Effects of hydrogen peroxide on the combustion and emissions of an ethanol/gasoline combined injection engine under different excess air ratios

Abstract

Hydrogen peroxide (H2O2) can prompt hydroxyl radicals and chain reactions in the combustion process. Compared with the research on compression ignition engines, the effects of H2O2 were less studied in spark ignition (SI) engines. In this paper, 30 % laboratory-grade H2O2 (H2O2-30 %) was utilized to obtain the H2O2-ethanol blend, which was applied to a direct injection system in a combined injection SI engine. Gasoline was used for the port injection system. The effects of H2O2-30 % ratio (H2O2r) = 0 %, 5 %, 10 %, 15 % and 20 % on combustion and emission performance of an ethanol/gasoline engine were explored at three excess air ratios (λ = 0.9, 1 and 1.2). Engine operating condition was set at engine speed = 1500 rpm and intake manifold pressure = 49.5 kPa. The results showed that H2O2-30 % could reduce the Tmax and Pmax, and extend CA0-10, CA50 and CA10-90. The inhibition effects of water on combustion performance can be alleviated due to the hyperactive H2O2 at the H2O2r > 5 %. Optimal H2O2r increased engine IMEP by 0.14 bar, 0.11 bar and 0.05 bar, and reduced BSHC and BSCO by 30.5 %, 36.6 %, 31.6 % and 17.9 %, 32.1 % and 40.8 %, respectively. BSNOx were reduced by an average of 38.0 %, 28.8 % and 42.2 % at λ = 0.9, 1 and 1.2, respectively.