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Show delivery strategies to achieve performance goals, are regularly limited by a reduction in combustion efficiency due to the typically lean operating conditions or diluent injection, which can result in poor CO and hydrocarbon burnout. In order to achieve further reductions in NOx without a sacrifice to combustion efficiency, it is essential to understand the processes by which NOx is formed in industrial burners. To that end, this paper investigates the near fuel injection region and the resulting flow fields from different fuel and air mixing strategies using velocity measurements and computational fluid dynamic modeling. BACKGROUND A 100,000 Btulhr model, industrial burner test stand was used in these studies and is described in more detail elsewhere [4, 5]. The burner and fuel injectors used in this study are shown in Figure 1. Three different fuel injection geometries were used to vary the fuel and air mixing and produce three different mixing strategies. The counter-swirl injector introduces the fuel in a direction opposing the swirling air flow; the radial injector introduces the fuel radially across the swirling air annulus; and the co-swirl injector introduces the fuel in the same direction as the swirling air. Previous emissions measurements of these injectors over their entire stability ranges have shown the optimum performance, in terms of low NOx and high combustion efficiency, occurs with the counter-swirl injector. The plots in Figure 2 represent performance in terms of low NOx and high combustion efficiency, where values close to 1.0 represent better performance. In order to gain insight into the reasons for these performance characteristics, several conditions for each injector were selected for more detailed investigation using non-intrusive, laser diagnostics. The selected conditions are shown in Table 1 and represented graphically in Figure 2. Table 1: Conditions for Investigation Condition Injector Excess Air Swirl Input, S' Performance, J I Co-swirl 5% 0.40 0.58 2 Co-swirl 20% 0.52 0.45 3 Radial 50/0 0.62 0.53 4 Radial 150/0 0.62 0.60 5 Counter-swirl 5% 0.72 0.52 6 Counter-swirl 20% 0.66 0.71 Measurements of velocity, temperature, and NO concentration have been acquired to quantify the aero-chemical flow-field downstream of the burner exit. For example, Figure 3 shows nonintrusive measurements of temperature and NO concentration for the counter-swirl injector at 5% excess air and swirl strength of 0.72 (condition @) at an axial location of 0.5 inches downstream of 2 |