Modelling the throttle effect in a mine drift

Rickard Hansen

doi:10.46873/2300-3960.1329

Abstract

The throttle effect is a phenomenon, which may occur during a fire underground, causing unforeseen smoke spread. This paper focuses on the modelling of the throttle effect in a mine drift, using a CFD software. The aim of the paper is to investigate whether the CFD tool is able to predict and reproduce the throttle effect for fire scenarios underground. Experimental data from fire experiments in a model-scale mine drift and modelling results from a CFD model were used during the analysis. It was found that the CFD model was not able to fully reproduce the throttle effect for fire scenarios in a mine drift. The inability was due to the under prediction of the fire gas temperature at the ceiling level and the over prediction of the temperatures at the lower levels. The difficulties occurred foremost during transient periods with high fire growth rates. Given the difficulties in modelling the thermal stratification and the throttle effect, the use of CFD models should be mainly for qualitative analysis. Qualitative analysis could possibly be performed for non-transient and low intensity fires.

Highlights

One of the key risks during a fire in an underground mine is the smoke spread, where an unforeseen smoke spread will increase the risks to the mining personnel even further
Experimental data from fire experiments in a model-scale mine drift and modelling results from a CFD model when analysing the possibility of reconstructing the throttle effect
It was found that the CFD model was not able to fully reproduce the throttle effect for fire scenarios in a mine drift

Summary

Introduction

One of the key risks during a fire in an underground mine is the smoke spread, where an unforeseen smoke spread will increase the risks to the mining personnel even further. One of the phenomena which may cause unforeseen smoke spread e initiating disturbances and air flow changes underground e is the throttle effect. The throttle effect will result in a reduction in the mass flow rate, which in turn may cause changes in ventilation flow directions and difficulties during the smoke extraction as well as the evacuation phase. When designing the fire safety of an underground mine, data from full-scale fire tests performed in similar surroundings and with similar fuel items would be key information. Performing full-scale fire experiments in an underground mine will be very costly, time consuming, etc. A tool, which could complement e but never fully replace e the full-scale experiments, is a CFD (Computational Fluid Dynamics) tool for modelling a fire underground

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