Nacelle Inlet Optimization at High Angles of Attack Based on the Ensemble Indicator Method

Abstract

Inlet separation is one of the primary sources of distortion at fan entrances. High angles of attack (AOAs) are the critical cause of inlet separation. Optimizing the inlet shape to increase the separation angle is of great engineering significance. However, calculating the separation angles of different inlet shapes requires extensive computation. To address this problem, an ensemble indicator, the antiseparation potential index (ASPI), is proposed in this paper. The ASPI is based on the circumferential distortion index (IDC) of the engine under multiple AOAs. The characteristics of both the separation angle and distortion level are comprehensively reflected in the ASPI. The use of this index can avoid the need for an enormous amount of computation and can better describe the ability of the inlet to resist separation at a higher AOA, both of which are more suitable for inlet design. A Kriging–particle swarm optimization (PSO) design model was applied to tackle the high-cost computational fluid dynamics (CFD) simulations and search for an optimal solution. The results show that the critical AOA at which intake separation occurs is successfully increased by approximately 8°, demonstrating the feasibility of the ASPI in engineering design.