不同偏流板角度的冲击射流噪声特性

Noise characteristics of jet impingement on a blast deflector at different angles

舰载机尾喷流冲击偏流板(挡焰板)产生高强度噪声。为研究不同偏流板角度对噪声的影响,在全消声室进行射流冲击实验。实验时收缩喷口直径D=56.4 mm,受冲击的偏流板长、宽均为600 mm,射流马赫数Ma=1.01。在偏流板角度β=45°、55°和65°条件下,利用传声器和流动显示对远场噪声和冲击流动进行观测。结果表明,不同冲击角度下壁面射流结构明显不同,总声压级及噪声辐射特性存在明显区别,随着冲击角度的增加,上游和下游极角总声压级分别出现上升和下降,β=65°时,下游总声压级最多降低7 dB,上游相应增加15 dB。流动和频谱结果表明下游主要受到后缘分离噪声影响,该噪声来自壁面射流从偏流板后缘分离产生的大尺度涡结构,低频占主导,并且互相关分析表明,偏流板角度越小,该噪声指向性越明显。上游噪声被冲击噪声所主导,虽然偏流板角度显著影响冲击噪声强度,但是相关分析表明,冲击噪声向各个极角辐射的指向性结构较为稳定。此外偏流板对边线形成低通高阻效应,边线噪声频谱最为陡峭,而且边线观测到的总声压级、频谱在不同冲击角度的差别均较小。本研究可为航母甲板噪声治理提供一定参考。

Hazardous noise of flight deck due to jet blast deflector impingement causes a serious damage to the health of crew members.An experiment of jet impinging on a blast deflector was carried out in a full an⁃echoic chamber to study the acoustic characteristics.With a diameter(D)of 56.4 mm,a convergent nozzle was used to investigate a Mach number of 1.01 jet impingement.Flow visualization and far-field microphones were employed to observe the flow field and measure the far-field noise,respectively.The test was performed on a 600 mm×600 mm deflector and with three inclined angles(β)of 45°,55°and 65°.The results show that the impact angle has a significant influence on the wall jet structure and overall sound pressure level(OASPL).With the increase of impact angle,the OASPL of upstream and downstream rise and fall respective⁃ly.It is found that the OASPL increases by 15 dB in the upstream direction and decreases by 7 dB in the downstream direction forβ=65°.Flow visualization and spectra analysis indicate that downstream directions are radiated by low frequency noise originated from trailing edge of the deflector due to separation of the large scale vortex.Specifically,it can be illustrated by correlation analysis that the directivity of the trailing separa⁃tion noise becomes more significant when the impact angle reduces.Upstream directions are dominated by impingement noise.Although impingement noise is significantly affected by impact angle,the radiation struc⁃ture of impingement acoustic wave under different impact angles is similar to each other according to the cor⁃relation analysis.In addition,the deflector forms a low-pass filtering effect on the impingement noise,and the sideline spectra have steep peaks.The OASPL and spectra of sideline directions are less affected by the impact angle.The research results are expected to be helpful for noise pollution control on carrier deck.