Perpustakaan Digital ITB

In the global transition to carbon-neutral energy, ammonia (NH3) is a promising but challenging fuel due to its low reactivity, poor flame stability, and high potential for NO emissions. This thesis investigates the combustion behavior of partially cracked ammonia diffusion flames by combining one-dimensional Cantera simulations with coflow burner experiments. Results show that increasing the cracking fraction from ???? = 0.28 to 0.50 expands the stability envelope tenfold and that a further increase to 0.75 yields another 1.5 × enlargement for an overall twenty-fold gain. Experiments confirm that flames with ???? = 0.28 extinguish at 190 LPM of coflow air while those with ???? ? 0.50 remain stable up to 250 LPM. Raising the fuel jet velocity from 1.0 m/s to 5.0 m/s increases global strain from 200 s-1 to 1000 s-1 and narrows the extinction window by about 30 percent. Simulated flame-shape analysis reveals that higher cracking fractions and aerodynamic strain compress the reaction zone, shifting the peak temperature by approximately 1 mm toward the stagnation plane and thinning the flame in proportion to the inverse square root of strain. Experimental observations mirror this trend, showing visible flame length shrinking from 17 cm to 12 cm as ???? rises, with additional reductions of up to 15 cm under turbulent flow and 10 cm with added coflow air. Nitric oxide emission simulations identify the ????+?????????????????+???????? pathway as the primary source of NO and ????????+?????????????+????????? together with ????+??????????????+???? as the main sinks, experiments show NO levels reduce in the order of 50?250 ppm. These findings demonstrate that optimized ammonia cracking and flow-control strategies markedly improve flame stability and minimize NO emissions.