Enhancement of flame stability by a short Pt segment for CH4/H2 blended fuels in a micro-flow reactor

Abstract

Effects of a Pt segment on flame stability of CH4/H2/air mixtures in a micro-flow reactor were numerically scrutinized, which demonstrated that flame instabilities were completely suppressed. In addition, the response of flame position to inlet velocity exhibited two C-shaped curves, which was divided into regimes A, B and C for high, medium and low inlet velocities, respectively. Flame bifurcation occurred in regime B. A case study of regime B showed that the increased generation rate of H(s) caused the main H2O(s) formation reaction shift from OH(s)+OH(s)=H2O(s)+O(s) to H(s)+OH(s)=H2O(s)+PT(s). This led to a decreased O(s) coverage and an increased PT(s) coverage, which prevented C(s) from reacting with sufficient O(s) to form CO2(s). As a result, CO(s) accumulated on the catalytic surface and flame bifurcation occurred. The dynamic processes from regime B to A and C were also examined, which manifested that a threshold value existed for the adsorption rate of H atoms. Once the threshold value was exceeded, the reaction pathway of OH(s) has undergone a transformation. In conclusion, this study uncovered the influence of heterogeneous reactions on gas combustion of CH4/H2 blends, and provided an effective and economic technology for flame stability enhancement in micro-flow reactors.