Effect of MgO nanoparticle concentration on the engine performance, combustion, emissions, and tribological characteristics of dual-biodiesel–n-butanol blends

Abstract This study investigates the effects of 5% n-butanol and green-synthesized MgO nanoparticles on the engine performance, combustion, emission, and tribological characteristics of dual-biodiesel-based fuel blends. MgO nanoparticles were synthesized using guava leaf extract and characterized by SEM, TEM, FTIR, and XRD, confirming a flake-like morphology with particle sizes below 50 nm. The tested fuels included D100, A10PJ10D80, A10PJ10D75B5, and MgO-containing blends at 30, 60, and 90 ppm. Engine experiments were performed under different load conditions, while friction and wear behaviour were evaluated using a four-ball tribometer and SEM analysis. At full load, 5% n-butanol reduced BSFC from 0.328 to 0.322 kg/kWh and increased BTE from 30.4% to 30.5%, with concurrent reductions in CO, HC, and smoke opacity. Increasing MgO concentration further improved engine characteristics, with 90 ppm MgO achieving a BSFC of 0.305 kg/kWh and BTE of 32.4%, while CO, HC, and smoke opacity decreased to 0.0561%, 39.2 ppm, and 44.2 HSU, respectively. However, NO X increased from 910 to 975 ppm, indicating a trade-off associated with enhanced combustion intensity. Peak in-cylinder pressure and HRR increased to 70.9 bar and 39.4 J/deg, respectively. The optimum tribological response occurred at 60 ppm MgO, with COF and WSD decreasing to 0.0795 and 0.458 mm, corresponding to reductions of 14.97% and 18.94% relative to D100.