新型桨尖抑制旋翼跨声速噪声特性的影响机理分析

Analyses about impact mechanism of new type blade-tip on inhibiting rotor transonic acoustic characteristics

为研究不同形式的新型桨尖在抑制旋翼跨声速噪声特性方面的作用机理,以UH-1H模型旋翼为基准,开展了多种后掠和前掠桨尖对旋翼高速脉冲噪声特性的数值分析研究。采用积分形式的可压缩雷诺平均NavierStokes(RANS)方程作为旋翼流场求解控制方程,时间推进方法采用高效的隐式LU-SGS格式,空间方向采用高精度的Roe-MUSCL格式,湍流模型选用Baldwin-Lomax模型。在CFD方法验证基础上,采用基于可穿透旋转积分面的鲁棒性较好的FW-H_pds方程来求解旋翼高速脉冲(high-speed impulsive,HSI)噪声,并通过对UH-1H模型旋翼的跨声速噪声的计算,验证了噪声预测方法的有效性。在此基础上,研究了在不同桨尖马赫数下的旋翼桨尖附近的离域化(delocalization)现象以及高速脉冲噪声特性,通过四极子噪声和单极子噪声的对比分析,揭示了旋翼跨声速噪声产生机理。然后,着重研究了不同外形参数的后掠和前掠桨尖旋翼在抑制旋翼跨声速特性方面的影响规律。计算结果表明:随着桨尖马赫数的增加,旋翼高速脉冲噪声辐射愈加强烈,离域化现象愈加明显;后掠和前掠桨尖旋翼均可以不同程度地减弱激波强度,能有效抑制离域化现象的产生,从而降低旋翼跨声速噪声水平;前掠桨尖旋翼还可以驱使激波位置向桨叶内侧移动,减弱其对桨叶外部空间区域的影响,能更有效地抑制离域化现象的产生。

To investigate the effects of different new types of blade-tip on transonic acoustic characteristics of a helicopter ro to r,numerical analyses about the impacts of blade-tips on the high-speed impulsive(H S I)noise characteristics have been carried out by taking the UH-1H model rotor as baseline.A CFD simulation method is developed by solving the compressible Reynolds-averaged Navier-Stokes(R A N S)equations with Baldwin-Lomax turbulence m o d e l and a high-precision Roe-MUSCL scheme and high-efficiency implicit LU-SGS scheme are employed for spatial and temporal discretization respectively.Based on the validation of CFD m ethod,a robust FW-H_pds m ethod based on the penetrable data surface is established for predicting rotor HIS noise,and the transonic acoustic characteristics of U H-1H model rotor have been simulated to verify t he effectiveness of t he present method.Based on t hese methods,t he influences of Mach number on t he phenomenon named“delocalization”nearby t he blade tip and t he HSI noise characteristics are analyzed,and t he generation mechanism of transonic noise is revealed by t he comparisons of t he monopole noise and quadrupole noise.Then,t he influences of both sweepback and sweep-forward blade-tip on nhibiting rot or transonic acoustic characteristics areanalyzed at a transonic state(Mach number0.9)respectively.The numerical results n d icate thatt he serious delocalization phenomenon and t he HSI noise radiation occur strongly with t hetncrease of t he blade-tip Mach number.Compared with rectangular blade the rot ors with sweepback or sweep-forward blade-tip can reduce HSI noise level at atransonic state by suppressing the supersonic flow and delaying the occurrence of delocalization effects.Furthermore,sweepforward blade-tip has a more remarkable effect on nhibiting delocalization effects by driving supersonic flow region to move to tnside of blade.