Modelling and Optimization of Combustion and Emission Characteristics in an HCCI Engine Fueled with Butanol–Diethyl Ether Blends

Abstract This study employs an integrated research approach based on Response Surface Methodology (RSM), combining experimental investigations with statistical analysis to examine HCCI engine performance, combustion behavior, and emissions. Three key independent parameters were investigated: the butanol blend ratio, the lambda value, and the engine speed. The experimental ranges included engine speeds of 800–1200 rpm, lambda values of 2.4–3, and butanol ratios of 15–45%. Within these ranges, critical parameters such as BSFC, IMEP, COV IMEP , MPRR, ITE, combustion phasing indicators (CA10 and CA50), combustion duration (CD), and CO and HC emissions were systematically analyzed. The RSM-designed experimental data were subjected to statistical analysis and optimization to determine the optimal combination of operating conditions. The optimization revealed that the highest overall desirability of 73.9% was achieved at a butanol ratio of 38.17%, a lambda value of 2.4, and an engine speed of 1200 rpm. Under these optimal conditions, the engine performance and emissions were as follows: BSFC of 195 g/kWh, IMEP of 4.78 bar, COV IMEP of 2.59%, MPRR of 8.12 bar/°CA, CA10 and CA50 values of − 3.29°CA and − 3.27°CA, respectively, CD of 21.24°CA, ITE of 38.37%, CO emissions of 0.063%, and HC emissions of 279.79 ppm. These results demonstrate that careful tuning of the butanol blend ratio, lambda value, and engine speed can significantly enhance combustion stability, efficiency, and emission performance in HCCI engines.