Speed-up drivers for [formula omitted]-enriched flames in Porous Media Burners.

An experimental study on the influence of porosity and hydrogen enrichment on the stabilization of premixed CH 4 -Air flames in Porous Media Burners (PMBs) is presented. Flame stabilization is analyzed via direct flame front tracking, which is made possible by a novel experimental apparatus. The use of additive manufacturing for computer-generated topologies allows making optically-accessible PMBs featuring see-through directions. This methodology also enables topology tailoring which is here exploited to study the influence of porosity on the performance of the burner. Flame front tracking reveals a different stabilization trend in highly H 2 -enriched flames. A comparison with a theoretical model is used to remove the effect of preheating and focus on other fuel properties. This suggests a flame-speed enhancement mechanism driven by Lewis number effects in Le < 1 mixtures. Together with recent 3D Direct Numerical Simulations, these results provide evidence that preferential diffusion effects are key in the stabilization of flames in PMBs. These phenomena, not considered in state-of-the art 1D-Volume Averaged Models, remain crucial for the design of efficient PMB using hydrogen as a fuel. [ABSTRACT FROM AUTHOR]