A simulation of ethanol substitution rate and EGR effect on combustion and emissions from a high-loaded diesel/ethanol dual-fuel engine

Abstract

In this study, the combined effects of the ESR (ethanol substitution rate) and the EGR on combustion and exhaust emissions from high-loaded RCCI engine were investigated numerically to improve the engine with high ESR. RCCI experimental data were obtained from a study performed on a 2.771-liter diesel engine fueled with diesel/ethanol fuels. The simulation was performed via Converge Computational Fluid Dynamics (CFD) code, and numerical results were validated with the experimental data. The parameters such as in-cylinder pressure, in-cylinder gas temperature, heat release rate, CA10, CA50, indicated thermal efficiency, maximum pressure rise rate, NOx, soot, HC and CO emissions were investigated at 2000 rpm engine speed and high engine load (80% full load). The results show that the in-cylinder pressure, the in-cylinder gas temperature, and the maximum pressure rise rate significantly increases due to the increase of ESR. The maximum pressure rise rate was obtained for ESR40 as 1.24 MPa/CAD. Knocking tendency were determined for various ESR, but it increases rapidly with increasing of ESR. The highest soot and CO in cylinder decreases, and the highest NOx and HC in cylinder increases due to ethanol addition. EGR has a significant effect on combustion and emission from high-loaded RCCI engine when keeping ESR constant as ESR40. In-cylinder pressure, maximum pressure rise rate and in-cylinder gas temperature decreases due to EGR addition, while at the same time, indicated thermal efficiency also decreases. The maximum pressure rise rate was obtained for EGR25 as 0.59 MPa/CAD, and the maximum indicated thermal efficiency is 42%. The highest NOx in cylinder decreases, and the highest soot, HC, and CO in cylinder increases due to EGR addition.