Multiobjective Optimization of Performance and Emission Profiles in a WCO–Butanol‐Fueled RCCI Engine: An RSM‐Based Investigation of EGR and Injection Duration Interactions

ABSTRACT This investigation develops a multiobjective optimization framework for Reactivity Controlled Compression Ignition (RCCI) engines utilizing a butanol, waste cooking oils–biodiesel, and diesel ternary blend. Moving beyond traditional parametric sweeps, the study employs Response Surface Methodology in conjunction with a Face‐Centered Central Composite Design to systematically decode the coupled influences of Injection Duration (ID), exhaust gas recirculation (EGR) rates, and engine load on combustion dynamics. Statistical validation via analysis of variance ensures high predictive fidelity, offering a robust mapping of the dual‐fuel reactivity landscape. Experimental results initially identified a peak brake thermal efficiency (BTE) of 32.0% at high‐load conditions (16 kg); however, this point exhibited significant NO x penalties. To reconcile the performance‐emission trade‐off, a multiobjective optimization was executed using desirability functions. The global optimum was identified at 5.68°CA ID, 13.58% EGR, and 6.66 kg load, yielding a predicted BTE of 23.73% and NO x emissions of 809.2 ppm. At this Pareto‐optimal point, NO x was reduced by 35% compared with baseline diesel through thermal dilution and reactivity stratification. The model was validated through confirmatory experiments, with a maximum error of 1.89%, confirming that the RCCI strategy offers superior environmental‐performance trade‐offs at midload conditions for sustainable, low‐carbon propulsion.