System Level Simulation of H2 ICE after Treatment System

Hydrogen Internal Combustion Engines (H₂ ICE) are gaining recognition as a nearly emission-free alternative to traditional ICE engines. However, H₂ ICE systems face challenges related to thermal management, N₂O emissions, and reduced SCR efficiency in high humidity conditions (15% H₂O). This study assesses how hydrogen in the exhaust affects after-treatment system components for H₂ ICE engines, such as Selective Catalytic Reduction (SCR), Hydrogen Oxidation Catalyst (HOC), and Ammonia Slip Catalyst (ASC). Steady-state experiments with inlet H₂ inlet concentrations of 0.25% to 1% and gas stream moisture levels of up to 15% H₂O were conducted to characterize the catalyst response to H₂ ICE exhaust. The data was used to calibrate and validate system component models, forming the basis for a system simulation. System model validation involved comparing the model against real-world data from production diesel engine after-treatment systems for transient cycles, including Federal Test Procedure (FTP) and Ramp model cycle (RMC) data. Subsequent simulations replicated H₂ ICE exhaust conditions for steady-state and transient scenarios, yielding insights for optimizing H₂ ICE applications. The paper’s final section presents results from an improved system comprising of HOC, SCR, ASC, and Hydrogen Particulate Filter (HPF), offering a potential pathway to achieving ultra-low NOx emissions in H₂ ICE engines while addressing challenges like thermal management, N₂O formation, and reduced SCR activity in high humidity conditions (15% H₂O).