激光聚焦点火区域流场演化的数值研究

激光聚焦点火区域形成的低密度球腔会制约吸气式高重频脉冲激光推进发动机的稳定工作。基于球形点火模型,用数值计算方法研究了等离子体的初始温度对球腔大小的影响以及球腔的演化特点。研究表明,当等离子体的能量较大时,它的初始温度对球腔大小的影响较小;球腔的密度不足环境气体密度的0.1倍,温度高达几千K,压强接近环境气体压强;球腔半径与等离子体动力学半径的比值稳定在0.29左右。通过对球腔演化规律的分析,为激光器参数的控制和聚焦系统的设计提供了一定的参考依据。

Numerical investigation on evolution of flow field in ignition area formed by laser focusing

The low density cavity in the ignition area formed by laser focusing can restrict the steady work of highly repetitive frequency air-breathing pulsed laser propulsion.The influence of the initial temperature of the plasma on the cavity size is studied and the evolution characteristic of the cavity is calculated numerically based on the global ignition model.The results suggest that the initial temperature of the plasma has little influence on the cavity size when the energy of the plasma is larger.The density in the cavity is lower than the tenth of the circumstance gas and its temperature is higher than several thousand K.Its pressure approaches that of the circumstance gas.The ratio between the radius of the cavity and the dynamic radius of the plasma stabilize about 0.29.It provides helpful insights for the control of laser parameters and designing focusing system by analyzing the characteristic of the cavity.