Real-time Health Condition Evaluation on Wind Turbines Based on Operational Condition Recognition

针对大型风电机组运行工况和状态信息复杂，健康状态难以准确评价的问题，提出基于工况辨识的健康状态实时评价方法。该方法充分考虑机组运行工况的复杂性和多变性，采用工况辨识实现运行工况空间的划分。在各运行工况子空间，建立基于高斯混合模型（gaussianmixturemodel，GMM）多状态特征融合的健康状态评价模型。采用健康衰退指数（healthdegradationindex，HDI）作为机组健康状态评价指标，并给出健康衰退报警限的确定方法。该方法用于某1．5MW风电机组传动系统故障前的健康状态评价。结果表明，该方法提前监测到机组健康状态的衰退趋势，可实现故障的早期预报，避免严重故障发生，并为合理调整运行和安排维修提供依据。

Transient response of enstrophy transport to opposition control in turbulent channel flow

The transient response of the turbulent enstrophy transport to opposition control in the turbulent channel flow is studied with the aid of direct numerical simulation. It is found that the streamwise enstrophy and the spanwise enstrophy are suppressed by the attenuation of the stretching terms at first, while the vertical enstrophy is reduced by inhibiting the tilt of the mean shear. In the initial period of the control, the streamwise enstrophy evolves much slower than the other two components. The vertical vorticity component exhibits a rapid monotonic decrease and also plays an important role in the attenuation of the other two components.