Blended Wing Body Aircraft Configuration Research Articles

A Fast Aerodynamic Model for Aircraft Multidisciplinary Design and Optimization Process

A multidisciplinary design analysis and optimization process is developed at ONERA for the design of tube and wing and blended wing–body aircraft configurations. This process is composed of different disciplinary modules (geometry, propulsion, aerodynamics, structure, handling qualities and flight mission), and the overall process considers different fidelity levels for these modules at each step of the design process. This article describes the low-fidelity aerodynamic module used during the preliminary design optimization process. Analytical formulations retained for lift and drag components are presented in the first part. Then, the performances estimated by the aerodynamic module on some reference configurations are compared with both numerical and experimental data, showing a quite good agreement for both tube and wing and blended wing–body configurations not only for global performance but also for individual drag components.

An assessment of distributed propulsion: Part B – Advanced propulsion system architectures for blended wing body aircraft configurations

Studies such as those by NASA predict large performance benefits when integrating Distributed Propulsion (DP) with the Blended Wing Body (BWB) aircraft configuration. This is because the BWB planform geometry is particularly suited to the ingestion of boundary layer air. The present study evaluates the relative benefit of DP through a comparison with an advanced turbofan reference system of the same technology level as in Part A of this two part paper. Fuel savings of 5.3% relative to the reference aircraft have been shown to be achievable, although it was found that the system is particularly sensitive to duct losses.

The impact of control allocation on trim drag of blended wing body aircraft

The trim drag of conventional aircraft configurations in cruise flight is in the order of 0–1% of the total aircraft drag. Blended wing body aircraft typically have multiple redundant flight control surfaces at the trailing edge with only a limited moment arm with respect to the center of gravity. This aircraft configuration therefore potentially has much more trim drag than conventional aircraft. The redundant set of control surfaces should therefore be deflected in an optimal way to minimize trim drag. A study is conducted to investigate the impact of three control allocation methods on the trim drag of a blended wing body aircraft configuration at relatively low airspeeds. The trim drag is measured by a wind tunnel test campaign. Results indicate that the type of control allocation method has a large influence on the trim drag. This effect must be taken into account in the early design stages of blended wing body aircraft since it will significantly affect the overall aircraft drag. Most control allocation schemes are based on a linear representation of the aerodynamics. Results for the test case indicate that a nonlinear aerodynamic database is required to assess the trim drag with sufficient accuracy. The two main nonlinear effects that must be included are the variations of control derivatives with (1) angle of attack and (2) control deflection. Control surface interaction effects have only a minor influence. The methodology developed to assess trim drag and to select a control allocation algorithm can be directly applied in the early design stages when numerical aerodynamic analysis tools are used instead of wind tunnel models.

Fire and evacuation analysis in BWB aircraft configurations: computer simulations and large-scale evacuation experiment

AbstractHow long would it take to evacuate a blended wing body (BWB) aircraft with around 1,000 passengers and crew? How long would it take an external post-crash fire to develop non-survivable conditions within the cabin of a BWB aircraft? Is it possible for all the passengers to safely evacuate from a BWB cabin subjected to a post-crash fire? These questions are explored in this paper through computer simulation. As part of project NACRE, the airEXODUS evacuation model was used to explore evacuation issues associated with BWB aircraft and to investigate fire issues, the CFD fire simulation software SMARTFIRE was used. The fire and evacuation simulations were then coupled to investigate how the evacuation would proceed under the conditions produced by a post-crash fire. In conjunction with this work, a large-scale evacuation experiment was conducted in February 2008 to verify evacuation model predictions. This paper presents some of the results produced from this analysis.

An all-composite, all-electric, morphing trailing edge device for flight control on a blended-wing-body airliner

For a significant improvement in the fuel efficiency of long-range transport aircraft, a transition to blended-wing-body (BWB) configurations will be required in the long term. Further efficiency improvements are expected from an all-composite primary structure, all-electric actuation, as well as from seamless control surfaces that provide reduced drag compared to conventional control surfaces. BWB configurations feature specific demands on the control system because of the high coupling between flap deflections and aircraft movements in all three axes. Thus, multi-objective control surfaces are required for flight control, as well as for active gust and manoeuvre load alleviation. A major challenge therefore is to provide sufficient yaw control and stability in the absence of a vertical tail. Generally, one engine inoperative poses an important sizing case for the control system design, especially for the control surfaces. In this article, the sizing of winglet flaps and crocodile flaps is performed for the preliminary design of an all-composite, all-electric BWB airliner. For further improvement in efficiency, a seamless morphing trailing edge device is designed that provides both crocodile flap and aileron modes at the same time. Based on these results, a composite morphing trailing edge demonstrator with an all-electric actuation system is investigated. Some open issues remain for investigation. Still, the proposed design provides a promising approach for further efficiency improvement on BWB aircraft configurations.