Integrated Thermophysical–Kinetic Screening of CH 4 and H 2 Blends for Lean Low-Temperature Combustion

Future energy systems require fuels capable of sustaining lean, low-temperature combustion to minimize NOₓ formation while reducing intrinsic carbon intensity. This study develops an engine-agnostic screening framework for CH4/H2 blends, integrating thermophysical analysis (Aspen Plus) with chemical-kinetic reactor modeling (ANSYS Chemkin-Pro), and Cantera-based detailed kinetic analysis. Neat fuels and their blends are evaluated over 20–60 bar and ϕ = 0.4–1.5. Hydrogen enrichment increased thermal diffusivity by ~60% (CH4 → H2), reduced ignition temperatures, and accelerated burn completion. While hydrogen shifted instantaneous NO formation toward NNH-mediated pathways, time-integrated NO formation remained dominated by thermal and N2O-intermediate chemistry across all blends. Under lean conditions (ϕ = 0.4, 60 bar), pilot-assisted autoignition reduced the minimum stable ignition temperature relative to homogeneous autoignition, while spark-assisted ignition extended the lower ignition limit, thereby directly suppressing thermally driven NOₓ formation, which remains the dominant pathway across all blends. Across the blend space, intermediate compositions demonstrated the most balanced performance, combining reduced carbon intensity (e.g. 23% reduction from CH4 to 50%H2/50%CH4 by mole fraction) with moderated NOₓ propensity and manageable ignition behavior. The proposed framework provides a transferable, chemistry-informed basis for early-stage fuel screening, supporting down-selection prior to detailed engine geometry-specific modeling and experimental validation.