Calculation of the Number of Electric Vehicles Carried by Roll-on Roll-off Vessels Based on Fire Dynamics Simulation

With the rapid development of the global cruise transportation industry and the worldwide increase of cruise ship transportation year by year, fire accidents on passenger and roll-on/roll-off ships (P/ROCs) pose a serious threat to economic properties.The article establishes a fire model of a passenger-roller ship carrying electric vehicles using the basic equation of dynamics, a large eddy simulation model, and a mixed fraction combustion model.The mesh division is used to improve the solving accuracy of the kinetic equations.The fire simulation conditions of the electric vehicle carried by a passenger-roller ship are designed to analyze the fire combustion characteristics of the passenger-roller ship transported in terms of wind speed, fire intensity, and ignition power in multiple dimensions using the FDS simulation software as a carrier.Based on the YOLOv5s network and combined with the improved non-great suppression algorithm, a statistical model for target detection of electric vehicles carried by a passenger-roller ship is designed, and the corresponding loss function is designed.When the external ambient wind speed was increased from 0.5 m/s to 6.5 m/s, the maximum temperature at the fire center of the electric vehicle carried by the passenger-roller ship was reduced from 883.93C to 748.57C.The improved YOLOv5s model has the highest mAP of 96.67% on the target detection of EVs after fire damage and an accuracy of 92.96% for counting the number of EVs after fire.The state of electric vehicles after fire damage can be obtained under fire dynamics simulation, and the target detection and quantity counting of electric vehicles can be effectively realized by combining deep learning technology.