IEC载荷工况与Bladed设置（3）风机设计等级

从今天这篇文章开始，将开始将详细的介绍IEC工况在bladed软件中怎么设置。下图是IEC61400-3-1海上风机工况表的发电工况。接下来重点介绍一下DLC1.1工况。从工况表中可以看出1.1工况的轮毂处正常湍流风的平均风速是在切入和切出风速之间，波浪是正常海况，风和波浪的方向是同向且是单向的，水位是平均海平面，计算应基于载荷响应结果的统计外推，校核极限强度，安全系数是正常但1.1用的是1.25而不是1.35（安全系数的详细介绍请参考以前的文章）。下面结合IEC标准详细的介绍一下这个工况，首先说说发电工况。In this design situation, an offshore wind turbine is running and connected to the electric load. The assumed wind turbine configuration shall take into account rotor imbalance. The maximum mass and aerodynamic imbalances (e.g. blade pitch and twist deviations) specified for rotor manufacture shall be used in the design calculations. In addition, deviations from theoretical optimum operating situations such as yaw misalignment and control system tracking errors shall be taken into account in the analyses of operational loads.该设计状态下，海上风力发电机组处于运行状态并有电力负载。海上风力发电机组总体布局应考虑风轮不平衡的影响。设计计算中应考虑风轮制造中所规定的最大质量和气动不平衡（如叶片的变桨角和扭转角偏差）。此外，在分析运行载荷时应考虑与理论最佳运行状态的偏差，例如偏航误差和控制系统跟踪误差等。DLC1.1的特殊要求，结合了1.2的共同特向做了介绍。Design load cases (DLCs) 1.1 and 1.2 embody the requirements for loads resulting from atmospheric turbulence (NTM) and stochastic sea states (NSS) that occur during normal operation of an offshore wind turbine throughout its lifetime.Analysis of DLC1.1 is required only for calculation of the ultimate loads acting on the rotor- nacelle assembly. The calculations for DLC1.1 shall be based on statistical extrapolation of the load response results of multiple simulations of stochastic sea states and turbulent inflow for a range of mean wind speed.For calculation of the loads acting on the rotor-nacelle assembly, the statistical analysis of DLC1.1 simulation data (see IEC 61400-1:2018, 7.6.2.2 and Annex G) shall include at least the calculation of extreme values of the blade root in-plane moment and out-of-plane moment and tip deflection. If the extreme design values of the blade root moments derived from DLC1.1 are exceeded by the extreme design values derived for DLC1.3, the further analysis of DLC1.1 may be omitted. If the extreme design values of the blade root moments derived from DLC1.1 are not exceeded by the extreme design values derived for DLC1.3, the factor c for the extreme turbulence model used in DLC1.3 (see IEC 61400-1) may be increased until the extreme design values of the blade root moments computed in DLC1.3 are equal to or exceed the relevant extremes. The characteristic values of the loads relevant for other turbine components may be determined from this analysis based on DLC1.3 with the increased c value. As an alternative to this analysis, the appropriate characteristic values of all load components relevant for each specific turbine component may be directly determined or extrapolated from the simulation.设计工况DLC1.1和1.2包含了在海上风力发电机组寿命期内正常运行期间，对由大气湍流（NTM）和随机海况（NSS）所引起的载荷要求。DLC1.1仅用于计算作用在风轮-机舱组件上的极限载荷。DLC1.1的计算应基于对随机海况和平均风速范围内湍流风多次仿真的载荷响应结果的统计外推。计算风轮-机舱组件的载荷时，DLC1.1仿真数据的统计分析(见IEC 61400-1:2018, 7.6.2.2和附录G)应至少包括叶片根部面内和面外弯矩以及叶尖挠度的极值计算。如果DLC1.3的叶根弯矩极限设计值超出DLC1.1的极限值，则可以省略DLC1.1的进一步分析。 如果DLC1.3的极限设计值未超出DLC1.1计算所得的叶根弯矩的极限设计值，可增加DLC1.3极端湍流模型所用到的参数c值（参照IEC 61400-1），直到DLC1.3计算的叶根弯矩等于或者超过相关极值。风力发电机组其他部件相关载荷的特征值可基于增加c值的DLC1.3来分析确定。作为分析的替代方案，风力发电机组各个特定部件相关的所有载荷的特征值可直接通过仿真结果确定或由外推得到。以上是IEC标准对DLC1.1工况的介绍，外推的详细方法将在介绍DLC1.3工况是在写。接下来就讲讲DLC1.1工况怎么在bladed中计算。Bladed的湍流风和不规则波的设置以前的文章都已经介绍了，水位和流的设置比较简单这里也不详细的讲了。接下来重点介绍风和波浪的详细设置。首先，平均风速的步长一般取两米，对于每个风速当小于额定风速减二时取六个种子，其他的风速取五十个种子。对于偏航误差取-8、0、和8三个方向，为了三个方向取相同的种子，所以实际取五十个种子的风速要取五十四个风种子。 下图分别举了六个和五十四个种子的风速的例子。 计算的时间长度可以取十分钟六百秒，外推载荷分量取叶根Mx和My，叶尖偏移。DLC1.1和DLC1.3联系的十分紧密，由于篇幅的原因，载荷外推的详细做法等内容将在DLC1.3的文章里详细介绍。 来源：智慧强学斋