Vertical seismic effect on fire structure and behaviour of pool fires

Fires and vibrations can occur simultaneously. Two obvious examples are ship fires and fires during earthquakes. One previous study has investigated the horizontal seismic effect on pool fires, showing higher heat release rate (HRR), shorter and wider flames. This study experimentally explored the effects of vertical vibrations on the structure and behavior of free-burning pool fires. The experimental set-up and design were similar to the previous study, i.e. burning wood cribs on a vibrator under an ISO 9705 hood. The preparation of wood-cribs and the ignition method followed ISO 15779. Moreover, the wood sticks were connected by nails and the wood cribs were fixed on the vibrator to avoid the influence of collapse of wood cribs. The vibrator can generate vertical vibrations, and different scales of seismic conditions, calculated by vibration amplitude and frequency, were applied. The parameters measured included flame height, flame diameter, flame frequency, flame temperature, air entrainment velocity and HRR. The experimental results showed that the flame were higher with the vibration scale, and the flame diameter did not change. The vertical vibration lengthened the flames, while some discontinuity was observed. This discontinuity was even enhanced with the increased vibration scale. Additionally, the flame frequency and the air entrainment velocity was increased due to the vertical vibrations. The air entrainment and the mixing of fuel volatiles and oxygen were enhanced. This argument can be proved by increased HRR. The HRR was increased with the increased vibration scale, but with an exception of the 6-Upper scale (the highest scale herein). This exception may be caused by decreased heat feedback in the test of 6-Upper scale. More discontinuity of flames and further distance between the flame (particularly the upper part flames) and the wood cribs due to lengthened flames decreased the heat feedback to the wood cribs.