Abstract: As an innovative configuration, the Blended-Wing-Body (BWB) configuration has become a worldwide research focus in civil aircrafts development. Compared to the conventional configuration, the BWB shows integrative benefits and becomes the most promising candidate for a safe, economical, comfortable, and environmentally friendly large aircraft. This paper emphasizes the fact that the present BWB designs focus on the high speed transonic performance but pay less attention to the low speed characteristics, which leads to the design challenge that the low speed characteristics of BWB configuration can hardly satisfy the severe requirement of "green aviation" for the next generation of aircrafts. To solve this problem, a tradeoff design method for high and low speed performance has been put forward. By analyzing the effects of conceptual design parameters, the wing loading is chosen as the primary parameter to coordinate low and high speed performance. Based on previous studies, a tradeoff design principle consisting of three main technological components has been proposed to balance the conflict between high and low speed performance. A multi-disciplinary design optimization platform is applied to obtain a tradeoff design for both cruise performance and low speed requirements. The CFD and wind tunnel results show significant improvement of low speed performance while maintaining high speed performance. This result is suitable for relieving the pressure of high-lift devices and control surface design, achieving both the cruise efficiency and the required high lift. The methods proposed in this study provides new designs and methods for improving BWB low speed performance, which can be applied to the further study of the BWB civil aircrafts and provide useful information for other applications.

Key words: blended-wing-body configuration, civil aircraft, high and low speed performance, tradeoff design, design philosophy