Mesoscale burner arrays allow combustion to be conducted in a distributed fashion at the millimeter (meso) scale. At this scale, diffusive processes are fast, but not yet dominant, such that a number of advantages over conventional burners can be achieved without giving up the possibility to use fluid inertia to advantage. Since the scale of the reaction zone follows from the scale at which the reactants are mixed, very compact flames result. We expect that this compact, distributed form of combustion can provide not only the opportunity of inter-turbine reheat, but also the potential for lean premixed or highly vitiated combustion to suppress NOX emissions. In previous work, a 4×4 array, with burner elements on 5-mm centers, was fabricated in silicon nitride using shape deposition manufacturing. Results from both fully premixed (mixing prior to the array) and partially premixed (mixing in the array) configurations demonstrated the degree to which premixed performance can be achieved with this design and pointed to ways in which the array design could be improved. In the present work, a next-generation 6×6 array has been developed and tested. Major design changes in this array include use of a combination of bluff-body and swirl flame stabilization and a multilayer architecture with a separate fuel manifold for more uniform fuel distribution. In this multilayer design, the array is fabricated in three separate pieces, one of which is a vaporization layer designed for use with liquid fuels. Results using gaseous fuel (methane) in a fully premixed operating condition, including pressure drop, flame stability, temperature distribution in the burned gas, and NOx emissions, are reported for both bluff-body and no-bluff-body configurations. Tests for a partially premixed configuration are being carried out to evaluate the potential of the design modifications.
Partially Premixed Ignition for a Bluff-Body Flameholder under Various Igniter and Inlet Conditions
