Numerical Modeling of Mixing-Controlled Combustion in Direct-Injected Compression-Ignition Hydrogen Engines

Abstract

Reducing greenhouse gases (GHG) is critical to addressing climate change. Using low- carbon, or potentially carbon-neutral, fuels can lower GHG emissions. Neat hydrogen direct injected compression ignition (DICI) is investigated to see if it can achieve the qualities found in diesel fueled engines. Hydrogen is a challenge to model and this study developed and validated a model for gas parcel injection relevant to engine design and analysis. The gas parcel model showed reduced grid dependency compared to the tra- ditional inflow model. This gas parcel method was incorporated into a DICI H2 engine model and was used to study different ignition strategies. Unassisted DICI was the con- trol and two glow plug based energy assisted compression ignition (EACI) strategies were studied. Temperature and pressure at intake valve closure (IVC) were swept to see sensi- tivity to initial conditions and EACI outperformed the unassisted strategy. Ringing was observed to be a major challenge with the unassisted case and was reduced using EACI methods. EACI strategies outperformed unassisted DICI in NOX emissions, ringing, and engine performance. These strategies enabled stable mixing-controlled compression igni- tion (CI) using direct injection (DI) of neat hydrogen. Overall an engineering level model for DICI using gas parcels showed that DICI of pure hydrogen could achieve diesel like combustion via energy assistance.