Application of Variational Asymptotic Method for Structural Analysis of Fan Rotor Blades in Boundary Layer Ingesting Flow Field

Abstract

Boundary Layer Ingestion (BLI) appears to be a promising technology for reducing aircraft fuel burn. Despite potential benefits, there are several challenges associated with BLI. A primary concern is the structural integrity of the fan blades experiencing unsteady forces due to unequal work input from the rotor at different circumferential locations of the engine annulus. In the conceptual design phase, rapid turnaround is as important as measuring the stresses accurately. Through the present work, the authors present a computationally efficient framework for measuring natural frequencies and analyzing time histories of 3-D stresses in nonlinear transient structural analyses of rotating fan blades. This framework uses state of the art tools developed for beam modeling based on Variational Asymptotic Method and the Geometrically Exact Beam Theory. The authors also provide verification of the present framework against 3-D finite element analysis performed in COMSOL.