喷管非轴对称性对超声速欠膨胀射流激波啸叫影响实验研究

Experimental study on effects of non-axisymmetric nozzle on screech tone of supersonic speed under-expansion jet

喷口外形是影响超声速射流激波啸叫模态特性的重要因素之一。对矩形射流以外的非轴对称喷管的超声速射流激波啸叫研究较为缺乏。为研究非轴对称收缩喷管对超声速射流激波啸叫的影响,针对圆形射流、正方形射流和正三角形射流的激波啸叫特性开展了实验研究。研究发现相比圆形喷管和正方形喷管,三角形喷管具有很大的抑制激波啸叫噪声的降噪潜力。采用方位角重构的方法对不同喷管外形的超声速射流激波啸叫开展了模态特性分析,结果表明,圆形射流、正方形射流和三角形射流激波啸叫A模态和B模态的基频模态特性基本一致,而A模态的倍频模态特性存在一定差异。在完全膨胀马赫数大于1.32时,三角形射流出现了特有的激波啸叫模态,其基频和倍频均为轴对称模态。

Nozzle shape is one of important factors affecting modal characteristics of supersonic speed jet screech tone.There is a lack of study on screech tone of supersonic speed jet in non-axisymmetric nozzle except rectangular jets.Here,to study effects of non-axisymmetric convergent nozzle on screech tone of supersonic speed jet,screech tone characteristics of circular jet,square jet and equilateral triangle jet were experimentally studied.The study showed that compared to circular and square nozzles,triangular nozzles have significant noise reduction potential to suppress screech tone.Then,modal characteristics of ultrasonic speed jet screech tone with different nozzle shapes were analyzed using the method of azimuth reconstruction.The results showed that fundamental frequency modal characteristics of circular jet,square jet,and triangular jet screech tone’s mode A and mode B are basically the same,while their mode A’s frequency-doubling modal characteristics have certain differences;when the fully expansion Mach number is larger than 1.32,specific screech tone modes appear in triangular jet,both fundamental frequency mode and frequency-doubling mode are axisymmetric.