# Mine Fire Behavior under Different Ventilation Conditions: Real-Scale Tests and CFD Modeling
## 3 Results and Discussion  
### Experimental Data  
Table 4 details the mean and maximum values of the pollutants and the maximum and minimum values of oxygen, based on data recorded downstream of the drift every minute for the five tests studied. CO\({}_{2}\) values below 1% were not detected due to the sensitivity of the measuring equipment used. Results from the previous table show almost constant oxygen levels in all cases, except when there was a very small opening of the air inlet door or it was closed, between 0% and 4%, lowering the oxygen level to 16% in these cases. Furthermore, it coincided with the highest levels of CO, NO\({}_{\times}\), and SO\({}_{2}\). Based on the experiments, it can be seen that an abrupt reduction in the air supply had a much greater impact on the variation of pollutant concentration than an increase in the fuel load. The CO\({}_{2}\) measurements only give an indicative value, since the sensor used was not entirely suitable for the kind of test performed due to a lack of sensitivity of the device, in the lower range. As mentioned in Section 2.3, the most representative fire scenarios are displayed in Figures 5-9, detailing the evolution of the pollutants, temperature, airflow, and pressure as a function of time and for each of the five main scenarios analyzed. Figure 4: XYZ meshing of the drift. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Stage** & **Features** & **Value** \\ \hline \multirow{3}{*}{Modeling design} & Cell size & \(0.6\times 0.6\times 0.6\) m \\  & Cell size rate & \(1\times 1\times 1\) \\  & Number of cells & 14,625 \\ \hline \multirow{3}{*}{Combustion parameters} & Surface type & BURNER \\  & HRR (heat release rate) & 2.220 kW/m\({}^{2}\) \\ \cline{1-1}  & Vessel dimensions & \(1.8\times 1.2\) m \\ \cline{1-1}  & Material of the vessel & Steel Sheet \\ \hline \multirow{3}{*}{Initial conditions} & Air temperature & \(10\)\({}^{\circ}\)C \\ \cline{1-1}  & Humidity & 80\% \\ \cline{1-1}  & Fan airflow & 30 m\({}^{3}\)/s \\ \hline \multirow{3}{*}{Simulation} & Type of simulation & LES (large eddy simulation) \\ \cline{1-1}  & Total time & 4800 s \\ \cline{1-1}  & Output data frames & 4800 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Modeling features. Figure 5: Evolution of the environmental conditions over time; test 1. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Conditions**} & \multicolumn{2}{c}{**O\({}_{2}\) (\%)**} & \multicolumn{2}{c}{**CO (ppm)**} & \multicolumn{2}{c}{**NO\({}_{\text{x}}\) (ppm)**} & \multicolumn{2}{c}{**SO\({}_{2}\) (ppm)**} & \multicolumn{2}{c}{**CO\({}_{2}\) (\%)**} \\ \cline{2-11}  & **Max.** & **Min.** & **Mean** & **Max.** & **Mean** & **Max.** & **Mean** & **Max.** & **Mean** & **Max.** \\ \hline
0\%, 180 L & 21 & 16 & 958 & 1063 & 6 & 16 & 79 & 102 & - & 3 \\ \hline
17\%, 180 L & 20 & 21 & 234 & 362 & 2 & 5 & 24 & 64 & 1 & 2 \\ \hline
100\%, 180 L & 20 & 21 & 67 & 91 & 2 & 4 & 19 & 26 & 1 & 1 \\ \hline
100\%, 360 L & 20 & 21 & 132 & 233 & 2 & 3 & 23 & 25 & 1 & 2 \\ \hline
100\%, 540 L & 20 & 21 & 219 & 284 & 4 & 5 & 19 & 21 & 1 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average values of the combustion pollutants. Figure 6: Evolution of the environmental conditions over time; test 2. Figure 7: Evolution of the environmental conditions over time; test 3. The dry temperature did not present any change with respect to the outside temperature except in Scenario 5, the test with the biggest fire load, having a small variation over time. On the other hand, the airflow was significantly affected by the fire evolution over time when the door was fully open. There was a variation between 12.5 m\({}^{3}\)/s and 20 m\({}^{3}\)/s for a load of 180 L of fuel, while, for loads of 360 and 540 L, the flow increased to 30 m\({}^{3}\)/s, representing a 60% increase for E3 scenario and between 150 and 200% for E4 and E5. This variation occurred after 960 s from the beginning of the fire in E3, while it happened at 450 and 420 s for E4 and E5, respectively.