掺杂对甘油激光烧蚀冲量耦合特性的影响

Effects of Dopant on Impulse Coupling of Laser Ablated Glycerin

关键词:  液体工质  掺杂  激光烧蚀  冲量耦合  激光推进

Key words:  Liquid propellant  Dopant  Laser ablation  Impulse coupling  Laser propulsion

摘要:

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 mN·s/J提高到1250mN·s/J。

Abstract:

Impulse coupling characteristics of laser ablated doped glycerin was experimentally studied in order to obtain the optimal dopant concentration in liquid propellant of laser propulsion. Nd:YAG laser of 10 ns pulse width and glycerin solution were used in experiment，and carbon nano-particle as dopant in glycerin to improve laser energy absorption was proposed. Shadow imaging technique was used to analyze ejection of ablation. Ablation resultant，plasma expansion，shock wave propagation and splashing behavior were comparatively analyzed with different dopant concentration glycerin. Torsional balance system was used to measure impulse，and influence of dopant concentration on impulse coupling coefficient was studied. Experimental results show that because of carbon nanoparticles dopant，the ejection behavior，shockwave velocity and impulse have been changed. The coupling coefficient and specific impulse enhanced evidently. Comprehensive analysis show that 1% was the optimal dopant concentration of carbon nano-particles in glycerin and the impulse coupling coefficient of laser ablated glycerin was improved from 67 mN·s/J to 1250 mN·s/J by doped 1% carbon nano-particles.