Hydrogen-enriched spark-ignition engine operation with gasoline–water–hydrogen peroxide blends: Performance, emissions and knock limit

In this study, gasoline–water–H 2 O 2 blends with 0%, 5%, 10%, 15%, and 20% water–H 2 O 2 (by volume) are prepared. The engine configuration with gasoline–water–H 2 O 2 direct injection and hydrogen port induction is employed; hydrogen supply is increased in 2 L/min steps until knock onset. Outcome exhibited that water–H 2 O 2 blending and hydrogen addition increased the BTE, whereas higher water–H 2 O 2 fraction and retarded spark timing led to performance deterioration. CO 2 and NO x emissions reduced at higher water–H 2 O 2 fraction due to the increased latent heat of the combustible mixture. Cyclic variation reduced and increased as the water–H 2 O 2 fraction increased. Notably, a higher water–H 2 O 2 fraction extends the hydrogen knock limit, increasing the maximum knock-free hydrogen flow rate from 8 to 10 L/min at 12° Crank angle (CA) BTDC and from 14 to 16 L/min at 4° CA BTDC at the expense of reduced engine performance. For higher performance, lower water–H 2 O 2 fractions are desirable. • Water–H 2 O 2 blending effects on hydrogen-gasoline SI engine performance. • Engine performance improved with water–H 2 O 2 blending at a smaller ratio. • Water–H 2 O 2 initially increased NO X emissions and hydrogen continuously increased. • Water–H 2 O 2 blending reduced the cyclic variation initially and then increased. • 15% and 20% water–H 2 O 2 blends raised the hydrogen knock limit to 10 LPM and 16 LPM.