微型共轴双旋翼气动性能数值模拟与试验分析

为研究悬停状态下旋翼的间距对微型共轴双旋翼气动性能的影响，文中通过搭建试验平台对间距比h/r分别为0.32、0.38、0.45、0.51、0.58、0.65和0.75下的共轴双旋翼进行气动性能测试，以测量不同旋翼转速下所得共轴双旋翼的拉力和功耗对共轴双旋翼气动布局进行优化，试图找出具有最佳气动特性的共轴旋翼布局。另外，通过试验误差分析确定了相应的拉力系数、功率系数和功率载荷，且试验误差均小于2%。同时，为更直观得到不同间距下气流干扰对旋翼系统气动性能的影响，文中采用数值模拟得到了不同间距比下旋翼的流线分布和压力分布。最后，对比试验结果，综合分析旋翼间气动干扰的影响，最终得到间距比h/r为0.38时的共轴双旋翼具有最佳的气动布局。研究结果表明，悬停状态的共轴双旋翼可以通过改变间距大大提高气动性能，且同一间距下转速越大虽然旋翼间干扰越强烈，但此时开始出现耦合，使得系统的气动性能可能更好，同时，由于上下旋翼间的相互诱导，虽然转速较低时升力较小，但是功耗明显低于高转速，使得系统具有更大的功率载荷。

Numerical simulation and experimental study on aerodynamics of the micro coaxial rotors

In order to study the effect of rotor spacing on the aerodynamic performance of small-scale coaxial rotor in hover, a platform is designed to test the aerodynamic characteristics of the coaxial rotor system with different rotor spacing ratios h/r of 0.32, 0.38, 0.45, 0.51, 0.58, 0.65 and 0.75. Rotor thrust and power obtained from measurement with different rotary speeds are used to estimate the aerodynamic characteristics of the rotor system. In the meantime, the uncertainty of the thrust coefficient, power coefficient and power loading (PL), and the calculated errors are all less than 2%. Distributions of streamline and pressure with different rotor spacing ratios are obtained from numerical simulation to analyze the interference between top and bottom rotors. Finally, in comparison with test results, the aerodynamic configuration is optimized with the rotor spacing ratio of 0.38. The results prove that the performance of coaxial rotor in hover can be improved with proper rotor spacing. With certain rotor spacing, aerodynamic performance at higher rotational speed is more prominent when the interference between the rotors is beneficial for the aerodynamics, and greater power loading is obtained at lower rotational speed with smaller interference.