Evolution characteristics of fire smoke layer thickness in a mechanical ventilation tunnel with multiple point extraction

A series of burning experiments were conducted in a model-scale mechanical ventilation tunnel to study the characteristics of smoke layer thickness and plug-holing with multiple point extraction system. Hot-wire anemometer and thermocouples trees were used to measure the flow velocity of ventilation outlet and vertical temperature profile in a mechanical ventilation tunnel, respectively. It was found that the smoke layer thickness was calculated by integral ratio method and within-class variance method were good agreement with visual observation value. The normalized temperature curves can be divided into two regions, such as, the plug-holing and without plug-holing. The smoke plug-holing exhaust rate and the d/H ratio of smoke layer depth to clear height decreased with increasing the number of point extraction opening for a given HRR.