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Show .- t- - separatslY.rand pass through flow straighteners before approaching the burner exit. The primary . , air passe~ through a high blockage swirler, providing a bluff body stabilization region with rapid mixing and sufficient axial velocity to keep the flame detached from the face of the swirler. The secondary air passes though an annulus -adjacent to the primary tube and has a small amount of swirl imparted by a set of low-blockage vanes set at 10° from the vertical. Six fuel tubes, terminated by nozzle tips, pass though this annulus to the burner exit where gaseous fuel is injected in multiple jets. Table ill lists the operating conditions for this study. The heat release rate was held at 50 kW providing an exhaust temperature of -1000 K without additional heat extraction. The primary-to-total air ratio was held flXed at 0.15, in keeping with normal operation of this type of Table III burner. Burner Reynolds number based on the total air flow at 298 K and throat exit diameter (51.6 mm) was 28,000. Two types of fuel nozzles were used, alternating among the six injection locations. Each had two main drillings, directed downstream, which provide the majority (34%) of the fuel injected in jets ~f Re = 4000. Additional drillings were provided on each nozzle in order to achieve rapid fueVair mixing in the stabilization zone adjacent to the primary air swider. The transition between the burner exit and the furnace was managed using a slowly diverging ceramic quarl to promote flame stability. The CSRB was operated in the Sandia Research Furnace to provide confinement with optical access to the flame (Fig. 3). The furnace is octagonal in cross section and utilizes fullsize fused-silica windows for configurable optical access. In the present studies, optical access w~ provided on five sides of the chamber. The three sides at the rear of the' chamber were configured with blackened silica ceramic panels to maximize contrast for flame visualization. Combustion air was metered using calibrated critical flow nozzles mounted in stagnation chambers. The fuel stream was blended on line using mass flow meters and a four-channel controller. Furnace operation was held steady by closed loop computer control of the firing rate, excess air, and primary air fraction. - 6- |