喷管间距对双喷流啸音影响的实验

实验详细测量了完全膨胀马赫数范围为110~160、喷管间距为16到32倍喷管出口直径的超声速双喷流近声场,分析了两个喷流各自发出的啸音在近声场的相位关系,研究了喷管间距对双喷流耦合的影响。结果表明:对比单喷流,双喷流耦合啸音在A模态时,呈现出反对称或对称模式,在反对称模式下,喷管中间区域啸音强度减小,对称模式下,双喷流中间区域啸音强度略大于单喷流啸音；B模态时，两个处于摆动模态的喷流啸音在喷管中间区域同相而发生耦合,极大地增强了B模态的幅值,达到160dB；C模态的相位关系还需进一步研究。对比不同喷管间距下的双喷流近声场,发现喷管间距过小或过大均不利于B模态的耦合；喷管间距对C模态影响最大,当喷管间距变大时,C模态幅值及主导马赫数范围均增大。 

Experiment of the effect of nozzle spacing on twin jet screech tones

The near field of the supersonic twin jet noise was measured experimentally with fully expanded Mach number ranging from 110 to 160 and nozzle spacing from 16-32 times of nozzle outlet diameter. The phase difference of the near field screech tones radiated from the two jets was analyzed in detail, and the effect of nozzle spacing on the coupling of the twin jet was explored. The experimental results showed that there were two different patterns for the A mode of twin jet screech tone, ie:symmetric and antisymmetric along the central plane of the two nozzles. In the antisymmetric mode, the intensity of the screech tone in the inter nozzle region decreased, which was slightly larger than the amplitude of the single jet in the symmetric mode. For the twin jet operating in B mode, the screech tone generated by the two jets were in phase in the inter nozzle region, which reinforced the oscillation of the twin jet, and the amplitude of the screech tone in the inter nozzle region can reach to 160dB. The phase difference of the C mode needs further study. Comparing the results with different nozzle spacing, it was found that the coupling was suppressed for the B mode when the nozzle spacing was larger or smaller, while both the amplitude and the dominant Mach number range of the C mode increased with the nozzle spacing.