Comparative Study on Injection Pressure and Timing Variations in Diesel Engines Fuelled with Renewable Energy Biodiesel Blends

Abstract

Biodiesel blends from animal fats support renewable fuel use in compression-ignition engines while addressing regulated exhaust pollutants. Quantified guidance on coupled injection pressure and timing settings for a 20% animal-fat biodiesel blend remains limited. This work evaluates and optimises fuel injection pressure and timing to maximise efficiency while curbing emissions using AFB20. Experiments were conducted on a vertical single-cylinder, four-stroke diesel engine using an eddy-current dynamometer and exhaust gas analyser. Fuel injection pressure was varied from 180 to 240 bar and injection timing was varied from 19° to 27° before Top Dead Centre (bTDC) across engine loads. The optimisation demonstrates that BSFC was 0.26 g/kWh at 200 bar and that this condition supports reduced fuel demand at high load. The timing sweep indicates that BTE was 33.8% at 23° bTDC and that this phasing supports efficient heat release. Emission data indicate that NOx was reduced by 15.07% at 23° bTDC and that moderated peak temperature limits thermal NO formation. These calibrated settings enable targeted tuning of biodiesel-fuelled diesel engines for compliant operation. The findings support deployment of animal-fat biodiesel in existing engines with minimal hardware changes. Future research will examine additional blend ratios and multi-cylinder validation under transient duty cycles to improve energy efficiency.