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为研究纳秒脉冲激光烧蚀典型材料推进流场瞬态流动过程,采用流场显示阴影技术,实现纳秒级时间分辨率、毫米级空间分辨率的流场演化信息定量测量,解决激光烧蚀推进羽流的时间、空间高分辨率测量难题。对典型金属材料铝和典型聚合物材料的流场特性进行测量分析,并研究激光能量密度对羽流特性的影响。在典型时间尺度上,定性分析激光作用典型材料羽流特征与推进性能之间的关系。由于纳秒激光峰值功率高,当烧蚀金属材料Al时容易形成高温高压的等离子体羽流,等离子体喷射速度超过17km/s,等离子体羽流在百纳秒时间尺度离开靶面,对靶的力的耦合结束;当烧蚀聚合物PMMA和PVC材料时,PVC材料羽流喷射以等离子体和细小颗粒为主,喷射量较大且集中、方向性好,实验测量得到PVC工质真空羽流速度达到1500m/s,因此带来的反喷冲量以及推力都会较高。
In order to study the transient flow process of nanosecond pulsed laser ablation, a flow field display shadow technique was used to quantitatively measure the flow field evolvement information of nanosecond time resolution and millimeter spatial resolution to solve the problem of laser ablation Promote the plume of time, high-resolution space measurement problems. The flow field characteristics of typical metallic materials such as aluminum and typical polymer materials were measured and analyzed, and the influence of laser energy density on plume characteristics was also studied. In a typical time scale, qualitative analysis of the relationship between laser plume characteristics and propulsion performance of a typical material. Due to the high peak power of nanosecond laser, a high temperature and high pressure plasma plume is easily formed when the metal material Al is ablated. The plasma jet velocity exceeds 17 km / s, and the plasma plume leaves the target surface on the hundred nanosecond time scale. When the polymer PMMA and PVC materials are ablated, the plume of PVC material is dominated by plasma and fine particles, and the jetting amount is large and concentrated with good directivity. The PVC plume Flow rate reached 1500m / s, so bring the anti-injection volume and thrust will be higher.