Optimization of performance and emission characteristics of a CRDI VCR engine fueled with cerium‐oxide‐enriched waste‐cooking biodiesel

The present study examines the impact of adding cerium oxide nanoparticles to waste cooking oil biodiesel on the performance and emission characteristics of a diesel engine under varying operating conditions. Response surface methodology was used to optimize the engine responses based on the following input parameters: fuel mixture ratio, injection pressure, compression ratio, and engine load. The multi‐objective nonlinear optimization aims to maximize brake thermal efficiency and minimize specific fuel consumption and exhaust emissions of carbon monoxide, unburned hydrocarbons, and nitrogen oxides. The developed quadratic models showed very strong statistical significance, confirming the robustness and predictive reliability of the RSM approach. The optimal operating conditions of the engine are identified as a nanoparticle‐enriched biodiesel blend ratio of −0.38 (coded value), an injection pressure of 0.28 (coded value), a compression ratio of 1.00, and an engine load of 9.0 kg. On these optimized conditions, the engine achieved a BTE of 33.17% and an SFC of 214.54 g/kWh, along with substantial emission reductions of CO (0.037%), HC (8.32 ppm), and NO x (1260.94 ppm). The close agreement between experimental and predicted results further validated the accuracy of the developed models. Consequently, the integration of cerium oxide nanoparticle‐enhanced waste cooking biodiesel with RSM‐based optimization explores a promising strategy for improving diesel engine performance while significantly mitigating harmful exhaust emissions.