Injection, Mixing and Auto-ignition of E-fuels for Compression Ignition Engines

The article delves into the physical and chemical behavior of liquid hydrocarbons from renewable energies during mixture formation and combustion in compression ignition engines. The FVV project 'eSpray' compares the injection, mixture formation, and ignition of oxygenated e-fuels like OME 3-5 and 1-octanol with diesel-like n-dodecane. Experiments conducted at Friedrich-Alexander-Universität Erlangen-Nürnberg and other international research institutes reveal that while vapor penetration depths are similar, liquid phase penetration lengths differ significantly. OME 3-5 and 1-octanol take longer to evaporate completely, influencing hydraulic behavior and injection duration. The study also finds that e-fuels burn further away from the nozzle tip and have shorter ignition delays and burnout phases, requiring engine adaptations. Notably, OME 3-5 burns soot-free, reducing the need for heat load reduction in pistons. The use of mid-infrared imaging technology in optical engines is highlighted for determining gaseous fuel penetration depth. CFD simulations further validate the experimental findings, showing that OME 3-5 combustion occurs closely around the stoichiometric combustion air ratio, minimizing soot formation. The project's results offer valuable insights into engine combustion, aiding in the design of future CI engines to harness the full potential of e-fuels, and potentially reducing NOx emissions significantly.