Asymptotic Analysis
The rate-ratio asymptotic analysis has been applied to predict the
flame structure and extinction diameter for methanol burning in
air. The flame structure is shown in the following figure, in which
Z is the mixture fraction, with Z = 0 in the atmasphere and Z = 1 in
the fuel.
The fuel-consumption zone is
located at Z0. In this layer, reaction I occurs where CH3OH
molecules are attacked by H atoms to form CO and H2. On the lean
side of the fuel-consumption layer exists a H2 and CO oxidation
layer, where H2 and CO are oxidized to form CO2 and H2O.
The predicted extinction diameters of pure methanol droplets,
burning in oxygen-nitrogen mixtures at 300 K, as function of the
ambient oxygen mole fraction, for three different pressures, is
shown in the following figure; solid
curves are for two-step chemistry and points for three-step
chemistry.
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