凹腔长深比对超声速燃烧室内振荡现象的影响
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摘要
为研究不同长深比的凹腔对超声速燃烧室内的流动状况及自激振荡现象的影响,采用数值模拟方法改变凹腔长深比由2至6研究入口来流马赫数为1.58的超声速燃烧室内的压力振荡现象,计算捕捉到了超声速燃烧室中的压力脉动和凹腔剪切层拟序结构的演化过程以及振荡频率和声压级的变化.研究发现:凹腔内剪切层状态决定凹腔前后缘激波的强弱;随着长深比增加,振荡增强、声压级变大,而振荡频率整体向低频转变;长深比不同时振荡主频也在变化.剪切层波动与声波传播相互耦合是导致自激振荡现象的主要原因.
In order to study the influence of different ratio of length to depth of cavity on the flow field and self-oscillation in supersonic combustion chamber, numerical simulation method is used by changing the ratio of length to depth from 2 to 6 to observe the phenomenon of pressure oscillation in supersonic combustion chamber when the inlet stream Mach number is 1.58. The scramjet combustor pressure pulsation, the cavity shear layer coherent structure evolution process and the change of oscillation frequency and sound pressure level were captured. It was found that the strength of the leading and trailing edge shock wave depends on the state of cavity shear layer. With length to depth ratio increased, the strength of oscillation and the sound pressure level increased, the overall oscillation frequency shifted to lower frequency. The ratio of length to depth affects the peak frequency too. The coupling between shear layer and acoustic wave is the major cause of self-excited oscillation in supersonic combustion chamber.
In order to study the influence of different ratio of length to depth of cavity on the flow field and self-oscillation in supersonic combustion chamber, numerical simulation method is used by changing the ratio of length to depth from 2 to 6 to observe the phenomenon of pressure oscillation in supersonic combustion chamber when the inlet stream Mach number is 1.58. The scramjet combustor pressure pulsation, the cavity shear layer coherent structure evolution process and the change of oscillation frequency and sound pressure level were captured. It was found that the strength of the leading and trailing edge shock wave depends on the state of cavity shear layer. With length to depth ratio increased, the strength of oscillation and the sound pressure level increased, the overall oscillation frequency shifted to lower frequency. The ratio of length to depth affects the peak frequency too. The coupling between shear layer and acoustic wave is the major cause of self-excited oscillation in supersonic combustion chamber.
引文
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[10] Ben-Yarkar A,Hanson R K. Supersonic combustion of cross-flow jets and the influence of cavity flame-holders[J]. AIAA,2011,30(1):49-71.
[11]汪洪波.超声速燃烧凹腔剪切层非定常特性研究[D].长沙:国防科学技术大学,2007.
[12] Thangamani V,Kurian J. Control of cavity oscillations in a supersonic flow by microjet injection[J]. Journal of Aircraft,2013,50(4):1305-1309.
[2] Dussauge J P,Piponniau S. Shock/boundary-layer interactions:possible sources of unsteadiness[J]. Journal of Fluids and Structures,2008,24(8):1166-1175.
[3] Li W,Nonomura T,Fujii K. On the feedback mechanism in supersonic cavity flows[J]. Physics of Fluids,25,2013,056101.
[4] Rossiter J E. Wind tunnel experiments of the flow over rectangular cavities at subsonic and transonic speeds[R]. A RCR and M,1964:3458.
[5] Heller H H,Bliss D B. Aerodynamically induced pressure oscillations in cavities[R]. Physical Mechanisms and Suppression Concepts. AFFDL-TR-74-133,1975.
[6] Bilanin A J,Covert E E. Estimation of possible excitation frequencies for shallow rectangular cavities[J]. AIA A Journal,1973,11(3):347-351.
[7] Tam C K W,Block P J W. On the tones and pressure oscillations induced by flow over rectangular cavities[J]. J Fluid Mech,1978,89(2):373-399.
[8]ünalmis N?H,Clemens N T,Dolling D S. Cavity oscillation mechanisms in high-speed flows[J]. AIAA Journal,2012,42(10):2035-2041.
[9] Kumar M,Vaidyanathan A. On shock train interaction with cavity oscillations in a confined supersonic flow[J]. Exp Therm Fluid Sci,2017. doi:10.1016/j.expthermflusci.2017.08.009.
[10] Ben-Yarkar A,Hanson R K. Supersonic combustion of cross-flow jets and the influence of cavity flame-holders[J]. AIAA,2011,30(1):49-71.
[11]汪洪波.超声速燃烧凹腔剪切层非定常特性研究[D].长沙:国防科学技术大学,2007.
[12] Thangamani V,Kurian J. Control of cavity oscillations in a supersonic flow by microjet injection[J]. Journal of Aircraft,2013,50(4):1305-1309.