Impacts of injection pressure on split-injection energy-assisted compression-ignition combustion of low cetane number SAFs with a Gaussian-shaped ribbed piston bowl design.

The impacts of injection pressure on a split-injection strategy used to enable mixing-controlled combustion of low cetane number sustainable aviation fuels using energy-assisted compression-ignition (EACI) operation with a Gaussian-shaped ribbed piston bowl design were investigated in an optically accessible research engine. Three injection pressures (600, 800, and 1000 bar) were investigated at three split-injection dwells (1.5, 2.0, and 2.5 ms) with a fixed second injection timing of -5.0 CAD. A Gaussian-shaped ribbed piston bowl design was employed to reliably position hot combustion gases from the first injection near the centrally located injector to enable rapid ignition and mixing-controlled combustion of the second injection. Results indicate that as injection dwell was shortened, relocation of hot combustion gases near the injector became increasingly more difficult due to the higher in-cylinder densities at start-of-injection (SOI) of the first injection. However, results also indicate that increased injection pressures can accelerate the ignition process of the first injection, potentially enabling operation with shorter injection dwells by reducing the time it takes for the combusted gases from the first injection to reach the location of the injector. These results suggest there is potential to achieve EACI operation at more application-relevant engine speeds through the utilization of custom piston bowl designs which allow for stable engine operation with higher injection pressures.