Multi-Dimensional Modeling of Mixture Formation In A Hydrogen-Fueled Heavy-Duty Optical Engine With Direct Injection

Hydrogen-fueled internal combustion engines have been receiving increasing attention, particularly in applications such as on-road/off-road heavy-duty transport and combined heat and power. Direct injection (DI) of gaseous hydrogen (H₂) into the combustion chamber offers great potential for achieving high power density and engine efficiency, while mitigating the risk of backfire and reducing preignition. However, the numerical simulation of H₂ DI system remains a formidable challenge and there is a lack of well-established and validated practices for the modeling of H₂ DI in large-bore engines. Therefore, this study focuses on computational modeling of the mixture formation process in a heavy-duty optical engine where gaseous hydrogen is injected into the combustion chamber via a centrally located outward opening hollow-cone injector at 40 bar. Both Large Eddy Simulations (LES) and Reynolds Averaged Navier-Stokes (RANS) simulations are performed and evaluated by systematically comparing numerical predictions for H₂ distribution in different horizontal and vertical planes during the compression stroke against the planar laser-induced fluorescence measurements. Overall, the LES approach using Dynamic Structure model is found to have good predictive capabilities for the early jet penetration as well as the later H₂ distributions. However, the unsteady RANS approach with the Renormalization Group k-∈ model significantly underpredicts the H₂ mixing, even at similar mesh resolution to that used in LES. These results indicate that there is a need for the improvement of mixing sub-models within the RANS approach when applied to H₂ DI simulations.