High Advance Ratio Effects on the Aerodynamics and Blade Dynamics of a Slowed Helicopter Rotor

医疗急救服务面临着在不到一小时的关键响应时间内到达偏远地区的挑战。具有额外螺旋桨的创新“复合”直升机，如空中客车直升机的原型X³，旨在通过高巡航速度和垂直起飞能力的组合来应对这一挑战。为了避免高巡航速度对前进桨叶的影响，复合式直升机的主旋翼以降低的转速运行。后掠桨叶上相应的回流对直升机的性能和稳定性有不利影响。该项目的重点是详细调查的反向流场，以提高我们的复合直升机空气动力学的知识，并最终设计更快的直升机，以减少响应时间的紧急情况。实验证据表明，反向流对转子功率和负载的影响。为了有效地抵消这些负面影响，本项目将研究反向流场本身及其对转子叶片变形的后续影响。反向流场的特点是高的前进比，飞行速度与叶尖速度的关系。通过控制进风比，我们可以测量其对减速转子的反向流场和叶片变形的影响。这些测量结果反过来将改进复合式直升机构型概念设计中使用的气动旋翼代码，目前这些代码不足以准确预测反向流场中复杂的流动物理特性。拟议的项目将与阿尔弗雷德·格索旋翼机中心和马里兰州大学琼斯空气动力学实验室合作进行。一个四叶，减速模型转子将在格伦L。马丁风洞采用时间分辨的立体粒子图像测速技术和立体摄影技术同时测量了叶片的反向流场和变形。最先进的设施、资金充足的风洞试验和研究人员在该项目中的专业知识相结合，对于研究减速旋翼上的反向流动和改进未来复合直升机的设计至关重要。

Medical emergency services face the challenge to reach remote locations within a critical response time of less than an hour. Innovative "compound" helicopters with additional propellers, such as Airbus Helicopters' prototype X³, are designed to meet this challenge through a combination of high cruise velocities and vertical take-off capability. To circumvent the impact of high cruise velocities on the advancing blade, the main rotor of a compound helicopter operates at a reduced rotational speed. The corresponding reverse flow on the retreating blade has detrimental effects on the performance and stability of the helicopter. This project focuses on the detailed investigation of the reverse flow field to advance our knowledge of compound helicopter aerodynamics and ultimately design faster helicopters that reduce response times for emergency situations.Experimental evidence shows the impact of reverse flow on the rotor power and loads. To effectively counteract these negative effects, this project will investigate the reverse flow field itself and its subsequent effects on rotor blade deformations. The reverse flow field is characterized by a high advance ratio, the relation of flight speed to blade tip velocity. By manipulating the advance ratio, we can measure its effects on the reverse flow field and blade deformations of a slowed rotor. These measurements, in turn, will improve the aerodynamic rotor codes used in the conceptual design of compound helicopter configurations, which are currently insufficient for accurate prediction of the complex flow physics in the reverse flow field. The proposed project will be carried out in cooperation with the Alfred Gessow Rotorcraft Center and Jones Aerodynamics Laboratory at the University of Maryland. A four-bladed, slowed model rotor will be tested at high advance ratio in the Glenn L. Martin Wind Tunnel. The reverse flow field and deformations of the retreating blade will be measured simultaneously by time-resolved stereo particle image velocimetry and stereo photogrammetry, respectively. The combination of state-of-the-art facilities, a fully funded wind tunnel test, and researcher expertise in this project is essential to investigate reverse flow on a slowed rotor and improve the design of future compound helicopters.