(98d) Effects of Season and Heating Mode on Ignition and Burning Behavior of Ten Species of LIVE FUEL Measured in a FLAT-Flame Burner System

The effect of season and heating mode on ignition and burning behavior of living vegetation were studied in a flat-flame burner system including a radiant panel.  The goal was to identify what plant characteristics have the greatest influence on burning behavior and to understand the effects of heating mode on ignition and burning.  Experiments were performed for ten species over a two-year period, with 25 runs completed each month for each species.  A flat flame burner (1000°C, 10 mol% O₂) and radiant panel (50 kW/m²) provided the convection and radiation sources, respectively.  Time-dependent mass, surface temperature and flame characteristics were measured.  Moisture content (dry basis) varied with season and location, with the lowest measured moisture content corresponding to the local fire season. The effect of moisture content on ignition time varied with species. Ignition time showed a strong dependence on heating mode, with broadleaf species showing a much stronger response to added radiation than non-broadleaf species.   No samples exposed to the radiant panel alone ignited.  Heating mode and moisture content affected flame characteristics and the relationship depended upon season and species.  The observed relationship between ignition time and moisture content did not agree with the relationship observed in wet wood.  Moisture content alone did not adequately describe seasonal changes in ignition behavior. However, by including other factors in the prediction model (e.g. surface area and mass), it is possible to predict live-fuel ignition (R² = 0.75). This implies that plant physiological processes play a role in the burning behavior of live fuels.