超声速气流中激光烧蚀金属壁面诱导等离子体点火机理及强化方法研究

Laser-induced plasma (LIP) ignition method has the advantages of spatially adjustable ignition locations, precisely controlled energy and frequency, and also minimum interference to the flowfield due to the absence of the electrodes, which is a promising ignition method in both scientific research and industry application fields. According to previous study, the plasma induced by laser ablation on metal walls could enhance the ignition process obviously comparing to the conventional LIP ignition method. Therefore, this project focuses on the laser ablation on metal walls induced plasma (LAMWIP) ignition process in a supersonic flow with a combination of advanced optical measurements, high resolvation numerical simulations and classical theoretical analysis. The effect of LAMWIP on the ignition process will be discussed and the flame kernel formation and propagation mechanisms of the LAMWIP ignition process inside a cavity flameholder will also be revealed. Then, the ignition mechanism of the LAMWIP ignition process and the corresponding ignition enhancement methods will be achieved. By conducting this project, theoretical foundation of revealing the ignition mechanism and enhancement methods of LAMWIP ignition process in a supersonic flow will be provided, new conceptions of reliable and repeatable ignition system for future hypersonic flight vehicle will also be proposed.

激光诱导等离子体点火方式具有点火位置、能量和频率可调节并且对流场无干扰等特点，在超声速气流中点火过程的学术研究和工程技术领域具有重要应用前景。申请人前期研究发现，相对于激光击穿空气诱导等离子体点火，采用激光烧蚀金属壁面诱导等离子体的点火方式能够起到明显的强化点火作用。鉴于此，本项目以超声速气流中激光烧蚀金属壁面诱导等离子体点火过程为研究对象，采用先进光学观测手段、高精度数值模拟方法以及经典理论分析相结合的方式，辨析激光烧蚀金属壁面对点火过程的影响及其作用机理，阐明在激光烧蚀金属壁面条件下凹腔点火过程中的火核形成与初始火焰传播机理，进而获得在激光烧蚀金属壁面诱导等离子体条件下的凹腔点火过程机理并发展相应的点火强化方法。本项目的实施，预期将为揭示超声速气流中激光烧蚀金属壁面诱导等离子体的点火机理及强化提供理论依据，为发展适用于未来高超声速飞行器的可靠可重复式点火系统提供新的思路。

相对于激光击穿空气诱导等离子体点火，采用激光烧蚀金属壁面诱导等离子体的点火方式能够起到明显的强化点火作用，这种点火方式在超声速气流中点火过程的学术研究和工程技术领域具有重要应用前景。本项目以超声速气流中激光烧蚀金属壁面诱导等离子体点火过程为研究对象，开展了先进光学观测以及高精度数值模拟研究。通过研究发现在相同激光能量条件下，激光烧蚀金属壁面诱导等离子体点火相比激光击穿空气诱导等离子体点火由于具有更高的能量利用效率、更长的作用时间以及生成更多组分的优点，能够在更多凹腔位置实现可靠点火。局部当量比、生成火核面积以及初始火焰传播路径都对凹腔点火模式起到重要影响。凹腔内被等离子体诱导的火焰再燃现象由于对剪切层火焰加入了额外的热量和活化组分，是实现凹腔点火强化的主要原因。通过本项目的开展揭示了超声速气流中激光烧蚀金属壁面诱导等离子体的点火机理，提供了激光烧蚀点火强化理论依据，发展了适用于未来高超声速飞行器的可靠可重复式点火系统。项目共发表SCI论文22篇，培养硕士研究生3人、博士研究生2人。