Thermal Decomposition of Vegetative Fuels and the Impact of Measured Variations on Simulations of Wildfire Spread

Published

May 1, 2023

Author(s)

Isaac Leventon, Jiuling Yang, Morgan Bruns

Abstract

This manuscript presents new measurement data from milligram-scale thermal decomposition experiments - thermogravimetric analysis (TGA) and microscale combustion calorimetry (MCC) – conducted on stems and leaves of six plant species commonly found across the United States. For each fuel, measurement data from TGA experiments was analyzed to determine effective thermal decomposition mechanisms and the associated kinetics of their constituent reactions. Results of this model calibration were compared to standard (i.e., 'generalized') approaches to obtain kinetic parameters available in the literature. MCC experiments were repeated under identical experimental conditions to determine the heats of complete combustion of all gaseous volatiles produced by these vegetative fuels and to validate the decomposition mechanisms and species char yields determined from TGA data. Through a coupled analysis of TGA and MCC measurement data, an estimate of the heats of combustion of the gaseous volatiles produced by individual reaction steps in the fuel's decomposition was also made. Between different fuels, distinct differences were measured in the onset temperature of decomposition, the temperature range of decomposition, the number of apparent reactions, and the peak measured mass loss and heat release rates (as well as the temperatures at which they occur). To analyze the impact of these variations on predictions of wildfire behavior, a modeling study was then conducted in which simulations of wildland fire experiments were repeated using the thermal decomposition mechanisms and heats of combustion determined for six of the fuel species tested in this work. Model-predicted fire spread rate in these simulations varied between 0.52 m s−1 and 1.07 m s−1 demonstrating not only a dependence on measured variations in thermal decomposition mechanism but also the use of either reaction-step-specific or single (global) heats of combustion.

Citation

Fire Safety Journal

Pub Type

Journals

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Keywords

Fire Modeling, Pyrolysis, Wildfire Spread

Citation

Leventon, I. , Yang, J. and Bruns, M. (2023), Thermal Decomposition of Vegetative Fuels and the Impact of Measured Variations on Simulations of Wildfire Spread, Fire Safety Journal, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933335 (Accessed September 14, 2024)