Using carbon free energy sources is one of the keys to mitigate climate change. Hydrogen promises to be one of these carbon free energies, but its storage is difficult and expensive. Ammonia, however, is interesting as it can store hydrogen safely and can be used in combustion engines instead of hydrocarbon fuels. In this experimental work, the spray characteristics of ammonia under different air densities and temperatures were investigated in constant volume and were compared to a biofuel, ethanol, and a common fuel, gasoline. The Schlieren technique was used to capture images of liquid and liquid + vapor spray. The penetration length, the angle near the injector and the angle at half-penetration length were measured. The results show that the spray geometry of ammonia differs from that of the other fuels and that its sensitivity to air density and temperature is greater. The flash boiling condition at ambient temperature was explored for ammonia and indicated a wider spray at half-penetration length at phase change. Moreover, a semi-empirical correlation for penetration length as a function of physical parameters was found with a high accuracy for the global spray. These experimental data provide the first information about ammonia injection with a current spark-ignition GDI injector.

Combustion and emissions characteristics of a spark-ignition engine using direct injection of ethanol blended with ammonia and also pure ammonia were investigated in this study. The experiments were conducted using five different fuel compositions of ethanol/ammonia (C₂H₅OH/NH₃): 100/0, 75/25, 50/50, 25/75, and 0/100. Two strategies of injection were conducted to reach homogenous or stratified conditions with three different intake pressures, 0.5, 1.0, and 1.5 bar corresponding to 2.8, 7.9, and 12 bar of IMEP. The performances and the pollutants emissions are compared as a function of fuel compositions at identical IMEP. High stability is observed for all blends and even for pure ammonia. However, operating conditions are more restrictive for pure ammonia: the injection must be executed during the intake phase to be in a fully premixed mode to guarantee engine stability. Delaying the injection time for pure ammonia is not possible and requires the split of injections with 50% of the ammonia amount injected during the intake. The thermal efficiency is improved by adding 25% of NH₃ in ethanol but NOx emissions increase. The stratified strategy for blends improves the combustion durations and the addition of ammonia decreases the NOx emission compared to the homogeneous strategy. On the contrary, CO emissions roughly increase for blends. The presence of NH₃ in the fuel composition clearly influences the change of formation of NOx and CO between both strategies.

With the aim of expanding the knowledge on liquid ammonia sprays, this paper investigates the injection process of ammonia through Computational Fluid Dynamics (CFD) using the Lagrangian particle method, within the Reynolds Averaged Navier Stokes (RANS) approach for turbulence modeling. Numerical results and experimental data are compared in terms of liquid and vapor tip penetration, local values of Sauter Mean Diameter (SMD) and global spray morphology. This model validation process allows to build a predictive simulation framework for ammonia injection. In order to explore also the flash boiling phenomenon, results of CFD simulations of ammonia spray and the comparison with experimental data are presented for different conditions, ranging from non-flashing regimes to flash boiling conditions. Breakup model constants need to be markedly tuned for each regime, and established values for traditional fuels, like gasoline, appear not to work well with ammonia. Ultimately, this study highlights that capturing spray local details (such as local SMD values) across all the regimes with a single model or setup is still challenging, especially with a new fuel such as ammonia, whose properties differ by a large amount from more established values for hydrocarbons.

Climate change and other environmental impacts have been an enormous worldwide concern in recent decades. Decarbonizing strategic and economic industries is mandatory. Using carbon-free fuels such as ammonia (NH3) has been promoted as a promising solution for decarbonizing both energy and industrial sectors. The use of biofuels has also been encouraged as an attractive alternative to replace conventional petroleum-based fuels in transportation. Therefore, the present study evaluates the environmental profile of using ammonia-ethanol blends in internal combustion engines (ICE) for power generation systems through a life cycle assessment (LCA) framework using the OpenLCA v1.10.3 software. The experiments were conducted in a single-cylinder spark-ignition engine that employs direct injection using three different fuel compositions (in mole fraction) of ethanol/ammonia (75/25, 50/50, and 25/75), with two different intake pressures (0.5 and 1 bar) at 1000 rpm. The functional unit (FU) was set at 1 kWh. The GWP results for 0.5 bar of intake pressure are between 0.07 and 0.95 kg CO2/kWh. The scenario running on Brazilian ethanol and green ammonia is the most environmentally friendly case. The carbon footprint for ethanol/ammonia-based ICE at 1 bar fluctuates between 0.052 and 0.68 kg CO2/kWh. Similarly, regarding GWP, there is a slight difference in Fossil Depletion Potential (FDP) when using ethanol from Brazil and ethanol from Ecuador due to the lack of circular economy strategies in Ecuador's agriculture, compared to Brazil. Regarding the contribution analysis, for a 50% green ammonia – 50% ethanol scenario for power generation, ethanol production has the highest contribution for global warming, fossil depletion, and freshwater eutrophication potential impacts. Compared to the analysed environmental impacts, some of our proposed scenarios depict better performance than the average electricity production in the United Kingdom, France and Europe. Therefore, ethanol-ammonia fuel-based for power generating systems could be an important option to contribute to the decarbonization of the electric sector.