Distributed Propulsion featuring Boundary Layer Ingestion Engines for the Blended Wing Body Subsonic Transport

The blended wing body aircraft is one of the promising contenders for the next generation large transport aircraft. This aircraft is particularly suitable for the use of boundary layer ingestion engines. Results published in literature suggest that it might be beneficial to have a large number of these engines (distributed propulsion). A conceptual design study is therefore performed to determine the potential benefits of boundary layer ingestion engines for a conventional number of engines increasing to a large number of engines. A gasturbine performance tool is combined with a weight prediction tool and a mission analysis tool to analyze aircraft-engine combinations. A genetic algorithm is used to find engine specifications that result in minimum fuel consumption for a given configuration (e.g. 8 engines). Results show that the potential of distributed propulsion systems relies heavily on a weak dominance of beneficial effects over negative effects of similar magnitude. From a performance point of view it is better to abandon the distributed propulsion concept and to focus on a small number of large boundary layer ingestion engines instead since they do not suffer high internal losses. A propulsion system with three boundary layer ingestion engines is shown to have a 5% performance improvement in terms of fuel consumption over a conventional strut mounted propulsion system