Comprehensive RSM-based optimization of intake charge and EGR strategies for minimizing pollutant emissions in diesel engines fueled with PODE/HVO/diesel ternary blend

Facing the depletion of traditional energy and stricter emissions regulations, the research and development and application of renewable clean fuels draw much attention. Hydrotreated vegetable oil (HVO), with abundant sources, environmental-friendliness and renewability, is a key candidate for energy transition. Polyoxymethylene dimethyl ether (PODE), having a high cetane index and oxygen content, is often an auxiliary diesel fuel. In this study, via numerical modeling, the combustion and emissions characteristics of a ternary blend of 2.5% PODE, 2.5% HVO and 95% diesel under ful-load were evaluated, and relevant engine control parameters were optimized. Analyses show that increasing initial pressure or exhaust gas recirculation (EGR) ratio delays the start of combustion (CA10), while raising initial temperature advances CA10. Initial pressure and temperature boost peak cylinder pressure for stronger power output, yet all three reduce the peak average in-cylinder temperature. Regarding emissions, response surface methodology (RSM) was used to analyze the significance of initial pressure, temperature and EGR rate. Results indicate EGR rate most significantly impacts NOx and soot emissions. Compared with the baseline engine settings, the parameter combination optimized by RSM cuts NOx emissions by 65.5% and soot emissions by 12.9%.