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Show D Ambient Combustion Air A proven conventional high velocity low NOx burner was used as the development platform for an LNI ambient air burner with capacities up to 18 M M BTU/h. The variables of injector offset, angle between air and fuel injectors, air velocity, fuel velocity, and number of fuel injectors were evaluated with the following objectives: Determine a configuration of burner and injector parameters to achieve the lowest NOx emissions with suitable combustion characteristics. Quantify the effect of the application-related parameters on N O x emissions. Quantify the effect of deviations from the optimum configuration to facilitate flexibility in application, particularly physically constrained retrofits. Air and fuel injector orientation The effects of offset distance and relative angle between fuel and air injectors are interdependent. Intuitively, either decreasing the angle between injector axis (i.e. approaching parallel) or increasing the injector offset distance will have the same effect: greater distance between the injector nozzles and the point that fuel and air streams begin to mix allows increased dilution and hence lower N O x emissions. Our results from testing of LNI with ambient combustion air support the intuitive conclusion to a degree. The injector offset parameter i may be defined as the ratio of the distance between fuel and air injector centers to the sum of the air and fuel injector radii: • D+d £ = x J Where: X = Distance between the air nozzle and fuel nozzle centers D = Diameter of the air nozzle d = Diameter of the fuel nozzles Offsets corresponding to I - 4 combined with angles of 5° produced unacceptable combustion results (stingers from furnace openings, swirling clouds of luminous combustion gases, and generally poor 7 |