Experimental study on standing wave regimes of premixed H2–air combustion in planar micro-combustors partially filled with porous medium

Abstract

Heat recirculation is of vital importance to micro/meso-scale combustion. Filling a micro-combustor with porous medium is intended to enhance heat recirculation from the reaction zone, besides the combustor wall. Typically, in large-scale porous burners with a constant cross-sectional area, once the fuel–air equivalence ratio (Φ) is fixed, there is only one corresponding filtration velocity (U) which gives rise to a stationary combustion wave. In our previous studies, a configuration of a planar micro-combustor partially filled with stainless steel mesh was proposed, and three critical conditions corresponding to the flame stability limits of premixed H2–air combustion were experimentally identified. In addition, we observed a regime, rather than a point (U and Φ), within which stationary combustion waves exist. As a follow-up, this study investigates the effects of width, filling position, porosity and wire diameter of the porous medium on the standing wave regime in an H=1mm planar micro-combustor. Furthermore, two more micro-combustors with H=1.5 and 2mm, respectively, are studied and the results compared with the case with H=1mm. It is shown that the combustor size has a significant influence on the standing wave regime. With the increase of combustor size, the standing wave regime shrinks rapidly. The finding clearly reveals the scale effect on the standing wave regime in filtration combustion.