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中文核心期刊

偏流板距离对亚声速射流冲击宽频噪声特性的影响

Broadband noise performance of subsonic jet with different impingement distances to a deflector

  • 摘要: 通过全消声室实验研究了不同冲击距离(L)下亚声速射流宽频噪声特性。利用远场传声器获得L = 30D~2D (D为喷口直径)的噪声数据, 并详细分析了频谱特性。试验结果表明, 减小冲击距离: (1) 上游所有频段的噪声都明显上升, 极角α = 120°总声压级(OASPL)在L < 10D时增加了10~17 dB; (2) 下游α = 30°的噪声能量向低频转移, 且频谱在L < 10D时变化不明显; (3) 偏流板产生噪声的中、高频段对边线影响较小, α = 90°的频谱迅速衰减, 在L < 10D时形成陡峭的峰值。研究证实在噪声最强的方向(α = 120°), 随冲击距离的减小偏流板贡献的噪声功率占比呈线性增加。冲击距离小于势流核时, 偏流板贡献大部分噪声能量, L = 7D~5D时占比超过80%。另外射流冲击产生的噪声指向性明显, 冲击噪声和后缘分离噪声在不同方向取得主导地位, 相应频谱分别在上游和下游呈现高频主导和低频占优的特性。

     

    Abstract: To study the broadband noise characteristics of jet impingement on defector with different impact distances, an experimental study is carried out by using far-field microphones in a full anechoic chamber. Comprehensive data of the nozzle-plate distance (L) range between 30D (D is the diameter of nozzle exit) and 2D are obtained and the spectral characteristics are discussed. Reducing the impact distance, the results indicate: (1) The spectra increase significantly in all frequency bands, leading to an increment of the overall sound pressure level by 10–17 dB in the direction of polar angles (α) of α = 120° when L < 10D; (2) The noise energy of downstream directions transfers to lower frequency and the spectra of α = 30° tend to collapse at different impingement distances when L < 10D; (3) Since medium and high frequency impingement noise has a little effect on the sideline directions, the spectra of polar angle of 90° attenuate rapidly which form a steep peak when L < 10D. The quantitative analysis prove that the proportion of sound power of defector increases linearly with the decrease of L in the direction of strongest noise (α = 120°). Most noise are produced by deflector for impingement distance less than the length of potential core, such as 80% at L = 7D–5D. Moreover, the directivity of deflector noise is obvious. Impingement noise or trailing edge separation noise is dominated in different directions. Correspondingly, the low frequency and high frequency noise plays a dominant role in the upstream and downstream directions respectively.

     

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