Effect of biodiesel–DEE premix ratios on PCCI engine performance and emissions: an experimental and statistical study

This study explores the parameters of low-temperature, premixed charge compression ignition (PCCI) combustion through a combination of experimental methods and response surface methodology (RSM) to facilitate clean operation in hybrid powertrains. Testing was carried out on a single-cylinder common-rail direct injection diesel engine operating at 1500 rpm. The engine was fueled via dual-injection strategies: direct injection of a 30% Mahua biodiesel and 70% diesel blend (M30) combined with port fuel (PF) injection of vaporized diethyl ether (DEE) across premixing ratios (PR) up to 40% and varying loads. Statistical optimisation through a central composite design (CCD) determined the optimal operational point at an engine load of 75.29% and a port-injected DEE PR quantity of 28.14%. Under these refined conditions, the setup expedited the heat release rate (HRR) and improved the brake thermal efficiency (BTE), while effectively overcoming the conventional diesel smoke–NOx trade-off. The engine accomplished a concurrent reduction of 33.3% in nitrogen oxides (NOx) and a 40.1% decrease in smoke when compared to conventional combustion. These significant environmental benefits were met with minor, manageable penalties of an 11.1% increase in unburned hydrocarbons (HC) and a 4.8% increase in carbon monoxide (CO). Validation assessments confirmed an error margin below 5%, demonstrating the RSM model’s reliability for series-hybrid powertrain applications.