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首页> 外文会议>ASME Turbo Expo: Turbomachinery Technical Conference and Exposition >AERODYNAMIC NUMERICAL INVESTIGATION OF LOW-PRESSURE STEAM TURBINE LAST STAGE UNDER LOW LOAD CONDITIONS WITH MODE DECOMPOSITION METHODS
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AERODYNAMIC NUMERICAL INVESTIGATION OF LOW-PRESSURE STEAM TURBINE LAST STAGE UNDER LOW LOAD CONDITIONS WITH MODE DECOMPOSITION METHODS

机译：低压汽轮机的空气动力学数值研究在低负载条件下的低压汽轮机与模式分解方法

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摘要

It is common that steam turbine works at different operating points, especially under low load conditions, to cater to complex and varied demands for power generation recently. Considering the long and thin shape of last stage moving blades (LSMBs) in a low-pressure (LP) steam turbine, there are many challenges to design a suitable case which balances global efficiency against sufficient structure strength when suffering excitations at low load operating points. In present work, the aim is to extract specific aerodynamic excitations and recognize their distribution and propagation features. Firstly, steady 3D computational fluid dynamics (CFD) calculations are simulated at 25GV and 17GV (25% and 17% of design mass flow conditions) and corresponding unsteady calculations are performed with enough rotor revolutions to obtain integrated flow periodicities. Unsteady pressure signals near tip region of LSMBs are monitored circumferen-tially in both static and rotating coordinates. The fast Fourier transformation (FFT) results of unsteady pressure signals show that there are broadband humps with small disturbance amplitudes in low frequency spectrum at 25GV, however, a sharp spike is shown in low frequency spectrum at 17GV. Further, circumferential mode decomposition (CMD) method has been applied to distinguish different fluctuations in frequency and the mode numbers and circumferential propagating pace of which have been obtained. Finally, dynamic mode decomposition (DMD) method has been performed to describe detailed mode shapes of featured flow perturbances both in static and rotating coordinate system. These analyses indicate that at 25GV, a band of unsteady responses with very low amplitude was noted which has some features similar to rotating instability (RI). However, distribution and propagation features of flow unsteadiness at 17GV are in good agreement with rotating stall (RS) in compressor.
机译：蒸汽轮机在不同的操作点工作，特别是在低负荷条件下，最近迎合了复杂和多种对发电的需求。考虑到最后阶段移动刀片（LSMB）的长而薄的形状，在低压（LP）汽轮机中，设计了许多挑战，设计适当的情况，在低负荷操作点遭受激发时平衡全球效率的全球效率。在目前的工作中，目的是提取特定的空气动力激励并识别它们的分布和传播特征。首先，在25GV和17GV（设计质量流动条件的25％和17％的25％和17％的25％和17％）中模拟稳定的3D计算流体动力学（CFD）计算，并且通过足够的转子转旋转来执行相应的不稳定计算，以获得集成的流量周期。在静态和旋转坐标中，在LSMB的尖端区域附近的不稳定压力信号被监视。不稳定压力信号的快速傅里叶变换（FFT）结果表明，在25gV的低频频谱中存在具有小扰动幅度的宽带驼峰，然而，在17gV的低频频谱中示出了尖锐尖峰。此外，已经应用了圆周模式分解（CMD）方法以区分频率和模式数的不同波动以及已经获得的圆周传播速度。最后，已经执行动态模式分解（DMD）方法来描述静态和旋转坐标系中的特色流动扰动的详细模式形状。这些分析表明，在25GV时，注意到具有非常低振幅的不稳定响应带，其具有类似于旋转不稳定性（RI）的特征。然而，在17GV下流动不稳定的分布和传播特征与压缩机中的旋转失速（RS）吻合良好。

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