Computational Model of Forward and Opposed Smoldering Combustion in Microgravity

Abstract

A novel computational model of smoldering combustion capable of predicting both forward and opposed propagation is developed. This is accomplished by considering the one-dimensional, transient, governing equations for smoldering combustion in a porous fuel accounting for improved chemical kinetics. The heterogeneous chemistry is modeled with a 5-step mechanism for polyurethane foam. The kinetic parameters for this mechanism were obtained from thermogravimetric data in the literature and reported by the authors elsewhere. The results from previously conducted microgravity experiments with flexible polyurethane foam are used for calibration and testing of the numerical results. Both forward and opposed smoldering configurations are examined. By considering the 5-step mechanism, the numerical model is able to predict qualitatively and quantitatively the smoldering behavior, reproducing the most important features of the process. Specifically, the model predicts the transient temperature profiles, the overall structure of the reaction-front, the onset of smoldering ignition, and the propagation rate. The fact that it is possible to predict the experimental observations in both opposed and forward propagation with a single model is a significant improvement in the development of numerical models of smoldering combustion. This is particularly relevant in multidimensional simulations where distinction between forward and opposed modes is no longer applicable.