涡扇排气系统结构参数对排气声压级影响

Effects of turbofan exhaust system geometry parameters on sound pressure level

关键词:  涡扇发动机  波瓣强迫混合器  声压级  数值计算

Key words:  Turbofan engine  Lobed forced mixer  Sound pressure level  Numerical computation

摘要:

基于三维CFD和宽带噪声模型,对不同结构的涡扇排气系统流场和出口声压场分布展开数值计算与分析,获得涵道比、波瓣强迫混合器穿透比和混合段长径比对排气出口声压级的影响规律。数值结果表明:排气系统出口声压级分布与径向速度梯度相对大小分布一致,排气出口速度梯度的减小可以降低排气噪声。涵道比在0.5～3.0,长径比在1～2之间,排气系统涵道比和排气混合段长径比的增加可以降低喷管出口平均噪声声压级;在相同涵道比下,波瓣强迫混合器穿透比的增加,出口平均噪声声压级先大幅减小后缓慢增加。

Abstract:

Based on three-dimension CFD and broadband noise model,the numerical simulation and analysis were conducted for the turbofan exhaust system.The effects of exhaust system geometry parameters on the sound pressure level(SPL) of hot exhaust gas are revealed.The numerical results show that the SPL distribution of exhaust gas has the same characteristics as that of radial velocity.The velocity gradient of flow decreasing could reduce the SPL of the exhaust.With the increasing of the bypass ratio or the length of mixing duct,the average of SPL at the outlet section of exhaust system can be reduced.At the same bypass ratio,the average of SPL can also be reduced by increasing the penetration ratio of the lobed forced mixer.