超音速冲击射流离散频率噪声的屏蔽抑制方法

根据导致超音速冲击射流离散频率噪声的反馈机理，提出了一种能够有效地破坏反馈环的形成，从而抑制超音速冲击射流离散频率噪声的喷嘴屏蔽方法。这种方法是通过阻隔反馈波使其不能到达喷嘴唇口从而破坏反馈环、同时屏蔽罩不与射流接触来实现降噪的目的的。本文介绍了这种方法的基本思想并提出了屏蔽罩的设计要点。实验结果表明，对于合适的屏蔽罩的参数，降噪效果达5分贝以上。应用LDV方法对超声速射流轴线速度进行了测量和比较，发现应用屏蔽降噪方法以后射流轴线速度显著增加，核心区长度增加50%左右。分析表明这种降噪方法对射流冲击障碍物的推力和除尘除水效率的提高有帮助。

A Kind of Shield Method Used to Suppress Supersonic Impinging Jet Discrete Frequency Noise

Based on understanding the feedback mechanism of discrete frequency noise supersonic impinging jet, a new kind of method is proposed to reduce the noise by destroying formation of the feedback loop effectively. The main idea is using a shield to prevent the feedback acoustic wave from arriving at the nozzle lip, which is required to be out of the jet boundary, so that no effect on the flow of impinging jet may occur. Experimental results show that the noise can be generally reduced by more than 5 dB at the right shield parameters. Moreover, measurements and analysis confirm that the method is helpful for the impinging jet to increase thrust and remove particles on the surface.