基于干扰距离控制的直升机桨-涡干扰噪声降噪方法

提出了一种适用于直升机旋翼桨-涡干扰距离计算的方法。针对桨-涡干扰距离计算中必需的旋翼桨盘入流及桨盘倾角，又分别建立了旋翼耦合N-S （Navier-Stokes）/自由尾迹模型和桨盘配平模型进行求解，其特点是兼顾计算精度和计算效率；并从悬停、前飞两方面验证了方法的有效性。应用所建立的桨-涡干扰距离计算方法，着重分析了直升机纵向平面力以及飞行参数对旋翼桨-涡干扰距离的影响机理，并进一步计算了不同纵向平面力作用下的旋翼地面声场特性及影响规律。结果表明:合理施加纵向平面力、加速度等措施后，地面最大噪声降低约4dB。同时，还通过研究桨-涡干扰距离与飞行参数的影响关系，得到了一些对直升机低噪声飞行具有实际指导意义的结论。 

Method on helicopter BVI noise reduction based onmiss-distance control

A method for calculating the miss-distance of helicopter rotor was proposed. For the calculation of miss-distance, rotor inflow and tip-path-plane angle were required firstly. The rotor coupled N-S(Navier-Stokes )/free-wake model and rotor trim model of high accuracy and high efficiency were developed respectively. The method was validated using several numerical examples in both hover and forward flight. Applying the developed method, the effect mechanism of longitudinal forces and flight parameters on miss-distance was analyzed. Further, the ground noise radiated from the helicopter rotor was calculated. It demonstrated that the maximum ground noise was reduced by 4dB through the longitudinal forces and acceleration. At the same time, the relationship between miss-distance and flight parameters was studied and some instructive conclusions for low-noise flight were obtained.