Enhancement of liquid ammonia combustion by a twin fluid atomizer

The effects of the atomizer type on flame stabilization and emissions from a liquid ammonia gas-turbine combustor was studied to explore the impact of enhanced fuel-air mixing. A twinfluid atomizer is expected to enhance the mixing of the atomized fuel and air, which may in turn decrease the amount of unburnt fuel at the combustor outlet due to improved combustion efficiency. Liquid ammonia was used as the fuel, and the combustor pressure was 0.25 MPa abs. The low combustor pressure tends to encourage partial vaporization of the liquid ammonia in the mixing chamber of the twin-fluid atomizer. When the pressure of the mixing chamber was below the design value, it was found that the lower pressure, which may encourage flash boiling and hence rapid atomization, enabled a decrease in the emission of unburnt NH3 as compared with that of the pressure-swirl atomizer. However, when the mixing chamber pressure was as high as the design value, higher levels of unburned ammonia emission was observed. This suggests that flash boiling which promotes atomization may enhance the combustion efficiency.