Numerical study on gas temperature and smoke control in blind roadway fires

Abstract

In this study, smoke movement characteristics and smoke temperature in the blind roadway and the connected main roadway were mainly investigated numerically. The outcomings indicate that as the fire source gradually moves away from the heading face, the flame tilts from the heading face to the portal of the blind roadway. The gas temperature in the blind roadway and the downstream of the main roadway during ventilation is higher than that in the situation without ventilation, and it depends only on the fire location. The high-temperature smoke will generate energy loss as it passed through the bifurcation structure, resulting in a sudden decline in the longitudinal temperature attenuation curve. In addition, blind roadway fires require a higher critical velocity than single-hole tunnel fires. For a given heat release rate, the critical velocity gradually decreases as the fire source approaches the heading face. Besides, the line of L*=1.5 divides the variation of the dimensionless variable Q˙*2/3/v*2 with the dimensionless backlayering length (L*) into two regions with different slopes. Moreover, prediction models take into account the fire location to predict the dimensionless backlayering length and dimensionless critical velocity of the blind roadway are proposed.