可用于复杂湍流燃烧速度场表征的飞秒激光调控长程丝状放电特性的实验及理论研究

Flow speed measurements with high accuracy and precision are much more demanded than ever in advanced research fields concerning energy and power, when charactering complex flow and combustion fields at high turbulence and wide operating conditions. The exist techniques for flow speed measurements are generally rather limited and are hardly available for extreme conditions (such as near wall or supersonic flows). This proposal is aiming at establishment of a novel powerful flow speed measurement technique by combining two recently well-investigated techniques, namely femtosecond laser-induced filamentation and gliding arc from high frequency alternative currently gas discharge, which have been part of the research focus of the applicant in recent years. . This project intends to carry out the experimental and theoretical researches on the precise space-time and energy regulation of the long-range filamentous discharge in the flow field and the combustion field by using femtosecond laser-induced filamentation, and reveals the governing mechanism of the femtosecond laser-induced filaments in controlling the long-range filamentary discharge, such as the formation and tracking of weakly ionized plasmas column to accurately measure the velocity field and to establish a laser-induced filamentary discharge velocity measurement technique, namely Filamentary Anemometry using Laser-induced Electronic Discharge, FALED.. This project will provide a powerful in situ anemometry tool for the flow field and combustion flow diagnosis in a wide range of operating conditions in energy and power research fields, providing new data for further understanding and control of gas flow and combustion especially under extreme conditions. This project will also benefit the general national interest in ’development of original scientific research equipment’

能源和动力等重大科研领域对于高湍流宽工况复杂流场和燃烧场的精确速度表征有迫切需求，现有速度测试技术在广谱性以及应对极端条件（例如近壁面和超音速）方面有很多不足。针对上述问题，并基于申请人近年来在飞秒激光成丝以及高频电压气体放电领域的科研积累，本项目提出，结合二者的优点，创建一种高精度可适用于极端条件的速度测量方法。. 本项目拟开展利用飞秒激光成丝进行流场和燃烧场中长程丝状放电精确时空和能量调控的实验及理论研究，揭示飞秒激光成丝调控长程丝状放电的规律和机理，实现亮度可控丝状弱电离等离子体的生成和追踪，从而精确测量速度场，并建立激光诱导丝状放电速度测量技术。. 本项目将为能源动力领域宽工况范围的流场和燃烧场诊断提供一种强有力在线速度测量工具，为进一步理解和控制极端条件下的气体流动和燃烧提供新的数据支撑，还对推动国内开发原创性的科研仪器设备具有重要意义

针对能源和动力领域对流场和燃烧场的精确速度表征需求，本项目围绕飞秒激光成丝诱导电极放电，拟通过对气体放电激发等离子体分子发光机理的探索，实现对于丝状放电过程的时空和强度调控以及等离子体通道余晖的有效追踪，从而建立一种具有开创性的针对复杂流场和燃烧场的广谱速度测量技术。首先，开展了飞秒激光电子激发标记测速技术研究，并将该技术应用到超声速射流二维速度场测量中，实验发现该技术信噪比较差。在此基础上进行了荧光标记信号增强研究，实验采用纳秒激光增强飞秒信号强度，信号强度提升约1倍。其次，开发了飞秒激光诱导化学发光测速技术，其信噪比提高了2个数量级，并实现了近壁面速度场测量。最后，采用飞秒激光成丝诱导长程丝状放电，利用飞秒激光成丝产生的弱等离子体通道，对放电等离子体产生的时间和空间进行精确调控，时间控制精度可以达到纳秒量级，空间控制精度达到微米量级，在此基础上利用多次放电方法，结合等离子体通道的记忆效应和随流特性实现了流场二维速度场测量。与飞秒激光电子激发标记测速技术相比，该技术信噪比提高3个数量级，采用普通的相机即可实现测量，且信号强度几乎不受周围环境的影响。