A numerical study of hetero-homogeneous ignition of hydrogen/air mixture over platinum

Abstract

The study numerically investigates the hetero-homogeneous ignition of H2/air jet over Pt surface by using 2D stagnation flow model. The surface ignition temperature is predicted to increase with the incident equivalence ratio φ due to H2 self-inhibition, but the post-ignition surface temperature does not follow the monotonic trend. It peaks at φ = 0.43, where the differential diffusion between H2 and O2 maximizes surface consumption, thereby most effectively inhibiting the shift to homogeneous ignition. The homogeneous ignition is facilitated at φ = 2.5, where the gas composition and temperature are suitably combined for ignition. Flames are then established above the surface and their variation in term of shape and strength are evaluated in conjunction with jet φ and speed.