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直升机在斜下降飞行时旋翼产生的桨涡干扰(BVI)噪声十分严重,桨距主动控制是降低旋翼BVI噪声的有效手段之一。为摸索其对旋翼BVI噪声的影响规律并阐释其机理,开展了开环桨距主动控制对旋翼BVI噪声的影响研究。建立能够计入开环桨距主动控制的旋翼自由尾迹模型,并结合翼型气动力模型及基于FW-H(Ffowcs Williams-Hawkings)方程的旋翼载荷噪声计算模型,建立旋翼BVI噪声开环主动控制模型。以40%缩比的4桨叶BO-105直升机模型旋翼为算例,在风洞配平状态下开展开环桨距主动控制对旋翼BVI噪声的影响研究。通过分析算例旋翼在不同相位、幅值的桨距主动控制下的BVI噪声声压级、桨盘气动载荷及桨盘迎角分布,总结出开环桨距主动控制影响旋翼BVI噪声的规律,并初步阐释了其机理:适当的桨距主动控制可改善桨盘迎角分布,降低桨涡干扰位置附近的桨叶气动载荷,从而降低BVI噪声。
Helicopter rotor vane interference (BVI) noise is very serious when the aircraft is flying obliquely. Propeller pitch control is one of the effective means to reduce the rotor BVI noise. In order to explore its influence on the rotor BVI noise and explain its mechanism, the influence of open-loop pitch active control on the rotor BVI noise was studied. A free-wake rotor model that can take account of the open-loop pitch active control is established and the open-loop BVI noise open-loop active control is established based on the aerodynamic model of the airfoil and the rotor load noise calculation model based on the FW-H (Ffowcs Williams-Hawkings) equation model. Taking the 40-blade 4-blade BO-105 helicopter model rotor as an example, the effect of active control of open-loop pitch on the rotor BVI noise is studied under the condition of wind tunnel leveling. By analyzing the BVI noise pressure level, the aerodynamic load and the angle of attack of the propeller rotor under the active control of the pitch and the pitch of the rotor with different phases and amplitudes, the law that the open-loop pitch actively controls the BVI noise of the rotor is analyzed, And the mechanism is explained. The proper pitch active control can improve the angle of attack of the propeller and reduce the aerodynamic load of the blades near the disturbance position of the propeller blades, so as to reduce the BVI noise.