【作者】 杜江；

【导师】 杜朝辉； 欧阳华；

【作者基本信息】 上海交通大学 ， 动力机械及工程， 2010， 博士

【摘要】 近十几年以来,有关空腔方面的研究已成为空气动力学界的一个研究热点,大多数研究工作局限于跨音速或超音速等气流条件下,简单腔体的气动声学特性研究,而在普通的工程实践中,气流速度通常小于声速,并且腔体结构比简单空腔更为复杂。在较低气流速度下,复杂结构腔体气动声学特性的研究更具有广泛的实用价值。尽管目前国内外关于气流流过简单空腔所引发的边界层分离、气动噪声、压缩波—剪切层相互干扰等一系列复杂问题的研究工作和发表的成果较多,但是关于复杂结构腔体方面的研究比较少见,公开发表成果也较少。本文以插入管型消声器和油液分离器模型两种常见复杂结构腔体为研究对象,采用实验测试、理论分析和有限元数值分析相结合的研究手段,对该两种复杂结构腔体的气动声学特性进行了较为详尽的研究,并对其峰值频率进行了预测,最后总结出复杂结构腔体气动声学特性研究的一般方法。本文主要的研究工作包括:1、研制了以低压低速开放式消声风洞为气流源的复杂结构腔体气动声学特性测试实验台。分析了流动、尾管、腔体、以及腔体内部流—声反馈机制等因素的影响。2、研究发现:插入管型消声器的主要气动声学特性包含三类哨音。第一类哨音同时出现在消声器内部和外部,与尾管声学模态关系密切;第二类哨音在小长径比消声器内外部均未出现,而出现在中长径比消声器内部和外部,且仅出现在大长径比消声器的内部,与腔体声学模态密切相关;第三类哨音在中、小长径比消声器内部出现,而未出现在大长径比消声器内部和外部,与腔体内部流—声反馈机制关系密切。3、分别采用一维平面波分析法、声传递矩阵法和二维理论分析法推导出插入管型消声器穿透损失的计算公式,并对各种方法进行了比较。同时研究表明,采用一维平面波分析法和三维有限元数值分析法预测第一类和第二类哨音的峰值频率是有效的和准确的。4、研究发现:油液分离器模型的主要气动声学特性包含两类哨音。第一类哨音同时在其内部和外部,与腔体的声学模态关系密切;第二类哨音仅出现在其外部,与尾管声学模态密切相关。5、油液分离器模型气动声学特性的分析方法目前仅限于一维平面波分析法和三维有限元数值分析法,而声传递矩阵法和二维理论分析法暂时无法使用。同时研究表明,采用一维平面波分析法和有限元数值分析法预测第一类哨音的峰值频率是有效的和准确的;对于第二类哨音峰值频率的预测,仅有一维平面波分析法是有效的和准确的,而有限元数值分析法是不适用的。6、将原本应用于简单空腔的修正Rossiter公式进行再次修正后应用于复杂结构腔体气动声学特性的研究。7、总结出复杂结构腔体气动声学特性研究的一般方法。更多还原

【Abstract】 Many aerodynamic investigations have been focused on the study of cavity problems over the past decades and most of them have been carried out on the simple cavity with transonic and supersonic speeds. But the cavity structures are more complex and the flow speeds are usually lower than the sound speed in the common engineering practices. So, the studies on aeroacoustic characteristics of the cavity with complex structure at quite low speeds are more valuable. However, there are few studies and published papers that focus on the problems of cavity with the complex structure, although many investigations have been carried out on the studies of some quite difficult problems for the simple cavity by the researchers at home and abroad, such as the shear layer separation, the aerodynamic noise, the interactions between compressed wave and shear layer, etc..The insert pipe muffler and the oil separator model were selected as the major research objects in present study. The studies on aeroacoustic characteristics of them were carried out and analyzed quite in detail by the experiments, the theory analysis and the FEM analysis. Moreover, the whistle tone frequencies are predicated. Finally, a general study method on the aeroacoustic characteristics of cavity with complex structure is put forward in this dissertation. The major research contents are presented as follows,1、The experimental test rig of study on the aeroacoustic characteristics of cavity with complex structure was set up and the flow was supplied by an open circuit centrifugal fan driven wind tunnel with low pressure and low speed. The effects of flow, tailpipe, cavity, flow-acoustic feedback loop inside the cavity, etc. were detailed analyzed.2、Three types of the whistle tones are included mainly in the aeroacoustic characteristics of insert pipe muffler. The first one appears both inside and outside the mufflers and it is closely related with the acoustic modes of tailpipe. The second one is not captured both inside and outside the muffler with small length-to-diameter ratio (L/D), but appears both inside and outside the muffler with middle L/D, and only inside the muffler with large L/D. Furthermore, it has a close relationship with the acoustic modes of cavity. The third one is captured only inside the mufflers with small and middle L/Ds, but disappeared both inside and outside the muffler with large L/D. Moreover, it is generated by the flow-acoustic feedback loop inside the cavity.3、The transmission loss (TL) formula of insert pipe muffler is given by the plane wave method, the acoustic transfer matrix method, and the two-dimensional theory method, as well as the comparisons of these methods are also presented. Furthermore, it is proved that the whistle peak frequencies of the first type and the second type whistle tones can be predicated accurately by the plane wave method and the 3D FEM method.4、Two types of the whistle tones are included mainly in the aeroacoustic characteristics of oil separator model. The first one appears both inside and outside the oil separator model and it is closely related with the acoustic modes of cavity. The second one is only captured outside the oil separator model and it has a close relationship with the acoustic modes of tailpipe.5、The study on aeroacoustic characteristics of the oil separator model can be carried out by the plane wave method and the 3D FEM method but not for the acoustic transfer matrix method and the two-dimensional theory method at present time. Moreover, it is found that the whistle peak frequencies of the first type whistle tones can be predicated accurately by the plane wave method and the 3D FEM method and for the second type whistle peaks, the plane wave method can be used efficiently but the 3D FEM method are not suitable for predication of the whistle peak frequencies.6、The study on aeroacoustic characteristics of the cavity with complex structure has been carried out by the Rossiter’s re-modified formula, which is revised based on the Rossiter’s modified formula that is widely used in the investigations of simple cavity problem.7、A general study method on the aeroacoustic characteristics of cavity with complex structure is put forward.更多还原