Three-Dimensional Numerical Simulations of Spherical Flame Evolutions in Shock and Reshock Accelerated Flows
Three-Dimensional Numerical Simulations of Spherical Flame Evolutions in Shock and Reshock Accelerated Flows
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DOI：
10.1080/00102202.2013.798656
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发表时间：
2013-05
影响因子：
1.9
通讯作者：
Yuejin Zhu;G. Dong;Yixin Liu
中科院分区：
文献类型：
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作者：
Yuejin Zhu;G. Dong;Yixin Liu
采用具有单步Arrhenius化学反应的可压缩反应Navier-Stokes方程，对入射和反射激波在矩形激波管内引起的三维球形火焰演化进行了数值模拟。考虑了火焰大小和数量、激波强度和混合气反应性等参数的变化情况，研究了这些参数对火焰演化和爆轰起爆的影响。得到了激波-火焰相互作用的三维可视化结果以及随时间变化的积分和统计结果。所有研究的火焰演化形态都显示出激波，特别是反射激波干扰下火焰的严重畸变、膨胀和波纹。随着火焰数量、激波强度或混合物反应性的增加，不稳定火焰产生三维反应性激波分岔（RSB）结构。此外，在不同情况下，爆轰可以通过冲击-爆轰-过渡（SDT）机制发生在火焰演化后期的不同三维空间位置。不同于研究案例中火焰模式和爆轰起爆位置的三维空间差异性，爆轰开始前火焰发展的时变积分和统计特性显示所有案例的行为更为相似。在激波和再激波的传递过程中，球形火焰受到压缩和扭曲，导致火焰内部涡量沉积，燃烧气体和未燃烧气体混合良好。物理过程主导了火焰演化的压缩阶段。随着激波和再激波的通过，充分的混合促进了化学热的释放，并使扭曲的火焰膨胀（加速）。化学过程变得更加突出，特别是在再冲击条件下。在火焰膨胀阶段，斜压效应减弱，旋涡拉伸效应随着火焰的发展而增强。此外，激波通过的充分混合促进了火焰的化学反应，而化学反应又烧毁了火焰的混合区，从而抑制了混合。
The three-dimensional spherical flame evolutions induced by incident and reflected shock waves in a rectangular shock tube are numerically simulated using the compressible reactive Navier–Stokes equations with a single-step Arrhenius chemical reaction. Four cases, including variable parameters of flame size and number, shock wave strength, and mixture reactivity, are considered in order to investigate the effects of these parameters on the flame evolutions and detonation onsets. The three-dimensional visualized results and the time-dependent integral and statistical results for the shock–flame interactions are obtained. The morphology of the flame evolutions for all cases studied shows the severe distortion, expansion, and corrugation of flame disturbed by shock waves, especially by a reflected shock wave. The unstable flame produces the three-dimensional reactive shock bifurcation (RSB) structure, as the flame number, the shock wave strength, or the mixture reactivity increase. Further, detonations can occur in a later stage of flame evolution at the different three-dimensional spatial locations for different cases through the shock–detonation–transition (SDT) mechanism. Unlike the three-dimensional spatial dissimilarities of flame patterns and detonation initiation locations among cases studied, the time-dependent integral and statistical properties of flame developments prior to detonation onset show the more similar behaviors for all cases. During the passage of shock and reshock waves, the spherical flames are compressed and distorted, resulting in the vorticity deposition within flame and the well-mixing between the burned and unburned gases. Physical process dominates the compression phases of the flame evolution. Following the passage of the shock and reshock waves, the well-mixing facilitates the chemical heat release and expands (accelerates) the distorted flame. The chemical process becomes more prominent, especially under the reshock condition. In the flame expansion phases, the baroclinic effect is weakened, and the vortex stretching effect is enhanced with the development of flame. In addition, the well-mixing by the passages of shock waves promotes the chemical reaction of the flame, which in turn burns out the mixing zone of flame and therefore inhibits the mixing.