Experimental and analytical investigation of lean premixed methane/air combustion in a mesoscale counter-flow reactor

Combustion-based personal power systems have great potential for applications that demand high energy density, compact, and durable components. Through the use of heat recirculation, increased combustor firing rates and extension of flammability limits can be achieved. This study examines the combustion of lean methane/air reactant mixtures below the conventional flammability limit in a mesoscale heat-recirculating counter-flow reactor. An analytical model, previously developed for reforming in the counter-flow reactor, was adapted and applied to study lean operation. Results qualitatively describe the operating principle of the reactor and its behavior in response to changes in inlet conditions. Experiments determined the stable operating range of the reactor. Peak reactor wall temperature measurements indicate superadiabatic operation. Exhaust emissions of CO and NOx range from 35 to 143 ppm and 5 to 25 ppm, respectively, and emission indices as a function of firing rate are presented. Unburned hydrocarbons were detected at the lowest firing rates. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.