Numerical investigation of CH4/H-2/air flame bifurcations in a micro flow reactor with controlled wall temperature profile

摘要

Flame characteristics of CH4/H-2/air (CH4:H-2 = 1:1) mixture in a cylindrical micro flow reactor with a controlled wall temperature distribution were numerically studied. Bifurcation phenomena were captured in both stable flame regime and FREI (Flame with Repetitive Extinction and Ignition) regime. For the stable flame regime, a normal flame and a weak flame co-exist in upstream and downstream of the channel, respectively. Analysis of reaction paths demonstrates that H-2 competes with CO for OH radical in upstream normal flame, which causes incomplete combustion and produces CO residual. When the residual CO moves to farther downstream with a higher wall temperature, CO and OH react completely and a weak flame is formed. For the unstable flame regime, twice bifurcations occur during one period of FREI. The first bifurcation mainly results from residual O-2 and CO after the re-ignition point, while the formation mechanism of the second bifurcation is similar to that of the co-existing weak flame which bifurcates from upstream stable flame. In a word, the present study discovered complex flame characteristics of CH4/H-2 blended fuels in a micro flow reactor with wall temperature gradient and revealed the underlying mechanisms responsible for these flame phenomena. (C) nbsp;2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.