Nonaxisymmetric casing on axial-flow compressors

A nonaxisymmetric casing was designed and studied on one tip critical subsonic compressor rotor. Both steady and unsteady CFD simulations are conducted for investigating its impact to rotor performance and stall margin. The unsteady interaction between the nonaxisymmetric casing and the main flow was presented. Preliminary design principle of nonaxisymmetric casing on subsonic axial compressor is summarized. For compressor rotor being studied, the performance of the nonaxisymmetric casing was compared with the circumferential grooved casing, and the slotted casing. Result shows, due to its effectively utilizing of the local favorable pressure gradient, and its smooth contour, the nonaxisymmetric casing can improve the rotor stall margin without sacrifice its performance. The potential of using nonaxisymmetric casing to improve compressor performance deserves more research in the future.