Experimental Study of a Multinozzle Combustor at Elevated Pressures

Emissions measurements and OH* chemiluminescence imaging were performed on a novel multipoint lean direct injection combustor designed for low-NOx emissions and with the flexibility to operate at both high- and low-power settings. The combustor has five rows of fuel nozzles that can be staged in three independent circuits as required. The fuel nozzle stages are not identical; instead, they are optimized for different power settings. NOx, CO, and unburned hydrocarbons were measured for a variety of settings, including lean blowout, idle, intermediate power, and simulated full power. Effects of pressure, inlet temperature, equivalence ratio, and fuel flow distribution were studied. OH* chemiluminescence was used to observe flame structure and interpret emissions trends. The local equivalence ratio, calculated with the fuel and air flow rates particular to each combustor stage, was a useful parameter for interpreting emissions. The combustor demonstrated the ability to operate at a wide range of conditions, from an overall equivalence ratio of 0.55 to lean blowout at 0.079. Low-NOx operation was achieved at high power by using all fuel stages and controlling fuel flow to obtain an even distribution among the nozzles and reduce peak temperatures while using staging to provide good stability at low power.