Experimental and kinetic of hydrogen blending effects on lean flammability limit of gasoline fuels

This study investigates the effects of hydrogen (H2) bending on lean flammability limits (LFL) of gasoline using a constant volume combustion bomb apparatus at an initial temperature (T) of 453 K under atmospheric conditions. To enable stable engine operation with lean mixtures, the influencing mechanisms of H2 on gasoline's LFL were further examined through chemical kinetic analyses. The experimental results reveal that H2 addition markedly extends LFL of gasoline, though this effect is nonlinear. At lower blending ratios, H2 addition produces a linear increase in LFL, while higher blending ratios yield a more pronounced enhancement. Kinetic analysis demonstrates that as the equivalence ratio decreases, the effect of flame thickness (reaction zone) causes the distribution of H radicals in TRF/H2 blends to shift from a single peak to a double peak. This study proposes a novel method for determining LFL of TRF/H2 blends by observing the transition in H radical distribution from bimodal to unimodal, reflecting a significant shift in flame structure and an increase in combustion stability and propagation speed. Compared to traditional methods, which rely on chain-branching (H+O2 = O+OH) and chain-termination (H+O2 (+M) = HO2 (+M)) reactions to estimate LFL, the new approach demonstrates superior alignment with experimental data.