Smoke Stratification in a Mine Drift with Multiple Objects Downstream

Abstract The smoke behaviour and smoke stratification of a fire in a mine drift will be one of the decisive factors affecting the risk to mining personnel during a fire. This paper studies the smoke stratification in a mine drift with multiple objects downstream of the fire, at varying distances and number of objects. Data for the study was provided from earlier model-scale fire experiments and CFD modelling was performed for in-depth analysis of specific phenomena. It was found that at considerable downstream distances from the fire, the smoke stratification differences were significant, reflecting the high impact of multiple objects. With an increasing distance between the objects downstream, an increased degree of mixing and decreased stratification occurred. With an increasing distance between the burning object and the second object, the smoke layer will descend further before encountering the object and the smoke stratification on the upstream side of the second object will decrease. The increased mixing of the hot gases flowing from the burning object will have a more significant effect on the overall stratification due to the higher temperatures. An increasing number of objects downstream will not by itself lead to increased stratification, with shorter distances between the objects and an increasing number of objects, the smoke stratification may instead be retained for a longer distance. An increasing flow velocity will result in decreasing stratification found foremost downstream of the burning object, as the tilt of the plume will increase and interact increasingly with the second object.