Over the last 10 years, the use of micro air vehicles has rapidly covered a broad range of civilian and military applications. While most missions require optimizing the endurance, a growing number of applications also require acoustic covertness. For rotorcraft micro air vehicles, combining endurance and covertness heavily relies on the capability to design new propulsion systems. The present paper aims at describing a complete methodology for designing quiet and efficient micro air vehicle rotors, ranging from preliminary aerodynamic prediction to aeroacoustic optimization to experimental validation. The present approach is suitable for engineering purposes and can be applied to any multirotor micro air vehicle. A fast-response and reliable aerodynamic design method based on the blade-element momentum theory has been used and coupled with an extended acoustic model based on the Ffowcs Williams and Hawkings equation as well as analytical formulations for broadband noise. The aerodynamic and acoustic solvers have been coupled within an optimization tool. Key design parameters include the number of blades, twist and chord distribution along the blade, as well as the choice of an optimal airfoil. An experimental test bench suitable for non-anechoic environment has been developed in order to assess the benefit of the new rotor designs. Optimal rotors can maintain high aerodynamic efficiency and low acoustic signature with noise reductions in the order of 10 dB(A).

中文翻译：

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一种安静且耐久的 MAV 旋翼设计方法

在过去的 10 年中，微型飞行器的使用迅速涵盖了广泛的民用和军用应用。虽然大多数任务需要优化续航能力，但越来越多的应用也需要声学隐蔽性。对于旋翼飞行器微型飞行器，结合耐力和隐蔽性在很大程度上依赖于设计新推进系统的能力。本文旨在描述一种完整的方法来设计安静高效的微型飞行器转子，从初步空气动力学预测到气动声学优化再到实验验证。本方法适用于工程目的，可应用于任何多旋翼微型飞行器。使用基于叶片元件动量理论的快速响应和可靠的空气动力学设计方法，并结合基于 Ffowcs Williams 和 Hawkings 方程的扩展声学模型以及宽带噪声分析公式。空气动力学和声学求解器已在优化工具中耦合。关键设计参数包括叶片数量、沿叶片的扭曲和弦分布，以及最佳翼型的选择。为了评估新转子设计的好处，已经开发了适用于非消声环境的实验测试台。最佳转子可以保持高空气动力学效率和低声学特征，噪声降低量级为 10 dB(A)。