Assessment of Propulsion System Configuration and Fuel Composition on Hybrid Wing Body Fuel Efficiency

** * † ‡ This paper presents results from a NASA sponsored program to evaluate subsonic fixed wing transport aircraft entering service in the 2030-2035 time frame. The paper describes the effects of propulsion system configuration and fuel type on the fuel burn performance of a Hybrid Wing Body (HWB) aircraft designed for a long-haul international market. The wide centerbody of the HWB can accommodate a highly integrated, distributed propulsion system, the large design space offers the possibility of performance improvements from the extended use of boundary layer ingestion (BLI), and the large internal volume of a HWB aircraft can accommodate low density, high specific energy fuels. In this work, mechanically geared (planetary and beveled) and electrical transmissions systems were considered with varied numbers of turbogenerators and propulsors alongside either Liquefied Natural Gas (LNG) or conventional jet fuel. For all of the proposed propulsion system configurations, the minimum fuel burn corresponds to the case with the largest amount of boundary layer ingestion, in contrast to results presented previously by the authors. The minimum fuel burn for the conventional jet fuel design is 55% below that of the Boeing 777-200LR reference aircraft. The use of LNG fuel with laminar flow on the outer wing bottom and a turboelectric transmission system results in a 57% fuel burn reduction.