NOx formation in ethylene-ethanol dual fuel counter-flow flames

Renewable based dual-fuel engine technologies are among these promising and feasible solutions for achieving low-carbon transportation in a near term. This study examines nitrogen oxides (NO x ) emissions on a counter-flow flame burner fueled with ethanol and ethylene at different supply ratios. Instead of air or oxygen, lean premixed ethanol/oxygen/nitrogen was supplied at one side of the burner, while mixture of ethylene/nitrogen was fed from the other side. In comparison to the ethylene–air counter-flow flame, introduction of ethanol from other side of the burner not only increased the maximum flame temperature by about 100⁰C but also produced a broader flame region, both contributing to elevated NO x emissions. Modeling these flames with detailed reaction mechanisms revealed the dominating role of the prompt NO pathway, in spite of the contribution of the thermal NO pathway to certain extent. Detailed reaction pathways of NO x formation were investigated and the dominating pathways suggest the increased oxygen availability in the extended reaction region and the higher flame temperature played significant roles. These findings indicate that introduction of ethanol to the oxidant side may affect the combustion efficiency and fuel chemistry, necessitating careful control of mitigating the NO x emission, which should provide insights for optimizing heavy-duty dual fuel combustion engines.