## 3 Analysis of Simulation Results
### Lithium Battery Vehicle Tunnel Fire Hazard  
#### 3.1.1 Impact of Heat Release Rate  
Figure 5 shows the variation of Heat Release Rate (HRR) over time for both heavy-duty gasoline vehicles (HGV) and electric trucks in the tunnel. The fuel composition for the HGV fire is set to 80% wood and 20% PE plastic, with thermal conductivity, density, and specific heat values of 0.12 (W/(m\(\cdot\)K)), 600 (kg/m\({}^{3}\)), 2.58 (kJ/(kg\(\cdot\)K)) for wood, and 0.64 (W/(m\(\cdot\)K)), 956 (kg/m\({}^{3}\)), 3 (kJ/(kg\(\cdot\)K)) for PE plastic, respectively [36]. The fire source is located 20 m from the left side of the tunnel, with dimensions of 10 \(\times\) 4 \(\times\) 3 m. The heat release rate is set using the predefined method, and the remaining boundary conditions and sensor point settings are the same as those in the electric truck model, with a simulation duration of 1500 s.  
As shown in Figure 5, the peak Heat Release Rate (HRR) for the heavy-duty gasoline vehicle (HGV) is approximately 200 MW, while the peak HRR for the lithium battery electric truck reaches around 260 MW. Within the first 5 min after the fire begins, the HRR of both the electric truck and the heavy-duty gasoline vehicle rapidly increases. Due to the thermal runaway of the electric truck's battery, the surrounding battery packs also catch fire, causing the fire size to grow more quickly than that of the gasoline vehicle. Between \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Condition** \\ **No.** \\ \end{tabular} } & \multirow{2}{*}{**Material Name**} & \multirow{2}{*}{\begin{tabular}{c} **Density** \\ **(kg/m\({}^{3}\))** \\ \end{tabular} } & \begin{tabular}{c} **Specific Heat** \\ **Capacity** \\ **KJ/(kg\(\cdot\)\({}^{\circ}\)C)** \\ \end{tabular} & \begin{tabular}{c} **Thermal** \\ **Conductivity** \\ **(m\(\cdot\)K)** \\ \end{tabular} & \
\begin{tabular}{c} **Emissivity** \\ **(mm)** \\ \end{tabular} &
\begin{tabular}{c} **Thickness** \\ **Power (kW)** \\ \end{tabular} \\ \hline
1 & Calcium Silicate & 600 & 1200 & 0.15 & 0.9 & 40 & 1500 \\
2 & Fireproof Coating & 600 & 1000 & 0.19 & 0.7 & 40 & 1500 \\
3 & Magnesium Oxide & 950 & 1000 & 0.19 & 0.5 & 40 & 1500 \\
4 & Concrete & 2100 & 880 & 1.0 & 0.7 & 40 & 1500 \\
5 & SiO\({}_{2}\) Gel & 2400 & 970 & 1.55 & - & 40 & 1500 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Thermal physical parameters of wall materials. 5 to 10 min, the HRR of the electric truck continues to rise, while the heavy-duty gasoline vehicle's HRR growth slows and reaches its peak. After the electric truck's HRR peaks, it rapidly decreases, and between 13 and 22 min, the HRR of the gasoline vehicle is lower than that of the electric truck. Around 22 min, the HRR of both vehicles stabilizes, but the electric truck's heat release rate remains higher than that of the gasoline vehicle's fire. This indicates that electric vehicles powered by lithium battery packs pose a greater fire risk. There are significant differences in temperature distribution between new energy truck fires and traditional combustion engine truck fires. Traditional fuel truck fires are mainly caused by fossil fuel combustion. The temperature distribution is characterized by high-temperature areas concentrated around the fire source. With the increase of distance, the heat gradually diffuses, and the temperature gradually decreases. Lithium battery electric vehicle fires are usually caused by thermal runaway of the battery. The chemical reaction inside the battery releases a lot of heat and smoke, resulting in a wider and longer temperature distribution in the high-temperature region. There are significant differences in temperature distribution between fires in new energy trucks and traditional fuel trucks. Fires in traditional fuel trucks are primarily caused by the combustion of fossil fuels, resulting in a temperature distribution where high temperatures are concentrated around the fire source, with heat gradually dispersing and temperature decreasing as distance increases.