Experimental investigation of gaseous reactive flows around catalytically coated micro-wires

The reactive flow around catalytically coated cylinders was investigated experimentally in the regime of Reynolds and Peclet numbers that are relevant to small-scale power generation devices. Methane combustion was established on the surface of the catalyst by placing the wire in the outlet flow of a pre-heater that controlled temperature, composition and velocity of the methane - air pre-mixture. The results highlight the combined importance of chemistry and transport phenomena for the determination of the structure of these flow fields. Specifically, the temperature of the catalytic wire was measured with a thermocouple welded to the support metal of the wire and the results indicated that because of the strongly non-adiabatic nature of the combustion, temperature maxima are affected by Re and appear for equivalence ratios significantly different than the ones predicted from thermochemistry. Particle image velocimetry measurements were performed and the resulting velocity fields show that both the Reynolds number and the equivalence ratio of the flow influence the structure of the flow field. Moreover, the catalytically coated wires were shown to affect a much larger region of the flow than what they physically block. Gas chromatography/mass spectroscopy of major combustion species was performed downstream the catalytic wire and showed that CH₄ and CO concentration increased with increasing equivalence ratio.