高阶谐波控制对旋翼桨-涡干扰载荷和噪声的影响

直升机小速度平飞和斜下降飞行时会产生严重的桨-涡干扰(BVI)噪声。基于修正Beddoes尾迹/桨叶动力学耦合方法和Farassat 1A公式,建立了一个新的能够计入高阶谐波控制(HHC)影响的旋翼桨-涡干扰气动载荷和噪声计算模型。在该模型中,高阶谐波控制引起的桨尖涡附加位移通过对高阶入流进行时间积分推导得出,而单一阶次的谐波输入引起的各阶谐波响应通过传递函数来确定,传递函数则由桨叶的动力学特性计算。首先对HARTⅡ旋翼斜下降飞行状态的桨-涡干扰气动载荷进行了计算模拟,验证了所建立方法的可靠性。然后,着重研究了在典型的三阶谐波桨根激励下,不同输入相位对HARTⅡ旋翼桨-涡干扰气动载荷和噪声特性的影响。结果表明:桨叶的动力学特性尤其是扭转特性对高阶谐波控制效果影响显著,且高阶谐波输入的相位选择对桨-涡干扰噪声的控制至关重要,若控制相位选择不当,反而会增大旋翼噪声。

Influence of higher harmonic control on airload and acoustics of rotor blade-vortex interaction

Harsh blade-vortex interaction (BVI) noise will be generated when a helicopter is flying at a moderate speed level flight or descending.Based on the modified Beddoes wake/blade structural dynamics coupling model and Farassat 1A formula,a rotor BVI airload and acoustics prediction method is proposed,in which the influence of higher harmonic control (HHC) can be included.The additional tip vortex vertical displacement caused by HHC is derived from time integration of higher harmonic inflow,and a transfer function that relates single HHC input to resulting response at the same and neighboring frequencies is identified by blade dynamic characteristics.The rotor airload of the baseline case in higher harmonic control aeroacoustics rotor Test Ⅱ (HART Ⅱ) is investigated and compared with experimental data firstly.The influencing mechanism and varying pattern of the rotor acoustic property at different 3/Rev control phases is then assessed.The results show that blade dynamic characteristics,especially torsional behaviors,are important for effectiveness of higher harmonic control.Selection of HHC phase input is significant to BVI noise control,and irrational HHC phase input will worsen noise radiation.