非定常激励抑制轴流叶栅分离的数值分析

NUMERICAL ANALYSIS OF CONTROLLING SEPARATION IN AXIAL CASCADE BY UNSTEADY EXCITATION

本文对大转角压气机叶栅大攻角工况在来流尾迹非定常激励作用下的时空结构进行了数值分析.合理的非定常激励明显提升了叶栅的时均性能,与激励频率对应的涡结构得到强化,其它频率的杂涡被卷吸,无序的吸力面分离流结构变得有序。文中分析了周期性来流尾迹控制分离结构的作用机理:波涡共振促进涡的卷起和配对;湍动能强化动量交换。基于此,比较了两种来流尾迹模式下分离结构对来流周期性的响应问题.另外,针对管道风扇引起的远场噪声,在来流尾迹非定常激励作用下对其降低的可能性进行了设想.

The numerical analysis of time-space structures in the large turning angle axial cascade with a certain large attack angle condition suffered from unsteady incoming wake excitation has been carried out. The results have shown that reasonable unsteady excitation could increase the time-averaged performance of axial cascade. As a result, the vortex structures corresponding to the external exciting frequency are strengthened and the disordered vortices of other scales are entrained, then the separation structures near suction surface is translated from disorder to order. The interaction mechanism between incoming periodic wakes and separation structures is analyzed, which indicate that wave-vortex resonance can promote rolled-up and matched pair of vortices and turbulent kinetic energy can enhance momentum interchange. Based on these, the responses of separation structures from two periodic incoming wake regimes are compared. In addition, considering the far-field noise from ducting fan, the feasibility of noise reduction by using periodic incoming wake is conceived.