、二阶扭振固有频率处的峰值最突出,工频及其二次谐波也比较明显,存在共振风险。因此两相短路故障对轴系安全性影响较大。(3)汽轮机瞬态过程的轴系异常振动分析。通过实际案例,对大容量火电机组出现的异常振动现象进行分析,探讨异常振动的响应特性,研究提取故障特征的信号分析方法,为进行轴系故障诊断提供依据。研究了某600MW机组高中压转子发生的缓慢热变形现象的振动特征,确定了导致转子热变形的原因,。提出了一种基于Gabor变换时频域滤波的提取振动信号中特殊频率成分,进行轴系稳定性分析和故障判断的方法。通过对升降速过程的振动信号、气流激振导致的不稳定振动信号的分析,证明了该方法的效果。(4)汽轮机碰磨故障监测诊断方法研究。汽轮发电机组发生轻微动静部件碰磨故障时,相对轴振响应信号中的故障信息非常微弱。针对这一特点,提出采用结构振动检测和信号分析处理相结合的碰磨故障监测诊断新方法,该方法利用碰磨引起的较高频率的冲击振动能量信息,适用于碰磨这类具有瞬时冲击特征的异常振动。由于相对轴振监测对碰磨引起的冲击振动响应不敏感,提出一种采用小波奇异值检测碰磨冲击故障的方法,用小波多分辨率分析获取在特定尺度上的碰磨瞬时冲击信号,提取该瞬时冲击信号的幅值包络,然后采用小波奇异值检测方法对碰磨引起的突变信息进行检测,可以明显改善微弱碰磨故障特征的提取效果。(5)汽轮机振动源的盲分离方法研究。采用频域ICA分析方法对多台大容量汽轮机组进行了多通道轴振信号振源分离,结果表明频域ICA能够更清楚地给出源信号的描述,分离结果更符合汽轮机转子系统振动源的实际情况。频域ICA可以分离出轴振测量信号中包含的可能很微弱的故障信息,分离结果的物理意义比较清晰明确。研究了利用单通道振动实测信号的ICA特征提取方法,结果表明,仅仅依靠单通道ICA分离出的基函数不足以反映机组运行状态的变化,需要进一步对各个基函数进行处理,验证其作为特征信息的有效性。更多还原

【Abstract】 With the rapid development of economy in our country, peak-valley difference of the electricity load increases gradually. In recent years, power equipment has gone through the industrial structure adjustment of developing large units and suppressing small ones aiming at the requirement for energy conservation and environmental protection. A large number of600MW or more thermal power units have been put into operation and it brings new affects for the changes of the load of grid, In this context, the capacity of power units is increasing and a lot of units with large capacity are put into operation for adjusting peak according to the demand of grid load. The key question for thermal power units participating in the peaking with wide range of load is the adaptation for rapid change of grid load and the stability for operating under low load. The power units of our country are mostly designed for carrying the middle load. This kind of units exist major security risks because there are many extreme operating conditions in peaking process and it brings new questions such as shafting structure thermal stress, deformation, shafting vibration, stability and so on. It is the key technical issue to improve the operating safety of units with large capacity under the condition of rapid changing of wide range load.The operating safety and stability for the units of large capacity that participate in the peaking is highlight in our country as the difference between our country and western countries but this aspect is lack of further study. Aiming at the particularity of thermal power units of large capacity, the6Q0MW steam power units are studied. Shafting dynamics and stability, vibration performance in fault condition and fault feature extraction methods are studied with the support of science and technology project of national and enterprise for providing reference basis for operation and fault diagnosis of units. Research results have practical implications in technology and engineering for improving the safety and reliability of units in peaking operation.The main research contents and achievement are as follows:(1) Structure and operating characteristics of600MW power units. Combined the two detailed rules, the effects of AGC operating mode for the life, materials, and shafting vibration characteristics of steam turbine are analyzed. The technical status of vibration monitoring and protection system of large capacity units (TSI system and TDM system) is summarized. Aiming at a600MW subcritical thermal power unit, the effects of the load, main steam pressure and changes of main stream flow rate for shafting vibration under AGC operating mode is analyzed with practical data. From the trend reflected of the operating data, the rapid change of load for unit has an effect on bearing vibration of high-intermediate pressure. From the transient vibration data, the changes of load have small effect on vibration signal waveform and frequency spectrum and vibration operation of the shaft of high-intermediate pressure does not change.(2) Calculation and analysis of shafting vibration characteristics. Aiming at a600MW subcritical thermal power unit, the shafting bending vibration and torsional vibration properties, shafting torsional vibration properties under rapid changes of load and two phase short circuit fault of generator are simulated and compared by using the transfer matrix method and finite element method. The results show that dangerous shaft section of600MW shafting is located at joint part between each rotor. When the load increases rapidly, shafting torsional response possesses damped oscillation property, which indicates that the shaft is in a stable state when the load increases rapidly. In the response of two phase short circuit fault, the peak value is highlighted at the first and second order natural frequency. Power frequency and second harmonics is obvious. So the fault of two phase short circuit has big effect on the shafting safety.(3) Shafting vibration analysis of steam turbine transient process. Through practical cases, the abnormal vibration phenomenon that appears on large capacity thermal power units is analyzed. Abnormal vibration response characteristics are investigated and signal feature extraction methods are studied for shafting fault diagnosis. Vibration characteristics of slow hot deformation phenomenon of a600MW unit rotor in high-intermediate pressure are researched and the cause of the rotor thermal deformation is confirmed. A method by extracting the special frequency component based on Gabor transform time-frequency filtering for shafting stability analysis and fault judgment is proposed. Through the analysis of the vibration signal in the process of speed up or speed down and the unstable signal caused by gas exciting, the effectiveness of the method is proved.(4) The research of methods of monitoring and diagnosis for steam turbine rubbing fault. When the slight rubbing fault occurs, fault information is very weak in the relative shaft vibration response signal. Aiming at this characteristic, a new fault monitoring and diagnosis method is proposed that combined structure vibration monitoring and signal processing. The information of high-frequency impact vibration energy is used in this method and is suitable for abnormal vibration of the rubbing fault that contains transient impact. As relative shaft vibration monitoring is insensitive for impact vibration response caused by rubbing, a rubbing fault detection method by using wavelet singular value is proposed. The rubbing transient impact signal at specific scales is obtained by the multi-resolution analysis of wavelet. The amplitude envelope of transient impact signal is extracted. Then wavelet singular value detection method is used for detecting the saltation information caused by rubbing fault. It improves the effect of extracting features for weak rubbing fault obviously.(5) The analysis of blind source separation for steam turbine vibration source. The signal of large subcritical pressure steam turbine power units has the characteristics of non-stationary, nonlinear. Its background noise jamming is serious. The approach of propagation process and attenuation characteristic is complex. And the signal is the superposition of many fault-source signals in an intricate way. According to the characteristics above, independent component analysis is used for noise reduction and separation of fault-source signals. A fault feature extraction method for f non-stationary and nonlinear is proposed. The separation for fault source and extraction for fault information under complex operating conditions is researched and verified by using practical steam turbine rotor system vibration signal. And the accurate fault feature information is obtained from monitored signal.更多还原