Conceptual Aircraft Design Activities Related to Blended Wing Body Configurations in the Scope of the DLR-Project SIAM
Creators: name:  M. IWANIZKI 
name:   L. BERTSCH 
name:   P. BALACK 
name:   D. KELLER 
name:   F.N. SCHMIDT 
name:   F. WIENKE 
name:   J. KURZ 
name:   Y.J. HASAN 
name:   B. FROEHLER 
name:   M. MOESSNER 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: AERONAUTICS
FUTURE DESIGN

description: The DLR-project SIAM (Schall-Immissions-Armes Mittelstreckenflugzeug, engl. low noise emission medium range aircraft) is addressing the conceptual and preliminary design of novel short- and medium range configurations aiming for a significant reduction of noise. The entry into service of these aircraft configurations is envisaged for the year 2035. The first work package is the conceptual aircraft design that covers a wide design space including tube and wing, blended wing body (BWB), turbofan- and turboprop-driven configurations. At the end of the work package, the most promising concept shall be selected for the preliminary design phase. This paper describes the conceptual design activities related to the BWB configurations in SIAM. The BWB with engines mounted above the center section of the wing is considered promising for noise reduction according to several publications [1,2]. One major reason is the large area that shields a significant amount of engine noise towards the ground. In the scope of the project, a conceptual design process for BWB configurations is built of semi-empirical and low-level physics-based tools and is implemented in the Remote Component Environment of DLR [3]. The physics-based aerodynamic tools enable the initial wing design including planform and twist that are crucial for the BWB configuration. In addition, RANS calculations of a representative reference geometry applying the DLR TAU code [4] provide data that cannot be calculated by the simple physics-based tools reliably. Also, sophisticated handling quality and approach flight analyses, both critical for the BWB, support the conceptual design process. Finally, acoustic analyses show the potential of different concepts with respect to the envisaged noise reduction. For the design of new configurations, top-level aircraft requirements as the payload capacity, the design range, the cruise Mach number and the field performance are derived from the Airbus A320-type aircraft. Furthermore, all new aircraft shall provide acceptable handling qualities without computational augmentation. This appears especially challenging for the BWBs due to short lever arms of the control surfaces and a notable center of gravity variation. In this project, the focus is on two main BWB layouts: a classical BWB configuration without a horizontal stabilizer, and one configuration with a T-tail, addressed as a hybrid wing body (HWB) in this paper. Parameter studies indicate that the BWB configuration cannot fulfill all the top-level requirements simultaneously. The major issues are the stability constraints and the insufficient low speed performance. The problems related to the flight mechanics could be mitigated by the limitation of the allowable center of gravity variation. But the insufficient low speed performance requires either a high lift system, or a very low wing loading. The first option introduces severe implication due to the induced pitching moment. The second deteriorates the efficiency of the aircraft notably. The HWB addresses those problems by the utilization of a horizontal stabilizer. Parameter studies indicate a higher block fuel efficiency for the HWB than for the BWB. However, it changes, if some of the design requirements are relaxed. Such details shall be discussed in the full paper. From the acoustic perspective, the HWB has some disadvantages. The horizontal stabilizer e.g. reflects the jet engine noise towards the ground. More sophisticated acoustic analyses are currently evaluating this issue. In the full paper, the aforementioned methods, the design decisions, the parameter studies, the mission performance and acoustic evaluation of different BWB and HWB configurations, and the comparison to the advanced baseline tube-and-wing aircraft shall be presented.