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.