A nacelle inlet design approach with more three-dimensional geometric consideration

Abstract Nacelle inlet withdraws designer's attention when considering the pressure distortion at fan entrance during aircraft takeoff at high angle-of-attack. Conventionally, the design is decomposed into separate streamwise profile optimization at several circumferential positions. This causes design efficiency loss since the three-dimensional geometric constraint and aerodynamic performance requests have to be transformed to adapt two-dimensional profile cases. As an attempt to solve this issue, this paper proposes a nacelle inlet design approach of introducing more three-dimensional geometric consideration. Firstly, a library of three-dimensional nacelle inlet geometries is established by fully sampling design space. The samples are then filtered by posing direct three-dimensional geometric constraints. Such design space now contains information relevant to the problem which is then extracted by Proper Orthogonal Decomposition (POD) in form of modes. The selected modes constitute the problem-oriented new design variables that will maintain more geometric three-dimensionality during optimization than conventional approach. The selection assures economical use of data according to the order of importance determined by corresponding eigenvalues of obtained modes. Finally, a proof-of-concept study thereby conducts a surrogate-base optimization (SBO) with Differential Evolution (DE) algorithm where a nacelle inlet is optimized with zero IDCMAX at angle-of-attack of 28° under flow of Ma 0.18, demonstrating the feasibility of the new approach.