Low air pressure effects on burning rates of ethanol and n-heptane pool fires under various feedback mechanisms of heat

• Pressure effects on flame temperature of pool fire were analyzed.
• The coupling influences of pressure and heat feedback were studied theoretically.
• An overall correlation of pressure effects on burning rate was proposed.

The present work is a theoretical investigation into the influence of reduced air pressure on pool fire burning rate with different domination of heat feedback mechanisms. The coupling effects of pressure and heat feedback on burning rate or other typical parameters, e.g., flame temperature and flame height, were discussed within 3 regions under conduction-controlled, convection-controlled and radiation-controlled, respectively. A comprehensive correlation of pressure effects on burning rate with increasing pool fire scale was formulated based on radiation fire modeling and classical fire dynamics theory, which was validated well by the previous experimental data (carried out in ~65 kPa and ~100 kPa atmospheric pressures). It was interesting that the influence of pressure on flame height was able to be predicted by combining the theoretical correlation established and the classical flame height equation. Also, pressure effects on burning rate and flame height with increasing pan diameter showed a similar trend.