自维持合成双射流对超声速燃烧室凹腔质量交换特性影响研究

Study on Effects of Self-Sustaining Dual Synthetic Jet to Mass Exchange Characteristics of Scramjet Combustor Cavity

关键词:  燃烧室凹腔  自维持合成双射流  质量交换  流动控制  驻留时间

Key words:  Scramjet combustor cavity  Self-sustaining dual synthetic jet  Mass exchange  Flow control  Residence time

摘要:

为了改善燃烧室凹腔与主流的掺混性能，提出了一种利用凹腔内压力差形成自维持合成射流的流场控制方法，在超声速冷流条件下，采用动网格技术对激励器的膜片振动过程进行模拟，详细分析了自维持合成双射流与凹腔相互作用的过程，研究了激励器出口位置、参数、凹腔构型以及来流Ma数等参数的影响。结果表明:加入自维持合成双射流激励器可以大幅提升凹腔的质量交换特性，减小气体在凹腔内的驻留时间；且激励器出口位置分布对控制效果影响较大，当激励器出口位于凹腔底部中间位置时，质量交换率最大能够提升49%。此外，凹腔构型以及来流条件都会影响自维持合成双射流对凹腔掺混的控制效果，在相同来流条件下，凹腔长深比越大，控制效果越显著，自维持合成双射流能使长深比L/D=7.76的凹腔质量交换率提升115%；对于同一凹腔，随着来流马赫数增加，激励器对凹腔质量交换特性控制效果提升更为明显，但改变振动膜片的振幅和频率对控制效果的改善不明显。

Abstract:

In order to enhance the mixing characteristic of cavity with mainstream in the scramjet engine， a flow field control method using self-sustaining dual synthetic jet is proposed by utilizing the pressure difference in the cavity. Adapting dynamic mesh technology， periodical vibration of the membrane are numerically studied under supersonic cold flow， and the interactions between self-sustaining dual synthetic and cavity are analyzed in detail. The impacts of outlet positions， driving parameters， cavity configurations and Mach numbers on control effects are mainly researched. The results show that self-sustaining dual synthetic jet actuator can improve the mass exchange characteristics of cavity and reduce the residence time of gas in the cavity. The position of the actuator’ outlet has a great influence on the control effect. The mass exchange rate can be improved by 49.2% when the position of outlet is located in the middle of cavity floor. Besides， cavity configurations and Mach numbers can also make a difference to the mixing characteristic. The results suggest that the cavity with a longer ratio of length and diameter (L/D) can obtain a better control effect when using self-sustaining dual synthetic jet actuator， and the mass exchange rate of cavity with L/D=7.76 can increase by 115%. For the same cavity， the mass exchange rate is improved when increasing the fluid velocity， but when changing amplitudes and frequencies of the membrane， the control effects are not obvious.