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吸气式激光推进的激光能量沉积过程主要发生在激光支持的爆轰波(LSD波)的形成与演化阶段,分析LSD波的传播规律和影响因素对揭示能量沉积机理起到基础性作用。利用纳秒四分幅高速相机和延长光路的纹影系统,拍摄了不同聚焦角度下CO2激光经透镜聚焦击穿空气流场的纹影照片,结合一维理论公式分析了LSD波速度。结果表明:在本文的实验条件下,吸气式激光推进击穿空气经历了LSD波和激光支持的燃烧波(LSC波)两个阶段,LSD波阶段的持续时间约7.1μs;3种聚焦角度下LSD波速度与理论公式预测的整体趋势比较吻合;聚焦角度越小,LSD波的初始速度越大,聚焦角度θ=4.29°时实验数据达到约14km/s。
Laser energy deposition process of aspirated laser propulsion mainly occurs in the formation and evolution of laser-supported detonation wave (LSD wave). Analyzing the propagation law and influencing factors of LSD wave plays a fundamental role in revealing energy deposition mechanism. Using the nanosecond high-speed four-camera and the lenticular lens system with extended optical path, we took the smear images of the CO2 laser focused lens through the lens and focused the punctured air flow field. The LSD wave velocity was analyzed based on the one-dimensional theoretical formula. The results show that under the experimental conditions, the aspirated laser propels the breakdown air to two stages, LSD wave and laser-supported combustion wave (LSC wave), the duration of LSD wave phase is about 7.1μs. Three kinds of focusing angles The LSD wave velocity is in good agreement with the overall trend predicted by the theoretical formula. The smaller the focusing angle is, the larger the initial velocity of the LSD wave is and the experimental data reaches about 14 km / s when the focusing angle θ = 4.29 °.