Abstract: The hot jet noise reduction of chevron nozzles with pylons was investigated on separate flow nozzles at a bypass ratio of 5.5. All the experiments were conducted on the hot jet noise rig located in the anechoic chamber. The effects of the chevron nozzles on far-field jet noise reduction were explored，such as structural parameters and their distribution. The experimental results of hot jet noise with pylons show that chevron nozzles reduce jet noise in the low frequencies and have the best low-frequency noise reduction at downstream. The distribution of chevrons was determined to be a primary factor in jet noise reduction. The high-frequency noise controlling was observed when chevrons were fixed only in primary nozzles which have the reduction in overall sound pressure level ranging from 1.4 to 2.4dB at downstream. Besides，the increase of chevron counts also has the ability of noise suppression in high frequencies. Slight differences were observed when varying chevron penetration angles，but it appears that the effect is less significant than the effect of distribution.

Key words: Hot jet；Chevron nozzles；Separate flow；Pylon；Jet noise

摘要： 利用位于全消声室中的热喷流噪声实验台对涵道比为5.5的分开式排气系统进行了吹风实验，研究了在热喷流状态下带有挂件的锯齿型喷口对分开式排气系统远声场的影响，进一步分析了锯齿的分布方式以及结构参数对喷流噪声降噪特性的影响。结果表明，锯齿型喷口可以降低喷流低频段的噪声，并且在下游方向具有最好的低频段降噪效果；锯齿的分布方式对降噪效果的影响最大，仅在内涵添加锯齿结构的喷口可以抑制高频噪声的产生，在下游的总声压级降噪量为1.4～2.4dB；齿数的增加可以抑制高频噪声的增加;切入角的变化对降噪效果有一定的影响，但是远小于分布方式的影响。

关键词: 热喷流；锯齿型喷口；分开式排气；挂件；喷流噪声