Stability limits of methane-hydrogen-air and ammonia-hydrogen-air swirl flames

Hydrogen is a promising carbon-free fuel for power generation in gas turbines. However, usage of hydrogen raises some challenges associated with its storage and distribution. Storing hydrogen chemically in the form of ammonia is considered a safe and efficient method. Therefore, the use of ammonia to fuel gas turbines is promising. However, ammonia features a low reactivity compared to hydrogen or natural gas and, as a consequence, stabilizing turbulent ammonia-air flames is challenging. In this study, the stability limits of premixed ammonia-hydrogen-air flames are measured for a wide range of ammonia additions in a laboratory-scale swirl burner. Results are compared to that obtained for reference methane-hydrogen-air mixtures. Data show that increasing the ammonia addition increases the equivalence ratio at the lean blowout limit but also reduces the flames' propensity to flashback. The latter effect is even more pronounced if the volume fraction of ammonia in the reactants exceeds that of hydrogen. In that case, increasing the equivalence ratio at a fixed bulk velocity does not yield flashback and rich blowout occurs instead.