Experimental investigation of the effect of CO2 dilution on the performance and hydrogen knock limit of a hydrogen–gasoline dual fuel spark ignition engine 1

Abstract

This study investigates the effect of CO2 dilution on the performance and hydrogen knock limit of a spark ignition engine fueled with hydrogen–gasoline mixtures. The experimental runs were performed on a Ricardo single-cylinder engine with direct gasoline injection and hydrogen port induction. The hydrogen flow rate was increased at a step size of 2 L per minute (LPM) until the onset of knock, and the CO2 gas was introduced to the intake manifold with flow rates of 2, 4, and 6 LPM. The results revealed that CO2 dilution deteriorated the engine performance regarding the brake mean effective pressure and brake thermal efficiency. The hydrogen enrichment shortens the combustion duration, enhancing the performance and combustion characteristics. Increasing CO2 dilution levels decreased NOx emissions and increased CO emissions. Moreover, CO2 dilution extended the hydrogen knock limit to 10 and 16 LPM for spark timings of 12° and 4° crank angles before top dead center, respectively.