Optimization of Performance and Emissions of RCCI Engine at Various Speed Conditions Using Response Surface Methodology Technique

Abstract

The demand for reduction of greenhouse gases and the implementation of stringent emission regulations have compelled researchers and engine makers to look for alternative approaches of increasing efficiency from the internal combustion engine. This study investigated the optimization of performance and emission characteristics of a reactivity-controlled compression ignition (RCCI) engine. A dual-fuel strategy was introduced by employing gasoline/n-butanol blends (G25n-b75, G50n-b50, and G75n-b25) as low reactivity fuels and a biodiesel blend (B20) as a high reactivity fuel. Experiments were carried out on a single-cylinder, water-cooled compression ignition engine under varying engine speeds (2400, 2600, and 2800 rpm). Response Surface Methodology (RSM) was used to evaluate the effects of engine speed and fuel blend ratio on brake torque (BT), brake power (BP), brake specific fuel consumption (BSFC), nitrogen oxides (NOx), hydrocarbons (HC), carbon dioxide (CO₂), and carbon monoxide (CO). The optimal operating condition was found at engine speed of 2557 rpm with a 47% n-butanol blend ratio, resulting in improved performance and reduced emissions, with BT, BP,  BSFC, NOx, HC, CO₂ and CO values of 14.86 Nm, 4.04 kW, 0.379 kg/kWh, 102 ppm, 32 ppm, 4.63%, and 0.87%, respectively. Analysis of Variance confirmed the statistical significance of the model with high R² values: BT (97.98%), BP (98.39%), BSFC (98.62%), CO₂ (94.72%), CO (98.89%), NOx (99.66%), and HC (97.14%). The findings demonstrated the synergistic potential of gasoline/n-butanol and biodiesel dual-fuel RCCI mode to enhance combustion efficiency and to reduce emissions, offering a viable alternative for sustainable engine operation.