Intermediate Reynolds/Peclet number, flat plate boundary layer flows over catalytic surfaces for micro-combustion applications

The reactive, flat plate boundary layer flow of close-to-stoichiometric, methane-air mixtures over small size Pt plates is studied experimentally for intermediate Reynolds and Peclet numbers which pertain to micro-combustion applications. The surface temperature was measured with infrared thermography and correlated to reactant concentration profiles acquired with line-Raman imaging. Three phases of combustion were observed. Immediately after the leading edge, a first phase was established with a high surface temperature (>1200°C) and intense fuel depletion. The Reynolds number and equivalence ratio strongly influenced this first phase. It was followed by a second, longer phase, where temperature reached an intermediate value near 1000°C that exhibited little sensitivity to Reynolds number and equivalence ratio. In a third phase, combustion was completed and the surface temperature was reduced to the free-stream mixture temperature. It is suggested that this ‘Phase I’ combustion can be used for burner miniaturisation through boundary layer interruption.