Ammonia Combustion with Active Pre-Chamber Spark Plug - a CO2-free Combustion Process

As a zero carbon fuel, ammonia has the potential to completely defossilize combustion engines. Due to the inert nitrogen present in the molecule, ammonia is difficult to ignite or burn. Even if the ammonia can be successfully ignited, combustion will be very slow and there is a risk of flame quenching, i.e. the flame going out before the ammonia-air mixture has been almost completely converted. Both the difficult flammability and the slow combustion result in high ammonia slip, which should be avoided at all costs. The engine efficiency is also greatly reduced. Safe ignition and burn-through can be achieved by drastically increasing the ignition energy and/or using a reaction accelerator such as hydrogen. The planned paper will use detailed 1D and 3D CFD calculations to show how high the potential of ammonia combustion in an internal combustion engine is when an active pre-chamber is used as the ignition system. As a result of the flare jets penetrating into the main combustion chamber filled with ammonia, this allows a so-called space ignition and a very high ignition energy to be achieved. The latter is particularly high if the fuel used in the pre-chamber is hydrogen, for example. As the hydrogen can be obtained directly from the ammonia via an on-board cracker in the vehicle, this would be a single-fuel combustion process. The paper will focus on the potential how fast and save the combustion can be, what combustion efficiencies can be optained and what amount of hydrogen is needed from the onboard cracker (operated with Waste heat from teh exhaust system) to build a vey stable and high efficient ammonia based passenger car combustion system.