基于IEC标准的风力发电机组声发射评估方法

研究了基于IEC61400—11测量标准,确保风力发电机组声学噪声评估过程准确、可重复的声学测试分析方法,如风速的测量与转换、1／3倍频程分析的背景噪声修正、整风速下的声压级等;推导了适用于工程实践的由声压级估算声功率级的计算公式;并详细分析了基于窄带谱与心理声学的音调及能听度的计算过程。对基于上述原理所开发的测量评估系统于2007年7月在新疆达坂城2号风场进行了为期三周的现场验证性试验,各模块的分析精度与频响范围均达到IEC标准1级仪器的要求,所有指标的评估结果均与MEASNET成员单位所做结论保持一致。     

Acoustic emission detection of fatigue cracks in wind turbine blades based on blind deconvolution separation

The occurrence and expansion of fatigue cracks in large wind turbine blades may lead to catastrophic blade failure. Each fatigue phase of a material has been associated with a typical set of acoustic emission (AE) signal frequency components, providing a logical base for establishing a clear connection between AE signals and the fatigue condition of a material. The relevance of efforts to relate recorded AE signals to a material's mechanical behaviour relies heavily on accurate AE signal processing. The main objective of the present study is to establish a direct correlation between the fatigue condition of a material and recorded AE signals. We introduce the blind deconvolution separation (BDS) approach because the result of AE monitoring is usually a convoluted mixture of signals from multiple sources. The method is implemented on data acquired from a fatigue test rig employing a wind turbine blade with an artificial transverse crack seeded in the surface at the base of the blade. Two different sets of fatigue loading were conducted. The convoluted signals are collected from the AE acquisition system, and the weak crack feature is extracted and analysed based on the BDS algorithm. The study reveals that the application of BDS‐based AE signal analysis is an appropriate approach for distinguishing and interpreting the different fatigue damage states of a wind turbine blade. The novel methodology proposed for fatigue crack identification will allow for improved predictive maintenance strategies for the glass‐epoxy blades of wind turbines. The experimental results clearly demonstrate that the AE signals generated by a fatigue crack on a wind turbine blade can be synchronously separated and identified. Characterizing and assessing fatigue conditions by AE monitoring based on BDS can prevent catastrophic failure and the development of secondary defects, as well as reduce unscheduled downtime and costs. The possibility of using AE monitoring to assess the fatigue condition of fibre composite blades is also considered.     

Loss of safety assessment and the IEC 61508 standard

The standard IEC 61508 contains a lot of useful information and guidance for safety improvement regarding the use of safety systems. However, some of the basic concepts and methods for loss of safety quantification are somewhat confusing. This paper discusses the failure classification, the various contributions to the safety unavailability, and in particular the common cause failure (CCF) model presented in this standard. Suggestions for clarifications and improvements are provided. In particular, a new CCF model is suggested, denoted the Multiple Beta Factor model.     

SCADA data based condition monitoring of wind turbines

Wind turbines(WTs) are quite expensive pieces of equipment in power industry. Maintenance and repair is a critical activity which also consumes lots of time and effort, hence making it a costly affair. Carefully planning the maintenance based upon condition of the equipment would make the process reasonable. Mostly the WTs are equipped with some kind of condition monitoring device/system, which provides the information about the device to the central data base i.e., supervisory control and data acquisition(SCADA) data base. These devices/systems make use of data processing techniques/methods in order to detect and predict faults. The information provided by condition monitoring equipments keeps on recoding in the SCADA data base. This paper dwells upon the techniques/methods/algorithms developed, to carry out diagnosis and prognosis of the faults, based upon SCADA data.Subsequently data driven approaching for SCADA data interpretation has been reviewed and an artificial intelligence(AI) based framework for fault diagnosis and prognosis of WTs using SCADA data is proposed.     

风电叶片复合材料拉伸损伤破坏声发射行为

通过风电叶片单向和多向复合材料拉伸力学性能实验,结合声发射技术,研究复合材料损伤演化特性及纤维预断缺陷对复合材料力学性能的影响.复合材料单向和加卸载拉伸实验时,采用声发射实时监测整个损伤破坏过程,获取复合材料试件的拉伸力学性能、损伤破坏特征及相应的声发射响应特征.结果表明:由于纤维预断缺陷的存在,单向复合材料加载到约30％破坏载荷时,缺陷位置及相邻区域的基体和界面开始出现明显损伤;加载到约60％破坏载荷时,含缺陷层和相邻的层出现明显的层间剪切破坏,导致刚度的急剧缩减,声发射撞击累积数明显高于无缺陷试件.含纤维预断多向复合材料加载到约60％破坏载荷时,纤维预断处树脂基体出现明显损伤;随相对应力水平的提高,多向复合材料的Felicity比下降较为平缓.     

风电叶片复合材料拉伸损伤破坏声发射行为

通过风电叶片单向和多向复合材料拉伸力学性能实验, 结合声发射技术, 研究复合材料损伤演化特性及纤维预断缺陷对复合材料力学性能的影响。复合材料单向和加卸载拉伸实验时, 采用声发射实时监测整个损伤破坏过程, 获取复合材料试件的拉伸力学性能、 损伤破坏特征及相应的声发射响应特征。结果表明: 由于纤维预断缺陷的存在, 单向复合材料加载到约30％破坏载荷时, 缺陷位置及相邻区域的基体和界面开始出现明显损伤; 加载到约60％破坏载荷时, 含缺陷层和相邻的层出现明显的层间剪切破坏, 导致刚度的急剧缩减, 声发射撞击累积数明显高于无缺陷试件。含纤维预断多向复合材料加载到约60％破坏载荷时, 纤维预断处树脂基体出现明显损伤; 随相对应力水平的提高, 多向复合材料的Felicity比下降较为平缓。     

基于LabVIEW和ZigBee的垂直轴风力机无线监测系统

风力机监测系统对风力发电机的研究应用具有重要意义。针对目前垂直轴风力机(vertical axis wind turbine,VAWT)监测系统发展不够成熟的问题,设计一种基于ZigBee无线通信技术的垂直轴风力机在线监测系统,并基于LabVIEW虚拟仪器技术编写上位机界面,实现监测参数在线采集与数据存储。实验表明:该系统能够实时采集风力机的运行参数与环境参数,完成监测任务,具有较好的应用前景。     

Acoustic emission based tensile characteristics of sandwich composites

Sandwich composite static and fatigue testing results indicated the predominant failure to be the core damage followed by interfacial debonding, resin cracking and fiber rupture. Under static testing, crack was observed to initiate in the core and ensue planar propagation near the interface with the facesheets; whereas, onset of crack initiation in the facesheets served as a precursor to the catastrophic failure. Multiple failure initiation and propagation sites in the core and intermittent interfacial debonding were consistently observed under fatigue. An acoustic emission based stiffness reduction model is presented that seems to accurately identify the extent of damage in sandwich composites subjected to fatigue loading conditions.     

Development of vertical axis wind turbines

This paper summarises the work done at the National Aeronautical Laboratory (NAL) between 1975 and 1977 on the development of vertical axis wind turbines based on the Darrieus rotor. On the analytical side, a performance analysis was developed which permits the estimation of the characteristics of such machines. A 5 m high wind turbine using curved wooden blades was designed, fabricated and tested. Both the theory and initial tests confirmed the low starting torque of the turbine. Wind tunnel tests were performed on model Savonius rotors to determine optimum starter bucket configurations. Finally a straight-bladed turbine was designed and constructed. It is concluded from our experience that darrieus burbines are likely to be useful in large systems used to generate electrical power for the grid; for direct water pumping purposes, however, these turbines are unlikely to be suitable.     

改进的台风下单桩海上风机易损性分析方法及应用EI北大核心CSCD

提出了一种改进的台风作用下单桩海上风机易损性分析方法,该方法包括:进行台风模拟,根据模拟台风确定单桩海上风机处的风浪强度指标;将风浪荷载施加在单桩海上风机上,在考虑荷载随机性的情况下得到风机塔筒和桩基的响应极值概率分布曲线;基于非线性屈曲分析得到风机主要构件的承载力概率分布曲线;结合风机主要构件的屈服和屈曲等承载力概率分布曲线,求得单桩海上风机在屈服或屈曲模式下的破坏概率。同时结合江苏某风电场的风浪特性对某5 MW风机进行了风致易损性分析。分析结果可为提升海上风机抗台风风险能力提供参考。