The aerodynamic performance analysis and blade planform design of a coaxial rigid rotor in forward flight were carried out utilizing CFD solver CLORNS. Firstly, the forward flow field characteristics of the coaxial rotor were analyzed. Shock-induced separation occurs at the advancing side blade tip and severe reverse flow occurs at the retreating side blade root. Then, the influence of geometrical parameters of the coaxial rigid rotor on forward performance was investigated. Results show that swept-back tip could reduce the advancing side compressibility drag and elliptic shape of blade planform could optimize the airload distribution at high advance ratio flights. A kind of blade planform combining swept-back tapered tip and nonlinear chord distribution was optimized to improve the rotor efficiency for a given high-speed level flight based on geometric parameter studies. The optimized coaxial rotor increases lift-to-drag ratio by 30% under the design conditions.

中文翻译：

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高速前进飞行中同轴刚性转子的几何设计

利用CFD求解器CLORNS对同轴刚性转子向前飞行进行了气动性能分析和叶片平面设计。首先，分析了同轴转子的正向流场特性。震动引起的分离发生在前进侧叶片的尖端，严重的逆流发生在后退侧叶片的根部。然后，研究了同轴刚性转子的几何参数对前进性能的影响。结果表明，后掠式尖端可以减小前进侧的可压缩阻力，并且叶片平面的椭圆形形状可以优化高提前比飞行中的空气负荷分布。基于几何参数研究，优化了一种结合了后掠式锥形尖端和非线性弦分布的叶片平面，以提高给定高速水平飞行的转子效率。经过优化的同轴转子在设计条件下可将提升/拖动比提高30％。