Effects of Heat Flux and Ignition Type on the Combustion of Live Pinus nigra Branches

This study investigates the influence of ignition type (piloted and unassisted) and heat flux levels on the combustion behaviour and gas products emissions of live Pinus nigra terminal branches. Samples were exposed to three heat flux levels (50, 60, and 70 kW/m2) using an adapted mass loss calorimeter coupled with an FTIR gas analyzer to simultaneously monitor flammability parameters and combustion product concentrations in real time. Results demonstrated that piloted ignition significantly reduced ignition times and enhanced heat release rates compared to unassisted ignition, particularly at lower heat fluxes. However, at 70 kW/m2, differences between ignition types diminished, indicating that higher incident radiant energy alone was sufficient to initiate flaming combustion. Combustion product analysis revealed that CO2, NO, CH4, and C2H4 concentrations followed heat release rate trends. During piloted ignition, higher concentrations of CO2 and NO and lower emissions of CO and CH4 were observed compared to unassisted ignition. Principal Component Analysis showed the combined effect of heat flux and ignition type on combustion efficiency and gas composition. These findings highlight the importance of ignition mechanisms in understanding vegetation flammability, providing valuable data for wildfire behaviour modeling and fire safety assessments.