Experimental study of ammonia addition in premixed methane flames

Ammonia is a hydrogen carrier fuel that does not produce CO2 emissions in direct combustion. While ammonia combustion systems have been successfully trialled in a wide range of applications including aircraft engines and gas turbines, ammonia’s low laminar burning velocity and high ignition energy is one of the barriers to its more widespread use. The design and use of ammonia-methane combustors helps overcome these barriers, while also acting as a pathway to a lower-carbon economy. Hence the purpose of this study was to investigate the flame behaviour in terms of stability and emissions production in premixed methane swirl stabilised flames with both diffusion and premixed ammonia injection configurations. Temperature measurements, OH*, and NH2* chemiluminescence measurements were taken. Product gas values were measured for up to 50% (vol.) of ammonia and for 0.8 to 1.4 equivalence ratios at two power ratings (i.e. 6.4 and 10.7 kW). Chemiluminescence results for these conditions show radical concentration’s centre of gravity moving lower with an increase in ammonia concentration. NH2* radicals peaking at 30% ammonia volume fraction. This study also found correlations between radical formation and temperature profiles for numerical validation purposes.