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Extension-twist coupling optimization in composite rotor blades.

机译：复合材料转子叶片中的拉伸-扭转耦合优化。

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For optimal rotor performance in a tiltrotor aircraft the difference in the inflow and the rotor speeds between the hover and cruise flight modes suggests different blade twist and chord distributions. The blade twist rates in current tiltrotor applications are defined based upon a compromise between the figure of merit in hover and propeller efficiency in airplane mode. However, when each operation mode is considered separately the optimum blade distributions are found to be considerably different.; Passive blade twist control, which uses the inherent variation in centrifugal forces on a rotor blade to achieve optimum blade twist distributions in each flight mode through the use of extension-twist coupled composite rotor blades, has been considered for performance improvement of tiltrotor aircraft over the last two decades. The challenge for this concept is to achieve the desired twisting deformations in the rotor blade without altering the aeroelastic characteristics of the vehicle. A concept referred to as the sliding mass concept is proposed in this work in order to increase the twist change with rotor speed for a closed-cell composite rotor blade cross-section to practical levels for performance improvement in a tiltrotor aircraft. The concept is based on load path changes for the centrifugal forces by utilizing non-structural masses readily available on a conventional blade, such as the leading edge balancing mass.; A multilevel optimization technique based on the simulated annealing method is applied to improve the performance of the XV15 tiltrotor aircraft. A cross-sectional analysis tool, VABS together with a multibody dynamics code, DYMORE are integrated into the optimization process. The optimization results revealed significant improvements in the power requirement in hover while preserving cruise efficiency. It is also shown that about 21% of the improvement is provided through the sliding mass concept pointing to the additional flexibility the concept provides for tailoring of the structure without any additional weight penalty on the system.
机译：为了使倾转旋翼飞机获得最佳的旋翼性能，悬停和巡航飞行模式之间的入流和旋翼速度的差异表明叶片的扭曲和弦分布不同。当前的倾转旋翼飞机应用中的叶片扭曲率是基于在悬停时的品质因数和飞机模式下螺旋桨效率之间的折衷来定义的。然而，当分别考虑每种操作模式时，发现最佳叶片分布明显不同。为了提高俯仰旋翼飞机的性能，已经考虑采用无源叶片扭转控制，该控制利用旋翼叶片上离心力的固有变化，通过使用加长扭转耦合的复合旋翼叶片，在每个飞行模式下获得最佳的叶片扭转分布。持续了二十年。该概念的挑战在于在不改变车辆的空气弹性特性的情况下在转子叶片中实现期望的扭曲变形。在这项工作中提出了一种称为滑动质量概念的概念，目的是将闭孔复合材料旋翼桨叶横截面的随转子速度的扭曲变化增加到实用水平，以提高倾转旋翼飞机的性能。该概念基于通过利用常规叶片上容易获得的非结构质量（例如前缘平衡质量）来改变离心力的载荷路径。运用基于模拟退火方法的多级优化技术来提高XV15倾转旋翼飞机的性能。横截面分析工具VABS和多体动力学代码DYMORE集成到了优化过程中。优化结果表明，在保持巡航效率的同时，悬停时的动力需求有了显着改善。还显示出，通过滑动质量概念提供了大约21％的改进，这表明该概念为结构的定制提供了额外的灵活性，而不会给系统带来任何额外的重量损失。

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