Performance testing of biodiesel blends with rapeseed oil focusing on combustion, performance, and emissions analysis

• R10-R40, R100 diesel-rapeseed oil biodiesel mixes tested for performance, emissions. • Research analyzed emission characteristics, engine performance, combustion behaviour. • Higher biodiesel (R30, R40, R100) lowered BTE, increased BSFC due to viscosity. • Biodiesel blends showed lower max cylinder pressures and heat release than diesel. The depletion of fossil fuel resources and rising greenhouse gas emissions have driven the search for environmentally sustainable alternative fuels. In this study, biodiesel blends derived from rapeseed oil R10 (10 % biodiesel), R20, R30, R40, and R100 (100 % biodiesel) were prepared via base-catalyzed transesterification and tested on a single-cylinder Kirloskar TV1 diesel engine. The experimental investigation focused on combustion characteristics, engine performance, and emissions analysis. The brake-specific fuel consumption (BSFC) increased with higher biodiesel content, with R100 showing a peak BSFC of 0.39 kg/kWh, compared to 0.25 kg/kWh for diesel at full load. Brake thermal efficiency (BTE) was highest for diesel (33.5 %) and declined with increasing biodiesel concentration, with R20 showing a BTE of 32.3 %, indicating close performance to diesel. R20 also exhibited favorable combustion behavior, with peak cylinder pressure reaching 64.8bar, closely matching diesel’s 67.6 bar. Emission analysis showed that R20 achieved reductions of 17.7 % in CO, 15.6 % in HC, and 6.7% in carbon dioxide compared to diesel. However, NOx emissions increased with biodiesel content; R100 showed a 14.3 % rise in NOx compared to diesel. The results demonstrate that R20 offers a practical trade-off between performance and emissions, whereas R100 presents challenges due to its higher BSFC and NOx emissions. The study confirms the viability of rapeseed oil biodiesel, particularly R20, as a sustainable alternative to diesel fuel.