Optimizing the Combined Effects of TiO2 and CuO Nanoparticles on CI Engine Performance and Emissions with Diesel-Methanol Blends Using Box Behnken Design

Abstract

Compression ignition (CI) engines continue to be the primary choice for transportation and power generation; however, their extensive use is limited by significant emissions of NOx, CO2 and particulate matter (PM), despite progress in engine and fuel technologies. Among various alternatives, methanol has emerged as a promising fuel due to its high oxygen content, elevated latent heat of vaporization, and rapid flame propagation characteristics, all of which support cleaner combustion. In parallel, the addition of metal oxides, specifically titanium oxide (TiO₂) and copper oxide (CuO), has shown potential in enhancing the thermophysical and physicochemical properties of fuel blends, further improving combustion efficiency and emission characteristics. This research focused on the experimental investigation and optimization of the effects of diesel–methanol blends augmented with TiO₂ and CuO nanoparticles on the performance and emission profiles of a CI engine. Fuel blends with 10%, 20%, and 30% methanol (M10, M20, and M30) were created using an ultrasonicator to guarantee consistent nanoparticle distribution. Engine load, TiO₂ concentration, and CuO concentration were chosen as independent variables, and response surface methodology (RSM) was utilized to identify optimal operating parameters. In comparison to baseline operation, the M10 blend demonstrated the most favorable reductions in emissions. Specifically, reductions in NOx and CO₂ emissions were observed at 7.43% and 5.38%, respectively, when compared to the CI baseline. Under the RSM-optimized conditions of 63% engine load, 90 ppm TiO₂, and 60 ppm CuO, the engine achieved a brake torque of 5.54 Nm, a brake power of 2.11 kW, and a brake specific fuel consumption of 0.356 kg/kWh. The emissions recorded were CO₂ at 3.514% vol, CO at 0.022% vol, NOx at 167 ppm, and HC at 18 ppm. These results validate that TiO₂/CuO nanoparticle-enhanced methanol blends can significantly improve the performance and emissions of CI engines.