Evaluation of General Performance of Advanced Noise Suppressors including Spherical Reflectors based on the Diagnosis of Aerodynamic Loss and Acoustic Power

这项研究是由本报告的作者在研究生和本科生以及一名博士后的帮助下完成的。垂直风洞的设计和建造：我们制作了一个可以产生垂直射流的垂直风洞。利用风洞法可以方便地测量消声器的推力损失。特别注意的是要避免出口法兰处的压降。推力的测量：带反射器和不带反射器的喷嘴发出的气流推力的比较。结果表明，安装反射器只会使推力减小一点。对射孔管的推力损失进行了测量。穿孔管的连接也减少了推力。射流损失随射流压力比的增大而减小。理论上讲，穿孔管可以在高压比下增加推力。声功率的测量：在一个混响室中，在2.0到6.0的压力比范围内，通过安装一个球形反射器来测量声功率的变化。对不同射孔管的声功率进行了测量。先进降噪器的一般性能评价：与射孔管相比，开槽管的推力损失更小。开孔管的降噪性能不如开孔管。从整体上看，在所有测试管中，孔隙度为0.03（实用值）的前斜射孔管表现最好。论文发表：本研究成果已在第7届ISAIF（东京，2005），第12届ICSV（里斯本，2005），第13届ICSV（2006，维也纳），ASA/AS联合会议（檀香山，2006），internoise 2006（檀香山，2006）和另外4次国际会议上发表，并发表了19篇论文。

This research has been carried out by the author of this report with the assistance of graduate and undergraduate students as well as a post doctorial student..1. Designing and construction of a vertical wind tunnel: We made a vertical wind tunnel that can generate a vertical jet. Measurement of thrust loss of noise suppressors was easily carried out by using the wind-tunnel. Special attention was paid to the avoidance of pressure drop at the flange of the exit.2. Measurement of thrust: Comparison between thrusts of flows issued from a nozzle with and without a reflector. It was found that the attachment of a reflector reduces a thrust only a little bit. Measurements of thrust loss of perforated tubes were also carried out. The attachment of a perforated tube also reduced the thrust. The amount of the loss, however, decreased as jet pressure ratio increased. Theoretically a perforated tube can increase a thrust at a high pressure ratio.3. Measurement of acoustic power: Change in acoustic power by the attachment of a spherical reflector has measured in a reverberant room in a pressure-ratio-range of 2.0 to 6.0. Measurements of acoustic power of various perforated tubes were also performed.4. Evaluation of General Performance of Advanced Noise Suppressors: Slotted tubes suffered from smaller thrust loss compared to perforated tubes. The performance of noise reduction of slotted tubes was inferior to perorated tubes. From overall view point, a tube with forward slanted perforation with a porosity of 0.03 (practical value) showed best performance among all tested tubes.5. Presentation and publishment :The results of the present research have been presented at 7th ISAIF (Tokyo, 2005), 12th ICSV (Lisbon, 2005), 13th ICSV(2006,Vienna), ASA/AS Joint meeting (Honolulu, 2006), internoise 2006 (Honolulu, 2006) and at another 4 international conference and 19 papers have been published.