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首页> 外文期刊>Journal of the American Helicopter Society >Aerodynamic Performance Considerations In The Design Of A Coaxial Proprotor
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Aerodynamic Performance Considerations In The Design Of A Coaxial Proprotor

机译：同轴Proprotor设计中的空气动力学性能考虑因素

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摘要

Aerodynamic issues in the design of a torque-balanced, contrarotating coaxial proprotor are discussed. A blade element momentum theory (BEMT), formulated to account for the interfering flows in a coaxial rotor system, was validated against performance measurements for a contrarotating coaxial propeller. The BEMT was then used to develop an initial series of blade shapes for a coaxial proprotor, with the goals of maximizing aerodynamic efficiency both in hover (as a pure lifter) and in forward flight (as a pure propulsor). Initially, separate blade performance optimization in hover and in axial flight was undertaken. The BEMT suggested that, besides the normal limiting problems of blade stall and compressibility losses, the overall performance of a coaxial proprotor can be limited by its inability to reach a torque-balanced state. Performance estimations were also supported by results from a free-vortex method, which provided information on the spanwise loads and downstream wake boundaries. A hybrid blade design for the coaxial proprotor was then obtained. The optimum blade twist for the upper proprotor was shown to be of conventional hyperbolic form, whereas the optimum twist on the lower proprotor must have a multipart hyperbolic form. The break points in the twist distributions are related to the average positions of where the wake boundaries from the upper proprotor are assumed to impinge upon the lower proprotor at the specified design conditions in hover and axial flight. The hybrid blade design was shown to give the proprotor good propulsive efficiency while still retaining relatively good hovering performance. The need for a unified composite efficiency metric to properly describe and compare the performance of coaxial proprotors over their entire operational envelope is also discussed.
机译：讨论了扭矩平衡，反向旋转的同轴proprotor设计中的空气动力学问题。针对同轴转子系统中的性能测量结果验证了公式化的叶片元素动量理论（BEMT），以说明同轴​​转子系统中的干扰流。然后，BEMT用于为同轴推进器开发一系列初始的叶片形状，其目标是在悬停（作为纯提升器）和向前飞行（作为纯推进器）中都最大化空气动力学效率。最初，在悬停和轴向飞行中分别进行了叶片性能优化。 BEMT建议，除了叶片失速和可压缩性损失的正常限制问题外，同轴proprotor的整体性能可能会因无法达到扭矩平衡状态而受到限制。自由涡流方法的结果也支持性能估计，该方法提供有关翼展方向载荷和下游尾流边界的信息。然后获得了用于同轴传动器的混合叶片设计。已显示上部proprotor的最佳叶片扭转为常规双曲线形式，而下部proprotor的最佳叶片扭转必须为多部分双曲线形式。扭曲分布中的断点与在悬停和轴向飞行中在指定的设计条件下假定来自上部质子的尾流边界撞击到下部质子的平均位置有关。混合桨叶设计显示出在赋予proprotor良好的推进效率的同时仍保持相对良好的悬停性能。还讨论了需要一个统一的复合效率指标来正确描述和比较同轴螺旋桨在其整个工作范围内的性能。

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