Aerodynamic instabilities of swept airfoil design in transonic axial-flow compressors

This paper investigates the effect of a swept airfoil design on the aerodynamic instabilities of transonic axial-flow compressors based on global stability analysis. An approach aimed at predicting the stall inception point is developed by integrating an improved blade force model and a new mathematical treatment method for steady flow. This approach takes both the concrete blade geometry and complicated base flow into consideration, which promises to provide a highly efficient assessment of the stall margin of a compressor in the design phase. Specifically, the relevant validation is conducted through a typical transonic axial-flow compressor, which shows that the predicted stall inception point agrees well with the experimental result. Furthermore, the compressor is also adopted as a prototype, from which a series of forward- and backward-swept rotors are modeled. Aerodynamic instabilities in the form of eigenvalues for each swept rotor, along with the throttling process, are predicted by solving the developed stall inception model. The comparison of the predicted results for these rotors shows that the backward sweep deteriorates the stall margin; the larger the backward-swept degree, the poorer the compressor stability becomes. However, the forward sweep does not exhibit remarkable and regular influence on the stall margin of the compressor in the present research. A discussion of the predicted results is made from the perspectives of blade loading and passage shock location.