涡扇发动机斜切喷口排气噪声抑制技术研究

发布时间：2018-03-19 07:08

  本文选题：喷流噪声　切入点：分开排气　出处：《南京航空航天大学》2014年硕士论文　论文类型：学位论文

【摘要】：喷流噪声是发动机噪声的主要噪声源之一。为了适应日益严格的飞机适航噪声标准,降低发动机喷流噪声是民用涡扇发动机设计时必须考虑的主要因素之一。针对这个背景,本文采用大涡模拟(LES)以及声学软件ACTRAN中的气动声学模块对喷流噪声的斜切喷管降噪进行了数值研究。分别选用分开排气系统和混合排气系统物理模型,研究分析了边界条件、斜切角度和斜切位置对排气喷流气动和声学特性的影响,同时对比分析了远场和近场噪声特征。研究结果表明:1、在分开排气系统中,边界条件和斜切角度共同影响降噪效果,斜切位置影响声场分布。喷管斜切后增加喷流与大气的掺混作用,使湍流核心区长度有所缩短,有效的使湍流混合噪声由低频段向高频段转移,内涵喷管斜切后总声压级分布降低幅度约2-5d B。外涵喷管斜切后,喷流偏转明显,使得总声压级分布在上方局部出现升高现象,其余范围降噪幅值1-6dB。总体相较内涵斜切比外涵斜切降噪效果好,且斜切角度越大,降噪效果越明显。2、在混合排气系统中,当喷管斜切时,流场中喷流明显发生了偏转,且斜切角度越大明显,湍流核心区长度也有所减小。总声压级分布也呈现了明显的不对称性,整体噪声较常规喷管减小幅值在2-6dB,且下方区域对比相应角度的上方总声压级有所减小,达到了减少噪声对地面的辐射作用。随着斜切角度的增大,降噪效果越明显。3、通过远场和近场噪声比较发现,当监测点距离增加时声波发生衰减导致噪声明显减小,同时远场噪声更能体现出声场的指向性。
[Abstract]:Jet noise is one of the main noise source of engine noise. In order to meet the increasingly stringent standards for aircraft airworthiness noise, reduce engine jet noise is one of the main factors to be considered civil turbofan engine design. According to this background, this paper uses large eddy simulation (LES) and acoustic software ACTRAN in Aeroacoustics module of jet noise the scarfed nozzle was numerically studied. Noise reduction were used to separate mixed physical exhaust system and exhaust system model, analyzed the influence of boundary conditions, and oblique position on miscut angle exhaust jet aerodynamic and acoustic characteristics, and comparative analysis of the far field and near field noise characteristics. The results show that: 1, in separate exhaust system in the boundary conditions and the influence of the noise reduction effect of common bevel angle, oblique position affect the sound field distribution. The nozzle and air jet oblique increased after mixing The length, the core area will be shortened, effectively make the turbulent mixing noise transfer from low to high frequency, the connotation of the total sound pressure distribution after oblique nozzle decreased about 2-5d B. by-pass nozzle oblique, jet deflection, the total sound pressure distribution is increased above the local phenomenon, the range of noise amplitude 1-6dB. compared with the overall connotation than the external oblique oblique culvert and good noise reduction effect, oblique angle increases, the noise reduction effect is more obvious in.2, mixed exhaust system, when the nozzle flow field in the jet was oblique, deflected, and oblique angle is more obvious, the length of turbulent core area decreased. The total sound pressure distribution presents the obvious asymmetry, the overall noise amplitude decreased in 2-6dB compared with the conventional nozzle, and the contrast area below the corresponding angle above the total sound pressure level decreases, so as to reduce the noise of the radiation. With the increase of oblique angle, the more obvious effect of noise reduction by.3, the far field and near field noise is found when the monitoring distance increased acoustic attenuation in noise is obviously reduced, reflecting the directivity is also far field noise.

【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：V235.13;TB535
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本文编号：1633326