2023 Roadmap on ammonia as a carbon-free fuel

The 15 short chapters that form this 2023 ammonia-for-energy roadmap provide a comprehensive assessment of the current worldwide ammonia landscape and the future opportunities and associated challenges facing the use of ammonia, not only in the part that it can play in terms of the future displacement of fossil-fuel reserves towards massive, long-term, carbon-free energy storage and heat and power provision, but also in its broader holistic impacts that touch all three components of the future global food-water-energy nexus

Operating Limits for Ammonia Fuel Spark-Ignition Engine

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

First Study on Ammonia Spray Characteristics with a Current GDI Engine Injector

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

Comparison of different chemical kinetics modeling codes

Various codes are available to model the chemical kinetics of reactive systems, e. g. COSILAB, OpenSMOKE, Cantera, CHEMKIN, CHEMID and others. However no proper comparison is made between the performances of different codes for various cases. To assess and compare the performance of COSILAB and OpenSMOKE, we simulated different laminar combustion cases of CH4/Air and CH4/H2/Air mixtures with both codes using the GRI30 mechanism and compared the obtained results. For ignition delays and mole fraction profiles in 1D flames simulations similar results are found with COSILAB and OpenSMOKE. However the laminar flame speeds obtained with the two codes differ

Ammonia as fuel for transportation to mitigate zero carbon impact

The idea of using ammonia as fuel is nothing new as the first well-known Belgium use of buses fleet during World War II. Even if several studies performed during the mid-60’s investigated the possibility to consider ammonia as fuel for internal combustion engines, mainly by means of CFR experiments or 0D modelling, ammonia-based combustion engine fueling methods are not ready to be marketed as the use of this toxic molecule still poses major problems not only because of supply and safety issues but also because of its physical characteristics compared to conventional fuels. As function of the target, i.e. to supply ammonia either partially in standard engines to limit carbon footprint or to employ it mainly in dedicated engines to reach zero footprint, the technological challenges (dual fuel or unique fuel, SI or CI engines …) could be different if it is as main power or auxiliary power unit (to extend battery vehicles) and as a function of the transportation type (mean duty or heavy duty engines for freight, construction, marine transportation, …). In this chapter new results of advanced researches will be discussed in order to highlight the potential of this future green fuel