Experimental investigation of species and temperature characteristics of intermediate Reynolds number reactive boundary layers in micro-combustion flows

The reactive, flat plate, boundary layer flow of close-to-stoichiometric, methane-air mixtures over small size Pt plates was studied experimentally for intermediate Reynolds and Peclet numbers which pertain to micro-combustion applications. Infrared thermography and Gas Chromatography/Mass Spectroscopy were used to measure the centerline profiles of temperature and major combustion species. Since both streamwise and transverse gradients were important in the intermediate flow regime, the results are significantly different from the usual high Reynolds number catalytic combustion. The surface reaction proceeded in three distinct phases. Immediately after the leading edge, a short, intense reaction occurred, producing high surface temperatures and rapid conversion of species. This is followed by a plateau-like region and finally by extinction. Equivalence ratio strongly affected the first two phases, with richer equivalence ratios resulting in higher peak temperatures, shorter reaction lengths, less replenishment of reactants, and increased carbon monoxide production. Reynolds number did not have a strong influence on the structure of combustion.