Impact of Dual Fire Sources on Temperature Distribution and Smoke Ventilation in Road Tunnels with Shafts.

This investigation, utilizing the Fire Dynamics Simulator (FDS), explored the impact of dual fire source scenarios within tunnels, particularly focusing on temperature distribution and natural smoke exhaust in tunnels equipped with shaft ventilation. The study compared these scenarios against those involving a single fire source by varying the spacing between fire sources and adjusting longitudinal wind speeds. It was found that the speed of smoke propagation accelerated as the distance between fire sources increased, under a constant power of the individual fire sources. The temperature profiles of the tunnel ceiling under various scenarios exhibited considerable consistency. At lower longitudinal wind speeds, the temperature upstream of the fire source was higher compared to the downstream area, with the minimum temperature recorded at the shaft entrance. Notably, the critical wind speed, defined for a single fire source scenario with power equivalent to the combined power of two closely spaced fire sources, decreased with increasing distance between the fire sources, revealing a finite limit. In the shaft, a pattern was observed where the smoke temperature, gas mass flow, and carbon monoxide concentration initially increased and then decreased with a rise in longitudinal wind speed, reaching optimal efficiency in smoke exhaust at a wind speed of 2m/s. The complexities inherent in dual fire source scenarios were more pronounced compared to single fire source scenarios, presenting increased risks to safety and health during a fire. This study underscores the need for strategic planning in tunnel design, particularly in accommodating ventilation systems that can effectively respond to varying fire source scenarios. [ABSTRACT FROM AUTHOR]