V形槽喷管在分开式排气系统中的降噪实验

利用位于全消声室中的喷流噪声实验台研究了V形槽喷管在分开式排气系统中的降噪特性,比较了在剪切速度比为0.92工况下V形槽喷管的结构参数以及分布方式在冷喷流中对降噪效果的影响.结果表明:V形槽喷管降低了低频段的喷流噪声并增大高频段的喷流噪声;在喷管的下游方向有最好的低频段降噪效果,并具有最小的高频段喷流噪声增加量;增大V形槽喷管切入角可以增加低频段的降噪量,其降噪量最高为5dB;仅在外涵添加V形槽喷管可以增大低频段的降噪量并抑制高频段的喷流噪声的增加;V形槽喷管齿数的变化对降噪效果有一定的影响,但其影响远小于切入角的变化对降噪效果的影响;另外V形槽喷管可以显著地降低喷管下游方向的声压级大小.

Experiment of noise reduction in separate flow system using chevron nozzles

The noise reduction characteristics of chevron nozzles was investigated in separate flow system. All the experiments were carried out on the jet noise rig in the anechoic chamber. The effect of the structural parameters and distribution of chevron nozzles on cold jet noise reduction was explored in which shear velocity ratio was 0.92. The results show that chevron nozzles reduce jet noise at low frequencies, but increase jet noise at high frequencies. Besides, chevron nozzles has a best low-frequency noise reduction at downstream with lowest high-frequency noise penalty. The noise is decreased at the low frequencies and the peak noise reduction is 5dB when penetration angles of chevron nozzles are increased. The chevron nozzle only on fan has a good low frequency noise reduction and an ability of noise suppression at high frequencies. Although slight differences are observed with varying number of chevron, it seems that the effect is less significant than that of the penetration angles. The sound pressure level downstream is reduced significantly by chevron nozzles.