Numerical study of the effects of heat transfer methods on CH4/(CH4 + H2)-AIR pre-mixed flames in a micro-stepped tube

In this study, an approach to modification and improvement of CH4/air pre-mixed flame in a micro-stepped tube is numerically studied. The effects of added hydrogen to methane as an additive, entrance mixture velocity and some physical properties such as the micro-stepped tube wall thermal conductivity and the outer wall convective and radiative heat transfer coefficients on temperature distribution and combustion progress in a micro-stepped tube are calculated using a high order, high accuracy 2D numerical laminar steady state code. The results show that adding hydrogen to methane in a micro-stepped tube can play a pivotal role in modification processes of combustion phenomena in a micro combustor. Also, it is found that adding hydrogen to CH4 can assure the flame presence in some certain conditions in comparison to the simple backward facing step method. Moreover, adding hydrogen can improve the concentration of the combustion vital radicals and also temperature distribution along the micro combustor, impressively. In this regard, adding hydrogen to methane as an additive sustains the combustion vital radicals against the variation of the heat transfer conditions in or around a micro-combustor. (C) 2012 Elsevier Ltd. All rights reserved.