Centres of Intensity in Ammonia/Hydrogen flames

Although ammonia can be used as a fuel, it also presents drawbacks that require further investigation before the chemical can overtake fossil fuels in combustion systems. The main barriers are the low flammability in combination with high NOx emissions. Although the first barrier can be surpassed doping ammonia with hydrogen, the second becomes more challenging under these conditions, as hydrogen increases NO emissions due to the increase in H radicals in the chemical pool of species. How the change in radicals impacts on the stability of the flame, its reactivity and emissions profile is of the greatest concern for the use of these net zero fuels. Thus, the work herein presented shows the trends of excited species such as NH, NH2* and OH* when using ammonia-hydrogen at 70/30% (vol) blending. Various equivalence ratios were employed from lean to rich conditions. The current Dataset denotes the variation in the radical formation through images taken using chemiluminescence cameras. Optical filters specifically selected for each specie were employed to obtain individual images that after averaging and Abel Deconvolution transformations showed the changes in intensity of the targe species. Out of these results, intensities and second moments of area were gathered, finally delivering the location of Centres of Intensity for each excited radical. These values were then compared, showing trends that are particular to each radical, with OH* and NH* following linear trends with equivalence ratio, whilst NH2* shows a polynomial increase. These results can be used to target these high intensity regions, presenting the possibility of mitigating emissions by using this information when combining these and other species such as NO.

尽管氨可用作燃料，但其弊端亦需深入探究，方能在燃烧系统中取代化石燃料。主要障碍包括低燃点和伴随的高氮氧化物排放。尽管通过掺杂氢气可以克服前者，但在这些条件下，氢气因增加化学物种池中的氢自由基而加剧了氮排放，使得后者变得更加具有挑战性。自由基的变化对火焰的稳定性、反应性和排放谱的影响，对于这些净零燃料的使用至关重要。因此，本文所示研究展示了在70/30%（体积比）氨-氢混合物中，激发物种如NH、NH2*和OH*的趋势。从贫燃到富燃条件，采用了各种当量比。当前数据集描绘了通过化学发光相机获取的图像中自由基形成的变异。针对每种物种特别选用的光学滤光片被用于获得单独的图像，经过平均化和阿贝尔逆卷积变换后，显示了目标物种强度的变化。从这些结果中，收集了强度和面积的第二矩，最终得出了每个激发自由基的强度中心位置。这些值随后被比较，显示出每个自由基特有的趋势，其中OH*和NH*随着当量比呈现线性趋势，而NH2*则表现出多项式增长。这些结果可用于针对这些高强度区域，并展示了利用这些信息结合其他物种（如NO）时，减轻排放的可能性。