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首页> 外文会议>AIAA/CEAS aeroacoustics conference >Effects of Extended Expansion Ramps on Flow and Acoustic Field of Low Supersonic Single Expansion Ramp Nozzles
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Effects of Extended Expansion Ramps on Flow and Acoustic Field of Low Supersonic Single Expansion Ramp Nozzles

机译：扩展膨胀斜面对低超声速单膨胀斜面喷嘴的流动和声场的影响

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摘要

The primary objective of this paper is to characterize the flow and acoustic field of high aspect ratio Single Expansion Ramp Nozzles and investigate changes in the characteristics when fitted with expansion ramps of different length past the exit of the nozzle. Nozzles under study have high throat aspect ratios ranging from 6 to 9 and the lengths of the ramps added range from 2.1 inches to 9 inches. Nozzles under study have an area ratio of 1.176 with the design Mach number of 1.5. The study is performed at both the design and off-design conditions. Flow field investigation showed that there is asymmetry in the structure of the jet potential core, shear layer, and shock cell system due to asymmetry in the diverging side of the nozzle about its major axis which results in azimuthal variation in the acoustic signature around the jet. Instability frequencies increase with the increase in nozzle aspect ratio and can be accurately predicted for any flow conditions. Increasing the aspect ratio of the nozzle increases the frequencies of other shock associated noise components as well. Amplitude of the fundamental instabilities can be up to 30 dB higher than the rest of the jet noise. Upon extension of the expanding side of the nozzle, these instabilities can be weakened or mitigated with a considerable reduction of overall sound pressure level in the ambience of the jet.
机译：本文的主要目的是表征高纵横比的单膨胀斜面喷嘴的流场和声场，并研究在安装了不同长度的膨胀斜面后经过喷嘴出口时特性的变化。所研究的喷嘴的高喉宽比为6到9，增加的坡道长度为2.1英寸到9英寸。研究中的喷嘴的面积比为1.176，设计马赫数为1.5。该研究是在设计和非设计条件下进行的。流场研究表明，由于喷嘴绕其主轴的发散面不对称，导致喷流势能芯，剪切层和激波单元系统的结构存在不对称性，从而导致喷流周围的声学特征发生方位角变化。 。不稳定频率随着喷嘴长宽比的增加而增加，并且可以在任何流动条件下准确预测。增加喷嘴的纵横比也会增加其他与冲击相关的噪声分量的频率。基本不稳定性的幅度可能比其余的喷气噪声高30 dB。在喷嘴的扩展侧延伸时，这些不稳定性可以通过在喷射器周围环境中总体声压水平的显着降低而减弱或减轻。

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