Experimental exergy and energy analysis of Ungurahui biodiesel blended with ethers to reduce emissions

• The incorporation of ethers increased the oxygen concentration of biodiesel–diesel blends by up to 4.33%. • Addition of UB10DEE10 showed reduced CO by 22.7% compared to diesel. • Ether blends showed lower cylinder pressures and higher heat release rates. • UB10TME10 showed lower NO x than other blends due to its shorter ignition delay. • HC emissions decreased by 16.67% for UB10DEE10 at 75% load compared to diesel. The study evaluates the combustion, emission, energy, and exergy performance of Ungurahui biodiesel–ether blends in a compression ignition engine operating at 2400 rpm. Four fuels were investigated: UB20 (20% Ungurahui biodiesel and 80% diesel), UB10DEE10 (10% biodiesel, 10% diethyl ether, 80% diesel), UB10DME10 (10% biodiesel, 10% diethylene glycol dimethyl ether, 80% diesel), and UB10TME10 (10% biodiesel, 10% tripropylene glycol monomethyl ether, 80% diesel) and compred the results with diesel. The incorporation of 10% oxygenated ethers increased the intrinsic oxygen content of the blends by 2.37% to 4.33% relative to diesel. Among the tested fuels, UB20 exhibited brake thermal efficiency comparable to diesel, reaching 30.52% at full load, while diesel achieved 30.84%. In contrast, UB10TME10 showed a lower efficiency of 27.11% due to its reduced heating value, resulting in an approximate 14% increase in brake-specific fuel consumption compared with diesel. At full load, CO emissions decreased by 14% and 9.9% for UB10TME10 and UB10DEE10, respectively, compared to diesel. Nitrogen oxide emissions increased moderately with all ether blends due to higher combustion temperatures. At 100% load, UB10DEE10 and UB10TME10 show increases of approximately 13% and 8%, respectively, compared with diesel. In contrast, compared with UB20, UB10TME10 exhibited lower NO x emissions at all loads, with reductions of approximately 5.5%, 5.0%, 2.9%, and 2.2% at 25%, 50%, 75%, and 100% loads, respectively. Furthermore, a 23% increase in peak heat release rate was observed for UB10TME10 than diesel. Overall, UB10TME10 provided a decent balance between reduced NO x emissions and thermodynamic performance. The study recommends lowering the ether concentration to minimise prolonged heat release while maintaining combustion benefits.