A hybrid wing body (HWB) concept is being considered by NASA as a potential subsonic transport aircraft that meets aerodynamic, fuel, emission, and noise goals in the time frame beyond 2035. While the concept promises advantages over a conventional wing-and-tube aircraft, it poses unknowns and risks, thus requiring in-depth and broad assessments. Specifically, the configuration entails a tight integration of the airframe and propulsion geometries; the aerodynamic impact has to be carefully evaluated. With the propulsion nacelle installed on the (upper) body, the lift and drag are affected by the mutual interference effects between the airframe and nacelle. The static margin for longitudinal stability is also adversely changed. In the present paper, a design approach is developed in which the integrated geometries of airframe (HWB) and propulsion are accounted for simultaneously in a simple algebraic manner, via parameterization of the planform and airfoils at the design sections of the wing body. This paper presents a design of a 300-passenger aircraft that employs distributed electric fans for the propulsion. The trim condition for stability is achieved through the use of the wing tip twist angle. The geometric shape variables are determined through the adjoint optimization method by minimizing the drag while subjecting them to lift, pitching moment, and geometry constraints. An Euler model-based aerodynamic shape optimization is employed to save the design cost for the evaluation of the static margin and longitudinal stability, while the performance of the optimized configuration is evaluated by the RANS model coupled with a drag decomposition method to assess the true aerodynamic performance. The design results clearly show the influence on the aerodynamic characteristics of the installed nacelle and trimming for stability. A drag minimization with the trim constraint yields a reduction of 10 counts in the drag coefficient from the baseline design N3-X configuration, which is comparable with 2000 lbs more payload on a conventional subsonic civil transport airplane.

中文翻译：

---

混合翼体飞机整体推进-机身构型的气动设计

美国宇航局正在考虑将混合翼体 (HWB) 概念作为一种潜在的亚音速运输机，在 2035 年以后的时间范围内满足空气动力学、燃料、排放和噪声目标。虽然该概念有望优于传统的翼管飞机，它带来未知数和风险，因此需要进行深入和广泛的评估。具体来说，该配置需要机身和推进几何结构的紧密集成；必须仔细评估空气动力学影响。由于推进短舱安装在（上）体上，升力和阻力受到机身和短舱之间相互干扰的影响。纵向稳定性的静态裕度也发生不利变化。在本文中，开发了一种设计方法，通过在翼身设计部分对平面和翼型进行参数化，以简单的代数方式同时考虑机身 (HWB) 和推进的集成几何形状。本文介绍了一种采用分布式电风扇进行推进的 300 名乘客飞机的设计。稳定性的配平条件是通过使用翼尖扭转角来实现的。几何形状变量是通过伴随优化方法确定的，通过最小化阻力，同时使它们受到升力、俯仰力矩和几何约束。采用基于欧拉模型的气动外形优化，以节省静态裕度和纵向稳定性评估的设计成本，而优化配置的性能则通过 RANS 模型结合阻力分解方法进行评估，以评估真实的空气动力学性能。设计结果清楚地显示了对已安装机舱的空气动力学特性的影响以及对稳定性的微调。具有配平约束的阻力最小化使阻力系数从基线设计 N3-X 配置减少 10 个计数，这与传统亚音速民用运输飞机的有效载荷增加 2000 磅相当。