Experimental study on trailing edge with gradual flow resistance suppressing noise diffraction of BWB engine
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摘要: 在翼身融合体（BWB）飞机外形布局中，利用机体部件对发动机噪声源的遮挡作用可以降低发动机对地面的噪声影响。流阻渐变分布的吸声材料可以有效抑制由于声压突然变化而导致的粒子振动速度变大，根据此边缘效应抑制机理，提出了一种新型流阻渐变型后缘来进一步降低BWB发动机对地面的噪声影响。为此，在具有全消声环境的0.55 m×0.4 m声学引导风洞中，利用"NACA0012翼型+旁侧圆柱"的简化模型类比翼身融合体飞机机体与背部发动机之间的外形布局，分别从经典声学和气动声学的角度探讨填充3种不同流阻率吸声材料的翼型后缘对旁侧噪声源衍射噪声的抑制效果，分析在不同来流风速下不同翼型后缘对另一侧声场噪声的不同影响。研究结果表明：旁侧噪声源在有翼型遮挡的情况下，噪声的声压级明显降低，最多能降低约5 dB；而将标准后缘分别更换为3种不同流阻渐变型后缘后，在不同程度上额外抑制了噪声组成中的衍射噪声，从而进一步降低了噪声；且降噪效果与流阻率正相关，其中流阻率最大的吸声材料降噪效果最好，能进一步降低噪声声压级约3 dB；可推测吸声材料流阻率在0~∞的范围中，降噪效果随流阻率r增加呈先增强后减弱的现象。Abstract: In the configuration of Blended Wing Body (BWB) aircraft, the noise effect of engine on the ground can be reduced by using the shielding effect of engine components on engine noise sources. According to the mechanism that the sound-absorbing materials with gradual distribution of flow resistance can effectively suppress the vibration velocity of particles caused by the sudden change of sound pressure in the edge effect, a new type of trailing edge with gradual flow resistance is proposed to further suppress the noise of BWB engine on the ground. Therefore, the simplified model of NACA0012 airfoil + side cylinder is used to simulate the configuration between the fused wing-body airframe and the back engine in a 0.55m×0.4m acoustically guided wind tunnel with full anechoic environment, and the effects of the trailing edge of airfoil filled with three kinds of sound-absorbing materials with different flow resistivity on the diffraction noise of side noise sources are discussed from the perspective of classical acoustics and aeroacoustics respectively. The different influence of different airfoil trailing edges on the sound field noise of the other side is analyzed under different incoming wind speeds. The results show that the sound pressure level of the noise can be reduced by about 5 dB at most when the side noise source is shielded by airfoil; When the standard trailing edge is replaced by three different trailing edges with gradual flow resistance, the diffraction noise in the noise composition is additionally suppressed to some extent, thus further reducing the noise. The noise reduction effect is positively related to the flow resistivity, and the sound-absorbing material with the largest flow resistivity has the best noise reduction effect, which can further reduce the noise sound pressure level by about 3 dB. It is also speculated that in the range of flow resistivity of sound-absorbing materials from 0 to ∞, the noise reduction effect increases firstly, and then decreases with the increase of flow resistivity.
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Key words:
- blended wing body /
- engine noise /
- gradual flow resistance /
- edge effect /
- trailing edge
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图 2 填充在后缘的3种吸声材料
Figure 2. Three kinds of sound-absorbing materials filled in the trailing edge
图 4 自制流阻测量设备设计草图
Figure 4. Design sketch of self-made flow resistance measuring device
图 8 流阻渐变分布的NACA0012翼型结构
Figure 8. The structure of the NACA0012 airfoil model with the gradational distribution flow resistance
图 12 静态声源的远场噪声数据分析
Figure 12. Far field noise data analysis of the static sound source
表 1 3种材料的流阻率
Table 1. Flow resistivity of three materials
No. 1 2 3 r/(Pa·s·m-2) 15 000 35 000 67 500 
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表 2 雷诺数
Table 2. Reynolds number
v∞/(m·s-1) Rerod Remodel 13 8.65×103 2.59×105 15 9.99×103 2.99×105 17 11.32×103 3.38×105
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表 3 G.R.A.S 46AE型传声器的主要技术指标
Table 3. Main technical specifications of G.R.A.S 46AE microphone
Parameter type 46AE Size/inch 1/2 Nominal sensitivity/(mV·Pa-1) 50 Frequency response (±3 dB)/Hz 3.15~20 k Upper limit (3% distortion)/dB 148 Microphone thermal noise/dB(A) 14.5
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