Multi-disciplinary investigation of a flap blown turboelectric distributed propulsion blended wing body aircraft.

Abstract

Growing concerns about the rising costs of fuel as well as environmental issues have led to multiple innovative and futuristic aircraft concepts to tackle these issues. Turboelectric Distributed Propulsion (TeDP) and boundary layer ingestion are two such concepts. When applied to a conceptual aircraft such as the N3-X, it results in a blended wing body (BWB) aircraft with an array of fan propulsors mounted near the rear of the aircraft body and driven by superconducting motors powered by superconducting generators in the wing tip mounted turbogenerators. The elevator flaps of such a BWB aircraft are located at the trailing edge of the aircraft body. Coupled with the exhaust mass flow from the propulsor fan nozzles, it presents a chance to utilize flap blowing and/or thrust vectoring to further improve on the aircraft performance. By utilizing boundary layer ingestion, there can be expected 5-6% total fuel savings while flap blowing can further enhance the fuel savings to a total of 8-9%. However, integration issues such as intake pressure losses, deficiency in fan propulsor efficiency tends to mitigate the benefits derived. Furthermore, it is difficult to separate various design disciplines such as aerodynamics and propulsion in such a high integrated aircraft. Flap blowing further correlates to both disciplines. This dissertation addresses a broad overall design methodology that is both multi-disciplinary and multi-fidelity, addressing the above mentioned issues. Flap blowing can be seen to be a linkage between the often separate aerodynamics and propulsion design disciplines in an aircraft. The strip method code, designed to incorporate flap blowing into the preliminary design and analysis is presented in this study, showing its impact on aerodynamic performance, flight dynamic response and propulsion system design. Furthermore, other disciplines such as boundary layer ingestion, weight, and flight dynamics are considered and incorporated into the methodology. The main figure of merit used is the total fuel consumption of the aircraft and in addition, take-off distances are also studied and analysed. Take-off distances incorporating flap blowing and thrust vectoring demonstrated a reduction in distances between 25-30%. The reduction in take-off distance also led to the study on the potential of re-sizing the BWB outer wings to further reduce total fuel consumption and has shown great promise.