分开排气式喷管喷流噪声预测及试验研究

为揭示涡扇发动机分开排气式喷管喷流噪声的频谱分布和指向特性,对喷管缩比模型远声场喷流噪声进行了预测及试验研究,并开展了全尺寸喷管基准型及锯齿型喷流噪声的预测工作。结果表明:采用Tam & Auriault方法可以预测出喷流噪声的声压级值和空间指向分布,喷流噪声具有明显的指向性。与基准型喷管相比,锯齿型喷管具有良好的降噪效果;内外涵锯齿型喷管在中低频段的降噪效果优于内涵锯齿型喷管,在高频段的降噪效果差于内涵锯齿型喷管;在本文研究参数范围内,指向角小于88°时内外涵锯齿型喷管总声压级(OASPL)值高于内涵锯齿型喷管。

Experimental and prediction research on jet noise for separated exhaust nozzle

In order to reveal the distribution of frequency spectrum and directivity for the separated exhaust nozzle, prediction and experiment are conducted for scaled mode, then full-scale nozzle model of basic and chevron are calculated. The result shows that Tam & Auriault's jet noise prediction theory is used to predict the noise spectra and direction of far-field noise, and jet noise possesses obvious direction. Compared with basic nozzle, the reduced effect of jet noise with chevron is better. Chevrons are fixed only in primary nozzles which have worse ability of low-frequency noise reduction and the high-frequency noise increase by contrast with chevrons which are fixed in primary and bypass nozzles. The overall sound pressure level (OASPL) value of chevrons which are fixed only in primary nozzles is less than that of chevrons fixed in primary and bypass nozzles at the angle of directivity smaller than 88° in this paper.