Combustion of Stratified Methane/Air Layers

Abstract

Combustion of horizontally layered methane/air mixtures have been studied. Methane-diluted with Ar, or N₂, or CO₂—and air, initially separated by a thin plate, form a flat combustible layer only by interdiffusional mixing upon withdrawal of the plate. Simultaneous line ignition was made at one side of the layer for the whole range of the combustible mixture ratio. The ignition took place at only a stoichiometric position and failed elsewhere. Addition of the inert gases caused serious ignition delay. The induction distance depends primarily on the amount of inert gases in the fuel. The flame speed first accelerated and, as the flame traveled way off the igniter wall it drastically decreased down to 1.5 times the burning velocity of the corresponding stoichiometric premixed flame. It has been found that a travel distance more than 5 cm is required for the flame to establish steady propagation.