Combustion modelling for forest fires: from detailed to skeletal and global models

摘要

This work aims to improve the understanding of the combustion of vegetative fuels. The degradation gases released by some Mediterranean species were determined. They mainly consist of CO, CH_4, CO_2, H_2O and other hydrocarbons. Then a study of the oxidation of a CO/CH_4/CO_2 mixture was performed with a perfectly stirred reactor (PSR) at atmospheric pressure over the temperature range 773-1273K. Mole fraction profiles as a function of temperature were compared to the numerical predictions obtained with the PSR code from CHEMKIN II using the full mechanism GRI-Mech 3.0. A skeletal mechanism was developed from the full mechanism. It was tested for laminar flames obtained with samples of crushed Mediterranean species. Different skeletal and global mechanisms were also tested. The comparison between the simulated and predicted temperatures points out that the common assumption of carbon monoxide burning in air is not appropriate at this scale. Methane should be included in the modelling to perform reliable simulations. This result leads to the proposal of a simple combustion mechanism to be included in models of wildland fire.