Analysis of Smoke-Spread Characteristics in Electric Vehicle Fires in a Two-Lane Tunnel with an Arched Ceiling

Abstract

With the rapid increase in electric vehicle ownership, fire risks associated with electric vehicles in tunnels have attracted increasing attention. In this study, a numerical model of an electric vehicle fire in a two-lane tunnel with an arched ceiling was established using the Fire Dynamics Simulator. The effects of transverse and longitudinal fire source locations on smoke layer thickness and longitudinal temperature distribution were investigated. Smoke layer thickness was identified using the visibility discontinuity method, and theoretical models incorporating the geometrical characteristics of the arched ceiling were established. The results indicate that fire source location exerts a marked influence on smoke layer development and longitudinal temperature attenuation. The maximum smoke-layer-thickness ratio exceeded unity in all cases and was generally greater downstream than upstream of the fire source. During the quasi-steady stage, the ceiling-temperature rise exhibited exponential decay along the tunnel. Relative to the centerline fire condition, displacement of the fire source to the center of the right lane increased the magnitude of the downstream composite attenuation coefficient by 5.6–11.2%; a further displacement toward the sidewall increased it by 20.6–34.1%. Most predictions from the proposed longitudinal temperature model agreed with the comparison data within ±20%. These findings underscore the need to jointly account for transverse and longitudinal fire-source locations in smoke-control design and evacuation-safety assessment for arched road tunnels.