Auto-ignition of methane–air mixtures flowing along an array of thin catalytic plates

Abstract

In this paper, the heterogeneous ignition of a methane–air mixture flowing along an infinite array of catalytic parallel plates has been studied by inclusion of gas expansion effects and the finite heat conduction on the plates. The system of equations considers the full compressible Navier–Stokes equations coupled with the energy equations of the plates. The gas expansion effects which arise from temperature changes have been considered. The heterogeneous kinetics considers the adsorption and desorption reactions for both reactants. The limits of large and small longitudinal thermal conductance of the plate material are analyzed and the critical conditions for ignition are obtained in closed form. The governing equations are solved numerically using finite differences. The results show that ignition is more easily produced as the longitudinal wall thermal conductance increases, and the effects of the gas expansion on the catalytic ignition process are rather small due to the large value of the activation energy of the desorption reaction of adsorbed oxygen atoms.

Keywords:

• catalytic combustion
• methane combustion
• monolithic catalytic combustor
• auto-ignition
• asymptotic analysis

Acknowledgements

The author acknowledges the support given by CONACyT with grant 00082002 and the DGAPA of UNAM (IN113508).