Synergistic optimization effect of the coupling of multi-fuel supply strategies on the combustion and emission characteristics of oxyhydrogen / bioethanol / gasoline combined supply engine

Oxyhydrogen, a hydrogen-based fuel, is commonly used to enhance the performance of ethanol–gasoline engines. We experimentally investigated the combustion characteristics and emissions of a multi-fuel combined supply system using oxyhydrogen negative pressure induction, bioethanol direct injection (BEDI), and gasoline port fuel injection. At 1500 rpm and excess air ratio 1, integrated oxyhydrogen technology improves combustion efficiency and significantly reduces CO and HC emissions; however, NOx emissions increase. With increasing BEDI pressure, the indicated mean effective pressure (IMEP) and maximum in-cylinder pressure increase initially and then decrease. CO and HC emissions show a similar trend, decreasing initially and then increasing, while NO is reduced by an average of 14.09%. Advancing BEDI timing benefits the cyclic coefficient of variation of IMEP. When the BEDI timing is within 250–300°CA BTDC, HC, CO, and particulate emissions reach their lowest levels, with particulates decreasing by up to 70.11%. • Constructed a BEDI + GPI + ONPI integrated combustion model. • Optimal oxyhydrogen dosing accelerates combustion, reducing exhaust CO and HC. • Raising BEDIP from 5 to 9 MPa optimizes the engine combustion process. • Right BEDIT boosts stability while lowering particulate emissions.