## 3 Analysis of the EV Thermal Runaway Fire Scenarios
### Analysis of Thermal Radiation from an EV Fire and the Damage Caused
\begin{array}{c}\frac{H_{f-H}}{\sqrt{L^{2}+\left(H _{f}-H\right)^{2}}}\Bigg{(}\tan^{-1}\!\frac{W_{f}+S}{\sqrt{L^{2}+\left(H_{f}- H\right)^{2}}}-\tan^{-1}\!\frac{S}{\sqrt{L^{2}+\left(H_{f}-H\right)^{2}}} \Bigg{)}\\ +\frac{H_{7}}{\sqrt{L^{2}+H_{2}^{2}}}\tan^{-1}\!\frac{W_{f}+S}{\sqrt{L^{2}+H_ {2}^{2}}}-\frac{\tan^{-1}\!\frac{S}{\sqrt{L^{2}+H_{2}^{2}}}}{\sqrt{L^{2}+\left( W_{f}-S\right)^{2}}}\\ +\frac{H_{7}}{\sqrt{L^{2}+\left(W_{f}+S\right)^{2}}}\tan^{-1}\!\frac{W_{f}-H} {\sqrt{L^{2}+\left(W_{f}+S\right)^{2}}}-\frac{S}{\sqrt{L^{2}+\left(S^{2}\right) }}\tan^{-1}\!\frac{H_{f}-H}{\sqrt{L^{2}+S^{2}}}\\ +\frac{W_{f}+S}{\sqrt{L^{2}+\left(W_{f}+S\right)^{2}}}\tan^{-1}\!\frac{H}{ \sqrt{L^{2}+\left(W_{f}+S\right)^{2}}}-\frac{S}{\sqrt{L^{2}+S^{2}}}\tan^{-1} \!\frac{H}{\sqrt{L^{2}+S^{2}}}\\ +\frac{W_{f}+S}{\sqrt{L^{2}+\left(W_{f}+S\right)^{2}}}\tan^{-1}\!\frac{H}{ \sqrt{L^{2}+\left(W_{f}+S\right)^{2}}}-\frac{S}{\sqrt{L^{2}+S^{2}}}\tan^{-1} \!\frac{H}{\sqrt{L^{2}+S^{2}}}\end{array} \right] \tag{6}\]  
For the tilted flame formed under the airflow conditions, the angle \(\varphi\) between the tilted flame surface and the vertical line should be considered when calculating the radiation view factor between the flame surfaces and the pedestrians. The sketch is shown in Figure 5.  
(ii)   Flame surface # 2--Pedestrian view factor is given by  
\[F_{\#2}=\frac{1}{2\pi}\left[\begin{array}{c}\frac{H_{2t}}{\sqrt{L_{2}^{2}+ H_{2t}}}\tan^{-1}\!\frac{S}{\sqrt{L_{2}^{2}+H_{2t}}}+\frac{S}{\sqrt{L_{2}^{2}+S^{2}}} \tan^{-1}\!\frac{H_{2t}}{\sqrt{L_{2}^{2}+S^{2}}}\\ +\frac{H_{7t}}{\sqrt{  
The radiation absorption rate, transmittance and reflectivity of the atmosphere are the key indicators when radiation passes through an air medium. The air transmittance \(\tau_{air}\) was calculated using the following estimation formula [38]:  
\[\tau_{air}=2.02(p_{w}X_{0})^{-0.09} \tag{8}\]  
where, \(p_{w}\) is the vapor pressure of the water in the atmosphere at the ambient temperature \(\left(\text{N}/\text{m}^{2}\right)\) and \(X_{0}\) is the distance from the target to the flame surface (m). According to the law of energy conservation, the absorption rate is \(\alpha_{a}=1-\tau_{air}\). The environmental temperature was set to 293.15 K because the distance between the flame front and the target was in the range of a few meters. The smoke generated by the combustion moved upward in the open direction; therefore, without airflow, there was little impact of the thermal radiation near the ground. The substances in air that can absorb thermal radiation are water vapor (H\({}_{2}\)O) and carbon dioxide (CO\({}_{2}\)). It is generally assumed that the absorption rates of the two in air are low. The air flow speed affects the combustion flame shape and direction of the combustion heat convection. When a flame intrudes into the sidewalk area under the influence of the airflow, the probability of pedestrian injury and fire accident propagation increases. With the statistical data from the Beijing Meteorological Service, the average air flow speed near the ground in Beijing from 2000 to 2020 was 2.2 m/s. The value for the airflow speed was set for typical scenarios as \(u_{w}=\{0,2.2\) m/s\(\}\). The empirical formula for the flame tilt angle \(\varphi\) was obtained from Guang [39] as follows:  
\[\varphi=47.39-\frac{46.94}{1+0.02u_{w}^{4.39}} \tag{9}\]  
According to (9), the flame tilt angle \(\varphi\) corresponding to the airflow speeds can be obtained as \(\sim\{0^{\circ},19^{\circ}\}\). (4) Analysis of the pedestrian thermal radiation damage. The complex pedestrian conditions are the key factors in the risk uncertainty of roadside parking lots in residential areas. The risk-avoidance behavior of a pedestrian is expressed by two parameters [20]: the evacuation speed and the evacuation direction. In addition, considering the complicated pedestrian conditions in the roadside parking scenario, there are old, young, weak and disabled people who may not be sensitive enough to the disaster signal and who may have a weak risk avoidance ability.