悬停状态倾转旋翼噪声试验及数值计算

结合消声室试验和数值计算研究了悬停状态倾转旋翼气动噪声特性。消声室试验采用孤立倾转旋翼模型,测试了不同总距角和桨尖马赫数状态的气动噪声数据。数值计算基于CFD(computational fluid dynamic)结合FW-H(Ffowcs Williams-Hawkings)声学方程的方法,采用试验数据验证了计算模型的可靠性。分析了倾转旋翼的噪声传播特点以及拉力系数和桨尖马赫数对噪声总声压级的影响,并对比了孤立旋翼和双旋翼状态的气动噪声特性。结果表明:倾转旋翼噪声随着拉力系数和桨尖马赫数的增加均有所增加,维持旋翼拉力不变时降低桨尖马赫数虽然使得拉力系数增加,旋翼噪声水平仍然降低;倾转双旋翼噪声相对纵向平面对称分布,在多个方位角区域存在着局部最大值,这和双旋翼噪声传播时的相互叠加以及双旋翼间气动干扰相关。 

Acoustic test and numerical analysis of tilt rotor in hover

The aeroacoustic characteristics of tilt rotor in hover were investigated based on acoustic test and numerical computation. The test was conducted with isolate model tilt rotor, and the acoustic data of different collective pitch angles and blade tip Mach number were measured. The numerical computation was made based on CFD (computational fluid dynamic) and FW-H(Ffowcs Williams-Hawkings) equation, and the calculation accuracy was validated by test data. The acoustic results of different observation positions were compared, the effects of thrust coefficients and blade tip Mach number on tilt rotor noise were analyzed, and the acoustic characteristics of isolate rotor and dual rotors were calculated. Results showed that, the overall sound pressure level of tilt rotor increased with thrust coefficients and blade tip Mach number, the decrease of tilt rotor blade tip Mach number can reduce overall sound pressure level although the thrust coefficient was increased to maintain rotor lift; the acoustic directivity of dual tilt rotors was longitudinally symmetrical, the local maximum overall sound pressure level occurred at several azimuths, due to the superposition in noise radiation and aerodynamic interaction of the two rotors.