Energy, exergy, and direct engine-out emission impact assessment of an ethyl acetate–diesel dual-fuel engine under different EGR rates

This study experimentally investigates the energy, exergy, and direct engine-out emission impacts of ethyl acetate (EA)–diesel dual-fuel operation under exhaust gas recirculation (EGR). Tests were conducted on a single-cylinder direct-injection diesel engine at 1800 rpm and 25–100% loads. EA injection durations of 1, 2, and 3 ms and EGR rates of 0%, 5%, 10%, and 20% were investigated. Energy and exergy balances were established, and direct emission impact was calculated from CO, CO 2 , HC, and NO x mass-flow rates derived from the measured exhaust-gas concentrations and intake-air flow. At full load, EA(2 ms) + 20% EGR increased energy and exergy efficiencies by 39.1% and 38.4%, respectively, and reduced exergy destruction by 42.5% relative to diesel operation without EGR, representing the thermodynamically preferred condition. EA(3 ms) without EGR produced the maximum pointwise direct emission-impact reduction of 72.5% at 25% load, whereas EA(3 ms) + 20% EGR provided the greatest average reduction of 35.8%. Condition-mean ANOVA showed that engine load accounted for 84.81%, 84.61%, and 91.70% of the variations in energy efficiency, exergy efficiency, and direct emission impact, respectively. Load-resolved TOPSIS identified EA(2 ms) + 20% EGR as the highest-ranked balanced compromise, with a mean closeness coefficient of 0.7781; however, EA(3 ms) + 20% EGR became preferable when direct emission impact received greater weight. The results demonstrate metric-specific optima and support load-dependent coordination of EA injection and EGR.