Hybrid-electric aircraft are a potential way to reduce the environmental footprint of aviation. Research aimed at this subject has been pursued over the last decade; nevertheless, at this stage, a full overall aircraft design procedure is still an open issue. This work proposes to enrich the procedure for the conceptual design of hybrid aircraft found in literature through the definition of a multidisciplinary design optimization (MDO) framework aimed at handling design problems for such kinds of aircraft. The MDO technique has been chosen because the hybrid aircraft design problem shows more interaction between disciplines than a conventional configuration, and the classical approach based on multidisciplinary design analysis may neglect relevant features. The procedure has been tested on the case study of a single-aisle aircraft featuring hybrid propulsion with distributed electric ducted fans. The analysis considers three configurations (with 16, 32, and 48 electric motors) compared with a conventional baseline at the same 2035 technological horizon. To demonstrate the framework’s capability, these configurations are optimized with respect to fuel and energy consumption. It is shown that the hybrid-electric concept consumes less fuel/energy when it flies on short range due to the partial mission electrification. When one increases the design range, penalties in weight introduced by hybrid propulsion overcome the advantages of electrified mission segment: the range for which hybrid aircraft have the same performance of the reference conventional aircraft is named the “breakdown range.” Starting from this range, the concept is no longer advantageous compared to conventional aircraft. Furthermore, a tradeoff between aerodynamic and propulsive efficiency is detected, and the optimal configuration is the one that balances these two effects. Finally, multiobjective optimization is performed to establish a tradeoff between airframe weight and energy consumption.

中文翻译：

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带有耦合微分计算的混合动力飞机多学科设计优化框架

混合动力飞机是减少航空环境足迹的一种潜在方式。在过去的十年中，一直致力于针对这一主题的研究。尽管如此，在现阶段，完整的整体飞机设计程序仍然是一个悬而未决的问题。这项工作旨在通过定义旨在处理此类飞机的设计问题的多学科设计优化 (MDO) 框架来丰富文献中发现的混合动力飞机概念设计程序。之所以选择 MDO 技术，是因为混合飞机设计问题比传统配置显示出更多学科之间的相互作用，而基于多学科设计分析的经典方法可能会忽略相关特征。该程序已经在单通道飞机的案例研究中进行了测试，该飞机具有分布式电动管道风扇的混合动力推进。该分析考虑了三种配置（具有 16、32 和 48 个电动机）与相同 2035 年技术水平的传统基线的比较。为了展示框架的功能，这些配置在燃料和能源消耗方面进行了优化。结果表明，由于部分任务电气化，混合动力概念在短距离飞行时消耗的燃料/能源更少。当增加设计航程时，混合动力推进引入的重量损失克服了电气化任务段的优势：混合动力飞机与参考常规飞机具有相同性能的航程被称为“故障航程”。”从这个范围开始，与传统飞机相比，这个概念不再具有优势。此外，检测到空气动力学和推进效率之间的权衡，最佳配置是平衡这两种影响的配置。最后，执行多目标优化以在机身重量和能耗之间进行权衡。