Experimental and numerical study on the transition conditions and influencing factors of hetero-/homogeneous reaction for H2/Air mixture in micro catalytic combustor

Premixed combustion of Hydrogen/Air in a rectangular micro-catalytic combustor was investigated experimentally and numerically. The distribution of OH radicals in the combustor was observed by Plane Laser Induced Fluorescence (PLIF). A method for determining the transition process of reaction types in the combustor by measuring temperature variation was proposed. The effects of combustor height and mixed gas flow rate on the transition characteristics of reaction type were analyzed and the results demonstrated that the reaction type would transform with the change of equivalence ratio between the coupled hetero-/homogeneous reaction (catalytic and gas phase reaction) and the pure heterogeneous reaction (pure catalytic reaction). The critical equivalence ratio from coupled hetero-/homogeneous reaction transforming into pure heterogeneous reaction is Phi(A). The critical equivalence ratio from pure heterogeneous reaction to coupled hetero-/homogeneous reaction is Phi(B). At different combustor heights and mixed gas flow rates, Phi(A) is always less than Phi(B). When the height of combustor increases, the critical equivalence ratio Phi(A) decreases while the critical equivalence ratio Phi(B) increases. The critical equivalence ratios Phi(A) and Phi(B) both decrease with the increase of mixed gas flow rate. Heat loss on the combustor outer wall has an important influence on the transformation of reaction type.