Balancing Efficiency and Stability in the Design of Transonic Compressor Stages

The paper describes an efficient design method for highly loaded transonic compressor stages which considers a balance between efficiency at the design point and stability at part-speed. Because of the high dimensionality of the problem, two levels of model complexity are included in the design method. The first level consists of optimizing the rotor and stator profiles positioned at three streamtubes along the span. The streamtube height and radius variations are included in the computational domain and it is analyzed using a 3D RANS solver incorporating a mixing plane between the components. Due to the relatively low complexity of this quasi-3D analysis, it is fast enough to explore a large design space. With the aid of the resulting pareto-fronts, the designer can select profiles with the appropriate trade between stability and efficiency. The initial 3D compressor stage is generated based on the selected 2D profiles and the method continues to the higher complexity mode where the 3D shapes of the rotor and stator are optimized to gain further performance improvements. To verify that the design method is feasible, it is used to re-design the first compressor stage of a three-stage highly loaded transonic compressor. The compressor stage designed with the presented design method has higher part-speed stability without a compromise in the efficiency compared to the original design. This is also verified when analyzing the new design in the full compressor module.