# Numerical Simulation of Co-Barrier Efficiency of Air Curtains in Mine Refuge Chambers
## 4 Discussion  
Thirty-three different conditions can be used to calculate the air curtain system barrier effectiveness at 5 min. The barrier effect of the air curtain is significantly influenced by the installation site and jet velocity, as shown in Table 1. The influence of the air curtain jet angle on the effectiveness of the air curtain barrier is not immediately apparent. The barrier effect of the air curtain installation position on the top side of the refuge door frame was 68.1% at a jet velocity of 22 m/s and a jet angle of 10\({}^{\circ}\) in an outside environment with a CO concentration of 1% for a hole diameter of 6 mm and a hole spacing of 15 mm.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Condition**} & **Installation** & \begin{tabular}{c} **Airflow** \\ **Velocity** \\ **(m/s)** \\ \end{tabular} & \begin{tabular}{c} **Hole** \\ **Diameter** \\ **(mm)** \\ \end{tabular} & \begin{tabular}{c} **Hole** \\ **Spacing** \\ **(mm)** \\ \end{tabular} & \
\begin{tabular}{c} **Airflow** \\ **Angle** \\ \end{tabular} &
\begin{tabular}{c} **Efficiency** \\ **at 5 min** \\ \end{tabular} \\ \hline
1 & Left side & 6 & 6 & 15 & 0\({}^{\circ}\) & 24.0\% \\
2 & Left side & 10 & 6 & 15 & 0\({}^{\circ}\) & 40.3\% \\
3 & Left side & 14 & 6 & 15 & 0\({}^{\circ}\) & 53.2\% \\
4 & Left side & 18 & 6 & 15 & 0\({}^{\circ}\) & 62.4\% \\
5 & Left side & 22 & 6 & 15 & 0\({}^{\circ}\) & 60.9\% \\
6 & Two sides & 6 & 6 & 15 & 0\({}^{\circ}\) & 23.6\% \\
7 & Two sides & 10 & 6 & 15 & 0\({}^{\circ}\) & 41.0\% \\
8 & Two sides & 14 & 6 & 15 & 0\({}^{\circ}\) & 57.7\% \\
9 & Two sides & 18 & 6 & 15 & 0\({}^{\circ}\) & 58.2\% \\
10 & Two sides & 22 & 6 & 15 & 0\({}^{\circ}\) & 58.6\% \\
11 & Top side & 6 & 6 & 15 & 0\({}^{\circ}\) & 10.5\% \\
12 & Top side & 10 & 6 & 15 & 0\({}^{\circ}\) & 24.7\% \\
13 & Top side & 14 & 6 & 15 & 0\({}^{\circ}\) & 40.7\% \\
14 & Top side & 18 & 6 & 15 & 0\({}^{\circ}\) & 52.5\% \\
15 & Top side & 22 & 6 & 15 & 0\({}^{\circ}\) & 66.8\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: The barrier efficiency of pipeline air curtain at 5 min in 33 kinds of conditions.  
Figure 19: The CO concentration cloud diagram of the transition room when the jet angle is 10\({}^{\circ}\) at Y = 1.805 m.  
Currently, people install air curtains in front of refuge chambers directly. This way cannot maximize the barrier effectiveness. At present, the hole diameter of the air curtain system used in mine is very small. In a dusty mine airflow environment, the airflow ports of the air curtain are easily blocked, thus reducing the effectiveness of the air curtain barrier. Compared to the air curtains currently installed in refuge chambers, the large hole diameter pipeline air curtain studied in this paper is not only more efficient in blocking CO, but also more stable in performance. The study of the impact of the installation position, angle, and jet velocity on CO barrier effectiveness serves as a guide for the installation and commissioning of air curtains. It provides guidance on the design of the structural parameters of the air curtain by studying how the structural factors of the air curtain affect the blocking effect.