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Show EXPERIMENT _. I' " 1 Fuel Composition Three fuel gas compositions were tested, as summarized in Table II. Each was a blend of highpurity bottled gas with compositions chosen to span the hydrogen content of the most common RFG streams. Methane was used both as a reference fuel and to represent the limit of hydrogenfree RFG. RFG6 and RFG3 were three-component blends of hydrogen (>99.99% purity), methane (>99.99% purity), and propane (>99% purity) containing approximately 1/6 and 1/3 hydrogen, respectively. In order to minimize changes in fluid mechanic inlet conditions between fuels, the RFG compositions were tailored to provide the same energy per unit volume as the neat methane. This ensured that, for any flXed fIring rate, the velocity of each of the fuel jets would be held constant. Note that since the densities of the fuels are also closely matched (-2%), the mass and momentum fluxes are effectively invariant between fuels. As shown in the table, the hydrogen/carbon ratio, stoichiometric air/fuel ratio (or mixture fraction), and dynamic viscosity are also closely matched. The result of designing the blended RFG fuels in this way is that for constant fIring rate, the velocities, mass flow rates, momentum fluxes, and Reynolds numbers of both the fuel and air streams at the inlet remain unchanged between the fuels. It should be noted, however, that signifIcant differences in transport properties (e.g. mass diffusivity) exist between the fuels due to the hydrogen content. 2 BumerlFumace Configuration The burner used in this study was the CoenlSandia Research Burner (CSRB) designed jointly with The Coen Company to provide a research-quality burner, but using industrial design principals. Shown in Fig. 2, it is capable of dual-fuel firing at 100 kW with a central atomizer for liquid fuels and a concentric ring of jets for gas frring. In this study only gas frring was utilized. Table II The combustion air is split into two streams-primary and secondary-which are metered Fig. 2 - 5 - |