对包括蜗壳的离心压气机整机模型进行了非定常数值模拟，获得不同工况下的非定常流场数据，采用动态模态分解(DMD)方法对设计工况与非稳定工况条件下蜗壳的三维非定常流场进行模态分解与重构.结果表明：在设计工况下，蜗壳内流场主要受到 4.421kHz的长叶片通过频率的影响，而 8.841kHz的长、短叶片通过频率的影响则受到抑制；在非稳定工况下，捕捉到了不稳定特征频率和所对应的流动模态，以及蜗壳内流场沿流向呈螺旋线型变化的速度脉动；基于频率特征的DMD方法得到了三维蜗壳模态.
Unsteady numerical simulations of the centrifugal compressor with and without volute were carried out to investigate the effect of vaneless diffuser and volute on compressor instability. Combined with dynamic mode decomposition (DMD) method, the three-dimensional flow field of the volute is decomposed and reconstructed under design and stall condition. It is shown that the dominating perturbation of volute under design condition is the one induced by main blade passing, while the perturbation with higher frequency due to main and splitter blades is suppressed by the volute. The occurrence of stall in the compressor is delayed by the volute compared with the compressor without volute. A standing wave comes into being in the volute during stall, and the flow filed of volute fluctuates along the tangential direction. The occurrence of volute stall indicates that the volute loses the ability to suppress the instability perturbation, and the compressor is occupied by stall. The application of DMD method on volute provides the detailed flow information under specific perturbation frequency before and after stall.
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