Analysis of Flow Control in Compressor Stator by Steady and Pulsed Jets Based on POD Method

Steady and pulsed jets were introduced to the compressor stator upper end-wall. The unsteady cascade flow field under flow was investigated using validated numerical simulations and the Proper Orthogonal Decomposition (POD) method. Detailed analysis was conducted on the vortex structure and the spatial-temporal characteristics of the main modes. The results show that as the jet position moves along the axial direction, the control effectiveness of both steady and pulsed jets gradually weakens. When the jet is injected before the separation point on the suction surface of the cascade, the steady jet can reduce the total pressure loss by up to 9.2% and 7.2%, respectively. In comparison, the pulsed jet can decrease it by 10.2% and 9.2%. The pulsed jet effectively inhibits the development of both the passage vortex and the trailing edge shedding vortex. Additionally, it suppresses the original turbulent pulsation, locks it to the excitation frequency and promotes the transition of the flow field to a more orderly state. The consequences of POD analysis show that the primary structure of the flow field is composed of the first four modes, and the frequencies of their corresponding time coefficients are the fundamental frequency and its harmonics. In the pulsed jet scheme, the time coefficient exhibits a sine-like function distribution, suggesting a stronger coupling between the jet and the flow field. The two jet schemes modified the energy distribution of the primary modes, and this perturbation does not change the number of main modes in the flow field. Compared with the steady jet scheme, the pulsed jet scheme demonstrated higher energy in the flow field and reconstructed the original flow field, further employing its periodic disturbances. Specifically, this reconstruction was mainly embodied in the decrease in the energy proportion of the first-order mode and to enhance in the energy proportion of the remaining main modes.

本研究将稳态射流与脉冲射流应用于压气机静子上端壁。采用经过验证的数值模拟方法与本征正交分解（Proper Orthogonal Decomposition, POD）方法，对该工况下的非定常叶栅流场开展研究，并针对涡结构以及各主导模态的时空特性展开详细分析。结果表明：随着射流位置沿轴向迁移，稳态射流与脉冲射流的流动控制效果均逐渐减弱。当射流从叶栅吸力面分离点上游注入时，稳态射流可使总压损失最高降低9.2%与7.2%；相比之下，脉冲射流可使总压损失降低10.2%与9.2%。脉冲射流可有效抑制通道涡与尾缘脱落涡的发展，此外还可抑制原始湍流脉动，将其锁定于激励频率，并促使流场向更有序的状态转变。本征正交分解分析结果显示，流场的主体结构由前四阶模态构成，各模态对应的时间系数频率为基频及其各次谐波。在脉冲射流方案中，时间系数呈现类正弦函数分布，表明射流与流场间的耦合作用更强。两种射流方案均改变了主导模态的能量分布，且该扰动并未改变流场中主导模态的数量。相较于稳态射流方案，脉冲射流方案可使流场拥有更高能量，并借助其周期性扰动对原始流场进行重构。具体而言，该重构主要体现为一阶模态的能量占比降低，而其余主导模态的能量占比提升。