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Show 3) An area reduction downstream of the secondary air injection shortens the downstream recirculation. A 25% area reduction causes some shortening but a 50% area reduction eliminates recirculation downstream of the restriction, possibly allowing for a shorter combustor. 4) In all cases studied the flow had a periodic wake regime concentrated at the plane of symmetry, resulting from the alternate growth and shedding of vortices produced by the interaction of the injected and bulk flows. Strong oscillations with frequencies from 0.7 to 1.6 Hz were identified, but what determined the shedding frequency was not established (although some dependence on the duct area reduction was indicated.) It has been shown, elsewhere, that data from subscale water flow models, scaled as in this study to match the bulk secondary to primary velocity and mass-flow-rate ratios, agree well with real combustor performance data. Therefore, conclusions from the cold flow model study are being used to define operational criteria for the CFFF secondary combustor, with due consideration given to the effects of density gradients produced by chemical reactions and the evolution and transfer of heat. For example, the CFFF secondary combustor will be operated with injector velocity ratios near 20 rather than 10, and modifications to increase the injector plane area restriction will be considered. REFERENCES 1) D. B. Spalding, "The Art of Partial Modeling", 9th Symposium (International) on Combustion, pp. 833 - 842, 1962. 2) A. E. Clarke, et al., "Some Experiences in Gas Turbine Combustion Chamber Practice Using Water Flow Visualization Techniques", 9th Symposium (International) on Combustion, pp. 878 - 891, 1962. 3) W. M. Farmer, et al., "Characterizing MHD Coal Combustor Particle Fluxes with Laser Velocimeters and Particle Sizing Interferometers", Proceedings of the 1981 Symposium on Instrumentation and Control for Fossil Energy Processes, ANL-81-62, CONF - 810607, Argonne National Laboratory, pp. 230 - 237, 1981. 4) J. P. Foote, "A Cold Flow Model Study of Turbulent Mixing in a Secondary Combustor", M.S. Thesis, The University of Tennessee, 1982. (Also United States Department of Energy Report DOE-ET-10815-87). 18 |