A novel catalytic-homogenous micro-combustor

Miniaturizing combustors from macro- down to micro-scales leads to an increase of the surface area to volume ratio and, thus, thermal and radical quenching may prevail. The ranges of operating conditions at which micro-combustors exhibit stable behaviors are very narrow unless a catalyst is employed. However, catalytic combustors face the problems of thermal control related to the formation of hot spots and the subsequent catalyst deactivation. In this paper, two-dimensional computational fluid dynamics (CFD) simulations are run to investigate into the opportunity of setting up a novel scheme of micro-combustor divided into two parts. In the first part, the walls of the micro-combustor are catalyst-coated, while in the second part, the catalyst is absent and only homogenous combustion can take place. Numerical results show that this hybrid micro-combustor (H mu C) allows operating at high inlet gas velocities and thus high input powers, without encountering blow-out and maintaining almost complete fuel conversions. This enlargement effect of the operating map on the high inlet velocity side increases on increasing the solid thermal conductivity. Furthermore, the catalytic wall temperature of such H mu C is controlled and taken below 1200 K, thus preserving the catalyst. (C) 2009 Elsevier B.V. All rights reserved.