Multidisciplinary Optimization Method for Designing Boundary-Layer-Ingesting Inlets

The blended wing body is a revolutionary conceptual aircraft design with rear-mounted, overwing engines. Two types of engine installations are being considered for this aircraft. The more conventional design has engines installed within nacelles that are mounted on pylons above the wing surface. The engines on the second design are partially buried in the wing and use boundary-layer-ingesting inlets mounted on the wing upper surface. For both designs, and especially for the latter, the tight coupling between the aircraft aerodynamics and the propulsion system presents a challenging design integration problem. This paper presents a design method that approaches the problem using multidisciplinary optimization. A Navier―Stokes flow solver, an engine analysis method, and a nonlinear optimizer are combined to create a design tool that properly addresses the tight coupling of the problem. The appropriate objective function and constraints are identified and an effective set of design variables is selected. The optimization method is then applied to both aircraft designs as sample problems to demonstrate the capabilities of the method and to provide some preliminary insight into advantages and disadvantages of both engine installations. Potential paths for future research in this field are also discussed.