Compressibility effects on the two generations of unsteady flow types in axial flow compressors

There occurred unsteady separated flows inside axial flow compressors, which was however not taken into consideration in the present aerodynamic design system. This discrepancy indicates that the potential underlying unsteady separated flows is yet to be explored, hence the present research team proposes the concept of two generations of unsteady flow types, i.e. Unsteady Natural Flow Type (UNFT) and Unsteady Cooperative Flow Type (UCFT). Numerical simulations are carried out in the present paper to study the compressibility effect on the unsteady cooperative flow type in axial flow compressors. The studies show that aerodynamic performances are remarkably enhanced by means of transforming the flow type from UNFT into UCFT by imposing unsteady excitations. In the case of 2D subsonic cascade, performances are greatly improved in a wide range of Ma number (Ma<0.8) and the maximum relative reduction of the loss coefficient reaches 40.2%. In the case of 2D trans-supersonic cascade, positive effects can't be captured. However, in the case of a 3D trans-supersonic single rotor, the adiabatic efficiency is increased from 87.0% to 90.2%.