滑动弧放电强化甲烷/空气预混火焰点火和燃烧机理的激光光谱学研究

Plasma-assisted ignition and combustion offer promising applications in reducing ignition delay time and ignition energy, improving combustion efficiency and reducing pollutant emissions. Many questions in plasma-assisted ignition and combustion are still unclear nowadays, such as what the most promising plasma source is, and what the best method to recognize the effects of plasma-assisted combustion is, as well as in which way plasmas contribute to combustion enhancement. In this application, a gliding arc discharge (GAD), which is advantageous in terms of simple geometry, high power density, large volume, and easy generation of non-equilibrium plasma at atmospheric pressure, is used to enhance ignition and combustion of premixed methane/air flames, and laser spectroscopy techniques are employed to perform real-time, non-intrusive, in-situ diagnostics of the effects and mechanisms of the GAD enhanced ignition and combustion. A well-designed reactor is built to integrate the gliding arc discharge with the premixed methane/air flame. Important parameters of the flame enhanced by the gliding arc discharge, such the flame structures, the NO concentration and the flame temperature, are obtained using planar laser induced fluorescence, saturated laser induced fluorescence and filtered Rayleigh scattering. The chemical effects, catalytic effects and thermal effects are diagnosed by these laser spectroscopy techniques to provide insight into the mechanisms of the GAD enhanced ignition and combustion. This study can theoretically and experimentally provide a better understanding for the mechanism of non-equilibrium plasma-assisted ignition and combustion, and play a significant role in promoting practical applications of plasma-assisted ignition and combustion in real engines.

等离子体助燃在减小点火延迟时间和点火能量、提高燃烧效率、降低污染物排放等方面具有重要的应用前景。目前，对助燃中应选择的等离子体种类、等离子体助燃的效果识别和机理诊断等方面的研究尚处于探索阶段。本申请拟采用具有结构简易、功率密度高、作用范围广、在常压下产生非平衡等离子体等优点的滑动弧放电，实现在甲烷/空气预混火焰中强化点火和燃烧，基于激光光谱技术对滑动弧放电助燃的效果和机理进行实时、非侵入的原位诊断。本申请拟建立滑动弧放电和甲烷/空气预混火焰一体化集成反应器，通过平面激光诱导荧光、饱和激光诱导荧光、过滤瑞利散射等技术手段，获得滑动弧放电作用下的火焰结构、NO浓度和温度等重要信息，研究滑动弧放电助燃时的化学效应、催化效应和热效应，揭示滑动弧放电强化点火和燃烧的效果和机理。该项目可为理解非平衡等离子体强化点火和燃烧机理提供理论指导和数据支撑，对推动等离子体强化点火和燃烧的工程化应用具有重要意义。

采用具有结构简易、功率密度高、作用范围广的非平衡滑动弧放电等离子体，实现甲烷/空气预混火焰的强化点火和燃烧。建立滑动弧放电和甲烷/空气预混火焰一体化集成反应器，将滑动弧放电直接耦合于火焰中，使滑动弧放电产生的活性组分能够与火焰瞬时地相接触和反应。利用平面激光诱导荧光(PLIF)、激光诱导瑞利散射、自发辐射光谱、电光同步诊断等非扰动光学诊断技术分别测量火焰结构、平动温度、转动和振动温度、滑动弧放电参数，研究滑动弧放电助燃时的化学效应、输运效应和热效应，揭示滑动弧放电强化点火和燃烧的效果和机理。滑动弧放电能够在强湍流、大功率、高流速下实现火焰的助燃。滑动弧放电在来流马赫数为2.92的超声速气流中实现成功点火，利用滑动弧放电等离子体点火能够精细观测超声速气流中火核形成、火焰传播和全局火焰建立等点火过程。初始火焰面积大小是决定全局火焰能否成功建立的关键因素，滑动弧产生的初始火焰面积越大，越有利于滑动弧放电成功点火。多组分同步OH/CH2O/CH PLIF测量结果表明，在滑动弧助燃时火焰结构呈现电弧核心区域、放电诱导OH区、火焰高温产物OH区、火焰面CH区、火焰预热CH2O区和未燃气体混合物区等六个区域。滑动弧放电在湍流作用下呈现辉光放电、火花放电和短切放电等几种放电模式，并且能够相互转换，电源电压恢复速率、输入功率、湍流的对流冷却和亚稳态组分输运作用是影响滑动弧放电特性的主要因素。滑动弧的平动温度约为1100K，电子温度约为9000K，表明滑动弧具有较强的非平衡特性。研究表明，滑动弧放电是一种很有潜力的等离子体源，有望应用于实际发动机的强化点火和助燃。在本项目执行期间，项目负责人入选2019年度湖湘青年英才支持计划，作国内外学术会议邀请报告4次。发表学术论文15篇，其中SCI检索13篇，EI检索1篇，会议论文1篇。