Effect of NH 3 /H 2 /O 2 premixed combustion on energy conversion enhancement and NO x emission reduction of the segmented nozzle micro-combustor in thermophotovoltaic system

In the context of international carbon neutrality, ammonia as a carbon-free energy has attracted extensive attention and research, and its renewability is the most prominent advantage. However, ammonia combustion is unstable, and harmful nitrogen oxides will be generated at the same time. In order to enhance the combustion stability of ammonia and control the emission of nitrogen oxides, the premixed combustion of NH 3 /H 2 /O 2 in a segmented nozzle micro-combustor is studied in this paper. The mean wall temperature of segmented microcombustor is 11.5 K higher than that of non-segmented micro combustor, and NO emission is reduced by 7.91 % at most. When mass fraction of hydrogen in the gas mixture X H2 increases from 10 % to 30 %, radiation efficiency increases by 13.5 %, but NO emission also increases. Considering that fuel-rich combustion can reduce NO emission, when hydrogen equivalence ratio Phi H2 = 1.0 and ammonia equivalence ratio NH3 Phi = 1.2, NO emission is reduced by 13.3 %, while radiation efficiency remains above 60 %. In addition, the radiation efficiency of the combustor increases by up to 4.15 % when the dimensionless length of segmented channel L 6 is 7.5 mm and the dimensionless width of segmented channel D 4 is 2.5 mm, and NO emission is reduced by 5.14 %.