Crosswise heat flux and temperature profiles over downstream surface of gas-fueled pool fires in relatively strong wind

Abstract

This paper reveals the crosswise profiles of heat flux and temperature over the downstream surface (ground) of a pool fire in relative strong wind, which was not well addressed in the past. Two square gaseous burners (25 cm, 30 cm) are used with propane as the fuel producing different heat release rates to simulate pool fires. The wind speed ranges from 1.5 m/s to 4 m/s (with 0.5 m/s intervals for various cases), concerning relatively strong wind conditions (Fr > 0.87). The crosswise heat flux profile first shows to be nearly stable (fluctuation less than 20 %) in the continuous flame region, then a sharp decrease in the intermittent flame region and finally goes to near zero. The temperature profile shows a similar trend as heat flux. For the near stable region, the flame boundary layer goes into the counter-rotating streamwise vortex pairs to form the streak like flames. And the counter-rotating pair (CVP) on the flame makes the streaks on the sides of the burner to be even larger, as verified by the CFD simulation. The heat flux is different under the streaks and troughs of the flame (higher under trough than in streaks), which interprets the fluctuation in the nearly stable region. Then the sharp decrease happens in the intermittent flame region. The flame half-width is obtained, which sits at about the middle of the sharp decrease region. And finally, for the position further away in the crosswise direction, the profile turns to be nearly zero. The crosswise profiles can be well represented by a Boltzmann function. The obtained experimental results and the proposed functions on the crosswise profiles of heat flux and temperature provide an essential base to estimate the heat feedback to the downstream surface of a wind-driven fire.