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 (nu(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 nu(N). As for emissions, the NG(PD) and NG(PH) combined modes significantly decreased the HC and CO emissions, but increased the NOX emissions. Among all the test conditions, the NG(PH) mode with 25% nu(N) obtained the best combustion quality. Additionally, the effect rules of nu(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. (C) 2020 Elsevier Ltd. All rights reserved.