Combustion and Emission Characteristics of an Ammonia Microgas Turbine Combustor With a Twin-Fluid Atomizer

In this study, combustion and emission characteristics in the test rig of microgas turbine with liquid ammonia fuel injection using the twin-fluid atomizers (TFAs) are investigated and compared with the previous result using the pressure-swirl atomizer (PSA). The combustion situation was simulated using the test rig of microgas turbine, and experiments were conducted by controlling the ratio of ammonia and methane to create a pure ammonia combustion situation. The TFA has spray cone angles of 60 deg, 90 deg, and 120 deg, and its combustion characteristics were analyzed and compared with the PSA. At 60 deg TFA, the blow-off of ammonia flame occurred before the pure ammonia combustion stage, and the flame blow-off occurred after the pure ammonia combustion at the 90 deg and 120 deg TFAs. This means that the blow-off of ammonia flame easily occurred when the spray cone angle of the atomizer is small, because the recirculation flow to the upstream of ammonia flame is weak. In addition, the 90 deg and 120 deg TFAs showed significantly reduced emissions of NO, N2O, and unburned NH3 compared to the 60 deg TFA and PSA. This can be concluded that a large spray cone angle forms a strong recirculation flow within the combustor, and emissions are reduced because the high-temperature zone sufficiently stays in the primary combustion zone.