December 2001

This report was prepared with the support of the U.S. Department of Energy, under Cooperative Agreement No. DE-FC21-92MC29061. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the DOE.

Research during the first six months of Subcontract No. 01-01-S090 has focused on a study of the effect of the combustor inlet fuel distribution on the stability and emissions characteristics of a laboratory dump combustor. This study was conducted in the optically accessible dump combustor shown schematically in Figure 1. As illustrated, this combustor provides for the fuel to be introduced at one or more of six different locations, thereby allowing for significant variations in the fuel distribution. At location (1) the fuel is introduced well upstream of the choked inlet to the mixing section. Fuel introduced at this location is thoroughly mixed with the air before entering the mixing section and results in a perfectly uniform fuel distribution at the combustor inlet. At location (2) the fuel is introduced through 4 injectors (diameter = 0.81 mm) located in the outer wall of the mixing tube at a position 110 mm upstream of the dump plane. This location is downstream of the choked inlet to the mixing section and upstream of the axial swirlers in the mixing section. At location (3) the fuel is injected into the mixing section through 12 holes (diameter = 0.34 mm) located around the circumference of the centerbody, 25 mm upstream of the dump plane. By varying the fuel split between these three injection locations, the spatial fuel distribution at the inlet to the combustor can be varied. Locations (3), (4) and (5) provide for what is called "targeted" injection and are intended to allow for fuel to be introduced directly into the combustor at locations which are likely to enhance flame stabilization. At location (4) the fuel is injected through 12 holes (diameter = 0.34 mm) equally spaced around the inner circumference of the dump plane. At location (5) the fuel is injected through 12 holes (diameter = 0.34 mm) equally spaced around the outer circumference of the end-face of the centerbody and angled at 45 degrees. At location (6) the fuel is injected through a single 1.18 mm diameter hole on the axis of the centerbody. These six injection locations not only provide a means to vary the spatial fuel distribution, but modulating the fuel flow to any of these injection locations also provides a means for varying the temporal fuel distribution.

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