激光支持等离子体爆轰波流场研究

Evolution of Laser Supported Detonation Waves

采用高速纹影摄影法记录激光支持等离子体爆轰波流场的演化,得到流场冲击波阵面形状和尺寸随时间变化规律。建立激光支持等离子体爆轰波流场演化的物理模型,采用计算流体力学方法模拟计算激光击穿空气后,激光作用时间内及激光作用结束后等离子体流场演化过程。结果表明,纹影摄影法能有效观测到激光支持等离子体爆轰波的传播情况。等离子体爆轰波在激光作用初期为椭球形,随着时间的增加逐渐转变为球形。计算的等离子体爆轰波流场密度分布图与实验结果基本吻合。

When a high intensity laser beam is focused into quiescent air, a laser induced plasma detonation wave is generated, which can be used for laser propulsion. It is important to study the ignition, growth and propagation of the laser supported detonation waves. In this paper a high speed shadow photography technique was used for recording the temporal evolution of laser induced plasma in air. A sequence of shadow photos were obtained. The experiments show that the shape of the shock wave front was elliptical in the early time and turned into spherical shape in the later time. Based on the experimental results, a physical model of laser induced plasma detonation waves is developed. In this model it is assumed that the shape of the focal area is elliptical and the laser energy is added into the conversation equation as the energy source. The numerical simulation study on the detonation wave flow field evolution was carried out using a gas dynamics code. The plasma temperature, shock wave pressure, air density and shock wave front radius were calculated. The calculated density distribution is in good agreement with the experimental results.