In addition, the onset conditions of the cellular instability are mapped as a function of stretch rates, initial mixture strengths, and flame curvature.
To examine the effects of curvature on extinction, the critical fuel dilution ratios at extinction are measured at various stretch rates, initial mixture strengths and flame curvature for fuels diluted in N2, He, Ar or CO2.
Cement addition increased the mixtures strength and reduced their erodibility and capillary flow characteristics, but increased shrinkage.
The Lewis numbers of the investigated near-extinction mixtures, based on the initial mixture strength ϕm and ambient conditions, varied in the ranges [1.1 1.3] for oxygen and [0.25 0.29] for hydrogen (ϕm is defined here as the fuel-to-oxygen mass ratio, normalized by the stoichiometric ratio).
The development has involved the implementation of an algebraic functional dependence of the laminar burning velocity on the reaction mixture strength, temperature, and pressure [1].
The transitions to cellularity, cellular structures, and extinction conditions were determined as a function of the initial mixture strength, stretch rate, and curvature.
The primary objective is to systematically identify the conditions for the onset of oscillations examining, in particular, the influence of differential diffusion, mixture strength, flow rate, and radiative heat losses.
Images are shown of rotating cellular flames and a cellular instability regime at an initial mixture strength greater than unity and away from extinction conditions.
The model shows generally good agreement with ignition delay times measured in a shock tube and a rapid compression machine and is sensitive to changes in temperature, pressure, and mixture strength.
