The objective of this paper is to provide new data about the possibility of using ammonia as a carbon-free fuel in a spark-ignition engine. A current GDI PSA engine (Compression Ratio 10.5:1) was chosen in order to update the results available in the literature mainly obtained in the CFR engine. Particular attention was paid to determine the lowest possible load limit when the engine is supplied with pure ammonia or a small amount of H2, depending on engine speed, in order to highlight the limitation during cold start conditions. It can be concluded that this engine can run stably in most of these operating conditions with less than 10% H2 (of the total fuel volume) added to NH3. Measurements of exhaust pollutants, and in particular NOx, have made it possible to evaluate the possibility of diluting the intake gases and its limitation during combustion with pure H2 under slightly supercharged conditions. In conclusion, the 10% dilution limit allows a reduction of up to 40% in NOx while guaranteeing stable operation.

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In a context of growing concerns over climate change, aluminum has the potential to serve as a dense energy carrier in order to replace fossil fuels and reduce greenhouse gases emissions. Indeed, its combustion in air may provide carbonfree energy for applications in which a high-energy storage capacity is required.However, attempts of designing a metal-fueled combustor will conflict with a relatively large dispersion of the burning velocity values reported in the literature, even when similar powders are used. This uncertainty is partially due to the range of experimental conditions and techniques used on those previous studies. In the present work, an experimental Bunsen-type aluminum-air burner is introduced.It is shown that the setup is capable of generating stable dust suspensions under well-controlled conditions. The stabilized aluminum-air flames are studied using emission spectroscopy, Particle Image Velocimetry, laser sheet tomography, and direct visualization of the AlO(g) emissions. The measured burning velocities are then compared to previous results obtained for similar powders as a function of dust concentration. A reasonable agreement is obtained, and it is shown that * *Revised unmarked manuscript metal flame tomography can yield a more precise indicator of the flame front position than AlO(g) emissions, helping to reduce the data scatter regarding dust-air burning velocities.