Experimental determination of the structure of catalytic micro-combustion flows over small-scale flat plates for methane and propane fuel

Surface oxidation on small-scale catalytic coupons of Pt foil was investigated experimentally for methane/air and propane/air mixtures of varying composition and flow speed. Infrared thermography was used for the measurement of temperature on the catalytic surface in tandem with gas-chromatography/mass spectroscopy measurements of major combustion products and combustion intermediates and particle image velocimetry of the flow field in the vicinity of the catalytic surface. It was shown that the surface reaction develops in three phases. In phase I, very close to the leading edge, a sharp temperature increase occurred on the catalytic surface with simultaneous fast depletion of the gaseous reactants and development of a strong transverse component of the velocity vector. This was followed by phase II in which surface temperature plateaued at a high value, and reactant concentrations remained low. In phase III the non-adiabatic reaction extinguished and, on occasion, reactant replenishment was observed from the free stream. It is suggested that the design of small-scale reactors should proceed by exploiting the intense reaction of phases I and II through boundary layer interruption and not allow the phenomenon to develop all the way into phase III thus achieving miniaturization of the required hardware.