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为了研究激光推进技术中液体工质的最优掺杂浓度,进行了激光烧蚀掺杂甘油液体工质的冲量耦合特性实验研究。实验中采用10ns脉宽的Nd:YAG激光器烧蚀粘性液体甘油,在甘油中混合了不同浓度的纳米碳粉作为掺杂剂,以提高对激光能量的吸收。运用阴影测量法观测了激光烧蚀羽流的喷射过程,对不同掺杂浓度甘油的烧蚀产物、等离子体膨胀、激波传播、飞溅现象进行了对比分析;运用激光干涉扭摆法测量了烧蚀冲量,并分析了掺杂浓度对冲量耦合系数的影响。实验结果表明,掺碳后甘油的喷射行为、激波速度和冲量都发生了改变,而且掺碳后甘油的冲量耦合系数和比冲有了显著提高。综合分析得到1%浓度碳粉是甘油的最优掺杂浓度,此时冲量耦合系数从无掺杂时的67 m N·s/J提高到1250m N·s/J。
In order to study the optimum doping concentration of liquid working fluid in laser propulsion technology, the impulse coupling characteristics of laser ablation doping glycerin liquid were experimentally studied. Experiments using 10ns pulse width Nd: YAG laser ablation of viscous liquid glycerol, glycerol mixed with different concentrations of nano-carbon powder as a dopant to improve the absorption of laser energy. The injection process of laser ablation plume was observed by shadow measurement method. The ablation products of different doping concentrations of glycerin, plasma expansion, shock wave propagation and spattering were compared and analyzed. The laser interference torsion method was used to measure the ablation Impulse, and analyzed the doping concentration impulse coupling coefficient. The experimental results show that the injection behavior, the shock velocity and the impulse of glycerol have all changed after carbon doping, and the impulse coupling coefficient and specific impulse of glycerol have been significantly increased after carbon doping. The results showed that 1% carbon powder was the optimal doping concentration of glycerol, and the impulse coupling coefficient increased from 67 m N · s / J without doping to 1250 m N · s / J.