Advancements in Sustainable Aviation Fuels: Impact of Nano-Additives and Ammonia-Based Strategies on Emissions

The increasing commitment to sustainable practices has intensified research into innovative methods to diminish the release of harmful pollutants and greenhouse gases, such as CO2, CO, and NOx, into our environment. A promising avenue of exploration lies in the adoption of fuel emulsions enriched with nano-additives aimed at curtailing NOx emissions. In this context, our study delves into the impact of nanoparticulate additives-specifically those based on ammonia and water-on the combustion characteristics of Jet-A1 aviation fuel. Utilizing a 300-kW liquid swirl combustor, we conducted a series of experiments across two global equivalence ratios (Φ=0.24 and Φ=0.40). Our investigation encompassed the analysis of laminar flame speed (LFS) and an in-depth examination of flame properties through advanced chemiluminescence imaging and modal analysis techniques. The primary objective was to unravel the complexities of how these nano-additives modulate flame dynamics and the intricate web of internal chemical reactions, alongside evaluating the broader environmental ramifications resulting from alterations in the combustion process. The experimental outcomes revealed that the integration of urea and water additives into the fuel matrix distinctly affected LFS, with observed enhancements at the lower global equivalence ratio and detrimental impacts when the ratio was increased. Through modal analysis, we discerned a notable stabilizing influence on the flame's behavior, which was particularly pronounced at leaner fuel conditions. From the study of the spray, the addition of water and urea appears to influence combustion chemistry, and more uniform sprays facilitate more complete combustion. Chemiluminescence imaging further illuminated these effects, demonstrating a higher emission intensity of NH2* radicals compared to NH* radicals, a variance contingent on the global equivalence ratio. Notably, the experimental data indicated a substantial abatement in NOx emissions, predominantly at the lower equivalence ratios. This reduction was accompanied by a marginal uptick in CO2 and CO emissions-a trade-off that warrants consideration.