This project aims to characterize the influence of hydrogen addition on the local flame structures and NOx emission formation in a premixed laminar counterflow configuration for carbon-free ammonia combustion using combined Raman/Rayleigh spectroscopy and

使用无碳燃料氨和氢作为可再生能源的化学储能对于某些部门（例如船舶推进）必要的脱碳非常重要。氨和氢的混合燃烧为克服单独使用两种燃料的困难提供了选择。氢可以高效地从绿色氨中产生。通过向氨中加入几摩尔的氢，可以观察到与具有类似层流燃烧速率的天然气燃烧相比，火焰稳定性显著增加。同时，氢的加入改变了火焰结构和局部氮氧化物的形成。到目前为止，这些现象主要是用数值方法研究的。文献中没有详细的实验研究，但迫切需要进一步理解和验证数学化学模型。本项目旨在从根本上了解加氢对氨/氢预混火焰火焰结构、火焰稳定性和一氧化氮形成的影响。使用先进的激光诊断方法，将研究空间分解热化学状态和反应区与烃基燃烧过程中非常不同的一氧化氮形成。为了分析加氢对火焰结构的影响以及火焰稳定性与一氧化氮形成的相互作用机制，将在气动消光极限下进行研究。在参数变化中，在逆流配置中系统地探索了不同的等效比和不同的氨/氢/氮/空气混合物。首先，加氢引起的机制将在层流条件下进行研究，并在第二个项目阶段进行湍流条件下的研究。热化学状态（温度、物质浓度）和火焰结构将通过一维空间分辨联合拉曼/瑞利光谱测量并随后分析。为此，我们通过实验确定了氨分子先前未知的、温度相关的拉曼散射截面。一氧化氮浓度也将定量测定使用激光诱导荧光。反应区附近的局部拉伸率将通过粒子图像测速法与激光诱导荧光同时测定的羟基自由基分布相结合来确定。这些实验数据将用于评估反应动力学模型，这些模型显示出明显的偏差，特别是在预测一氧化氮形成和消失极限方面。这些综合研究旨在填补知识空白，以关闭绿色氨氢混合物的热利用潜力。

The use of the carbon-free fuels ammonia and hydrogen as chemical energy storage for renewable energies is of great importance for the necessary decarbonization in some sectors (e.g. maritime propulsion). Co-combustion of ammonia and hydrogen opens up options to overcome the difficulties of using the two fuels individually. Hydrogen can be produced energy-efficiently from green ammonia. By adding a few mole fractions of hydrogen to ammonia, a significant increase in flame stability is observed compared to, for example, natural gas combustion, with similar laminar burning rates. At the same time, the addition of hydrogen changes the flame structure and the local formation of nitrogen oxides. So far, these phenomena have been investigated mainly numerically. Detailed experimental investigations are not available in the literature, but are urgently needed for further understanding and validation of mathematical-chemical models. The aim of this project is to fundamentally understand the influence of hydrogen addition on flame structure, flame stability and nitric oxide formation for premixed ammonia/hydrogen flames. Using advanced laser diagnostic methods, spatially resolved thermochemical states and the very different nitric oxide formation in the reaction zone compared to hydrocarbon-based combustion processes will be investigated. The investigations will be carried out up to the aerodynamic extinction limit in order to analyze the impact of hydrogen addition on the flame structure and the interacting mechanisms of flame stability and nitric oxide formation. In a parametric variation, different equivalence ratios and different ammonia/hydrogen/nitrogen/air mixtures are systematically explored in a counterflow configuration. Initially, the mechanisms caused by hydrogen addition will be investigated for laminar flow conditions, and in a second project phase for turbulent flow conditions. Thermochemical states (temperature, species concentrations) and flame structures will be measured by one-dimensional spatially resolved combined Raman/Rayleigh spectroscopy and subsequently analyzed. In preparation for this, the previously unknown, temperature-dependent Raman scattering cross sections of the ammonia molecule are determined experimentally. Nitric oxide concentration will also be quantitatively determined using laser-induced fluorescence. Local stretching rates near the reaction zone will be identified by particle image velocimetry in combination with the simultaneously determined hydroxyl radical distribution via laser-induced fluorescence. These experimental data will be used to evaluate reaction kinetic models that show significant deviations, particularly in predicting nitric oxide formation and extinction limits. These comprehensive investigations are intended to fill a knowledge gap in order to close the potentials of the thermal utilization of green ammonia-hydrogen mixtures.