Abstract
This research work investigates the effects of adding ethanol to biodiesel–diesel blends on the performance and emissions of a single-cylinder, four-stroke, air-cooled compression-ignition engine. The engine was half-loaded within a speed range of 1000–2500 rpm. Four different fuel blends are considered: B0 (no biodiesel or ethanol), B10 (10% biodiesel), B10E2.5 (10% biodiesel with 2.5% ethanol), and B10E5 (10% biodiesel with 5% ethanol). The findings show that adding biodiesel slightly affects the engine power at low and medium speeds but increases power by approximately 6% at high speeds. Ethanol addition has a more significant impact, with an increase in engine power of 16% at 1700 rpm and 13% at 2500 rpm for 2.5% and 5% ethanol blends, respectively. All blends show an increase in brake mean effective pressure (BMEP) compared to B0, with the maximum enhancement observed in B10 with an average increase of 13% across all speeds. Specific fuel consumption is reduced with both biodiesel and ethanol addition, with a slight advantage for biodiesel, particularly at low and medium speeds. Thermal efficiency shows a reverse behaviour, with a small negative impact of ethanol addition. Biodiesel addition significantly increases carbon monoxide (CO) emissions, reaching an average of 190% across all speeds. However, adding ethanol helps mitigate this increase, especially at low and medium speeds, with an average decrease of 32% for a 2.5% ethanol blend compared to B0. Carbon dioxide (CO2) and nitrogen oxides (NOx) emissions are reduced with biodiesel addition and further reduced with ethanol addition. Overall, CO2 and NOx emissions are reduced with both biodiesel and ethanol addition.