Experimental assessment of SWCNT-added waste cooking oil biodiesel–diesel blend in a single-cylinder diesel generator: performance, emissions, energy, exergy, sustainability, and exergoeconomic analyses

In this study, the effects of adding 50 and 100 ppm of single-walled carbon nanotubes (SWCNTs) to D85B15 fuel, prepared from biodiesel derived from waste cooking oil, on the performance, exhaust emissions, energy, exergy, sustainability, and exergoeconomic indicators of a single-cylinder diesel engine-generator system were experimentally investigated. D100, B100, D85B15, D85B15S50, and D85B15S100 fuels were tested at a constant engine speed of 3000 rpm and in the range of 1000–5000 W active electrical output power. The reported power values correspond to the active electrical output measured at the generator terminals; engine shaft power was not measured separately. The addition of SWCNT reduced specific fuel consumption and increased electrical thermal efficiency compared to the additive-free D85B15. The increase in electrical thermal efficiency at 5000 W for D85B15S100 fuel was approximately 11.24%. Exergy destruction in D85B15S50 and D85B15S100 fuels decreased by 14.33–16.32% and 16.88–19.69%, respectively, compared to D85B15. The addition of SWCNTs decreased CO and smoke values while increasing NOx and CO₂ concentrations. The increase in CO₂ was evaluated not only as a positive indicator of further oxidation but also alongside fuel consumption, carbon content, and exhaust flow conditions. The addition of SWCNT increased the sustainability index derived from exergy efficiency, but also raised the fuel cost flow rate depending on the additive cost. Under the tested conditions, the 100 ppm SWCNT blend generally exhibited slightly more favorable mean technical and thermodynamic values than the 50 ppm blend; however, these differences should be interpreted as numerical trends rather than statistically demonstrated concentration effects.