Three-Dimensional Numerical Analysis of Longitudinal Thermoacoustic Instability in a Single-Element Rocket Combustor
Three-Dimensional Numerical Analysis of Longitudinal Thermoacoustic Instability in a Single-Element Rocket Combustor
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DOI：
10.3389/fenrg.2022.835977
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
Kangkang Guo;Xu Boqi;Yongjie Ren;Yiheng Tong;W. Nie
中科院分区：
文献类型：
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作者：
Kangkang Guo;Xu Boqi;Yongjie Ren;Yiheng Tong;W. Nie
本文采用雷诺平均N-S方法和大涡模拟相结合的方法，对某火箭燃烧室的热声燃烧不稳定特性进行了数值模拟。采用小火焰面生成流形方法处理湍流-燃烧相互作用。对一个不稳定的情况进行了详细的反应机理模拟(GRI-Mech 3.0)。在压力振荡频率和功率谱密度谱方面，得到的结果与普渡大学的实验数据符合得很好。通过动态模型分解方法，确定燃烧不稳定模式与燃烧室第一纵声模耦合。根据瑞利指数分析发现，不稳定的驱动源位于燃烧室台阶附近，时间平均流场进一步证实了这一点。详细地跟踪了燃烧室台阶处三维涡环脱落的演化过程，具有很好的时间分辨率。结果表明，燃烧不稳定是由于燃烧室台阶处周期性涡环脱落并与燃烧室壁面相互作用造成的。未燃烧的反应物被脱落的涡环卷起，直到与腔壁相撞才会解体。因此，混合性能显著提高，导致突然放热。因此，热能被添加到声场中，从而增强了第一纵模，引起了大幅度的轴向速度振荡，从而促使新涡环的产生。本次研究的结果将为高性能火箭发动机的设计和开发提供支持。
This study numerically investigated the thermoacoustic combustion instability characteristics of a scaled rocket combustor based on a hybrid of the Reynolds-averaged Navier–Stokes and large–eddy simulation method. The turbulence–combustion interactions were treated using flamelet generated manifold approach. An unstable case was simulated with detailed reaction mechanisms (GRI-Mech 3.0). The obtained results agree well with experiment data from Purdue University, in terms of pressure oscillations frequency and power spectral density spectrum. The combustion instability mode was identified to be coupled with the first longitudinal acoustic mode of the combustion chamber by dynamic model decomposition method. According to Rayleigh index analysis, the unstable driving source was found to be located near the combustor step, which was further confirmed by time-averaged flow fields. Detailed three-dimensional vortex ring shedding evolutions at the combustor step were tracked with fine time resolution. Results indicate that the combustion instability arises from periodic vortex ring shedding at the combustor step and interacting with the chamber wall. The unburnt reactants were rolled up by the shedding vortex ring, which would not break up until impact with the chamber wall. Therefore, the mixing performance was significantly enhanced, leading to sudden heat release. Consequently, the thermal energy is added to the acoustic field, and the first longitudinal mode is thus reinforced, giving rise to large amplitude axial velocity oscillations which prompt the generation of the new vortex ring. The results of the present investigation will support the design and development of high-performance rocket engines.