Investigation of non-uniform leading-edge tubercles in compressor cascade: Based on multi-objective optimization and data mining

Corner stall receives noticeable attention in the aeroengine field as an important phenomenon in highly-load compressors. Non-uniform leading-edge tubercles, as an effective method to delay stall, are introduced into the compressor. In this paper, the shape of leading-edge tubercles was controlled by a third-order Fourier function. To judge corner stall, a more precise stall indicator for compressor cascade with flow control methods was defined. Besides, the total kinetic energy of the secondary flow at large incidence was adopted as a parameter for stall evaluation to save computing resources. The results of multiobjective optimization reveal that the loss coefficient exhibited negligible variation at design incidence, while the total kinetic energy of secondary flow showed a significant reduction at large incidence, resulting in a substantial increase in stall incidence. In the optimal profiling cases, the stall incidence was delayed from 7.9 degrees to 11.6 degrees. The major purpose of the research is to provide proper design guidelines for nonuniform leading-edge tubercles and uncover the flow control mechanisms of leading-edge profiling. Hence, the geometric features that meet different optimization objectives were extracted through geometric analysis near the Pareto Front and through Self-Organizing Map (SOM) data mining methods in the optimization database. Besides, flow field analysis reveals the flow control mechanism of leading-edge tubercles. The convex-concave-convex structure at the 0%-70% blade height region can form two branches of leading-edge vortex pairs that are opposite in the rotation direction to the passage vortex. The two branches of leading-edge vortex pairs mixed with the leading-edge separation vortex to form two stronger mixed vortices, which can effectively suppress the development of passage vortex and delay stall incidence. (c) 2024 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).