Full and Partial-Annulus Casing Treatment Impact on a Single-Stage High-Speed Axial Compressor

A series of experimental and computational studies were conducted to understand the impact of a full and partial-annulus casing treatment design on the performance of a modern, 1.5 stage, transonic axial compressor. Experiments consisted of two studies. The first investigated compressor performance impact with the newly designed axial casing treatment. The results showed the full-annulus casing treatment configuration measured higher pressure ratio, temperature ratio, and range of stable operation than the smooth wall configuration across all speed lines. Furthermore, efficiency increases at higher speed lines were observed with the casing treatment. The configurations were investigated two-dimensionally to understand spanwise performance changes with the casing treatment. Further experiments investigated the impact of a partial-annulus casing treatment design on compressor performance. The casing treatment design covered 56% of the annulus. Compressor map results showed that the partial-annulus casing treatment improved performance and operating range compared to the smooth wall configuration, although improvements were not as large as observed with full-annulus casing treatment. Detailed circumferential measurements of pressure ratio, temperature ratio, and inlet Mach number showed that the partial-annulus casing treatment design impacted the inlet flow field and resulting performance in a non-axisymmetric manner. A simplified theoretical model was derived to relate inlet flow fluctuations and compressor pressure rise fluctuations and compared to experiments. The computational study in this paper performed Unsteady Reynolds-Averaged Navier-Stokes simulations to investigate blade passage response to instantaneous boundary condition changes. This passage was subjected to two sets of boundary conditions - one for a smooth wall shroud and one with tip injection applied. Passage performance response to the boundary condition change was observed to occur on the order of 50% of a rotor revolution, and the results were used to increase understanding of the experiments.