Evaluation of classical MILD combustion criteria for binary blends of ammonia, methane and hydrogen

The global transition towards low -carbon and renewable energy necessitates fuel flexibility, emphasizing the critical role of alternative fuel options. This study investigates the potential of Moderate or Intense Low Oxygen Dilution (MILD) combustion for binary blends of ammonia, methane, and hydrogen. Utilizing temperaturebased criteria in perfectly stirred reactor (PSR) simulations, multiple detailed chemical kinetic schemes are employed to update combustion regime maps, incorporating NOx emissions. The analysis begins with an exploration of pure fuels and subsequently introduces binary blends, including CH4-H2, NH3-CH4, and NH3-H2. The investigation focuses on their transition to the MILD combustion regime by achieving the requisite oxygen content (X*??????2) at the minimum inlet temperature. Noteworthy findings include the non -monotonic behavior in self -ignition temperature observed in NH3-CH4 combustion, influenced by the impact of nitrogen chemistry on CH4 oxidation. To address uncertainties, three different kinetic schemes are employed. In NH3-H2 blends, a modest addition of hydrogen (10%-20%) significantly reduces X*??????2, self -ignition temperature (Tsi), and NOx emissions. However, further increases in hydrogen content yield diminishing effects. Importantly, ammonia blends require additional dilution (2%-6% oxygen) to maintain NOx levels at 100 ppm under stoichiometric conditions, surpassing traditional MILD criteria. The research underscores the significant potential of binary fuel blends for MILD combustion, offering valuable insights into their performance. The numerical findings on the target regime and emissions trends contribute to optimizing operating conditions and aiding combustion diagnostics.