圆盘结构下旋转爆震波的不稳定传播特性

Characteristics of unstable propagation of rotating detonation wave in plane-radial structure

为研究圆盘结构下旋转爆震波的不稳定传播特性,以2H2+O2+3.76N2为反应混合物,开展该结构下的二维数值研究。详细分析了旋转爆震波不稳定传播模态的流场特征,以及爆震波参数、出口流场参数和增压比的变化。结果表明,不稳定传播模态下,旋转爆震波重复进行"解耦—再起爆"过程,内圆扩张曲面的发散作用,使出口附近的爆震波首先解耦,解耦区域逐渐往流场内部扩张;反射激波与前导激波的碰撞产生局部热点,促使爆震波重新起爆;爆震波的压力、温度以及传播速度皆随爆震波的解耦及再起爆过程发生变化;旋转爆震波的不稳定传播对出口速度分量及马赫数的影响很小;出口增压比受不稳定传播的影响较大,随时间呈周期性变化,变化幅值较高且不稳定。出口增压比的循环周期与爆震波"解耦—再起爆"的周期一致,稳定后两者的循环频率约为21.6kHz。

To reveal the characteristics of unstable propagation of the rotating detonation wave in the plane-radial structure,a two-dimensional numerical simulation of the structure was conducted with 2 H2＋O2＋3.76 N2 being the reaction mixture.The flow field structure under the unstable propagation mode was analyzed,as well as variation of detonation parameters,flow parameters and the pressure amplification ratio at the exit.Results indicate that decoupling and re-initiation of the rotating detonation wave occur repeatedly under the unstable propagation mode.The diffraction of the inner circle geometry weakens the intensity of the detonation wave.The detonation wave decouples first near the exit,and then the decoupling region expands to the interior flow field gradually.The collision of the reflected wave and the leading shock wave urges the formation of the hot spot in the flow field,initiating the detonation wave again.The detonation pressure,temperature and propagating velocity vary with the＂decoupling and re-initiation＂process of the detonation wave.The unstable propagation of the rotating detonation wave has only a small effect on the velocity components and Mach number in the exit,but a significant effect on the exit pressure amplification ratio.The pressure amplification ratio varies periodically with time,and the amplitude is high and unsteady.The cycle period of the pressure amplifying ratio is consistent with the period of＂decoupling and re-initiation＂process,and the cycle frequency is about 21.6 kHz after dynamic stability.