effects of Combustor Inlet Conditions on Flame Stability

Abstract

A model for predicting flame ignition and blowout in a combustor primary zone is presented. The model employs a Monte Carlo calculation procedure to follow a chemical reaction through a mixing process to account for composition nonuniformities in the primary zone. The fuel oxidation process is described by an overall kinetic rate equation. The model is used to predict the lean ignition and blowout limits of premixed turbulent flames; the effect of composition nonuniformity on the lean ignition limit is explored using an assumed distribution of fuel fraction. The predicted trends are verified using data from the literature and by experimental work on an atmospheric pressure, constant cross-sectional area tubular combustor. Data on the effects of variations in inlet temperature, reference velocity and mixture uniformity on the lean ignition and blowout limits of gaseous propane-air flames are presented. The variations of the predicted lean limits with mixture temperature, pressure and velocity compare favorably with experimental magnitudes and trends. With increased mixture nonuniformity, the model predictions and the data show a substantial reduction in the lean ignition limit.