Comparative study on effects of injection mode on combustion and emission characteristics of a combined injection n-butanol/gasoline SI engine with hydrogen direct injection.

In this paper, on the basis of combined injection technique, three injection modes with five n-butanol/gasoline volume ratios (ν N) were put forward, aiming to compare and evaluate the relationship between the injection mode and the combustion and emission characteristics of an n-butanol/gasoline SI engine equipped with an extra hydrogen direct injection system. The results indicated that under low load condition, compared with NG P (n-butanol/gasoline port injection) mode, the NG PD (n-butanol/gasoline combined injection) mode and NG PH (n-butanol/gasoline with hydrogen combined injection) mode can both improve the combustion performance. The peak cylinder pressure of NG PD and NG PH mode was 5.58% and 11.63% higher than that of NG P mode on average, respectively. Furthermore, the combined injection modes concentrated the process of heat release, shortened the combustion duration, increased the power performance and improved the combustion stability at all ν N. As for emissions, the NG PD and NG PH combined modes significantly decreased the HC and CO emissions, but increased the NO X emissions. Among all the test conditions, the NG PH mode with 25% ν N obtained the best combustion quality. Additionally, the effect rules of ν N on combustion and emission characteristics under NG P mode were found to be consistent with those under NG PD and NG PH combined modes. • An n-butanol/gasoline SI engine with hydrogen direct injection is proposed. • The low load performance versus n-butanol ratio under 3 injection modes are compared. • The change of combustion parameters with n-butanol ratio is consistent under 3 modes. • Combined injection and hydrogen can make up for the innate issues of n-butanol. [ABSTRACT FROM AUTHOR]