Working Paper 01
Fuel composition as a dynamic control variable in spark-ignition engines: chemistry, operating regimes, and the limits of blend scheduling
September 2026
Abstract
This paper tests dynamic fuel-composition scheduling across operating points, ambient conditions, and equivalence ratios using zero-dimensional chemical kinetics coupled to a calibrated knock-limited spark-ignition model. Three findings emerge: stoichiometric blend scheduling adds 0.015 efficiency points, ambient-adaptive selection adds 0.05 points, and lean load-adaptive switching between hydrogen and a hydrogen–methane blend adds 0.95 points, or 1.44 points under drive-weighting, over the best fixed fuel. The larger stoichiometric gain of 1.20 points comes from fuel choice and compression ratio selected together rather than from changing the blend at each operating point.