Dynamic behaviors of premixed hydrogen–air flames in a planar micro-combustor filled with porous medium

• Premixed hydrogen-air combustion in a planar micro-combustor was studied.
• Flame stability limits for different combustor configurations were identified.
• Porous medium was found to be effective in enlarging the operation window.
• Blow-off limits are nearly independent of combustor configurations.
• Flashback limits are greatly influenced by the parameters of the porous medium.

The micro-combustor is a key component of the micro-thermophotovoltaic (TPV) system, and the flame stability limits are very important to its design and operation. An experimental study on the dynamic behaviors of premixed hydrogen–air flames in an H = 1 mm planar micro-combustor is undertaken. The combustor is partially filled with porous medium to enhance heat transfer and flame stabilities. Critical conditions (Φ1 for blow-off, Φ2 for flashback, and Φ3 for breaking through the porous medium) are experimentally identified for different combustor configurations. It is shown that the blow-off limits are nearly independent of the combustor configuration, while the flashback limits are strongly affected by the combustor configuration as well as the parameters of the inserted porous medium, including the position (Lout), the width (W) and the porosity (ε) of the porous medium. Most of the results can be explained by the classic boundary velocity gradient theory by von Elbe and Lewis in a qualitative sense. Based on the experimental findings, widening the operation window of the planar micro-combustor partially filled with porous medium is possible when the parameters are chosen properly.