Topics on conceptual design of the D8 aircraft : fuel burn uncertainty estimate and BLI propulsor loss modeling

Abstract

This thesis addresses two topics related to the D8 transport aircraft, developed by MIT under NASA's N+3 program. The first is the reduction in fuel burn specifically attributable to the novel design features of the D8, which include a lifting nose, a double bubble fuselage, and aft mounted engines that ingest part of the fuselage boundary layer. This fuel burn benefit is determined to be (18.0 ± 2.2)% for aircraft with a cruise Mach of 0.72 and (20.1 ± 2.6)% for aircraft with a cruise Mach of 0.78. The benefit is shown to be robust to changes in technology assumptions and uncertainty in specified design parameters. The presented results refine previous conceptual studies and provide strong support for further development of the D8 by reducing the uncertainty in its performance estimates. The second topic addressed in this thesis is the modeling of Boundary Layer Ingesting (BLI) propulsor losses at a level of fidelity appropriate for turbomachinery conceptual design analysis, i.e. nonaxisymmetric throughflow analysis. Two contributions to such an analysis based on a body force framework are presented in this thesis: a description of blade profile losses in incompressible flow, and a roadmap for the development of corrections that capture the endwall effects on the flow through the propulsor.