An Engineering Modification of the Blade Element Momentum Equation for Vertical Descent: An Autorotation Case Study
An Engineering Modification of the Blade Element Momentum Equation for Vertical Descent: An Autorotation Case Study
复制标题
垂直下降叶片单元动量方程的工程修正：自转案例研究
DOI：
--
复制
发表时间：
2006
期刊：
影响因子：
--
通讯作者：
J. L. Espino
中科院分区：
文献类型：
--
作者：
Á. Cuerva;Á. Sanz;J. Meseguer;J. L. Espino
本文应用叶素/动量理论的工程修正来描述直升机旋翼的垂直自转。一个完整的非线性空气动力学模型被认为是翼型，考虑到升力和阻力系数的攻角和雷诺数的依赖。所提出的模型，这已在以前的工作中得到验证，允许识别不同的自转模式，这取决于下降速度和扭曲的转子叶片。这些模式呈现出不同的驱动和驱动叶片区域的径向分布，以及不同的径向上洗/下洗模式。零切向力的叶片部分的数量，在转子盘中的下洗区域的存在，自转状态的稳定性，和整体转子自转效率，都分析了飞行速度和转子的特性。结果表明，在垂直自转，较大的叶片扭曲导致较小的值的下降速度为一个给定的推力所产生的转子在自转状态。
An engineering modification of blade element/momentum theory is applied to describe the vertical autorotation of helicopter rotors. A full non-linear aerodynamic model is considered for the airfoils, taking into account the dependence of lift and drag coefficients on both the angle of attack and the Reynolds number. The proposed model, which has been validated in previous work, has allowed the identification of different autorotation modes, which depend on the descent velocity and the twist of the rotor blades. These modes present different radial distributions of driven and driving blade regions, as well as different radial upwash/downwash patterns. The number of blade sections with zero tangential force, the existence of a downwash region in the rotor disk, the stability of the autorotation state, and the overall rotor autorotation efficiency, are all analyzed in terms of the flight velocity and the characteristics of the rotor. It is shown that, in vertical autorotation, larger blade twist leads to smaller values of descent velocity for a given thrust generated by the rotor in the autorotational state.