Image-based in-situ Diagnostics in the Spray Flame Synthesis of Nanoparticles

原位诊断成像是定量可视化和更好地理解喷射火焰合成过程的必要工具，并为验证化学动力学模型和底层气相和颗粒形成途径的流体动力学模拟提供有价值的数据。该项目的目的是在喷射火焰合成的恶劣条件下（湍流反应流，液滴和/或颗粒的存在），对标准化SpraySyn燃烧器中的温度，中间物质浓度和颗粒进行定量（主要基于激光）单脉冲成像诊断。除了液相和气相的温度外，测量还集中在重要的化学中间物质（进程变量）上，这些物质与其他SPP研究小组进行的全球颗粒合成过程的模型开发和模拟有关。流动系统中单个原子/分子的基本光谱研究（激发/荧光光谱，荧光寿命）应该初步确定最佳的激发/检测策略，以便后期定量激光诱导荧光（LIF）成像。然后，在SpraySyn火焰中的分子示踪剂(如NO（新鲜气体的外部混合物）或OH、BaO或Fe（作为反应中间体存在）上，通过单脉冲双线LIF测温对气相温度进行成像。瞬时温度值还以测量标量的平均值、标准偏差和直方图的形式提供火焰统计数据。用双色单脉冲LIF测定了OH、Fe、FeO或Ba等各种重要中间体在电子基态的浓化值，从而确定了类似的数量。两个独立可调激光波长和两个相机探测器的组合可以通过同时检测两种不同的物质来实现浓度波动的相关测量，例如，燃料标记物和中间产物，表明探针体积中存在燃料和前体分解的中间产物。除气相外，还将首次使用双色LIF方法，通过添加非蒸发染料（香豆素、罗丹明），对液相（燃料射流、液滴）进行平面单脉冲温度成像。粒子云通过瑞利散射或激光诱导白炽（LII）定性地可视化，并确定与反应物质（通过LIF）的统计相关性。所有结果将有助于进一步扩展已经存在的SpraySyn数据库。这不仅为模拟过程的项目提供了验证数据，而且还支持Mohri项目与他们的火焰化学发光和颗粒分布的层析重建结果进行比较，以及Kaiser项目处理跌落爆炸的微观检查。

In-situ diagnostics imaging is a necessary tool to for the quantitative visualization and a better understanding of the processes taking place in spray flame synthesis, and provide valuable data for validations of chemical-kinetic models and fluid-dynamic simulations of the underlying gas phase and particle formation pathways. The aim of this project is the quantitative (mostly laser-based) single-pulse imaging diagnostics of temperature, intermediate species concentration and particle in the standardized SpraySyn burner under the harsh conditions of spray flame synthesis (turbulent reactive flow, presence of droplets and / or particles). Besides temperature for the liquid and gaseous phase, the measurements concentrate on important chemical intermediate species (progress variables) relevant for model development and simulation of the global particle synthesis process performed in other SPP research groups. Fundamental spectroscopic investigations (excitation/fluorescence spectra, fluorescence lifetimes) of individual atomic / molecular species in a flow system should initially define optimal excitation / detection strategies for later quantitative laser-induced fluorescence (LIF) imaging. Imaging of gas phase temperatures is then performed by single-pulse two-line LIF thermometry on molecular tracers such as NO (external admixture to the fresh gases) or e.g. OH, BaO or Fe (present as a reactive intermediate) in the SpraySyn flame. The instantaneous temperature values then also provide flame statistics in the form of mean values, standard deviation and histograms of the measured scalars. Similar quantities are determined with concentration values of various important intermediates such as OH, Fe, FeO, or Ba recorded in their electronic ground states by two-color single pulse LIF. The combination of two independently tunable laser wavelengths and two camera detectors enables correlated measurements of concentration fluctuations by the simultaneous detection of two different species, e.g., a fuel marker and intermediates indicating the presence of fuel and an intermediate product of precursor decomposition in the probe volume. In addition to the gas phase, planar single-pulse temperature imaging of the liquid phase (fuel jet, droplets) will be carried out for the first time using the two-color LIF method by adding non-evaporating dyes (coumarin, rhodamine). The particle clouds are visualized qualitatively via Rayleigh scattering or laser-induced incandescence (LII), and statistical correlations with reactive species (via LIF) are determined. All results will contribute to further extending the already existing SpraySyn database. This not only provides validation data for projects modeling the processes, but also supports the project Mohri in comparing with results of their tomographic reconstruction of flame chemiluminescence and particle distribution, as well as the project Kaiser dealing with the microscopic examination of drop explosions.