Improving performance and hydrogen knock limit in SI engines using acetone–gasoline blends

Acetone was blended with gasoline at volume fractions of 20 %, 35 %, and 50 %. The supply strategy involves direct injection of the acetone–gasoline blend and port fuel induction of hydrogen. The hydrogen flow rate was increased incrementally by 2 LPM until the onset of knock. Combined acetone blending and hydrogen addition enhanced engine performance, as indicated by improvements in the brake mean effective pressure, brake thermal efficiency, and in-cylinder pressure. Moreover, advanced spark timing improved these parameters. The coefficient of variation of the peak in-cylinder pressure decreased with both acetone blending and hydrogen enrichment, indicating more stable combustion. While NO_X emissions decreased with increasing acetone content, they increased significantly with hydrogen addition. Notably, acetone blending extended the hydrogen knock limit, increasing it from 8 to 10 LPM at 12° crank angle (CA) before top dead center (BTDC) and from 14 to 16 LPM at 4°CA BTDC.