Experimental investigation of equivalence ratio effects on combustion and emissions characteristics of an H2/methanol dual-injection engine under different spark timings

The addition of H-2 is an effective way to enhance the speed of propagation of a flame and extend the lean-burn limit of spark ignition (SI) engines. An H-2 port-injection and methanol direct-injection dual-fuel SI engines were used in this study to investigate the effect of the equivalence ratio on the combustion and emissions characteristics of the engine at low speed using the late injection strategy for methanol. The results show that 3%-6% of H-2-enriched methanol can effectively expand the lean-burn limit from an equivalence ratio of 0.625 of pure methanol to that of 0.455. The spark timing of H2 addition must be optimized by different equivalence ratios and ratios of H-2 addition to implement ideal combustion phasing at 16 degrees CA ATDC and 10 degrees CA ATDC of p(max) and HRRmax, respectively. H-2 addition can significantly shorten both CA0-10 and CA10-90, and can quickly advance CA50. For 6% of H-2 added, when the equivalence ratio was over 0.5, the COVimep was below 3.5%. This addition significantly improved the lean-burn characteristics of the H-2/methanol SI engine. BSHC emissions with the addition of 6% H-2 was much lower than that of the pure methanol engine at equivalence ratios of over 0.625. When H-2 was added, BSCO emissions increased rapidly in terms of both lean and stoichiometric equivalence ratios, compared with the case when no H-2 was added.