Mass flow during fire experiments in a model-scale mine drift with longitudinal ventilation

ABSTRACT Fires in underground mines may cause dangerous phenomena to mining personnel. One of these phenomena is the throttle effect, reducing the mass flow. This paper investigates the nature of the throttle effect. Data was provided from fire experiments in a model-scale mine drift. With an increasing heat release rate the reduction in the mass flow will increase. An increasing ventilation velocity may initially cause a reduction of the mass flow. With a further increase of the flow velocity the mitigating effect of the forced flow will increase. A dimensional analysis resulted in an equation where the mass flow reduction could be reasonably well described. It was found that the flow velocity had a weak effect on the mass flow reduction. Nevertheless, the flow velocity influence the initiation of the reduced mass flow. A full-scale flow velocity of 3.5 m/s was found to prevent the throttle effect for typical fires underground.