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

Abstract

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 multi-objective 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° to 11.6°. The major purpose of the research is to provide proper design guidelines for non-uniform 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.

Topics & Concepts