Laminar burning velocity measurements of NH3/H2+Air 3 /H 2+Air mixtures at elevated temperatures

This paper presents detailed investigations of the combustion characteristics of NH3/H2 blends as a possible alternative fuel to address the pressing environmental and energy security challenges. The experimental measurements of laminar burning velocity (LBV) are reported for a range of mixture equivalence ratios (phi) varied from 0.8 to 1.2 and mixture temperatures up to 720 K using the externally heated diverging channel (EHDC) method. It is observed that LBV increases nearly four times for specific NH3/H2 blends with an increase in mixture temperature from 300 K to 650 K. While predictions from various kinetic models align well at ambient conditions, discrepancies emerge at higher temperatures, emphasizing the need for refining these models to accurately predict flame propagation behaviour. A detailed sensitivity analysis of the NH3/H2/air fuel blend provides insights into critical reactions and species influencing burning velocity across different mixture conditions. Notably, reactions involving NNH radicals are found to strongly influence LBV for low hydrogen fractions in NH3. Additionally, reaction pathway analysis (RPA) highlights dominant reactions under various conditions and reveals temperature-dependent NO emissions. The present study helps highlight the importance of understanding the combustion behaviour of NH3/H2 blends for achieving carbon-free energy needs. The experimental data at elevated temperatures offers valuable insights into the combustion behaviour of these mixtures, enabling the advancements for cleaner energy solutions.