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Show INTRODUCTION In the open cycle magnetohydrodynamic (MHD) electrical power generation systems tested at The University of Tennessee Space Institute (UTSI), fossil fuels (coal and oil) are burned in a two-stage combustion process to minimize the formation and release of nitrogen oxides (NOx) to the atmosphere. This two-stage combustion process is employed in the Low Mass Flow (LMF) experimental MHD test train of the U. S. Department of Energy Coal Fired Flow Facility (CFFF) located at UTSI. The LMF primary combustor burns a mixture of pulverized coal and fuel oil, together with K2CO3 "seed" to provide an electrically conducting gas for the MHD process. To limit NOx formation the fuels are burned with stoichiometric ratios ranging from 0.8 5 to 0.9 5 at combustion temperatures of about 3000K. Downstream of the MHD channel the gas is cooled slowly in a radiant furnace for thermal NOx decomposition and exits, at about 1367K, into a secondary combustor where air is added to burn the remaining combustibles, primarily CO and H2. The gas temperature rises to about 1533K with a stoichiometric ratio of 1.05-1.10 in the secondary combustor allowing the increased thermal energy of the gas to be extracted in a conventional steam generation cycle with minimal NOx formation. The secondary combustor must burn the remaining combustibles efficiently in order to recover as much chemical energy as possible for use in the steam cycle and eliminate the CO species in the gas. The chemical kinetics of the combustion reactions involving CO and H2 are much faster than mixing rates of the primary gas and secondary air stream; hence, the mixing effectiveness is the primary factor that determines the combustion efficiency and performance of the secondary combustor. Because the secondary combustor performance is dominated by fluid mixing phenomena, an experimental program using a 1/6 scale flow model, geometrically similar to the LMF secondary combustor, was undertaken in order to obtain some basic understanding of the mixing and flow in this type of device. By employing a dual Bragg cell laser velocimeter to map the velocity field, detailed velocity and turbulence data were obtained for various combustor geometries and operating conditions. In order to estimate scaling effects for the model, references on the subject of combustion modeling using water as the test fluid were studied. Discussions 2 |